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CC - Drainage Report
Prepared For: Hill's Century Farms Townhomes Subdivision Brighton Development, Inc., ACHD, and City of Meridian Meridian, Idaho Storm Drainage Report SS\pNAL fNG E N S F Digitally signed by Lachlin Kinsella,P.E. 16860 Date:2026.02.06 11:19:06 -07'00' u�, 2/6/26 o Q 9C, qTF OF /N C. K�N� Reviewed By: Lachlin Kinsella, P.E. Prepared By: Jacob O'Gorman Project Engineer KM Engineering, LLP 5725 North Discovery Way Boise, I D 83713 208.639.6939 jogorman@kmengllp.com Ian February, 2026 E N G I N E E R I N G Project No: 25-243 TABLE OF CONTENTS Introduction ................................................................................................................................. 1 ProjectDescription ...................................................................................................................... 1 SiteDescription............................................................................................................................... 1 Scopeand Methods........................................................................................................................ 1 Existing Drainage Conditions .......................................................................................................... 1 Proposed Drainage Conditions and Analysis .................................................................................. 1 Inletand Gutter Capacities ............................................................................................................. 2 SeepageBeds.................................................................................................................................. 2 Temporary Pond Calculations......................................................................................................... 2 Summary......................................................................................................................................... 2 APPENDICES Appendix A - Figures Figure 1 - Vicinity Map Figure 2 - Post-Development Drainage Map Figure 3 - Storm Water Improvement Plans Appendix B - Tables Table 1 - Peak Flow Rates and Runoff Volumes Appendix C - Calculations Post-Development Calculations Inlet and Gutter Capacities Seepage Bed Calculations Temporary Pond Calculations Appendix D - Geotechnical Engineering Report & Groundwater Data Geotechnical Investigation Century Farms Townhomes (Atlas, 4/4/2025) Ground water monitoring report—CF Townhomes (Syman, 11/12/2024) INTRODUCTION The purpose of this report is to show that the storm drainage facilities for the proposed Hill's Century Farms Townhomes (Project) are designed to meet Ada County Highway District (ACHD), City of Meridian, and the water quality requirements of the Idaho Department of Environmental Quality (DEQ). This report has been prepared at the request of the developer, Brighton Development, Inc. PROJECT DESCRIPTION The project consists of a residential subdivision that includes 69 single-family residential lots and 16 common lots. The proposed improvements to the site include roadways, sidewalks, lot grading, and site utilities. SITE DESCRIPTION The project site is located south of E. Amity Ave. near the intersection of S. Tavistock Ave. in Meridian, Idaho. See Appendix A, Figure 1 for a vicinity map of the project. The proposed project area is 9.10 acres. SCOPE AND METHODS The stormwater system for the Project has been designed per the 2017 ACHD Stormwater Policy. The Rational Method is the standard method for small catchments and was used to calculate post-development peak runoff rates and runoff volumes. The Rational Method provided in the ACHD calculation sheets was used to calculate the storm water volumes and flow rates for this project (see Appendix C - Calculations). Flow rates and storm volumes were established for each basin for the 25-year and 100-year storms. Refer to Appendix B, Table 1 - Peak Flow Rates and Runoff Volumes, for a summary of flow rates and runoff volumes. Calculations for the seepage beds and temporary pond were completed to verify capacity. EXISTING DRAINAGE CONDITIONS The pre-project watershed consists primarily of an undeveloped site. The stormwater runoff is currently being collected by inlets on E. Hill Park St. south of the Project site. PROPOSED DRAINAGE CONDITIONS AND ANALYSIS The proposed drainage system improvements consist of roadway inlets and gutters, sand and grease traps, manholes, seepage beds, and temporary ponds. The post-development site was broken into eighteen (18) basins as shown in Appendix A, Figure 2 - Post-Development Drainage Map. For land use type and runoff coefficients (0.1 — open space, .95 — impervious, 0.50 — lots) for each basin, refer to Basin Calculations in Appendix C. Each basin was delineated according to the tributary area draining to each drainage structure or facility such as gutter, catch basin inlet, etc. For individual sub-basin peak flow calculations, in addition to combined sub-basin peak flows used for downstream facility sizing and analysis, see Figure 3 (Post-Development Peak Flow Rate Summary). 1 The proposed drainage basins include the front half of the lots and all the proposed roadways, curb and gutters, and sidewalks. Storm water runoff consists of overland sheet flow over short grass that is conveyed with curb and gutter to catch basin inlets. The storm water runoff is then conveyed from the catch basin inlets to the proposed seepage beds or temporary ponds. INLET AND GUTTER CAPACITIES The catch basin inlets should be built per the details shown on the civil construction plans. There are a total of eighteen (18) single inlets. Based on our calculations, all inlets will require a single sump grate inlet to intercept the flows. The gutter capacity of the proposed roadways was verified to ensure that overtopping of the curb would not occur in the 25-year and 100-year storm event (refer to Appendix C— Inlet and Gutter Capacities). SEEPAGE BEDS The Project includes nine (9) seepage beds (SB #1-9) that should be built per the details shown on the civil construction plans. Based on our calculations, the seepage beds are adequately sized to ensure that no ponding should occur on the surface and the volume required to retain the 100-year storm event are met. Once the sizes of the seepage beds were calculated, the times necessary for 90% of the 100-year storm events to be infiltrated into the ground were calculated at less than 48- hours for each of the seepage beds. The design infiltration rate varies per seepage bed and is based on the recommended design infiltration rates from the geotechnical report prepared by Atlas (See Appendix D). The calculations included with this report show the volumes that are required to be retained for the 100-year storm and the drain time through the bottom of the seepage beds. Refer to Appendix B, Tables and Appendix C, Seepage Bed Calculations. TEMPORARY POND There are two (2) temporary ponds proposed that should be built per the civil construction plans and located outside of the project boundary. The temporary ponds have been sized to store the 100-year volume and infiltrate 90% of the required volume within a 48-hour period. SUMMARY This report determines that the Project storm water design sizing and analysis should conform to ACHD and the water quality requirements of the Idaho Department of Environmental Quality (DEQ). The post-development storm water runoff for half of the proposed residential lots and the entire roadway, curb and gutters, and sidewalks should be completely retained onsite through the proposed seepage beds and temporary ponds. 2 APPENDIX A - FIGURES go III■■ ■■■■■11`�_ _ .`�� �rrrrrrri, �■ ■■ ■■ ■ IIII 11■ - - _ = - -- �I�1■ ■111■ ■111111111 J _111111111111111111r ��■■,� a 111-1 ■1�;: I IIIIII ■11 IIIIIII == �II��111� ` ■1 ■■� .� IIL,♦\ IIIII� 11■ IIIIII 11111111 _� !� � ''♦ uuu IIIII IIII ��!IIII, IIII` ! �� , 11 �� �C 11■ nnn IIIIII p�lllll "IIII ������� IIIIII I �■ 11■ NINE uuu•Iu=I1 �' �� it 1► �II1 ■ —�I� 11 �111111111� ■ 1111�� 1� . 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III-I I1=1I I- I \ I O m W W m w z (n o_ m v F- F- F- F- F- F- F- F- _ W� ¢ O w w w w w w w w =11 III- w V) N N- w III IIII J m O d J N L — J a ? w Lea = 00 m m > > > > > > > > w 8 312JbA I ,2 cn z � _ �Z�i o o N O V) z,J v Of Of Of Of af af af Of Ii1]13 'H d0 W01100 Ol JN31Xd S-T2JVA Hld3 z � z Iw o N W o a j w � X a m O z O W z z o w?0 ZQ 0 Wv W � LU Z VI W Q U = N N Z O¢U- m - U) m m m m m m m m m m J m' m O O Z Q CCY Z N 0 N N N N N N N Ld o nmcn M a ¢ oo J CL = o � z N ~ ae ¢ w a = o o Nx o w U) 0= 0 U a E 0o V) z LL Q o o ¢ N [30d]I b£XZZ'£Jd'(M9)SSL3dl N0NVJ'9Z0Z/9/Z'NVVU09,0 90JVf'9M0'39VNIVPIO-O£bZ-SZ\SNVId NOIlDndiSNOJ\0V0\IIAIJ\£bZ-SZ\:d APPENDIX B - TABLES Figure 3 - Storm Drainage System Summary (ACHD IDF) Table 1 - Pre & Post-Development Peak Flow Rate Summary Basin Properties Peak Flow Rate c A Tc i25 i100 Q25 Q100 Acres min. in/hr in/hr cfs cfs Basin Al 0.57 0.31 10.0 1.85 2.58 0.33 0.46 Basin A2 0.63 0.55 23.7 1.30 1.81 0.45 0.62 Basin B1 0.56 1.30 24.3 1.30 1.81 0.94 1.31 Basin B2 0.57 0.60 22.2 1.30 1.81 0.45 0.62 Basin C1 0.56 0.93 23.7 1.30 1.81 0.68 0.95 Basin C2 0.66 0.54 10.0 1.85 2.58 0.66 0.92 Basin D1 0.58 0.70 22.7 1.30 1.81 0.53 0.74 Basin D2 0.49 0.53 21.6 1.30 1.81 0.34 0.48 Basin E1 0.62 0.19 10.0 1.85 2.58 0.21 0.30 Basin E2 0.63 0.19 10.0 1.85 2.58 0.21 0.30 Basin F1 0.56 1.00 22.2 1.30 1.81 0.73 1.02 Basin G1 0.95 0.08 10.0 1.85 2.58 0.15 0.20 Basin G2 0.76 0.11 10.0 1.85 2.58 0.16 0.22 Basin H1 0.50 0.18 10.0 1.85 2.58 0.16 0.23 Basin H2 O.43 0.49 21.3 1.30 1.81 0.27 0.38 Basin 11 0.95 0.09 10.0 1.85 2.58 0.15 0.21 Basin J1 0.61 0.22 10.0 1.85 2.58 0.25 0.35 Basin J2 0.95 0.09 10.0 1.85 2.58 0.17 0.23 Design Point 1 0.57 0.31 10.0 1.85 2.58 0.33 0.46 Design Point 2 0.63 0.55 23.7 1.30 1.81 0.45 0.62 Design Point 3 0.61 0.86 23.7 1.30 1.81 0.68 0.95 Design Point 4 0.56 1.30 24.3 1.30 1.81 0.94 1.31 Design Point 5 0.57 0.60 22.2 1.30 1.81 0.45 0.62 Design Point 6 0.56 1.90 24.3 1.30 1.81 1.39 1.93 Design Point 7 0.56 0.93 23.7 1.30 1.81 0.68 0.95 Design Point 8 0.66 0.54 10.0 1.85 2.58 0.66 0.92 Design Point 9 0.60 1.47 23.7 1.30 1.81 1.15 1.59 Design Point 10 0.58 0.70 22.7 1.30 1.81 0.53 0.74 Design Point 11 0.49 0.53 21.6 1.30 1.81 0.34 0.48 Design Point 12 0.55 1.23 22.7 1.30 1.81 0.87 1.21 Design Point 13 0.62 0.19 10.0 1.85 2.58 0.21 0.30 Design Point 14 0.63 0.19 10.0 1.85 2.58 0.21 0.30 Design Point 15 0.62 0.37 10.0 1.85 2.58 0.43 0.60 Design Point 16 0.56 1.00 22.2 1.30 1.81 0.73 1.02 Design Point 17 0.95 0.08 10.0 1.85 2.58 0.15 0.20 Design Point 18 0.76 0.11 10.0 1.85 2.58 0.16 0.22 Design Point 19 0.84 0.19 10.0 1.85 2.58 0.30 0.42 Design Point 20 0.50 0.18 10.0 1.85 2.58 0.16 0.23 Design Point 21 0.43 0.49 21.3 1.30 1.81 0.27 0.38 Design Point 22 0.45 0.66 21.3 1.30 1.81 0.39 0.54 Design Point 23 0.95 0.09 10.0 1.85 2.58 0.15 0.21 Design Point 24 0.61 0.22 10.0 1.85 2.58 0.25 0.35 Design Point 25 0.95 0.09 10.0 1.85 2.58 0.17 0.23 KM Engineering,v2.3 Page 1 of 1 25-243 Storm Drainage System Summary Template v2.6.xlsx APPENDIX C - CALCULATIONS POST-DEVELOPMENT CALCULATIONS E Z E E E E M N vt MO N 0 0 0 0 00 0 0 0 . 0 0 0 �D il1 N V ill ill 00 N A I tMvf ^ � tmvl V O tOvf O o O M NO O C O c oc w a oc .i n w a 'o � w n ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti ti V o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ro .rv. v vO1i � °1 m ao m a in a ti � v � o0 0'0 in m m in o 0 o m m a 11 n 1c �c n oo .-ivorvo oivvn oivmvi-dv 'o w 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 W 1� N N n ti 1p O O N O 1� W N a a C N N N N N M N N N N N N M eel N rl .i E e01 M n M N m Q N I I N O O O N O eQi O 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Q V M N M N OM1 n lui e eM e eel l Ml 0 0 01 O O N O a ` O O eel O O O m m m m eel m m m m m m m Q I� M uD Ii uD tD W g N M uD N �D O M N N Si l0 N N N l0 N Q l0 l0 N O1 O1 N 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 V p � V Z Q W Q Q m aN0 U U C C u�i uNi LL l7 lN7 2 2 =� C C C C C C 'N C C C C C C C C C C C C Z N N N N N N N g q N '.n N N N m m m V m m m m m m m m O O m m m m m J Q V z # N N MQ 0 Q Q m m V V C C W LL l7 l7 S S e_i _ W f E Z E E E g E E C co a a c c_ 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 . . . . . . . . . . . . . . . . . . E 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o ,n 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 >c x o eo a � a � m °p v` L o i a t c_ 1 0 m V a m N I I W IR N CD m N N N o N W CO N 1� N . . . . . m O CO O O t G N N M eel N N N eel eel eel eel eel eel eel O eel eel eel a 'E m IR p mi CD YI N Ot c V In In m m o In In �uo m n .-I In uo n L o O O o ~ ei N N N N N IYI . ei N N N N 0 o E w x Y P v � � C � o O - - � V 0 1p `o o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 - . H o 16 i 6 o in n ti n ti n N N a a n a ry a N a �c m M vom MVM nao a h o 0 0 0 0 0 0 0 0 0 0 0 o 0 0 0 0 0 u°1`o o.o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 o O en o �i Q Q Q Q Y1 M Q Q W W O ri N W O N Q Q - G_ O ei O O ei O O O IYI IYI O O N 0 0 0 0 0 F N m m m m N m m m m In N o a In m N ao y 0 0 0 0 0 0 0 0 0 eel I� cm! 1O N o a _ LL 'h 0 0 0 0 0 0 0 0 0 a o 0 0 0 0 o d Z > n O a3 L N N ill ill N N V il1 N N O O O O O O O o r G.t O O O O O O O O O O O O O O O O O O Z W `o C1 Z n N a N ro m u ao n w o tp O W W I4 N N n �R Li O O N O I� W N O In b O ~ LL O o C W NG �y N eel 'o No = NS `c W LL {J r f E Z E E E E Q O V m H tt 0 C O a m G H N m c u a C O V H tt N N N O rl N M rl N n N O ei eel N O Q Q '� f0 f0 a V V n G C rl W W eel W {7 l7 eel 2 2 N — W n n N N N n earl n b N b O O O N O n n W N N 0 OOi O C N M O O M M M N eel N N N N N N M M eel eel eel eel ey F. 'E N N N N N N N N N N N N N e01 M uii n M O uii M W O N N I I N vni 0 0 e0�1 O N M O .�-� O 0 0 0 0 o eel O C C C C C C C C C C C O C 0 0 0 0 0 Q V M N W M N 001 In O n N N .O1-i .°1i M O O I I I a N O N O a ` O 0 0 eel O eel 0 0 eel 0 0 eel 0 0 0 eel 0 0 0 0 0 0 0 0 0 Q Z O O m . m N M N . m , V M m m Yf m %q l0 N N N N %q l0 N O N %q %q l0 N 01 n CD N a a m �o m 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 V O E V U Q .yNMaM �onmm .oi •• m .aiN � .ni .ao. � o a E Z a° a a a a a a a a a a a a a a a a a a a a a a a 0 a z m m m m m m m m m c c c c c c c c c c c c c c c c d o 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Z V� tt O N M Q Y1 tD n m OI O N M Q Y1 W 0 M O N l0 n 00 OI „q „9 e9 e9 e9 e9 e9 e9 e9 e9 N N N N N N f INLET CAPACITIES Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 1A - Design Point 1 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.46 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.46 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.46 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.60 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 4.27 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest 0.13 5 2 77 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 2A - Design Point 4 - 100 year Drop Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 1.31 Throat Height (in) = -0- Grate Area (sqft) = 3.44 Highlighted Grate Width (ft) = 1.48 Q Total (cfs) = 1.31 Grate Length (ft) = 2.33 Q Capt (cfs) = 1.31 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.78 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.052 Gutter Spread (ft) = 9.71 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 4.00 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest 2.M d—, 2.85 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 2B - Design Point 5 - 100 year Drop Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.62 Throat Height (in) = -0- Grate Area (sqft) = 3.44 Highlighted Grate Width (ft) = 1.48 Q Total (cfs) = 0.62 Grate Length (ft) = 2.33 Q Capt (cfs) = 0.62 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.08 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.052 Gutter Spread (ft) = 7.47 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 4.00 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest 1.73 d.p". 