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CC - Storm Drainage CalcsFINAL STORMWATER RUNOFF CALCULATIONS for PERA PLACE SUBDIVISION Meridian, Idaho C E 17650 ry9r� OF 1 -2 -2i— Z LEAVITT & ASSOCIATES ENGINEERS, INC. 6 IA6W— W*ft D —1t1g XWSM /WN NU W STAB$ 1324 151 Street South, Nampa Idaho 83651 — (208) 463-7670 — www.leavittengineers.com Revision # Prepared by Reviewed and certified by Project # 0 Sa ar Gaire Nathan Porter, P.E. SD099.001 DESIGN CRITERIA: ACHD Stormwater Policy Manual - 2017 100-year Design Storm Frequency for Storage Facilities 25-year Design Storm Frequency for Primary Conveyance Systems 100-year Storm Frequency for Secondary Conveyance Systems TABLE OF CONTENTS Project Description----------------------------------------------------------------------------- 1 --------------- Methodsand scope------------------------------------------------------------------------------------------1-3 Summary--------------------------------------------------------------- Appendix A: Pre and post development Drainage Calculation Appendix B: Geotechnical Engineering report NOVEMBER 11, 2021 PROJECT DESCRIPTION: Leavitt & Associates Engineers, Inc. has prepared the preliminary stormwater design and calculations for the retention and infiltration of stormwater for the Pera Place Subdivision. It is located North of Daphne Street and East of North Black Cat Road, or more particularly within section 27, Township 4 North, Range 1 West, Meridian, Ada County, Idaho. The proposed project site consists of an irregularly shaped parcel totaling approximately 16.7 acres which when developed will consist of single-family residential home sites. The stormwater runoff report presents calculations for both pre- and post -development conditions and facility sizing based on the available information and preliminary design. This report will describe the existing on -site hydrological conditions for the proposed development and will also observe the post -developed situation to validate that storm runoff fulfills the requirements of ADA County Highway District (ACHD), the City of Meridian as well as the water quality requirement of the Idaho Department of Environmental Quality (DEQ). METHODS AND SCOPES: This report evaluates the pre -development conditions using the Rational Method and designates where the current runoff enters and exits the site. The post -development condition will then be evaluated using the same method for sizing of retention areas based upon the geotechnical report and upon the proposed project. These volumes of runoff will then be used to confirm the appropriate capacity in the design of stormwater retention and detention areas. TIME OF CONCENTRATION: Time of concentration influences the configuration of the stormwater runoff. Developing a watershed usually decreases the Tc and increases the peak discharge rate. Time of concentration (Tc) is the time required for runoff to travel from the hydraulically most distant point in the watershed to the outlet. The hydraulically most distant point is the point with the longest travel time to the drainage facility, and not necessarily the point with the longest flow distance to the facility. There are many methods available to estimate the time of concentration including the Kirpich formula, Kerby formula, NRCS Velocity Method, and NRCS Lag Method. The Tc values for the proposed subdivision were calculated based on the Kirpich equation. Kirpich formula Method: This method is used to estimate the time of concentration used in surface runoff design ranging from 1.25 to 112 acres and this method is also suitable for catchment sizes between 0.25 and 450 square miles, for slopes between 0.002 and 0.1 (ft/ft). Data used to compute the Tc using the Kirpich formula is shown below. Tc = Time of Concentration, based on Kirpichs equation for flow on concrete or asphalt L1.5 0.77 TC = 0.0078 x yos� 2 L = Length of roadway from furthest point to drainage facility (ft) h = elevation change from furthest point to top of drainage facility (ft) Note: If Tc > 1 hr., use 60 min RUNOFF COEFFICIENT: The runoff coefficient (C) is a dimensionless coefficient relating the amount of runoff to the amount of precipitation received. It is a larger value for areas with low infiltration and high runoff (pavement, steep gradient), and lower for permeable, well -vegetated areas (forest, flat land). It is often desirable to develop a composite runoff coefficient based on the percentage of different types of surfaces in the drainage areas. Data used to compute the runoff coefficient is shown below: Cmodified = Roof Area (0.95) + Paved Area (0.90) + Landscaped Area (0.20) + Gravel Area (0.4) + Undeveloped Area (0.15) Total Area Suggested Runoff Coefficients for Developed coefficient a. 0.40 Residential - Rural b. 0.50 Residential - Single Family c. 0.70 Residential - Multi -Family d. 0.70 Commercial - Light e. 0.95 Commercial - Heavy If developed runoff coefficient is less use modified value of C from the above equation. DESIGN STORMS: The 2, 5, 10, 25, 50, and 100-year design storms were used to evaluate the pre- and post - development discharge rates as well as for sizing the proposed drainage facilities. The primary and secondary conveyance systems were designed to accommodate the peak discharge of the 25 and 100-year storm events respectively with an associated rainfall intensity taken from the ACHD Intensity -Duration Frequency (IDF) curve since the rational method was used to determine peak runoff volumes. POST -DEVELOPMENT RUNOFF: Post -development runoff to be retained on site was calculated using the rational method. The rational method is a simple and efficient way of determining the peak runoff volumes in a small area of interest. This method utilizes the area of the drainage basin, the rainfall intensity of the peak flow design storm, as well as a runoff coefficient that represents the land use type. Data used to calculate the post -development runoff is mentioned below. Qd= RUNOFF FLOW, CFS = C * i * A i = Rainfal Intensity A = Runoff Area, Acres C = Runoff Coefficient Once the peak flow was determined the rational method was used to compute the required storage volume from the peak flow design storm. SUMMARY: This report utilized the rational method to calculate the pre- and post -development peak discharge rates and volume. For the proposed project street drainage and drainage from the commercial area are regulated by Ada County Highway District (ACHD). For post -development, the entire project area was broken into 4 major post -development drainage facilities that are defined by the