1.73 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 1 B - Design Point 2 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.62 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.62 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.62 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.86 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 5.34 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All d i m ens Inns I n feet - - -- -------------------------------------------- 9.15 5 3.84 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 3A - Design Point 7 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.95 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.95 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.95 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 2.32 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 7.28 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest G.15 1 5 5 78 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 3B - Design Point 8 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.92 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.92 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.92 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 2.28 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 7.11 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest T T71. 5.- Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 4A - Design Point 10 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.74 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.74 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.74 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 2.03 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 6.07 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest Jr� __._. ........... ... ............................................................................................. �, 1 1.E 3.57 Yam_ r' Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 4B - Design Point 11 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.48 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.48 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.48 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.64 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 4.41 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest @1A 15 291 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 5A - Design Point 13 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.30 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.30 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.30 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.31 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 3.08 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest ___ ........ .......... ------------------------------------- D11 1 5 I.58 f. Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 5B - Design Point 14 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.30 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.30 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.30 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.31 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 3.08 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest ___ ........ .......... ------------------------------------- D11 1 5 I.58 f. Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 6A - Design Point 16 - 100 year Drop Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 1.02 Throat Height (in) = -0- Grate Area (sqft) = 3.44 Highlighted Grate Width (ft) = 1.48 Q Total (cfs) = 1.02 Grate Length (ft) = 2.33 Q Capt (cfs) = 1.02 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.51 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.052 Gutter Spread (ft) = 8.83 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 4.00 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest 242 4—, 242 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 7A - Design Point 17 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.20 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.20 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.20 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.11 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 2.22 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest ---------------- 0.05 15 ❑72 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 7B - Design Point 18 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.22 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.22 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.22 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.15 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 2.40 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest D.1 15 09 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 8A - Design Point 20 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.23 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.23 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.23 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.17 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 2.49 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest 3.1 15 099 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 8B - Design Point 21 - 100 year Drop Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.38 Throat Height (in) = -0- Grate Area (sqft) = 3.44 Highlighted Grate Width (ft) = 1.48 Q Total (cfs) = 0.38 Grate Length (ft) = 2.33 Q Capt (cfs) = 0.38 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 0.78 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.052 Gutter Spread (ft) = 6.50 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 4.00 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest 1 25 d.p". 1 25 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 9A - Design Point 24 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.35 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.35 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.35 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.41 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 3.47 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest D12 15 197 Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 10 - Design Point 23 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.21 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.21 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.21 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.13 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 2.31 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest a oD — 15 osi Inlet Report Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Wednesday,Jan 28 2026 Inlet 11 - Design Point 25 - 100 year Grate Inlet Calculations Location = Sag Compute by: Known Q Curb Length (ft) = -0- Q (cfs) = 0.23 Throat Height (in) = -0- Grate Area (sqft) = 3.22 Highlighted Grate Width (ft) = 1.42 Q Total (cfs) = 0.23 Grate Length (ft) = 2.27 Q Capt (cfs) = 0.23 Q Bypass (cfs) = -0- Gutter Depth at Inlet (in) = 1.17 Slope, Sw (ft/ft) = 0.052 Efficiency (%) = 100 Slope, Sx (ft/ft) = 0.020 Gutter Spread (ft) = 2.49 Local Depr (in) = -0- Gutter Vel (ft/s) = -0- Gutter Width (ft) = 1.50 Bypass Spread (ft) = -0- Gutter Slope (%) = -0- Bypass Depth (in) = -0- Gutter n-value = -0- All dimensions Infest 3.1 15 099 SEEPAGE BED CALCULATIONS ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Steps for Seepage Beds Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seepage Bed 1 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100'QV' 4 Weighted Runoff Coefficient C 0.61 Link to: LQv 5 Area A(Acres) 0.86 acres ON TR55 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? No V 2,266 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 12.0 ft 9 Set Total Design Depth of All Drain Rock D 4.1 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 2.00 in/hr 12 Size of WQ Perf Pipe(Pert 180°) Dia pipe 18 in 1.8 13 Size of Overflow Perf Pipe(Perfs 3601),READ if Q300>3.3 cfs in 0.0 14 Calculate Total Storage per Foot Spf 21.9 ft3/ft 15 Calculate Design Length L 104 ft 103.6876787 Override Value Required for Chambers 16 Variable Infiltration Window L SWL 104 ft 17 Variable Infiltration Window W SWW 12.0 ft 18 Time to Drain 9.8 hours 90%volume in 48-hours minimum OK 19 Length of WQ&Overflow Perf Pipes 104 ft 20 Perf Pipe Checks.Qperf>=Qpeak; OK where Qperf=CdxAxV(2xgxH) d 0.0313 ft Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft'/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft'/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain #DIV/O! hours 90%volume in 48-hours minimum #DIV/01 P:\25-243\Civil\Calculations&Reports\Storm Drainage\Calcs\Basin A_ACHD_SD_CALCS_112018.xlsm 2/6/2026,9:11 AM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Steps for Seepage Beds Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seepage Bed 2 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100'QV' 4 Weighted Runoff Coefficient C 0.56 Link to: LQv 5 Area A(Acres) 1.90 acres ON TR55 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? no V 4,596 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 15.0 ft 9 Set Total Design Depth of All Drain Rock D 9.1 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 8.00 in/hr 12 Size of WQ Perf Pipe(Pert 180°) Dia pipe 18 in 1.8 13 Size of Overflow Perf Pipe(Perfs 3601),READ if Q300>3.3 cfs in 0.0 14 Calculate Total Storage per Foot Spf 64.8 ft3/ft 15 Calculate Design Length L 71 ft 70.95883188 Override Value Required for Chambers 16 Variable Infiltration Window L SWL 71 ft 17 Variable Infiltration Window W SWW 15.0 ft 18 Time to Drain 5.8 hours 90%volume in 48-hours minimum OK 19 Length of WQ&Overflow Perf Pipes 71 ft 20 Perf Pipe Checks.Qperf>=Qpeak; OK where Qperf=CdxAxV(2xgxH) d 0.0313 ft Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft'/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft'/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain #DIV/O! hours 90%volume in 48-hours minimum #DIV/01 P:\25-243\Civil\Calculations&Reports\Storm Drainage\Calcs\Basin B_ACHD_SD_CALCS_112018.xlsm 2/6/2026,9:12 AM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Steps for Seepage Beds Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seepage Bed 3 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100'QV' 4 Weighted Runoff Coefficient C 0.60 Link to: LQv S Area A(Acres) 1.47 acres ON TR55 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? No V 3,810 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 12.0 ft 9 Set Total Design Depth of All Drain Rock D 7.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 3.50 in/hr 12 Size of WQ Perf Pipe(Pert 180°) Dia pipe 18 in 1.8 13 Size of Overflow Perf Pipe(Perfs 3601),READ if Q300>3.3 cfs in 0.0 14 Calculate Total Storage per Foot Spf 37.3 ft3/ft 15 Calculate Design Length L 102 ft 102.2150166 Override Value Required for Chambers 16 Variable Infiltration Window L SWL 102 ft 17 Variable Infiltration Window W SWW 12.0 ft 18 Time to Drain 9.6 hours 90%volume in 48-hours minimum OK 19 Length of WQ&Overflow Perf Pipes 102 ft 20 Perf Pipe Checks.Qperf>=Qpeak; OK where Qperf=CdxAxV(2xgxH) d 0.0313 ft Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft'/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft'/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain #DIV/0! hours 90%volume in 48-hours minimum #DIV/01 P:\25-243\Civil\Calculations&Reports\Storm Drainage\Calcs\Basin C_ACHD_SD_CALCS_112018.xlsm 2/6/2026,9:14 AM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Steps for Seepage Beds Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seepage Bed 4 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100'QV' 4 Weighted Runoff Coefficient C 0.55 Link to: LQv 5 Area A(Acres) 1.23 acres ON TR55 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? No V 2,922 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 12.0 ft 9 Set Total Design Depth of All Drain Rock D 6.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 0.50 in/hr 12 Size of WQ Perf Pipe(Pert 180°) Dia pipe 18 in 1.8 13 Size of Overflow Perf Pipe(Perfs 3601),READ if Q300>3.3 cfs in 0.0 14 Calculate Total Storage per Foot Spf 29.5 ft3/ft 15 Calculate Design Length L 112 ft 111.924766 Override Value Required for Chambers 16 Variable Infiltration Window L SWL 112 ft 17 Variable Infiltration Window W SWW 12.0 ft 18 Time to Drain 47.0 hours 90%volume in 48-hours minimum OK 19 Length of WQ&Overflow Perf Pipes 112 ft 20 Perf Pipe Checks.Qperf>=Qpeak; OK where Qperf=CdxAxV(2xgxH) d 0.0313 ft Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft'/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft'/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain #DIV/0! hours 90%volume in 48-hours minimum #DIV/01 P:\25-243\Civil\Calculations&Reports\Storm Drainage\Calcs\Basin D_ACHD_SD_CALCS_112018.xlsm 2/6/2026,9:15 AM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Steps for Seepage Beds Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seepage Bed 5 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100'QV' 4 Weighted Runoff Coefficient C 0.62 Link to: LQv 5 Area A(Acres) 0.37 acres ON TR55 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? No V 991 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 10.0 ft 9 Set Total Design Depth of All Drain Rock D 4.7 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 1.70 in/hr 12 Size of WQ Perf Pipe(Pert 180°) Dia pipe 18 in 1.8 13 Size of Overflow Perf Pipe(Perfs 3601),READ if Q300>3.3 cfs in 0.0 14 Calculate Total Storage per Foot Spf 20.4 ft3/ft 15 Calculate Design Length L 49 ft 48.59458996 Override Value Required for Chambers 16 Variable Infiltration Window L SWL 49 ft 17 Variable Infiltration Window W SWW 10.0 ft 18 Time to Drain 13.0 hours 90%volume in 48-hours minimum OK 19 Length of WQ&Overflow Perf Pipes 49 ft 20 Perf Pipe Checks.Qperf>=Qpeak; OK where Qperf=CdxAxV(2xgxH) d 0.0313 ft Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft'/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft'/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain #DIV/0! hours 90%volume in 48-hours minimum #DIV/01 P:\25-243\Civil\Calculations&Reports\Storm Drainage\Calcs\Basin E_ACHD_SD_CALCS_112018.xlsm 2/6/2026,9:28 AM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Steps for Seepage Beds Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seepage Bed 6 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100'QV' 4 Weighted Runoff Coefficient C 0.56 Link to: LQv 5 Area A(Acres) 1.00 acres ON TR55 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? No V 2,419 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 10.8 ft 9 Set Total Design Depth of All Drain Rock D 6.8 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 1.70 in/hr 12 Size of WQ Perf Pipe(Pert 180°) Dia pipe 18 in 1.8 13 Size of Overflow Perf Pipe(Perfs 3601),READ if Q300>3.3 cfs in 0.0 14 Calculate Total Storage per Foot Spf 30.9 ft3/ft 15 Calculate Design Length L 78 ft 78.19097714 Override Value Required for Chambers 16 Variable Infiltration Window L SWL 78 ft 17 Variable Infiltration Window W SWW 10.8 ft 18 Time to Drain 18.7 hours 90%volume in 48-hours minimum OK 19 Length of WQ&Overflow Perf Pipes 78 ft 20 Perf Pipe Checks.Qperf>=Qpeak; OK where Qperf=CdxAxV(2xgxH) d 0.0313 ft Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft'/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft'/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain #DIV/0! hours 90%volume in 48-hours minimum #DIV/01 P:\25-243\Civil\Calculations&Reports\Storm Drainage\Calcs\Basin F_ACHD_SD_CALCS_112018.xlsm 2/6/2026,9:29 AM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Steps for Seepage Beds Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seepage Bed 7 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100'QV' 4 Weighted Runoff Coefficient C 0.84 Link to: LQv ON TR55 5 Area A(Acres) 0.19 acres 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? No V 689 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 9.0 ft 9 Set Total Design Depth of All Drain Rock D 6.