location of the proposed infiltration facilities. Please see the drainage map and appendix A for more information. Contributing areas have been used to calculate the design coefficient. These calculations show that the modified coefficient (0.35, 0.47, and 0.38 for areas 1, 2, and 3 respectively) was less than the standard coefficient (0.50); the developed runoff coefficient was used for the design of those areas. But, for area 4 (0.91) modified coefficient was greater than the development coefficient (0.50) therefore modified runoff coefficient was used for the design. Surfaces contributing to stormwater have been calculated to include the new roadway right-of-way, driveway, roof, and landscape. Most of the building and landscape from areas 1, 2, and 3 will drain into the Permeable Interlocking Concrete Pavements (PICP) this provides an alternative to conventional pavement systems (concrete and asphalt) that permit stormwater to infiltrate through crushed rock particles between precast concrete pavers for temporary storage, infiltration into subsurface soils and/or discharge to another location once stormwater passes through the pavement structure. Also, for Area 2 and 3 water will infiltrate through permeable pavers and enter infiltration trench 1 and 2 respectively and N Black Cat Road (Area 1) drainage will be collected by shallow infiltration swale. All the designed facilities match the pavement ratio, seasonal high groundwater separation, side slope, freeboard, and runoff requirement for the permeable paver's set up by the ACHD design manual. Please see the attached calculation in appendix A for more information about the facilities sizing and calculation and appendix B for the Geotechnical report for groundwater separation, test pit's location, and infiltration rate used for sizing the facilities. APPENDIX A Stormwater Runoff Calculations NOVEMBER 11, 2021 TABLE OF CONTENTS Runoff Area Map ---------------------------------------- Subdivision Information and Predevelopment flow Subdivision Areas ----------------------------------------------------------------- Summary of Rational Methods -------------------------------------------------- Area #1 Post Development Flow ------------------------------------------------ Area #1 Site Infiltration Facility Sizing ---------------------------------------- Area #2 Post Development Flow ------------------------------------------------ Area #2 Site Infiltration Facility Sizing ---------------------------------------- Area #3 Post Development Flow ------------------------------------------------ Area #3 Site Infiltration Facility Sizing ---------------------------------------- Area #4 Post Development Flow ------------------------------------------------ Area #4 Site Infiltration Facility Sizing ---------------------------------------- Permeable pavement ratio checks----------------------------------------------- 2 NOVEMBER11,2021 J- DRAINAGE AREA MAP r. Project APPLIED MEDIA, INC. PERA PLACE SUBDIVISION 6518 N. FAIRBORN AVE. Job Number. I scale: MERIDIAN, ID 83646 SD099.001 1 200' (949)463-1531 Designed by:PDL I Drawn by:PDL cneckedbrtVJF T. TOTAL: 479,195 SQFT. PAVEMENT: 127,529 SQFT. ROOF: 52,500 SQFT. LANDSCAPE: 299,166 SQFT. LEAVITT & ASSOCIATES ENGINEERS, INC. STRUCTURAL *CIVIL 19 SURVEYING 1324 FIRST STREET