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 8.00 in/hr 12 Size of WQ Perf Pipe(Pert 180°) Dia pipe 18 in 1.8 13 Size of Overflow Perf Pipe(Perfs 3601),READ if Q300>3.3 cfs in 0.0 14 Calculate Total Storage per Foot Spf 27.8 Oft 15 Calculate Design Length L 25 ft 24.82194206 Override Value Required for Chambers 16 Variable Infiltration Window L SWL 25 ft 17 Variable Infiltration Window W SWW 9.0 ft 18 Time to Drain 4.2 hours 90%volume in 48-hours minimum OK 19 Length of WQ&Overflow Perf Pipes 25 ft 20 Perf Pipe Checks.Qperf>=Qpeak; OK where Qperf=CdxAxV(2xgxH) d 0.0313 ft Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft'/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft'/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain #DIV/O! hours 90%volume in 48-hours minimum #DIV/01 P:\25-243\Civil\Calculations&Reports\Storm Drainage\Calcs\Basin G_ACHD_SD_CALCS_112018.xlsm 2/6/2026,9:29 AM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Steps for Seepage Beds Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seepage Bed 8 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100'QV' 4 Weighted Runoff Coefficient C 0.45 Link to: LQv 5 Area A(Acres) 0.66 acres ON TR55 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? No V 1,283 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 15.0 ft 9 Set Total Design Depth of All Drain Rock D 6.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 1.00 in/hr 12 Size of WQ Perf Pipe(Pert 180°) Dia pipe 18 in 1.8 13 Size of Overflow Perf Pipe(Perfs 3601),READ if Q300>3.3 cfs in 0.0 14 Calculate Total Storage per Foot Spf 37.4 ft3/ft 15 Calculate Design Length L 34 ft 34.28139537 Override Value Required for Chambers 16 Variable Infiltration Window L SWL 34 ft 17 Variable Infiltration Window W SWW 15.0 ft 18 Time to Drain 26.9 hours 90%volume in 48-hours minimum OK 19 Length of WQ&Overflow Perf Pipes 34 ft 20 Perf Pipe Checks.Qperf>=Qpeak; OK where Qperf=CdxAxV(2xgxH) d 0.0313 ft Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft'/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft'/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain #DIV/0! hours 90%volume in 48-hours minimum #DIV/01 P:\25-243\Civil\Calculations&Reports\Storm Drainage\Calcs\Basin H_ACHD_SD_CALCS_112018.xlsm 2/6/2026,9:30 AM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Steps for Seepage Beds Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seepage Bed 9 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100'QV' 4 Weighted Runoff Coefficient C 0.61 Link to: LQv 5 Area A(Acres) 0.22 acres ON TR55 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? No V 580 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 10.0 ft 9 Set Total Design Depth of All Drain Rock D 6.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 0.36 in/hr 12 Size of WQ Perf Pipe(Pert 180°) Dia pipe 18 in 1.8 13 Size of Overflow Perf Pipe(Perfs 3601),READ if Q300>3.3 cfs in 0.0 14 Calculate Total Storage per Foot Spf 24.5 Oft 15 Calculate Design Length L 37 ft 37.00493617 Override Value Required for Chambers 16 Variable Infiltration Window L SWL 37 ft 17 Variable Infiltration Window W SWW 10.0 ft 18 Time to Drain 47.0 hours 90%volume in 48-hours minimum OK 19 Length of WQ&Overflow Perf Pipes 37 ft 20 Perf Pipe Checks.Qperf>=Qpeak; OK where Qperf=CdxAxV(2xgxH) d 0.0313 ft Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft'/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft'/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain #DIV/0! hours 90%volume in 48-hours minimum #DIV/01 P:\25-243\Civil\Calculations&Reports\Storm Drainage\Calcs\Basin J1_ACHD_SD_CALCS_112018.xlsm 2/6/2026,9:35 AM Version 10.5,November 2018 TEMPORARY POND CALCULATIONS ACHD Calculation Sheet for Sizing Basins NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology.These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Steps for Sizing Basins:Size for forebay and print then size for primary storage/treatment basin. User input in yellow cells. 1 Project Name Temporary Basin 1 2 Enter number of Basins(25 max) 1 3 Number of Cells(Forebay+primary=2,Primary Only=1) 1 4 Design Storm 100 a V' Link to:LQ,y 5 Weighted Runoff Coefficient C 0.95 0.v TR55 6 Area A(Acres) 0.09 acres 7 Approved Discharge Rate(if applicable) 0.00 cfs 8 2-Primary Treatment/Storage V 295 ft' Toggle between Forebay and Primary Basin,enter data and print for each *11*,, Side SIm Z S*�s FL.w' w �� w SSie Sleet �...L..� -.---------C---.----> SYe SbFZ L d Primary Basin 9 Select Primary Basin Shape 3-Rectangle 10 Width of Primary Basin Bottom W 12.0 ft 11 Length of Primary Basin Bottom L 12.0 ft 12 Side Slopes(H:1) HA 3.00 13 Enter Bottom Elevation 2687.56 ft 14 Enter Top Bank Elevation 2690.56 ft 15 Enter Water Surface Elevation(WSE) 2689.56 ft 16 Distance Between Forebay and Primary Basin(blank if na) 0.00 ft 17 Enter Elevation Berm 2687.56 ft 18 Enter High Groundwater Elevation 2676.14 ft 19 Min.Freeboard Requirement 0.50 20 Freeboard Provided 1.00 21 Infiltration Area for Primary/Storage Basin Infiltration? 0.50 in/hr Note:infiltration required if Design Infiltration Rate,Enter 0 for no infiltration bottom sloped%or 0 outflow 22 Infiltration Area for Primary As, 144 ftz Enter 0 for no infiltration 23 Adjusted Storage Required Storm Duration i total q Runoff Vol Perc Vol Pre-Dev Total Max Vol Discharge Discharge Reqd Min Hr in/hr cfs ft3 ft3 W W W 60 1.00 0.96 0.08 295 6 0 6 289 24 Depth-Storage Relationship: Saved Surface Basin Basin Surface Surface Area A at Volume Saved Stage Side Slope Width at Length at Area A at Area A at Stage(ft) Below Stage (ft) New Stage(ft) (H:V) Stage(ft) Stage(ft) Stage(ft) Stage(ft) OVERIDE (ft) 2687.56 2687.56 3.000 12.0 12.0 144 0.00 0 2689.56 2689.56 3.000 24.0 24.0 576 0.00 720 0.00 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00 0 2.00 ft depth for storage STORAGE OK 25 Does primary/storage basin have capacity? YES 26 Time to drain primary/storage basin 44.3 hours 90%volume in 48-hours minimum OK P:\25-243\Civil\Calculations&Reports\Storm Drainage\Calcs\Basin I1_ACHD_SD_CALCS_112018.xlsm 2/6/2026,9:34 AM Version 10.5,November 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Steps for Seepage Beds Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name Seepage Bed 9 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100'QV' 4 Weighted Runoff Coefficient C 0.61 Link to: LQv 5 Area A(Acres) 0.22 acres ON TR55 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? No V 580 ft3 25%Sediment 8 Set Total Design Width of All Drain Rock W 10.0 ft 9 Set Total Design Depth of All Drain Rock D 6.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 0.36 in/hr 12 Size of WQ Perf Pipe(Pert 180°) Dia pipe 18 in 1.8 13 Size of Overflow Perf Pipe(Perfs 3601),READ if Q300>3.3 cfs in 0.0 14 Calculate Total Storage per Foot Spf 24.5 Oft 15 Calculate Design Length L 37 ft 37.00493617 Override Value Required for Chambers 16 Variable Infiltration Window L SWL 37 ft 17 Variable Infiltration Window W SWW 10.0 ft 18 Time to Drain 47.0 hours 90%volume in 48-hours minimum OK 19 Length of WQ&Overflow Perf Pipes 37 ft 20 Perf Pipe Checks.Qperf>=Qpeak; OK where Qperf=CdxAxV(2xgxH) d 0.0313 ft Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft'/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft'/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain #DIV/0! hours 90%volume in 48-hours minimum #DIV/01 P:\25-243\Civil\Calculations&Reports\Storm Drainage\Calcs\Basin J1_ACHD_SD_CALCS_112018.xlsm 2/6/2026,9:35 AM Version 10.5,November 2018 APPENDIX D - GEOTECHNICAL ENGINEERING REPORT & GROUNDWATER DATA GEOTECHNICAL INVESTIGATION, CENTUTY FARM TOWNHOMES (ATLAS, 4/4/2025) I i t i •► - F r �� d — r e A .s GEOTECHNICAL INVESTIGATION CENTURY FARM TOWNHOMES 3872 East Hill Park Street Meridian, ID PREPARED FOR: Tyler Gardner Brighton Development Inc. 2929 West Navigator Drive, Suite 400 Meridian, ID 83642 PREPARED BY: Atlas Technical Consultants, LLC 2791 South Victory View Way April 4, 2025 Boise, ID 83709 83642 April 4, 2025 Atlas No. 83642 Tyler Gardner Brighton Development Inc. 2929 West Navigator Drive, Suite 400 Meridian, ID 83642 Subject: GeotechnicalInvestigation Century Farm Townhomes 3872 East Hill Park Street Meridian, ID Dear Tyler Gardner: In compliance with your instructions, Atlas has conducted a soils exploration and foundation evaluation for the above referenced development. Fieldwork for this investigation was conducted from March 18 and 19, 2025. Data have been analyzed to evaluate pertinent geotechnical conditions. Results of this investigation, together with our recommendations, are to be found in the following report. We have provided a PDF copy for your review and distribution. Often, questions arise concerning soil conditions because of design and construction details that occur on a project. Atlas would be pleased to continue our role as geotechnical engineers during project implementation. If you have any questions, please call us at (208) 376-4748. Respectfully submitted, �SS�pNAL FNc E Ns 0 2 14898 4/7/2025 Sydney Shockley Elizabeth Brown, s� Pao Staff Geologist Principal Geotech �rFe� �Z48ETHBR� Clinton Wyllie, PG Senior Geologist Atlas No. 83642 Page I i Copyright©2025 Atlas Technical Consultants CONTENTS 1. INTRODUCTION ...................................................................................................................2 1.1 Project Description........................................................................................................2 1.2 Scope of Investigation...................................................................................................2 2. SITE DESCRIPTION .............................................................................................................3 2.1 Regional Geology .........................................................................................................3 2.2 General Site Characteristics .........................................................................................3 3. SEISMIC SITE EVALUATION...............................................................................................4 3.1 Geoseismic Setting.......................................................................................................4 3.2 Seismic Design Parameter Values ...............................................................................4 4. SOILS EXPLORATION .........................................................................................................4 4.1 Exploration and Sampling Procedures..........................................................................4 4.2 Laboratory Testing Program .........................................................................................5 4.3 Soil and Sediment Profile..............................................................................................5 4.4 Volatile Organic Scan ...................................................................................................6 5. SITE HYDROLOGY...............................................................................................................6 5.1 Groundwater.................................................................................................................6 5.2 Soil Infiltration Rates.....................................................................................................7 5.3 Infiltration Testing..........................................................................................................7 6. FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS.............................8 6.1 Foundation Loading Information ...................................................................................8 6.2 Foundation Design Recommendations.........................................................................9 6.3 Crawl Space Recommendations.................................................................................10 6.4 Floor, Patio, and Garage Slab-on-Grade....................................................................10 7. CONSTRUCTION CONSIDERATIONS ..............................................................................11 7.1 Earthwork....................................................................................................................11 7.2 Grading .......................................................................................................................11 7.3 Dry Weather................................................................................................................11 7.4 Wet Weather...............................................................................................................12 7.5 Soft Subgrade Soils....................................................................................................12 7.6 Frozen Subgrade Soils ...............................................................................................12 7.7 Structural Fill...............................................................................................................13 7.8 Fill Placement and Compaction ..................................................................................13 7.9 Backfill of Walls...........................................................................................................15 7.10 Excavations...............................................................................................................15 7.11 Groundwater Control.................................................................................................16 8. GENERAL COMMENTS .....................................................................................................16 9. REFERENCES ....................................................................................................................17 Atlas No. 83642 Page I ii Copyright©2025 Atlas Technical Consultants Orl co TABLES Table1 — Seismic Design Values .................................................................................................4 Table 2 —Typical Soil Profiles.......................................................................................................5 Table3 — Groundwater Data.........................................................................................................6 Table 4 — Generalized Soil Infiltration Rates.................................................................................7 Table 5 — Infiltration Test Results .................................................................................................7 Table 6 — Design Infiltration Rates................................................................................................8 Table7 — Soil Bearing Capacity....................................................................................................9 Table 8 — Fill Material Criteria..................................................................................................... 13 Table 9 — Fill Placement and Compaction Requirements........................................................... 14 APPENDICES Appendix I Warranty and Limiting Conditions Appendix 11 Vicinity Map Appendix III Site Map Appendix IV Geotechnical Investigation Test Pit Log Appendix V Geotechnical General Notes Appendix VI Important Information About This Geotechnical Engineering Report Atlas No. 83642 Page I iii Copyright©2025 Atlas Technical Consultants ONE 1. INTRODUCTION This report presents results of a geotechnical investigation and analysis in support of data utilized in design of structures as defined in the 2018 International Building Code (IBC). Information in support of groundwater and stormwater issues pertinent to the practice of Civil Engineering is included. Observations and recommendations relevant to the earthwork phase of the project are also presented. Revisions in plans or drawings for the proposed development from those enumerated in this report should be brought to the attention of the soils engineer to determine whether changes in the provided recommendations are required. Deviations from noted subsurface conditions, if encountered during construction, should also be brought to the attention of the soils engineer. 1.1 Project Description The proposed development is in the City of Meridian, Ada County, ID, and occupies a portion of the NE'/4NW'/4 of Section 33, Township 3 North, Range 1 East, Boise Meridian. The site to be developed is approximately 9.15 acres. Site maps included in the Appendix show the project location. Atlas previously conducted a subsurface geotechnical investigation for the overall development. Data from the previous investigation has been used to supplement this new report. This project will consist of a 116-lot townhome development with associated paved areas. Retaining walls are not anticipated as part of the project. Drainage is expected to be directed to a series of seepage beds across the site. Atlas has not been informed of the proposed grading plan. 1.2 Scope of Investigation Our scope of work was completed in general accordance with our proposal dated March 10, 2025 and authorized on March 11, 2025. Said authorization is subject to terms, conditions, and limitations described in the Professional Services Contract entered into between Brighton Development Inc. and Atlas. Atlas' scope of services included the following: Subsurface exploration via test pits. Infiltration testing for stormwater management planning. Field and laboratory testing of materials encountered and collected. Preparation of this report, which includes project description, site conditions, and our engineering analysis and evaluation for the project. Atlas No. 83642 Page 12 Copyright©2025 Atlas Technical Consultants _�rN+=M AVT _ . 2. SITE DESCRIPTION 2.1 Regional Geology The project site is located within the western Snake River Plain of southwestern Idaho. The plain is a northwest trending rift basin, about 45 miles wide and 200 miles long, that developed about 14 million years ago (Ma) and has since been occupied sporadically by large inland lakes. Geologic materials found within and along the plain's margins reflect volcanic and fluvial/lacustrine sedimentary processes that have led to an accumulation of approximately 1 to 2 km of interbedded volcanic and sedimentary deposits within the plain. Along the margins of the plain, streams that drained the highlands to the north and south provided coarse to fine-grained sediments eroded from granitic and volcanic rocks, respectively. About 2 million years ago the last of the lakes was drained and since that time fluvial erosion and deposition has dominated the evolution of the landscape. The majority of the project site is underlain by"Gravel of Sunrise Terrace" as mapped by Othberg and Stanford (1993). The Sunrise terrace is the third terrace above the modern Boise River in the eastern Boise Valley, composed of sandy pebble and cobble gravel, and is about 115 feet above river level. Quaternary faulting has probably truncated and tilted this terrace along with older surfaces. The surface of this deposit is mantled with 3-7 feet of loess containing a weakly to moderately developed duripan. Based on stratigraphic correlation the Sunrise terrace may be correlative with the Wilder terrace further to the west. The eastern portion of the project site is underlain by the "Gravel of Gowen Terrace" as mapped by Othberg and Stanford (1993). Sediments of the Gowen terrace consist of sandy pebble and cobble gravel. The Gowen terrace is the fourth terrace above modern Boise River floodplain, is thickest toward its eastern extent, and is mantled with 2-6 feet of loess. 2.2 General Site Characteristics The following details regarding site conditions are based on visual observations and review of available geologic and topographic maps and imagery: • Current Site Conditions: The site is approximately 9.15 acres and consists primarily of undeveloped land. The site is located at the southeastern corner of Amity Road and Tavistock Avenue. The northwestern corner of property is bisected by an east-west trending paved roadway. Public utility manholes were observed within the central and southwest corner of the property. A gravel surfaced road runs north and south through the central portion of the site. To the east of the gravel surfaced roadway, stockpiles of soil were observed. • Vegetation: Vegetation on the site consists primarily of native weeds and grasses. However, a landscaped area is present along the paved roadway bisecting the northwestern part of the site and consists of landscape trees and shrubs. Atlas No. 83642 Page 13 Copyright©2025 Atlas Technical Consultants ® Topography: The portion of the site to the east of gravel road is relatively flat and level. Heading west from the gravel road, the property gradually slopes downwards roughly 8 feet in elevation and gradually gains back elevation to meet grades with Tavistock Avenue along the western boundary. The northwestern corner of the site is relatively flat and level. Drainage: Stormwater drainage for the site is achieved by percolation through surficial soils. The site is situated so that it is unlikely that it will receive any drainage from off-site sources. 3. SEISMIC SITE EVALUATION 3.1 Geoseismic Setting Soils on site are classed as Site Class D in accordance with Chapter 20 of the American Society of Civil Engineers (ASCE) publication ASCE/SEI 7-16. Structures constructed on this site should be designed per IBC requirements for such a seismic classification. Our investigation revealed low hazard potential resulting from potential earthquake motions including: slope instability, liquefaction, and surface rupture caused by faulting or lateral spreading. 3.2 Seismic Design Parameter Value-- The ASCE 7-16 seismic design parameter values have been provided below. Table 1 — Seismic Design Values Seismic Design Parameter_J�Design Value Site Class D "Default' Site Modified Peak Ground 0.196 Acceleration, PGAm Ss 0.287 (g) S, 0.105 (g) Fa 1.570 Fv 2.391 SMs 0.451 Smi 0.250 Sos 0.301 SDI 0.167 4. SOILS EXPLORATION 4.1 Exploration and Sampling Procedures Field exploration conducted to determine engineering characteristics of subsurface materials included a reconnaissance of the project site and investigation by test pit. A site map with test pit locations was provided to Atlas by Tyler Gardner of Brighton Development. Test pit sites were located in the field by means of a Global Positioning System (GPS) device and are reportedly accurate to within ten feet. Atlas No. 83642 Page 14 Copyright©2025 Atlas Technical Consultants Test pit locations were staked in the field and ground surface elevations were provided by Brighton Development. Upon completion of investigation, each test pit was backfilled with loose excavated materials. Re-excavation and compaction of these test pit areas are required prior to construction. Samples obtained have been visually classified in the field, identified according to test pit number and depth, placed in sealed containers, and transported to our laboratory for additional testing. Subsurface materials have been described in detail on logs provided in the Appendix. Results of field and laboratory tests are also presented in the Appendix. Atlas recommends that these logs not be used to estimate fill material quantities. 4.2 Laboratory Testing Program Along with our field investigation, a supplemental laboratory testing program was conducted to determine additional pertinent engineering characteristics of subsurface materials. Laboratory tests were conducted in accordance with current specifications. The laboratory testing program for this report included: • Atterberg Limits Testing —ASTM D4318 • Grain Size Analysis—ASTM C117/C136 • Resistance Value (R-value) and Expansion Pressure of Compacted Soils — Idaho T-8 As to date, the R-value test results have not been received and, therefore, have not been included within this report. Atlas will forward the results in the form of an addendum once the R-value test results have been received. 4.3 Soil and Sediment Profile The profile below represents a generalized interpretation for the project site. Note that on site soils strata, encountered between test pit locations, may vary from the individual soil profiles presented in the logs. Table 2 —Typical Soil Profiles ApproximateSoil Horizons Depths Clayey Gravel with Sand Fill, Silty Gravel Fill Materials' 0 to 3.0 feet with Sand Fill, Poorly Graded Gravel with Loose to Dense Sand Fill Surficial Soils2 0 to 7.5 feet Lean Clay with Sand, Silt with Sand, Stiff to Hard Sandy Silt Intermediate Poorly Graded Gravel with Sand, Poorly Soils2 3 to 15 feet Graded Gravel with Clay and Sand, Dense to Very Dense Clayey Gravel with Sand Deeper Soils3 8 to 14 feet Clayey Sand, Silty Sand Medium Dense to Very Dense 'Fills were not encountered in Test Pit 1. 2Calcium carbonate cementation/induration was noted within portions of these horizons. 'Clayey sand sediments and silty sand sediments were only encountered in test pits 5 and 6. Atlas No. 83642 Page 15 Copyright©2025 Atlas Technical Consultants During excavation sloughing of test pit sidewalls was observed. In general, fine-grained soils remained stable while more granular sediments readily sloughed. However, moisture contents will also affect wall competency with saturated soils having a tendency to readily slough when under load and unsupported. 4.4 Volatile Organic Scan Soils obtained during on-site activities were not assessed for volatile organic compounds by portable photoionization detector. Samples obtained during our exploration activities exhibited no apparent odors or discoloration typically associated with this type of contamination. No groundwater was encountered. 5. SITE HYDROLOGY Existing surface drainage conditions are defined in the General Site Characteristics section. Information provided in this section is limited to observations made at the time of the investigation. Either regional or local ordinances may require information beyond the scope of this report. 5.1 Groundwater During this field investigation groundwater was not encountered in test pits advanced to a maximum depth of 14.8 feet bgs. Atlas has previously performed 7 geotechnical investigations within 0.10 mile of the project site. Information from these investigations has been provided in the table below. Table 3 — Groundwater Data April 2015 0.05 South Not Encountered to 18.3 September 2016 Onsite Onsite 7.6 to 10.6* September 2017 0.02 North Not Encountered to 16.4 May 2019 0.08 South Not Encountered to 16.5 August 2019 Onsite Onsite Not Encountered to 18.6 March 2020 0.02 North Not Encountered to 16.0 February 2025 0.02 Northeast Not Encountered to 12.5 *Perched water encountered above clayey gravel sediments and poorly graded gravel with clay and sand sediments. Based on evidence of this investigation and background knowledge of the area, Atlas has determined that the typical seasonal high groundwater should remain greater than approximately 15 feet bgs. However, perched water may be encountered through portions of the year above the clayey gravel and poorly graded gravel with clay and sand sediments. This depth can be confirmed through long-term groundwater monitoring. If desired, Atlas is available to perform this monitoring from piezometers installed in the test pits. Atlas No. 83642 Page 16 Copyright©2025 Atlas Technical Consultants 5.2 Soil Infiltration Rates Soil permeability, which is a measure of the ability of a soil to transmit a fluid, was tested in the field. For this report, an estimation of infiltration is also presented using generally recognized values. Typical infiltration rates comprising the generalized soil profile for this study have been provided in the table below. Table 4— Generalized Soil Infiltration Rates Soil Type Lean Clay with Sand <2 Silt with Sand Sandy Silt 2 to 4* Clayey Sand Clayey Gravel with Sand <2 to 6* Poorly Graded Gravel with Clay and Sand Silty Sand 4 to 8* Poorly Graded Gravel with Sand >12 *The presence of cementation/induration may reduce infiltration rates to near zero. 5.3 Infiltration Testing Infiltration testing was conducted using an open test pit method. Test locations were presoaked prior to testing. Pre-soaking increases soil moistures, which allows the tested soils to reach a saturated condition more readily during testing. Saturation of the tested soils is desirable in order to isolate the vertical component of infiltration by inhibiting horizontal seepage during testing. Testing was conducted on March 19, 2024. Details and results of testing are as follows: Table 5— Infiltration Test Results 7TP-2 9.0 Clayey Gravel with Sand 0.72 7_8 Poorly Graded Gravel with Clay 6.96 and Sand TP-3 8.0 Poorly Graded Gravel with Sand >12.0 TP-4 8.4 Poorly Graded Gravel with Sand >12.0 TP-5 7.6 Clayey Sand 2.4 TP-6 6.7 Poorly Graded Gravel with Clay 3.36 and Sand TP-7 6.0 Clayey Gravel with Sand 0.96 TP-8 11.0 Poorly Graded Gravel with Sand >12.0 Atlas No. 83642 Page 17 Copyright©2025 Atlas Technical Consultants Appropriate factors of safety have been applied to the stabilized infiltration rates achieved during testing to obtain the design infiltration rates listed below. Table 6— Design Infiltration Rates Test Test - . Location (feet bgs) (inches/hour) TP-1 9.0 Clayey Gravel with Sand 0.36 TP-2 7.8 Poorly Graded Gravel with Clay 3.5 and Sand TP-3 8.0 Poorly Graded Gravel with Sand 8.0 TP-4 8.4 Poorly Graded Gravel with Sand 8.0 TP-5 7.6 Clayey Sand 1.2 TP-6 6.7 Poorly Graded Gravel with Clay 1.7 and Sand TP-7 6.0 Clayey Gravel with Sand 0.5 TP-8 4.0 Poorly Graded Gravel with Sand 8.0 The reason for the decreased infiltration rate is to account for long term saturation of the soils and the potential for less permeable soils to settle into the bottom of the infiltration facilities. Atlas recommends that all infiltration facilities be constructed in accordance with the local municipality requirements. 