SOUTH, NAMPA, IDAHO 83651 PHONE (208)463-0333/463-7670 FAX (208)463-9M Page 2 LEAVITT & ASSOCIATES ENGINEERS, INC. 1324 1st Street South Nampa, Idaho 83651 (208) 463-0333 Design Criteria ACHD Subdivision Information Total Area: 723866 sf = 16.62 acres Type of Area: Urban Construction Type: Average Slope: 1% Policy Manual: ACHD Policy Manual - Section 8000, Drainage -2017 Rainfall Intesity Area Classification: Primary Conveyance Design Storm Frequency: Secondary Conveyance Design Storm Frequency: Minimum Depth of Freeboard: Maximum Side Slope of Infiltration Swales Minimum Depth of Bottom of Infiltration Facility to Groundwater: Minimum Depth of Bottom of Infiltration Facility to Bedrock: JOB: Pera Place Subdivision JOB NUMBER: SD099.001 DATE: 11 /22/2021 FILE: Residential - Single Family Zone A 25 yr 100 yr 6 in 3:1 3ft 3ft Time of Infiltration Until No Visible Water Exists After Primary Storm: 48 hrs Time of Infiltration Until No Visible Water Exists After Secondary Storm: 72 hrs Predevelopment Flow C = 0.13 Qu = CiA 2 25 50 100 I(60min) (In/hr) 0.26 0.69 0.82 0.96 i(24hr) (in/hr) 0.04 0.08 0.09 0.10 QU(60min) (Cf5) 0.56 1.49 1.77 2.07 Qu(24hr) (cfs) 0.09 0.17 0.19 0.22 Storm Conveyance Statement The primary flow will be conveyed through gutters, sand & grease traps, catch basins, drop inlets & grates, and pipes with minimum impact or inconvenience to the public. The following items will be designed based on the primary flow: Permeable Pavement infiltration swale/ditch infiltration trench Page S LEAVITT & ASSOCIATES ENGINEERS, INC. JOB: Pera Place Subdivision 1324 1st Street South JOB NUMBER: SD099.001 Nampa, Idaho 83651 DATE: 11/22/2021 (208) 463-0333 FILE: 0 Runoff Areas & Runoff Coefficients Cd = Developed runoff coefficient = 0.50 (or use Cmodired value if higher) Cmodifietl - Roof Area(0.95) + Paved Area(0.90) + Landscaped Area(0.20) + Gravel Area(0.4) + Undeveloped Area(0.15) Total Area Tc = Time of Concentration, based on Kirpichs equation for flow on concrete or asphalt L1.5 rc = 0.0078 X( h0 s \0.77 L = Length of roadway from furthest point to drainage facility (ft) h = elevation change from furthest point to top of drainage facility (ft) * if Tc > 1 hr, use 60 min Area 1 ft2 acres Total Area = 60,894 1.40 Total Hardsurface = 9,853 0.23 Roof Area 3,000 0.07 Total Landscape 48,041 1 1.10 Length of Drainage Path, L (ft) = 60 Elevation Change, h (ft) = 1.5 Effective Area = Hardsurface + Roof + Landscape 45,040 1.40 Cmodified = 0.35 Use 0.50 Tc (min) = 1 min Use 10 Area 4 ft2 acres Total Area = 13,662 0.31 Total Hardsurface = 4,632 0.11 Roof Area 0 0.00 Total Landscape 9,030 0.21 Length of Drainage Path, L (ft) = 250 Elevation Change, h (ft) = 1.0 Effective Area = Hardsurface + Roof + Landscape 10,682 0.31 Cmodified = 0.44 Use 0.50 Tc (min) = 5 min Use 10 Area 2 ft2 acres Total Area = 479,195 11.00 Total Hardsurface = 127,529 2.93 Roof Area 52,500 1.21 Total Landscape 299,166 6.87 Length of Drainage Path, L (ft 530 Elevation Change, h (ft) = 3.5 Effective Area = Hardsurface + Roof + Landscape 380,470 11.00 Cmodified - 0.47 Use 0.50 Tc (min) = 7 min Use 10 Area 3 ft2 acres Total Area = 170,115 3.91 Total Hardsurface = 33,251 0.76 Roof Area 10,000 0.23 Total Landscape 126,864 2.91 Length of Drainage Path, L ( 250 Elevation Change, h (ft) = 2.7 Effective Area = Hardsurface + Roof + Landscape 128,250 3.91 Cmodified = 0.38 Use 0.50 Tc (min) = 3 min Use 10 LEAVITT d ASSOCIATES ENGINEERS, INC. 1324 1st Street South Nampa, Idaho 83651 2081463-0333 STORM RUNOFF CALCULATIONS - RATIONAL METHOD SUMMARY OF RATIONAL METHOD FLOW CALCULATION Qa RUNOFF FLOW, CFS = C - i' A i = Rainfal Intensity - From Table 1: Zone Rainfal Intensity A = Runoff Area, Acres C = Runoff Coefficient Qu = UNDEVELOPED RUNOFF. CFS (FROM PRE -DEVELOPMENT) Oi = INFILTRATATION, CFS A„ = Area of Infiltration at Bottom of Pond, sf (does not include area of sand window) I„ = Infiltration Rate of Native Soil at Bottom of Pond, in/hr A, = Area of Infiltration of Trench, sf I, = Infiltration Rate of Native Soil at Bottom of Trench, in/hr A,,,„ = Area of Infiltration at Sand Window, sf I,„, = Infiltration Rate of Native Soil at Bottom of Sand Window, in/hr I_= Infiltration Rate of Deeper Soil at Sand Wndow, in/hr Oi = E[A (sf)' I (in/hr)]* (1 HRJ3600 SEC)' (1 FT/12 IN) VOLUME CALCULATION Vnet = NET VOLUME REQUIRED FOR POND AND/OR SUMP STORAGE. CF #### < 5 O.K. Qnet - (60 secJmin)' Duration (min) Onet = NET DISCHARGE FLOW WHICH FILLS THE POND OR SUMP. CFS = Qd-Qu-Qi Add 15 % For Sedimen Vreq = Vnet x 1.15 Vs = VOLUME OF SURFACE STORAGE, CF Vs = Vnet - Subsurface Storage Capacity TIME OF INFILTRATION CALCULATIONS Time to Fill Subsurface Layer, sec = Volume of Subsurface Storage/ Os where Os = SAND INFILTRATATION. CFS As= Area of Trench or Sand Window Is = Infiltration Rate of ASTM C-33 Sand = 8 in/hr Os = As (so' Is (IN/HR)' (1 HR/3600 SEC)' (1 FT/12 IN) Time Until No Visible Water Exists, sec = Time to Fill Subsurface Layer • Volume Surface Storage/Oi Total Time of Infiltration, sec = Total Required Volume/Qi JOB: Pera Place Subdivision JOBNUIVIBER' SD099.001 DATE: 11/22/2021 FILE: 1 0 Table 1: Zone A Rainfat Intensit , t (inhhr) Duration 2 25 50 100 10 0.69 1.85 2,20 2.58 15 0.59 1.56 1.86 2.18 20 0.49 1.30 1,54 1.81 25 0.43 1,14 1,35 1.58 30 0.41 1,08 1.29 1.51 35 0.34 0.90 1,07 1.25 40 0.31 0.82 0,98 1.15 45 0.29 0.77 0.91 1 1.07 50 0.27 0,72 0,85 1.00 55 0.26 0,69 0.82 0.96 60 0.26 0.69 0.82 0.96 120 0.16 0,39 0,46 0.54 180 0.13 0.29 0,34 0.40 360 0.09 0.18 0.21 0.25 720 0.06 0.12 0,14 0.16 1440 0.04 0.08 0.09 0.10 Table 2: Standard Soil Infiltration Rates' Soil Class Soil Type " Rate A-1 Medium Sand 8 A-21p Fine Sand Loamy Sand 2 B-1 Sandy Loam 1 B-2 Loam Silt Loam 0.5 G7 Sandy or Silty Clay Loam 0.25' C-2 Clay Loam 0.15 D Clays, Organic Muck Cunpan. Hardpan, Clayp < 0.09 Infilrabon rate determined by percolation test may also be used ' Minimum rate, soils with lesser rates shall not be considered as candidates for infiltration facilities Ga+ee I I I Tp� 16l(Tp)-- Modified Triangular Hydrograph Page 5 LEAVITT & ASSOCIATES ENGINEERS, INC. JOB: Pera Place Subdivision 1324 1st Street South JOB NUMBER: SD099.001 Nampa, Idaho 83651 DATE: 11122/2021 208/463-0333 FILE: 0 STORM RUNOFF CALCULATIONS - RATIONAL METHOD Storm Runoff for Area 1 Effective Area 1.40 Design Runnoff Coefficient, C 0.50 Time of Concentration, Tc 10 min POST -DEVELOPMENT FLOW Soil Profile Test Pit # 1 Depth (ft) Classificalio Infiltration Rate I 0 to 1.0 A-2b 2.80 1.0 2.0 A-2b 2.80 2.0 5.0 A-2b 2.80 8.0 Groundwater Test pit 5 Permeable PavementlTrench Summary I (in/hr) A x I Area (sf) Depth (ft) Infiltration