6. FOUNDATION AND SLAB DISCUSSION AND RECOMMENDATIONS Various foundation types have been considered for support of the proposed development. Two requirements must be met in the design of foundations. First, the applied bearing stress must be less than the ultimate bearing capacity of foundation soils to maintain stability. Second, total and differential settlement must not exceed an amount that will produce an adverse behavior of the superstructure. Allowable settlement is usually exceeded before bearing capacity considerations become important; thus, allowable bearing pressure is normally controlled by settlement considerations. 6.1 Foundation Loading Information Loads of up to 4,000 pounds per lineal foot for wall footings, and column loads of up to 50,000 pounds were assumed for settlement calculations. Total settlement should be limited to approximately 1 inch and differential settlement should be limited to approximately '/z inch, provided the following design and construction recommendations are observed. Atlas No. 83642 Page 18 Copyright©2025 Atlas Technical Consultants _�rN+=M AVT _ . 6.2 Foundation Design Recommendations Considering subsurface conditions and the proposed construction, it is recommended that the structure be founded upon conventional spread footings and continuous wall footings. The following recommendations are not specific to the individual structures, but rather should be viewed as guidelines for the subdivision-wide development. Based on data obtained from the site and test results from various laboratory tests performed, Atlas recommends the following guidelines for the net allowable soil bearing capacity: Table 7 — Soil Bearing Capacity Footing 7Not .. . . . •. Footings must bear on competent, undisturbed, 1,5001bs/ft2 native silt with sand soils, lean clay with sand soils, Required for Native or compacted granular structural fill. Existing fill Soil A /3 increase is allowable materials and organics must be completely removed if the alternative basic from below foundation elements.' Excavation load combinations of depths ranging from roughly 0.4 to 4.5 feet bgs 95% for Granular Section 1605.3.2 of the should be anticipated to expose proper bearing Structural Fill 2018 IBC are used in soils.2 design. 'It will be required for Atlas personnel to verify the bearing soil suitability for each structure at the time of construction. 2Depending on the time of year construction takes place,the subgrade soils may be unstable because of high moisture contents. If unstable conditions are encountered,over-excavation and replacement with granular structural fill and/or use of geotextiles may be required. The following sliding frictional coefficient values should be used: 1) 0.35 for footings bearing on native silt with sand soils and lean clay with sand soils and 2)0.45 for footings bearing on granular structural fill. A passive lateral earth pressure of 315 pounds per square foot per foot (psf/ft) should be used for lean clay with sand soils and a lateral earth pressure of 330 psf/ft should be used for silt with sand soils. For granular structural fill, a passive lateral earth pressure of 496 psf/ft should be used. Footings should be proportioned to meet either the stated soil bearing capacity or the 2018 IBC minimum requirements. Foundation over-excavation must be replaced with granular structural fill. Excessively loose or soft areas that are encountered in the footings subgrade will require over- excavation and backfilling with granular structural fill. To minimize the effects of slight differential movement that may occur because of variations in the character of supporting soils and seasonal moisture content, Atlas recommends continuous footings be suitably reinforced to make them as rigid as possible. For frost protection, the bottom of external footings should be 24 inches below finished grade. Foundations must be backfilled in accordance with the Backfill of Walls section. Atlas No. 83642 Page 19 Copyright©2025 Atlas Technical Consultants _�rN+=M AVT _ . 6.3 Crawl Space Recommendations All residences constructed with crawl spaces should be designed in a manner that will inhibit water in the crawl spaces. Atlas recommends that roof drains carry stormwater at least 10 feet away from each residence. Grades should be at least 5 percent for a distance of 10 feet away from all residences. In addition, rain gutters should be placed around all sides of residences, and backfill around stem walls should be placed and compacted in a controlled manner. 6.4 Floor, Patio, and Garage Slab-on-Grade Uncontrolled fill was encountered across the majority of the site. Atlas recommends that these fill materials be removed to a depth of at least 1'/2 feet below existing grade. If fill materials remain after excavation, the exposed subgrade must be compacted to at least 95 percent of the maximum dry density as determined by ASTM D1557. The excavated fill materials can be replaced in accordance with the Fill Placement and Compaction section provided that all organic material and debris is completely removed. Once final grades have been determined, Atlas is available to provide additional recommendations. Organic, loose, or obviously compressive materials must be removed prior to placement of concrete floors or floor-supporting fill. In addition, the remaining subgrade should be treated in accordance with guidelines presented in the Earthwork section. Areas of excessive yielding should be excavated and backfilled with granular structural fill or suitable structural fill. Fill used to increase the elevation of the floor slab should consist of granular structural fill and suitable structural fill meeting the requirements detailed in the Structural Fill section. Fill materials must be compacted to a minimum 95 percent of the maximum dry density as determined by ASTM D1557. A free-draining granular mat should be provided below slabs-on-grade to provide drainage and a uniform and stable bearing surface. This should be a minimum of 4 inches in thickness and compacted to at least 95 percent of the maximum dry density as determined by ASTM D1557. The mat must consist of aggregate base material as specified in the Structural Fill section. A moisture-retarder should be placed beneath floor slabs to minimize potential ground moisture effects on moisture-sensitive floor coverings. The moisture-retarder should be at least 15-mil in thickness and have a permeance of less than 0.01 US perms as determined by ASTM E96. Placement of the moisture-retarder will require special consideration with regard to effects on the slab-on-grade and should adhere to recommendations outlined in the ACI 302.1 R and ASTM E1745 publications. Upon request, Atlas can provide further consultation regarding installation. Atlas No. 83642 Page 1 10 Copyright©2025 Atlas Technical Consultants 7. CONSTRUCTION CONSIDERATIONS 7.1 Earthwork Excessively organic soils, deleterious materials, or disturbed soils generally undergo high volume changes when subjected to loads, which is detrimental to subgrade behavior in the area of pavements, floor slabs, structural fills, and foundations. Brush and grasses with associated root systems were noted at the time of our investigation. It is recommended that organic or disturbed soils, if encountered, be removed to depths of 1 foot(minimum), and wasted or stockpiled for later use. Stripping depths should be adjusted in the field to assure that the entire root zone or disturbed zone or topsoil are removed prior to placement and compaction of fill materials. Exact removal depths should be determined during grading operations by Atlas personnel, and should be based upon subgrade soil type, composition, and firmness or soil stability. If underground storage tanks, underground utilities, wells, or septic systems are discovered during construction activities, they must be decommissioned then removed or abandoned in accordance with governing Federal, State, and local agencies. Excavations developed as the result of such removal must be backfilled with fill materials as defined in the Structural Fill section. Atlas should oversee subgrade conditions (i.e., moisture content) as well as placement and compaction of new fill (if required) after native soils are excavated to design grade. Recommendations for structural fill presented in this report can be used to minimize volume changes and differential settlements that are detrimental to the behavior of footings, pavements, and floor slabs. Sufficient density tests should be performed to properly monitor compaction. 7.2 Grading Positive grades must be maintained surrounding structures and pavements, including exterior slabs. The interface of plant bedding materials and underlying soils should be graded to provide drainage away from site elements. Otherwise, bedding materials may direct water to underlying fine-grained soils, which increases the potential for localized heave. Excessive watering of landscaping should be avoided. 7.3 Dry Weather If construction is to be conducted during dry seasonal conditions, many problems associated with soft soils may be avoided. However, some rutting of subgrade soils may be induced by shallow groundwater conditions related to springtime runoff or irrigation activities during late summer through early fall. Solutions to problems associated with soft subgrade soils are outlined in the Soft Subarade Soils section. Problems may also arise because of lack of moisture in native soils and fill materials at time of placement. This will require the addition of water to achieve near- optimum moisture levels. Low-cohesion soils exposed in excavations may become friable, increasing chances of sloughing or caving. Measures to control excessive dust should be considered as part of the overall health and safety management plan. Atlas No. 83642 Page 1 11 Copyright©2025 Atlas Technical Consultants MEN 7.4 Wet Weather If construction is to be conducted during wet seasonal conditions (commonly from mid-November through May), problems associated with soft soils must be considered as part of the construction plan. During this time of year, fine-grained soils such as silts and clays will become unstable with increased moisture content, and eventually deform or rut. Additionally, constant low temperatures reduce the possibility of drying soils to near optimum conditions. 7.5 Soft Subgrade Soils Shallow fine-grained subgrade soils that are high in moisture content should be expected to pump and rut under construction traffic. During periods of wet weather, construction may become very difficult if not impossible. The following recommendations and options have been included for dealing with soft subgrade conditions: Track-mounted vehicles should be used to strip the subgrade of root matter and other deleterious debris and to perform any other necessary excavations. Heavy rubber-tired equipment should be prohibited from operating directly on the native subgrade and areas in which fill materials have been placed. Construction traffic should be restricted to designated roadways that do not cross, or cross on a limited basis, proposed roadway or parking areas. Soft areas can be over-excavated and replaced with granular structural fill. Construction roadways on soft subgrade soils should consist of a minimum 2-foot thickness of large cobbles of 4 to 6 inches in diameter with sufficient sand and fines to fill voids. Construction entrances should consist of a 6-inch thickness of clean, 2-inch minimum, angular drain-rock and must be a minimum of 10 feet wide and 30 to 50 feet long. During the construction process, top dressing of the entrance may be required for maintenance. Scarification and aeration of subgrade soils can be employed to reduce the moisture content of wet subgrade soils. After stripping is complete, the exposed subgrade should be ripped or disked to a depth of 1'/2 feet and allowed to air dry for 2 to 4 weeks. Further disking should be performed on a weekly basis to aid the aeration process. Alternative soil stabilization methods include use of geotextiles, lime, and cement stabilization. Atlas is available to provide recommendations and guidelines at your request. 7.6 Frozen Subgrade Soils Prior to placement of fill materials or foundation elements, frozen subgrade soils must either be allowed to thaw or be stripped to depths that expose non-frozen soils and wasted or stockpiled for later use. Stockpiled materials must be allowed to thaw and return to near-optimal conditions prior to use as fill. Atlas No. 83642 Page112 Copyright©2025 Atlas Technical Consultants The onsite shallow clayey and silty soils are susceptible to frost heave during freezing temperatures. For exterior flatwork and other structural elements, adequate drainage away from subgrades is critical. Compaction and use of granular structural fill will also help to mitigate the potential for frost heave. Complete removal of frost susceptible soils for the full frost depth, followed by replacement with a non-frost susceptible granular structural fill, can also be used to mitigate the potential for frost heave. Atlas is available to provide further guidance/assistance upon request. 7.7 Structural Fill The following table defines the types of fill material that is suitable for use on the project. Refer to the Fill Placement and Compaction section for recommended placement locations for each fill type listed below. Table 8 — Fill Material Criteria Fill Type Material Maximum Lift ISPWC Section 801 for 1-inch, 3-inch, or 6- Granular Structural Fill inch Uncrushed Aggregate and 12 inches ISPWC Section 802 Aggregate Base Aggregate Base ISPWC Section 802 for Type 1 Crushed 12 inches Aggregate Base Structural Subbase ISPWC Section 801 for 3-inch or 6-inch 12 inches Uncrushed Aggregate Suitable Structural Fill** Onsite/imported ML, SM, and GM soils that 6 inches are free of organics and debris "Initial loose thickness,prior to compaction. **Onsite CL soils are unsuitable for use as fill material. 