at Permeable Pavement Bottom 0 0.0 2.8 0.00 Infiltration Area of Trench 0 0.0 2.8 0.00 Permeable Bottom 4285 2.0 2.8 11998.00 E (AA) = 11998.00 sf x in/hr Qu = Discharge flow, if allowed, see predevelompent fl 0.000 cfs Assume Constant for all storm durations after lc Qi = 11998 sf x in/hr x 1 hr/ 3600 sec x 1f /12in = 0.278 cfs Assume Constant for all stone durations after tc Qs = JOU4 I .UU 4285 sf x 8 in/hr x 1 hr/ 3600sec x 1f /12in = 0.79 cfs Assume Constant for all stone durations after tc SECONDARY RUNOFF EVENT FREQUENCY: Duration (Min) i (in.lhr) Qd (cfs) Vnet (cf) 10 2.58 1.803 1222.0 15 2.18 1.524 1497.1 20 1.81 1.265 1581.8 25 1.58 1.104 1655.3 30 1.51 1.055 1868.8 35 1.25 0.874 1670.8 40 1.15 0.804 1685.6 45 1.07 0.748 1694.7 50 1.00 0.699 1687.0 55 0.96 0.671 1732.6 60 0.96 0.671 1890.1 120 0.54 0.377 958.4 180 0.40 0.280 26.7 360 0.25 0.175 0.0 720 0.16 0.112 0.0 1440 0.10 0.070 0.0 100 PRIMARY RUNOFF EVENT FREQUENCY: 25 SECONDARY CONVEYANCE FLOW RATE, 0100= PRIMARY CONVEYANCE FLOW RATE, Q25= REQUIRED STORAGE VOLUME (Add 15 For Sediment) = VOLUME OF SUBSURFACE STORAGE= REQUIRED ABOVE SURFACE STORAGE VOLUME= TIME OF INFILTRIATION INTO SUBSURFACE LAYER= TIME UNTIL NO VISIBLE WATER EXISTS AFTER PRIMARY STORM = TIME OF UN11L NO VISIBLE WATER EXISTS AFTER SECONDARY STORM = Duration (Min) i (in./hr) Qd (cfs) Vnel (cf) 10 1.85 1.293 813.3 15 1.56 1.090 976.4 20 1.30 0.909 1010.7 25 1.14 0.797 1039.5 30 1.08 0.755 1146.6 35 0.90 0.629 985.0 40 0.82 0.573 946.5 45 0.77 0.538 938.9 50 0.72 0.503 903.2 55 0.69 0.482 901.2 60 0.69 0.482 983.1 120 0.39 0.273 0.0 180 0.29 0.203 0.0 360 0.18 0.126 0.0 720 0.12 0.084 0.0 1440 0.08 0.056 0.0 1.80 cfs (at Tc) 1.29 cfs (at Tc) 2174 cf 2571 cf 0 cf 3240 sec 1662 sec = 3240 sec = 0.46 hrs <48hrs O.K. 0.90 hrs <72hrs O.K. DEPTH FROM BOTTOM OF FACILITY TO GROUNDWATER = 6.00 ft ok DEPTH FROM BOTTOM OF FACILITY TO BEDROCK = 12.00 ft ok No Bed rock was encountered Page 6 LEAVITT & ASSOCIATES ENGINEERS, INC. 1324 1 st Street South Nampa, Idaho 83651 208/463-0333 Permeable Pavement Size Area 1- Permeable Pavement Sizing Total Required Storage Volume = 2.174 cf Permeable Pavement 1 (No.8 Aggregate) Bedding Course = 2.00 in. (Thick No.57 Stone) Open -Graded Base= 4.00 in. Permeable Pavement Width = 19 ft. Permeable Pavement Length = 226 ft. No.2 Stone Subbase = 1.50 ft. Sand Depth = 0.0 ft. Permeable Pavement Storage Volume = Total Above Surface Storage Volume = Total Subsurface Storage Volume = Total Storage Volume = Required Storage Volume = Summary of Infiltration Areas Infiltration at Bottom Sidewall Infiltration (Includes Sand) Permeable Area Joe Pera Place Subdivision JOB NUMBER. SDO99.001 DATE 11/22/2021 FILE 0 Perimeter = 489 ft. Total Required Permeable area = 4,285 ftsq. Void of Gravel = 40 Void of Sand = 25 (EArea x Depth x Void) 2,571 cf cf 2,571 cf 2,571 cf > Required Volume, Dimensions Good! 2,174 cf Depth from Area (so Grade (ft) Notes 0 0.0 Does not include area of sand window or trench 0 0 Area = 213 (Wall Depth x Perimeter) 4285 2.0 Page I LEAVITT & ASSOCIATES ENGINEERS, INC. JOB: Pera Place Subdivision 1324 1st Street South JOB NUMBER: SD099.001 Nampa, Idaho 83651 DATE: 12/10/2021 208/463-0333 FILE: 0 STORM RUNOFF CALCULATIONS - RATIONAL METHOD POST -DEVELOPMENT FLOW Storm Runoff for Area 2 Effective Area 