7.8 Fill Placement and Compaction Requirements for fill material type and compaction effort are dependent on the planned use of the material. The following table specifies material type and compaction requirements based on the placement location of the fill material. Atlas No. 83642 Page 113 Copyright©2025 Atlas Technical Consultants Table 9— Fill Placement and Compaction Requirements Fill Location Material Type Compaction Foundations Granular Structural Fill 95% of ASTM D1557 Interior Slab-on-Grade Granular Structural Fill or 95% of ASTM D1557 Suitable Structural Fill Top 4 Inches of Interior and Exterior Aggregate Base Material 95% of ASTM D1557 Slab-on-Grade Below Flexible Pavement Subgrade Granular Structural Fill or 95% of ASTM D698 or and Exterior Flatwork Areas Suitable Structural Fill 92% of ASTM D1557 Foundation and Wall Backfill* Granular Structural Fill or 95% of ASTM D1557 Suitable Structural Fill Utility Trench Backfill Granular Structural Fill or Per ISPWC Section 306 Suitable Structural Fill *Wall backfill material cannot exceed a maximum particle size of 4-inches. Prior to placement of fill materials, surfaces must be prepared as outlined in the Earthwork section. Fill material must be placed in horizontal lifts not exceeding 6-inches in thickness for fine-grained soils and 12-inches in thickness for granular structural fill, aggregate base material, and subbase material. All fill material must be moisture-conditioned to achieve optimum moisture content prior to compaction. During placement all fill materials must be monitored and tested to confirm compaction requirements have been achieved, as specified above, prior to placement of subsequent lifts. In addition, compacted surfaces must be in a firm and unyielding condition. Atlas personnel should be onsite to verify suitability of subgrade soil conditions, identify whether further work is necessary, and perform in-place moisture density testing. Sufficient density tests should be performed to properly monitor compaction. At a minimum, Atlas recommends one test per lift as follows: • Structures — 1 test every 5,000 square feet • Pavement and Exterior Flatwork Areas — 1 test every 10,000 square feet • Foundation and Wall Backfill — 1 test every 500 square feet • Utility Trench Backfill — 1 test every 100 linear feet Silty soils require very high moisture contents for compaction, require a long time to dry out if natural moisture contents are too high, and may also be susceptible to frost heave under certain conditions. Therefore, these materials can be quite difficult to work with as moisture content, lift thickness, and compactive effort becomes difficult to control. If silty soil is used for fill, lift thicknesses should not exceed 6 inches (loose), and fill material moisture must be closely monitored at both the working elevation and the elevations of materials already placed. Following placement, the exposed surface must be protected from degradation resulting from construction traffic or subsequent construction. It is anticipated that fine-grained soils will not be suitable for reuse during the wet season. Atlas No. 83642 Pagej14 Copyright©2025 Atlas Technical Consultants Use of silty soils (GM, SM, and ML) as structural fill below footings is prohibited. For structural fill below footings, areas of compacted backfill must extend outside the perimeter of the footings for a distance equal to the thickness of fill between the bottom of foundation and underlying soils, or 5 feet, whichever is less. If material contains more than 40 percent but less than 50 percent oversize (greater than 3/4-inch) particles, compaction of fill must be confirmed per ISPWC Section 202.3.8.C.3. Material should contain sufficient fines to fill void spaces and must not contain more than 50 percent oversize particles. 7.9 Backfill of Walls Backfill materials must conform to the requirements of structural fill, as defined in this report. For wall heights greater than 2.5 feet, the maximum material size should not exceed 4 inches in diameter. Placing oversized material against rigid surfaces interferes with proper compaction and can induce excessive point loads on walls. Backfill shall not commence until the wall has gained sufficient strength to resist placement and compaction forces. Further, retaining walls above 2.5 feet in height shall be backfilled in a manner that will limit the potential for damage from compaction methods and/or equipment. It is recommended that only small hand-operated compaction equipment be used for compaction of Backfill within a horizontal distance equal to the height of the wall, measured from the back face of the wall. Backfill should be compacted in accordance with the specifications in the Fill Placement and Compaction section, except in those areas where it is determined that future settlement is not a concern, such as planter areas. In nonstructural areas, backfill must be compacted to a firm and unyielding condition. Atlas recommends in these areas that the top 12 inches must consist of a low permeability (clay or silt) soil to limit surface water infiltration. Proper grading away from structures is critical. The surface must be graded away from the structure. In addition, Atlas recommends that roof drains carry stormwater at least 10 feet away from the structure. 7.10 Excavations Shallow excavations that do not exceed 4 feet in depth may be constructed with side slopes approaching vertical. Below this depth, it is recommended that slopes be constructed in accordance with Occupational Safety and Health Administration (OSHA) regulations, Section 1926, Subpart P. Based on these regulations, on-site soils are classified as type "C" soil, and as such, excavations within these soils should be constructed at a maximum slope of 1'/2 feet horizontal to 1 foot vertical (1'/2:1) for excavations up to 20 feet in height. Excavations in excess of 20 feet will require additional analysis. Note that these slope angles are considered stable for short-term conditions only, and will not be stable for long-term conditions. Atlas No. 83642 Page 115 Copyright©2025 Atlas Technical Consultants During the subsurface exploration,test pit sidewalls generally exhibited little indication of collapse; however, sloughing of fill materials and native granular sediments from test pit sidewalls was observed. For deep excavations, native granular sediments cannot be expected to remain in position. These materials are prone to failure and may collapse, thereby undermining upper soil layers. This is especially true when excavations approach depths near the water table. Care must be taken to ensure that excavations are properly backfilled in accordance with procedures outlined in this report. 7.11 Groundwater Control Groundwater was not encountered during the investigation and is anticipated to be below the depth of most construction. Excavations below the water table will require a dewatering program. Special precautions may be required for control of surface runoff and subsurface seepage. It is recommended that runoff be directed away from open excavations. Silty and clayey soils may become soft and pump if subjected to excessive traffic during time of surface runoff. Ponded water in construction areas should be drained through methods such as trenching, sloping, crowning grades, nightly smooth drum rolling, or installing a French drain system. Additionally, temporary or permanent driveway sections should be constructed if extended wet weather is forecasted. 8. GENERAL COMMENTS Based on the subsurface conditions encountered during this investigation and available information regarding the proposed development, the site is adequate for the planned construction. When plans and specifications are complete, and if significant changes are made in the character or location of the proposed development, consultation with Atlas must be arranged as supplementary recommendations may be required. Suitability of subgrade soils and compaction of fill materials must be verified by Atlas personnel prior to placement of structural elements. Additionally, monitoring and testing should be performed to verify that suitable materials are used for fill and that proper placement and compaction techniques are utilized. Atlas No. 83642 Page116 Copyright©2025 Atlas Technical Consultants 9. REFERENCES Ada County Highway District(ACHD) (2017). Ada County Highway District Policy Manual. Garden City, ID: Author. American Concrete Institute (ACI) (2015). Guide for Concrete Floor and Slab Construction: ACI 302.1 R. Farmington Hills, MI: ACI. American Society of Civil Engineers (2021). ASCE 7 Hazards Tool: Web Interface. [Online] Available: <https://asce7hazardtool.online/> (2023). American Society of Civil Engineers (ASCE) (2017). Minimum Design Loads for Buildings and Other Structures: ASCE/SEI 7-16. Reston, VA: ASCE. American Society for Testing and Materials (ASTM) (2017). Standard Test Method for Materials Finer than 75-um (No. 200) Sieve in Mineral Aggregates by Washing: ASTM C117. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2019). Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates: ASTM C136. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2021). Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Standard Effort: ASTM D698. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2021). Standard Test Methods for Laboratory Compaction Characteristics of Soil Using Modified Effort: ASTM D1557. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2018). Standard Test Methods for Resistance Value (R-Value) and Expansion Pressure of Compacted Soils: ASTM D2844. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2017). Standard Practice for Classification of Soils for Engineering Purposes(Unified Soil Classification System):ASTM D2487.West Conshohocken, PA:ASTM. American Society for Testing and Materials (ASTM) (2017). Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils: ASTM D4318. West Conshohocken, PA: ASTM. American Society for Testing and Materials (ASTM) (2017). Standard Specification for Plastic Water Vapor Retarders Used in Contact with Soil or Granular Fill Under Concrete Slabs: ASTM E1745. West Conshohocken, PA: ASTM. International Building Code Council (2018). International Building Code. Country Club Hills, IL: Author. Local Highway Technical Assistance Council (LHTAC) (2020). Idaho Standards for Public Works Construction. Boise, ID: Author. Othberg, K. L. and Stanford, L. A., Idaho Geologic Society (1993). Geologic Map of the Boise Valley and Adloining Area, Western Snake River Plain, Idaho. (scale 1:100,000). Boise, ID: Joslyn and Morris. U.S. Department of Labor, Occupational Safety and Health Administration 2020 . CFR 29, Part 1926, Subpart P Appendix A: Safety and Health Regulations for Construction, Excavations. Washington D.C.: OSHA. Atlas No. 83642 Page 117 Copyright©2025 Atlas Technical Consultants Oro I APPENDIX I WARRANTY AND LIMITING CONDITIONS Atlas warrants that findings and conclusions contained herein have been formulated in accordance with generally accepted professional engineering practice in the fields of foundation engineering, soil mechanics, and engineering geology only for the site and project described in this report. These engineering methods have been developed to provide the client with information regarding apparent or potential engineering conditions relating to the site within the scope cited above and are necessarily limited to conditions observed at the time of the site visit and research. Field observations and research reported herein are considered sufficient in detail and scope to form a reasonable basis for the purposes cited above. Exclusive Use This report was prepared for exclusive use of the property owner(s), at the time of the report, and their retained design consultants ("Client"). Conclusions and recommendations presented in this report are based on the agreed-upon scope of work outlined in this report together with the Contract for Professional Services between the Client and Atlas Technical Consultants ("Consultant"). Use or misuse of this report, or reliance upon findings hereof, by parties other than the Client is at their own risk. Neither Client nor Consultant make representation of warranty to such other parties as to accuracy or completeness of this report or suitability of its use by such other parties for purposes whatsoever, known or unknown, to Client nor Consultant. Neither Client nor Consultant shall have liability to indemnify or hold harmless third parties for losses incurred by actual or purported use or misuse of this report. No other warranties are implied or expressed. Report Recommendations are Limited and Subject to Misinterpretation There is a distinct possibility that conditions may exist that could not be identified within the scope of the investigation or that were not apparent during our site investigation. Findings of this report are limited to data collected from noted explorations advanced and do not account for unidentified fill zones, unsuitable soil types or conditions, and variability in soil moisture and groundwater conditions. To avoid possible misinterpretations of findings, conclusions, and implications of this report, Atlas should be retained to explain the report contents to other design professionals as well as construction professionals. Since actual subsurface conditions on the site can only be verified by earthwork, note that construction recommendations are based on general assumptions from selective observations and selective field exploratory sampling. Upon commencement of construction, such conditions may be identified that require corrective actions, and these required corrective actions may impact the project budget. Therefore, construction recommendations in this report should be considered preliminary, and Atlas should be retained to observe actual subsurface conditions during earthwork construction activities to provide additional construction recommendations as needed. Atlas No. 83642 Page118 Copyright©2025 Atlas Technical Consultants _�rN+=M AVT - . Since geotechnical reports are subject to misinterpretation, do not separate the soil logs from the report. Rather, provide a copy of, or authorize for their use, the complete report to other design professionals or contractors. Locations of exploratory sites referenced within this report should be considered approximate locations only. For more accurate locations, services of a professional land surveyor are recommended. This report is also limited to information available at the time it was prepared. In the event additional information is provided to Atlas following publication of our report, it will be forwarded to the client for evaluation in the form received. Environmental Concerns Comments in this report concerning either onsite conditions or observations, including soil appearances and odors, are provided as general information. These comments are not intended to describe, quantify, or evaluate environmental concerns or situations. Since personnel, skills, procedures, standards, and equipment differ, a geotechnical investigation report is not intended to substitute for a geoenvironmental investigation or a Phase II/III Environmental Site Assessment. If environmental services are needed, Atlas can provide, via a separate contract, those personnel who are trained to investigate and delineate soil and water contamination. Atlas No. 83642 Page 119 Copyright©2025 Atlas Technical Consultants Vicinity Map Figure 1 Storey Park Meridian MAP NOTES: tCe •Not to Scale metery � Sair.7 .L LOW, �'MerDdun „r Medical = `ss Ce"ter m'Je;ecans Memoral Ft V Q LEGEND ±5 3f) © Approximate Site Location M ire _ w 0—1-0 Rd Playa a �k 4 d _ v-,Rd w Virtrvry f7A v Site Location, Ten M� SOUTHWEST ADA COUNTY Century FarmsTownhomes ALLIANCE 3872 East Hill Park Street Meridian,ID Modified by:CRM March 21,2025 Drawing:B250365g Lake �r T Harrel Micdle School 2791 S.Victory View Way Phone:(208)376-4748 Boise,ID 83709 Fax:(208)322-6515 .om�'. Web:oneatlas.com Site Map Figure 2 ® NOTES: N •Not to Scale AMITY ROAD LEGEND -----------�`�'- Approximate Site Boundary 1I Approximate Atlas Test Pit Location � _ with Piezometer I TP W �� ,A, , ,Q - o TP-7 - i4. : . . F 1 F TP-3 TP 5 1 © ffI o R d -----. -—-—-—-—-—-—-— Q — — x . TP 6 II' TP-8 �� ��• : a � ... .