11.00 Design Runnoff Coefficient, C 0.50 Time of Concentration, Tc 10 min Permeable Pavement/Trench Summary Infiltration at Permeable Pavement Bottom Infiltration Area of Trench Sand Window or Trench Bottom Soil Profile Test Pit # 1 Depth (ft) Classificatio Infiltration Rate I 0 to 1 2.0 A-2b 11.50 2.0 1 3.0 A-2b 11.50 3.0 1 7.5 A-2b 12.60 7.1 Ground Water Area M Depth ft I in/hr A x I 35510 0 1200 2.0 0.0 3.3 1.5 0.0 2.6 53264.42 0.00 r 3 772.00 'From Perk Test rest pit 9 (Axt) = 56336.42 sf x in/hr Qu = Discharge flow, if allowed, see predevelompent fl 0.000 cfs Assume Constant for all storm durations after lc Qi = 56336 sf x in/hr x 1hrl 3600 sec x 1f /12in = 1.304 cfs Assume Constant for all storm durations after tc Qs = 1200 sf x 8 inlhr x 1 hr/ 3600sec x 1 f /12in = 0.22 cfs Assume Constant for all storm durations after tc SECONDARY RUNOFF EVENT FREQUENCY: 100 PRIMARY RUNOFF EVENT FREQUENCY: 25 Duration (Min) i (in./hr) Qd (cfs) Vnet (cf) 10 2.58 14.191 10322.4 15 2.18 11.991 12840.2 20 1.81 9.956 13859.9 25 1.58 8.691 14791.6 30 1.51 8.306 16824.7 35 1.25 6.876 15619.5 40 1.15 6.325 16088.5 45 1.07 5.885 16513.5 50 1.00 5.500 1 16806.3 55 0.96 5.280 17517.6 60 0.96 5.280 19110.1 120 0.54 2.970 16014.9 180 0.40 2.200 12919.6 360 0.25 1.375 2047.8 720 0.16 0.880 0.0 1 1440 0.10 0.550 0.0 SECONDARY CONVEYANCE FLOW RATE, Q100= PRIMARY CONVEYANCE FLOW RATE, Q25= REQUIRED STORAGE VOLUME (Add 15 For Sediment) = VOLUME OF SUBSURFACE STORAGE= REQUIRED ABOVE SURFACE STORAGE VOLUME= TIME OF INFILTRIATION INTO SUBSURFACE LAYER= TIME UNTIL NO VISIBLE WATER EXISTS AFTER PRIMARY STORM = TIME OF UNTIL NO VISIBLE WATER EXISTS AFTER SECONDARY STORM = Duration (Min) i (in.fhr) Qd (cfs) Vnet (cf) 10 1.85 10.176 7106.2 15 1.56 8.581 8742.8 20 1.30 7.151 9366.0 25 1.14 6.270 9945.2 30 1.08 5,940 11141A 35 0.90 4.950 10222.3 40 0.82 4.510 10272.8 45 0.77 4.235 10565.6 50 0.72 3.960 10638.1 55 0.69 3.795 10975.0 60 0.69 3.795 11972.7 120 0.39 2.145 8084.4 180 0.29 1.595 4196.1 360 0.18 0.990 0.0 720 0.12 0.660 0.0 1440 0.08 0.440 0.0 14.19 cfs (at Tc) 10.18 cfs (at Tc) 21977 cf 22506 cf 0 cf 101276 sec 61959 sec = 101276 sec = 17.21 hrs<48hrs O.K. 28.13 hrs <72hrs O.K. DEPTH FROM BOTTOM OF FACILITY TO GROUNDWATER = 3.80 ft ok DEPTH FROM BOTTOM OF FACILITY TO BEDROCK = 12.00 ft ok No Bed rock was encountered Page P LEAVITT & ASSOCIATES ENGINEERS, INC. 1324 1st Slreel South Nampa, Idaho 83651 208/463-0333 Permeable Pavement Size Area 2- Permeable Pavement Sizing Total Required Storage Volume = 21,977 cf Permeable Pavement #2 (No.8 Aggregate) Bedding Course = 2.00 in. (Thick No.57 Stone) Open -Graded Base= 4.00 in. Permeable Pavement Width = 28 ft. Permeable Pavement Length = 1,287 ft. No.2 Stone Subbase = 1.50 ft. Sand Depth = 0.0 ft. Permeable Pavement Storage Volume = JOB. Pera Place Subdivision JOB NUMBER. SDO99.001 DATE 12/10/2021 FILE: 0 Perimeter = 2,630 ft. Total Required Permeable area = 35,510 ftsq. Void of Gravel = 40 Void of Sand = 25 (LArea x Depth x Void) = 21,306 cf Infiltration Trench 1 Freeboard = 1.00 ft. Trench Width = 5 ft. Perimeter = 410 ft. Trench Length = 200 ft. Area = 1,000 ftsq. Gravel Depth = 3.0 ft. Void of Gravel = 40 Sand Depth = 3.0 ft. Void of Sand = 25 Trench Storage Volume = (!:Area x Depth x Void) Total Above Surface Storage Volume = Total