-may _� ,. `-- '----=a -. ® I Century Farms Townhomes i 3872 East Hill Park Street - - -- - Meridian,ID 1. \ —_—_—_—_—_ HILL PARK STREET^ k -—- —___ Modified by:CRM I — i March 21,2025 T -------- Drawing:B250365------ ----- 2791 S.Victory View Way Phone:(208)376-4748 Boise,ID 83709 Fax:(208)322-6515 Web:oneaUas.com APPENDIX IV GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log#: TP-1 Latitude: 43.560889 Date Advanced: March 18, 2025 Longitude: -116.348573 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 12.5 feet bgs Ground Surface Elevation: 2,686.31 feet Groundwater Table Elevation: Not Encountered DepthDepth ld Description and USCS Soil an Lm Sample Sample 1. . .. ig� As bgs) Test I Silt with Sand (ML): Brown, dry to slightly A 0.0-7.3 moist, stiff to very stiff, with fine-grained sand. Bulk 1.0-2.0 1.75-2.0 R Value --Organics noted to 0.4 foot bgs. Clayey Gravel with Sand (GC): Light brown to 7.3-12.5 brown, slightly moist to moist, dense to very dense, with fine to coarse-grained sand, fine to coarse gravel, and 6-inch minus cobbles. Notes:See Site Map for test pit location. Infiltration testing conducted at a depth of 9.0 feet bgs. Piezometer installed to a depth of 12.5 feet bgs. Passing)Lab Test ID Moisture LL Pi Sieve Analysis (% 1 1 11 11 A 23.6 33 7 89 87 81 77 70.8 Atlas No. 83642 Page 122 Copyright©2025 Atlas Technical Consultants GEOTECHNIGAL INVESTIGATION TEST PIT LOG Test Pit Log#: TP-2 Latitude: 43.560365 Date Advanced: March 18, 2025 Longitude: -116.347518 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 13.4 feet bgs Ground Surface Elevation: 2,696.49 feet Groundwater Table Elevation: Not Encountered Depth Field Description and USCS Soil and Samplo Sample Depth e . .. . . Test ID Clayey Gravel with Sand Fill (GC-FILL): Brown, slightly moist, loose to medium dense, 0.0-3.2 with fine to coarse-grained sand,fine to coarse gravel, and 4-inch minus cobbles. --Organics noted to 0.3 foot bgs. Lean Clay with Sand (CL): Brown, dry to 3.2-6.7 slightly moist, stiff to very stiff, with fine- grained sand. Poorly Graded Gravel with Clay and Sand (GP-GC): Light brown to brown, dry to slightly 6.7-13.4 moist, dense to very dense, with fine to coarse-grained sand, fine to coarse gravel, and 6-inch minus cobbles. Notes:See Site Map for test pit location. Infiltration testing conducted at a depth of 7.8 feet bgs. Piezometer installed to a depth of 13.4 feet bgs. Atlas No. 83642 Page 123 Copyright©2025 Atlas Technical Consultants GEOTECHNIGAL INVESTIGATION TEST PIT LOG Test Pit Log#: TP-3 Latitude: 43.559793 Date Advanced: March 18, 2025 Longitude: -116.347991 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 13.5 feet bgs Ground Surface Elevation: 2,691.33 feet Groundwater Table Elevation: Not Encountered Depth Field Description and USCS Soil and Samplo Sample Depth e . .. . . Test ID Silty Gravel with Sand Fill (GM-FILL): Brown, slightly moist, loose to medium dense, with 0.0-2.4 fine to coarse-grained sand, fine to coarse gravel, and 4-inch minus cobbles. --Organics noted to 0.3 foot bgs. Lean Clay with Sand (CL): Brown, dry to 2.4-4.5 slightly moist,very stiff,with fine-grained sand. 2.5 Sandy Silt (ML): Brown, dry to slightly moist, 4.5-7.2 very stiff to hard, with fine-grained sand. --Weak calcium carbonate cementation encountered throughout. Poorly Graded Gravel with Sand (GP): Light brown to brown, dry to slightly moist, dense to 7.2-13.5 very dense, with fine to coarse-grained sand, fine to coarse gravel, and 6-inch minus cobbles. Notes:See Site Map for test pit location. Infiltration testing conducted at a depth of 8.0 feet bgs. Piezometer installed to a depth of 13.5 feet bgs. Atlas No. 83642 Page 124 Copyright©2025 Atlas Technical Consultants GEOTECHNIGAL INVESTIGATION TEST PIT LOG Test Pit Log#: TP-4 Latitude: 43.559515 Date Advanced: March 18, 2025 Longitude: -116.347893 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 14.8 feet bgs Ground Surface Elevation: 2,697.12 feet Groundwater Table Elevation: Not Encountered Depth Field Description and USCS Soil and Samplo Sample Depth e . .. . . Test ID Silty Gravel with Sand Fill (GM-FILL): Brown, slightly moist, loose to medium dense, with 0.0-2.8 fine to coarse-grained sand, fine to coarse gravel, and 4-inch minus cobbles. --Organics noted to 0.3 foot bgs. Lean Clay with Sand (CL): Brown, dry to 2.8-5.5 slightly moist, stiff to very stiff, with fine- grained sand. Sandy Silt (ML): Brown, dry to slightly moist, 5.5-6.8 very stiff to hard, with fine-grained sand. --Weak calcium carbonate cementation encountered throughout. Poorly Graded Gravel with Sand (GP): Light brown to brown, dry to slightly moist, dense to 6.8-14.8 very dense, with fine to coarse-grained sand, fine to coarse gravel, and 6-inch minus cobbles. Notes:See Site Map for test pit location. Infiltration testing conducted at a depth of 8.4 feet bgs. Piezometer installed to a depth of 14.8 feet bgs. Atlas No. 83642 Page 125 Copyright©2025 Atlas Technical Consultants GEOTECHNIGAL INVESTIGATION TEST PIT LOG Test Pit Log#: TP-5 Latitude: 43.559778 Date Advanced: March 18, 2025 Longitude: -116.346994 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 14.0 feet bgs Ground Surface Elevation: 2,688.62 feet Groundwater Table Elevation: Not Encountered Depth Field Description and USCS Soil and Samplo Sample Depth e . .. . . Test ID Silty Gravel with Sand Fill (GM-FILL): Brown, slightly moist, loose to medium dense, with 0.0-0.6 fine to coarse-grained sand, fine to coarse gravel, and 4-inch minus cobbles. --Organics noted to 0.3 foot bgs. 0.6-5.8 Lean Clay with Sand (CL): Brown, dry to 4 5+ slightly moist, hard, with fine-grained sand. Poorly Graded Gravel with Clay and Sand (GP-GC): Light brown to brown, dry to slightly 5.8-7.6 moist, dense to very dense, with fine to coarse-grained sand, fine to coarse gravel, and 6-inch minus cobbles. Clayey Sand (SC): Light brown to brown, dry 7.6-14.0 to slightly moist, medium dense to dense, with fine to medium-grained sand. Notes:See Site Map for test pit location. Infiltration testing conducted at a depth of 7.6 feet bgs. Piezometer installed to a depth of 14.0 feet bgs. Atlas No. 83642 Page 126 Copyright©2025 Atlas Technical Consultants GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log#: TP-6 Latitude: 43.559522 Date Advanced: March 18, 2025 Longitude: -116.346981 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 13.3 feet bgs Ground Surface Elevation: 2,689.52 feet Groundwater Table Elevation: Not Encountered Depth ield Description and USCS Soil and Samp Sample Depth e . . . .. bgs) Test ID Silty Gravel with Sand Fill (GM-FILL): Brown, slightly moist, loose to medium dense, with 0.0-1.5 fine to coarse-grained sand, fine to coarse gravel, and 4-inch minus cobbles. --Organics noted to 0.3 foot bgs. 1.5-4.3 Lean Clay with Sand (CL): Brown, dry to GS 2.0-3.0 4.5+ B slightly moist, hard, with fine-grained sand. Poorly Graded Gravel with Clay and Sand (GP-GC): Light brown to brown, dry to slightly 4.3-10.7 moist, dense to very dense, with fine to coarse-grained sand, fine to coarse gravel, and 6-inch minus cobbles. Silty Sand (SM): Brown, slightly moist, very 10.7-13.3 dense, with fine-grained sand. --Moderate to strong induration encountered throughout. Notes:See Site Map for test pit location. Infiltration testing conducted at a depth of 6.7 feet bgs. Piezometer installed to a depth of 13.3 feet bgs. . • Test ID Moisture LL Pi Sieve Analysis (% Passing) 1 #40 #100 #200 B 22.6 31 9 100 99 95 91 83.6 Atlas No. 83642 Page 127 Copyright©2025 Atlas Technical Consultants GEOTECHNIGAL INVESTIGATION TEST PIT LOG Test Pit Log#: TP-7 Latitude: 43.560009 Date Advanced: March 18, 2025 Longitude: -116.346498 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 13.9 feet bgs Ground Surface Elevation: 2,694.65 feet Groundwater Table Elevation: Not Encountered Depth Field Description and USCS Soil and Samplo Sample Depth e . .. . . Test ID Silty Gravel with Sand Fill (GM-FILL): Brown, slightly moist, loose to medium dense, with 0.0-0.9 fine to coarse-grained sand, fine to coarse gravel, and 4-inch minus cobbles. --Organics noted to 0.3 foot bgs. 0.9-3.0 Silt with Sand (ML): Brown, dry to slightly moist,very stiff to hard,with fine-grained sand. Clayey Gravel with Sand (GC): Light brown to brown, dry to slightly moist, dense to very 3.0-13.9 dense, with fine to coarse-grained sand, fine to coarse gravel, and 6-inch minus cobbles. --Moderate calcium carbonate cementation encountered from 3.0 to 5.0 feet bgs. Notes:See Site Map for test pit location. Infiltration testing conducted at a depth of 6.0 feet bgs. Piezometer installed to a depth of 13.9 feet bgs. Atlas No. 83642 Page 128 Copyright©2025 Atlas Technical Consultants GEOTECHNIGAL INVESTIGATION TEST PIT LOG Test Pit Log#: TP-8 Latitude: 43.559585 Date Advanced: March 18, 2025 Longitude: -116.345349 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 14.2 feet bgs Ground Surface Elevation: 2,695.37 feet Groundwater Table Elevation: Not Encountered Depth Field Description and USCS Soil and Samplo Sample Depth e . .. . . Test ID Silty Gravel with Sand Fill (GM-FILL): Brown, slightly moist, loose to medium dense, with 0.0-0.5 fine to coarse-grained sand and fine to coarse gravel. --Organics noted to 0.3 foot bgs. Poorly Graded Gravel with Sand Fill (GP-Fill): 0.5-4.5 Light brown,dry, medium dense to dense,with fine to coarse-grained sand, fine to coarse gravel, and 6-inch minus cobbles. Silt with Sand (ML): Brown, dry to slightly 4.5-10.6 moist,very stiff to hard,with fine-grained sand. --Moderate to strong induration encountered throughout. Poorly Graded Gravel Sand (GP): Light brown 10.6-14.2 to brown, dry to slightly moist, dense to very dense, with fine to coarse-grained sand, fine to coarse gravel, and 6-inch minus cobbles. Notes:See Site Map for test pit location. Infiltration testing conducted at a depth of 11.0 feet bgs. Piezometer installed to a depth of 14.2 feet bgs. Atlas No. 83642 Page129 Copyright©2025 Atlas Technical Consultants APPENDIX V GEOTECHNICAL GENERAL NOTES Unified Soil Classification System Major Divisions Symbol Soil Descriptions Gravel & GW Well-graded ravels; ravel/sand mixtures with little or no fines Coarse- Gravelly Soils GP Poorly-graded ravels; ravel/sand mixtures with little or no fines Grained < 50% GM Silty gravels; poorly-graded ravel/sand/silt mixtures Soils < coarse GC Clayey gravels; poorly-graded gravel/sand/clay mixtures 50% Sand & Sandy SW Well-graded sands; gravelly sands with little or no fines passes Soils > 50% SP Poorly-graded sands; gravelly sands with little or no fines No.200 coarse SM Silty sands; poorly-graded sand/gravel/silt mixtures sieve fraction SC Clayey sands; poorly-graded sand/gravel/clay mixtures Fine- ML Inorganic silts; sandy, gravelly or clayey silts Grained Silts & Clays CL Lean clays; inorganic, gravelly, sandy, or silty, low to medium- Soils > LL < 50 plasticity clays 50% OL Organic, low-plasticity clays and silts passes MH Inorganic, elastic silts; sandy, gravelly or clayey elastic silts No.200 Silts & Clays CH Fat clays; high-plasticity, inorganic clays sieve LL > 50 OH Organic, medium to high-plasticity clays and silts Highly Organic Soils PT Peat, humus, hydric soils with high organic content Relative Density and Consistency Moisture Content and Cementation L -Classification Classification Coarse-Grained Soils SPT Blow Counts N Description Field Test Very Loose: <4 Dry Absence of moisture, dry to touch Loose: 4-10 Slightly Moist Damp, but no visible moisture Medium Dense: 10-30 Moist Visible moisture Dense: 30-50 Wet Visible free water Very Dense: > 50 Saturated Soil is usually below water table Fine-Grained Soils SPT Blow Counts N Description Field Test Very Soft: < 2 Weak Crumbles or breaks with handling or Soft: 2-4 slight finger pressure Medium Stiff: 4-8 Moderate Crumbles or breaks with Stiff: 8-15 considerable finger pressure Very Stiff: 15-30 Strong Will not crumble or break with finger Hard: > 30 pressure Particle Size Acronym List Boulders: > 12 in. GS I grab sample Cobbles: 12 to 3 in. LL Liquid Limit Gravel: 3 in. to 5 mm M moisture content Coarse-Grained Sand: 5 to 0.6 mm NP non-plastic Medium-Grained Sand: 0.6 to 0.2 mm PI Plasticity Index Fine-Grained Sand: 0.2 to 0.075 mm QP penetrometer value, unconfined compressive Silts: 0.075 to 0.005 mm strength, tsf Clays: < 0.005 mm V vane value, ultimate shearing strength, tsf Atlas No. 83642 Page 130 Copyright©2025 Atlas Technical Consultants hapoplant Infopmation ahoul GeolechnicalmEngineeping Subsurface problems are a principal cause of construction delays, cost overruns, claims, and disputes. While you cannot eliminate all such risks, you can manage them. The following information is provided to help. The Geoprofessional Business Association (GBA) will not likely meet the needs of a civil-works constructor or even a has prepared this advisory to help you—assumedly different civil engineer.Because each geotechnical-engineering study a client representative—interpret and apply this is unique,each geotechnical-engineering report is unique,prepared geotechnical-engineering report as effectively as Solely for the client. possible. In that way, you can benefit from a lowered exposure to problems associated with subsurface Likewise,geotechnical-engineering services are performed for a specific project and purpose.For example,it is unlikely that a geotechnical- conditions at project sites and development of engineering study for a refrigerated warehouse will be the same as them that, for decades, have been a principal cause one prepared for a parking garage;and a few borings drilled during of construction delays, cost overruns, claims, a preliminary study to evaluate site feasibility will not be adequate to and disputes. If you have questions or want more develop geotechnical design recommendations for the project. information about any of the issues discussed herein, contact your GBA-member geotechnical engineer. Do not rely on this report if your geotechnical engineer prepared it: Active engagement in GBA exposes geotechnical for a different client; engineers to a wide array of risk-confrontation for a different project or purpose; techniques that can be of genuine benefit for for a different site(that may or may not include all or a portion of everyone involved with a construction project. the original site);or before important events occurred at the site or adjacent to it; e.g.,man-made events like construction or environmental Understand the Geotechnical-Engineering Services remediation,or natural events like floods,droughts,earthquakes, Provided for this Report or groundwater fluctuations. Geotechnical-engineering services typically include the planning, collection,interpretation,and analysis of exploratory data from Note,too,the reliability of a geotechnical-engineering report can widely spaced borings and/or test pits.Field data are combined be affected by the passage of time,because of factors like changed with results from laboratory tests of soil and rock samples obtained subsurface conditions;new or modified codes,standards,or from field exploration(if applicable),observations made during site regulations;or new techniques or tools.If you are the least bit uncertain reconnaissance,and historical information to form one or more models about the continued reliability of this report,contact your geotechnical of the expected subsurface conditions beneath the site.Local geology engineer before applying the recommendations in it.A minor amount and alterations of the site surface and subsurface by previous and of additional testing or analysis after the passage of time-if any is proposed construction are also important considerations.Geotechnical required at all-could prevent major problems. engineers apply their engineering training,experience,and judgment to adapt the requirements of the prospective project to the subsurface Read this Report in Full model(s). Estimates are made of the subsurface conditions that Costly problems have occurred because those relying on a geotechnical- will likely be exposed during construction as well as the expected engineering report did not read the report in its entirety.Do not rely on performance of foundations and other structures being planned and/or an executive summary.Do not read selective elements only.Read and affected by construction activities. refer to the report in full. The culmination of these geotechnical-engineering services is typically a You Need to Inform Your Geotechnical Engineer geotechnical-engineering report providing the data obtained,a discussion About Change of the subsurface model(s),the engineering and geologic engineering Your geotechnical engineer considered unique,project-specific factors assessments and analyses made,and the recommendations developed when developing the scope of study behind this report and developing to satisfy the given requirements of the project.These reports may be the confirmation-dependent recommendations the report conveys. titled investigations,explorations,studies,assessments,or evaluations. Typical changes that could erode the reliability of this report include Regardless of the title used,the geotechnical-engineering report is an those that affect: engineering interpretation of the subsurface conditions within the context of the project and does not represent a close examination,systematic • the site's size shape; c inquiry,or thorough investigation of all site and subsurface conditions. the elevation,configuration,location,orientation, function or weight of the proposed structure and Geotechnical-Engineering Services are Performed the desired performance criteria; for Specific Purposes, Persons, and Projects, • the composition of the design team;or and At Specific Times • project ownership. Geotechnical engineers structure their services to meet the specific As a general rule,always inform your geotechnical engineer of project needs,goals,and risk management preferences of their clients.A or site changes-even minor ones-and request an assessment of their geotechnical-engineering study conducted for a given civil engineer impact.The geotechnical engineer who prepared this report cannot accept responsibility or liability for problems that arise because the geotechnical conspicuously that you've included the material for information purposes engineer was not informed about developments the engineer otherwise only.To avoid misunderstanding,you may also want to note that would have considered. "informational purposes"means constructors have no right to rely on the interpretations,opinions,conclusions,or recommendations in the Most of the"Findings" Related in This Report report.Be certain that constructors know they may learn about specific Are Professional Opinions project requirements,including options selected from the report,only Before construction begins,geotechnical engineers explore a site's from the design drawings and specifications.Remind constructors subsurface using various sampling and testing procedures.Geotechnical that they may perform their own studies if they want to,and be sure to engineers can observe actual subsurface conditions only at those specific allow enough time to permit them to do so.Only then might you be in locations where sampling and testing is performed.The data derived from a position to give constructors the information available to you,while that sampling and testing were reviewed by your geotechnical engineer, requiring them to at least share some of the financial responsibilities who then applied professional judgement to form opinions about stemming from unanticipated conditions.Conducting prebid and subsurface conditions throughout the site.Actual sitewide-subsurface preconstruction conferences can also be valuable in this respect. conditions may differ-maybe significantly-from those indicated in this report.Confront that risk by retaining your geotechnical engineer Read Responsibility Provisions Closely to serve on the design team through project completion to obtain Some client representatives,design professionals,and constructors do informed guidance quickly,whenever needed. not realize that geotechnical engineering is far less exact than other engineering disciplines.This happens in part because soil and rock on This Report's Recommendations Are project sites are typically heterogeneous and not manufactured materials Confirmation-Dependent with well-defined engineering properties like steel and concrete.That The recommendations included in this report-including any options or lack of understanding has nurtured unrealistic expectations that have alternatives-are confirmation-dependent.In other words,they are not resulted in disappointments,delays,cost overruns,claims,and disputes. final,because the geotechnical engineer who developed them relied heavily To confront that risk,geotechnical engineers commonly include on judgement and opinion to do so.Your geotechnical engineer can finalize explanatory provisions in their reports.Sometimes labeled"limitations; the recommendations only after observing actual subsurface conditions many of these provisions indicate where geotechnical engineers' exposed during construction.If through observation your geotechnical responsibilities begin and end,to help others recognize their own engineer confirms that the conditions assumed to exist actually do exist, responsibilities and risks.Read these provisions closely.Ask questions. the recommendations can be relied upon,assuming no other changes have Your geotechnical engineer should respond fully and frankly. occurred.The geotechnical engineer who prepared this report cannot assume responsibility or liability for confirmation-dependent recommendations ifyou Geoenvironmental Concerns Are Not Covered fail to retain that engineer to perform construction observation. The personnel,equipment,and techniques used to perform an environmental study-e.g.,a"phase-one"or"phase-two"environmental This Report Could Be Misinterpreted site assessment-differ significantly from those used to perform a Other design professionals'misinterpretation of geotechnical- geotechnical-engineering study.For that reason,a geotechnical-engineering engineering reports has resulted in costly problems.Confront that risk report does not usually provide environmental findings,conclusions,or by having your geotechnical engineer serve as a continuing member of recommendations;e.g.,about the likelihood of encountering underground the design team,to: storage tanks or regulated contaminants.Unanticipated subsurface confer with other design-team members; environmental problems have led to project failures.If you have not help develop specifications; obtained your own environmental information about the project site, review pertinent elements of other design professionals'plans and ask your geotechnical consultant for a recommendation on how to find specifications;and environmental risk-management guidance. be available whenever geotechnical-engineering guidance is needed. Obtain Professional Assistance to Deal with You should also confront the risk of constructors misinterpreting this Moisture Infiltration and Mold report.Do so by retaining your geotechnical engineer to participate in While your geotechnical engineer may have addressed groundwater, prebid and preconstruction conferences and to perform construction- water infiltration,or similar issues in this report,the engineer's phase observations. services were not designed,conducted,or intended to prevent migration of moisture-including water vapor-from the soil Give Constructors a Complete Report and Guidance through building slabs and walls and into the building interior,where Some owners and design professionals mistakenly believe they can shift it can cause mold growth and material-performance deficiencies. unanticipated-subsurface-conditions liability to constructors by limiting Accordingly,proper implementation of the geotechnical engineer's the information they provide for bid preparation.To help prevent recommendations will not of itself be sufficient to prevent the costly,contentious problems this practice has caused,include the moisture infiltration.Confront the risk of moisture infiltration by complete geotechnical-engineering report,along with any attachments including building-envelope or mold specialists on the design team. or appendices,with your contract documents,but be certain to note Geotechnical engineers are not building-envelope or mold specialists. Iff:VA GEOPROFESSIONAL AFM BUSINESS - ASSOCIATION Telephone:301/565-2733 e-mail:info@geoprofessional.org www.geoprofessional.org Copyright 2019 by Geoprofessional Business Association(GBA).Duplication,reproduction,or copying of this document,in whole or in part,by any means whatsoever,is strictly prohibited,except with GBA's specific written permission.Excerpting,quoting,or otherwise extracting wording from this document is permitted only with the express written permission of GBA,and only for purposes of scholarly research or book review.Only members of GBA may use this document or its wording as a complement to or as an element of a report of any kind. Any other firm,individual,or other entity that so uses this document without being a GBA member could be committing negligent or intentional(fraudulent)misrepresentation. GROUND WATER MONITORING REPORT - CIF TOWNHOMES (SYMAN, 11/12/2024) SYMAN Ground Water Monitoring Report For Project: CF Townhomes Meridian, Ada County, Idaho 83709 Prepared by: Syman, Inc. Contact: Preston Christensen 2101 Delta Dr. Nampa, Idaho 83687 Office: (208) 287-8420 Email: P.Christensen@SymanCompany.com Signature: B.S. Biology SYMAN, LLC 2101 Delta Drive Nampa, Idaho 83687 208-287-8420 Any reproduction of or amendment to this document without the consent of Syman,LLC is prohibited. CSYMADAN November 12, 2024 Syman File No. 240684 Brighton Corporation 2929 W. Navigator Dr., Ste. 400 Boise, ID 83642 Attention: Daniel Frisby Subj ect: Groundwater Monitoring Report RE: CF Townhomes E. Amity Rd. & S. Tavistock Ave. Meridian, Idaho 83709 1. Introduction This report presents the results of groundwater monitoring at the CF Townhomes project site, located at the intersection of E. Amity Rd. & S. Tavistock Ave. The purpose of this monitoring effort is to assess groundwater levels to inform engineering design for a new development. Monitoring was conducted at two observation wells (TP-2 and TP-7)positioned across the project site. Ground elevations were pulled from KM Engineering Piezometer data logs. It is recommended that surface elevations be verified with methods that meet the accuracy requirements of the designer and revised prior to engineering design. 2. Site Overview The CF Townhomes site encompasses approximately 4.25 acres. Groundwater data was collected over a period spanning May to October 2024,providing insights into seasonal groundwater fluctuations and general site hydrology. 3. Monitoring Program Groundwater monitoring was conducted at the following two observation wells: • TP-2: Positioned at latitude 43.5602074 and longitude -116.3474579, with an estimated ground elevation of 2688 ft. • TP-7: Positioned at latitude 43.5595016 and longitude -116.3469925, with an estimated ground elevation of 2687 ft. SYMAN, LLC Any reproduction of or amendment to this document without the consent of Syman,LLC is prohibited. Page 2 CSYMADAN Measurements were recorded biweekly from May 23, 2024, through October 24, 2024, to capture potential seasonal variations in groundwater levels and to understand the site's water table dynamics. 4. Data Summary The table below provides a summary of groundwater elevations observed at each well over the monitoring period: TP-2 Ground TP-2 Groundwater TP-7 Ground TP-7 Groundwater Date Elevation Elevation Elevation Elevation 5/23/2024 2688 2676.3 2687 2678.65 6/6/2024 2688 2676.3 2687 2678.25 6/20/2024 2688 2676.3 2687 2678.45 7/5/2024 2688 2676.3 2687 2678.6 7/18/2024 2688 2676.3 2687 2678.65 8/1/2024 2688 2676.3 2687 2679.05 8/15/2024 2688 2676.3 2687 2678.55 8/29/2024 2688 2676.3 2687 2678.25 5. Observations and Analysis • TP-2 Observations: Groundwater levels at TP-2 remained constant at 2676.3 ft below the ground surface for all measurements. • TP-7 Observations: Groundwater levels at TP-7 showed minor fluctuations ranging from 2678.25 ft to 2679.05 ft, with a slight peak in early August. These variations may reflect SYMAN, LLC Any reproduction of or amendment to this document without the consent of Syman,LLC is prohibited. Page 3 CSYMADAN seasonal or localized hydrological influences,potentially from nearby surface drainage or rainfall events. TP-2 2690 2688 2688 TP-2 2686 Ground Elevation F C 2684 0 > 2682 w 2680 c» m cn In m rq rm cn rq nn cn r» 2678 LO W W LO W � W LO � W LO � N N N N N N N N N N N N 2676 O�� O�� O�� O�� O�� O�� O�� O�� O� O�� O�� O�� 00\��ti %\""'��ti TP-7 2688 2687 2686 TP-7 2684 Ground Elevation c 2682 > Ln v Ln Ln o LL' � �n LO I Ln Ln Ln 2680 LO 000 N r, 00 00 O 0 Ln N l0 ko N N N N lD lD I� l0 N N N lD N N N 2678 2676 - O�tx O�N tx tx CIIV 61t� O'V 6V (Sv O'V CIIV (9 CJT IV h\"��ti �\ 1\��ti �\� �\��ti �\���ti �\ C\� �\���ti *** Ground Elevations are estimated based on data collected from Google Earth.*** SYMAN, LLC Any reproduction of or amendment to this document without the consent of Syman,LLC is prohibited. Page 4 CSYMADAN 6. Site Maps SYMAN, LLC Any reproduction of or amendment to this document without the consent of Syman,LLC is prohibited. 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