Subsurface Storage Volume = Total Storage Volume = Required Storage Volume = Summary of Infiltration Areas Infiltration at Bottom of Permeable Pavement Sidewall Infiltration (Includes Sand) Sand Window or Trench Area 1,200 cf cf 22,506 cf 22,506 cf > Required Volume, Dimensions Good! 21.977 cf Depth from Area (sf) Grade (ft) Notes 35510 2.0 Does not include area of sand window or trench 0 0 Area of Bottom of Trench = Width x Length 1200 4.0 Page 9 LEAVITT & ASSOCIATES ENGINEERS, INC. JOB: Pera Place Subdivision 1324 tsl Street South JOB NUMBER: SD099.001 Nampa, Idaho 83651 DATE: 11/22/2021 208/463-0333 FILE: 0 STORM RUNOFF CALCULATIONS - RATIONAL METHOD POST -DEVELOPMENT FLOW Storm Runoff for Area 3 Effective Area 3.91 Design Runnoff Coefficient, C 0.50 Time of Concentration, Tc 10 min Permeable Pavement/Trench Summary Infiltration at Permeable Pavement Bottom Infiltration Area of Trench Sand Window or Trench Bottom Soil Profile Test Pit# 1 Depth (ft) Classificatior Infiltration Rate I 0 to 1.0 B-1 1.00 1.0 2.0 B-1 1.00 3.0 9.0 A-2b 2.40 6.5 Groundwater Area (so Depth ft I in/hr A x I 14417 0 425 2.0 0.0 3.5 1.0 0.0 2.4 14417.00 0.00 1 220.00 'From Perk Test Test pit#3 r (Axt) = 15437.00 sf x in/hr Qu = Discharge flow, if allowed, see predevelompent fl 0.000 cfs Assume Constant for all storm durations after tc Qi = 15437 sf x in/hr x lhr/ 3600 sec x 1f /12in = 0.357 cfs Assume Constant for all storm durations aftertc Qs = 425 sf x 8 inlhr x 1hr/ 3600sec x 1f /12in = 0.08 cfs Assume Constant for all storm durations aftertc SECONDARY RUNOFF EVENT FREQUENCY: 100 PRIMARY RUNOFF EVENT FREQUENCY: 25 Duration (Min) i (in./hr) Qd (cfs) Vnet (cf) 10 2.58 5.038 3749.1 15 2.18 4.257 4685.2 20 1.81 3.534 5089.5 25 1.58 3.085 5462.5 30 1.51 2.949 6226.6 35 1.25 2.441 5841.0 40 1.15 2.246 6049.8 45 1.07 2,089 6243.0 50 1.00 1.953 6389.2 55 0.96 1.875 6684.1 60 0.96 1.875 7291.7 120 0.54 1.054 6700.5 180 0.40 0.781 1 6109.2 360 0.25 0.488 3772.5 720 0.16 1 0.312 1 0.0 1440 0.10 1 0,195 1 0.0 SECONDARY CONVEYANCE FLOW RATE, Q100= PRIMARY CONVEYANCE FLOW RATE, 025= REQUIRED STORAGE VOLUME (Add 15 For Sediment) = VOLUME OF SUBSURFACE STORAGE= REQUIRED ABOVE SURFACE STORAGE VOLUME= TIME OF INFILTRIATION INTO SUBSURFACE LAYER= TIME UNTIL NO VISIBLE WATER EXISTS AFTER PRIMARY STORM = TIME OF UNTIL NO VISIBLE WATER EXISTS AFTER SECONDARY STORM = Duration (Min) i (in./hr) Qd (cfs) Vnet (cf) 10 1.85 3.612 2607.3 15 1.56 3.046 3230.6 20 1.30 2.538 3494.1 25 1.14 2.226 3742.0 30 1.08 2.109 4208.9 35 0.90 1.757 3925.0 40 0.82 1.601 3985.3 45 0.77 1.504 4131.5 50 0.72 1.406 4199.5 55 0.69 1.347 4361.4 60 0.69 1.347 4757.9 120 0.39 0.762 3885.1 180 0.29 0.566 3012.4 360 0.18 0.351 0.0 720 0.12 0.234 0.0 1440 0.08 0.156 0.0 5.04 cfs (at Tc) 3.61 cfs (at Tc) 8385 cf 9075 cf 0 cf 115308 sec 69521 sec = 115308 sec = 19.31 hrs<48hrs O.K. 32.03 hrs<72hrs O.K. DEPTH FROM BOTTOM OF FACILITY TO GROUNDWATER = 3.20 ft ok DEPTH FROM BOTTOM OF FACILITY TO BEDROCK = 12.00 ft ok No Bed rock was encountered Page ( G LEAVITT & ASSOCIATES ENGINEERS, INC. 1324 1st Street South Nampa, Idaho 83651 208/463-0333 Permeable Pavement Size Area 3- Permeable Pavement Sizing Total Required Storage Volume = 8,385 cf Permeable Pavement 3 (No.8 Aggregate) Bedding Course = 2.00 in. (Thick No.57 Stone) Open -Graded Base= 4.00 in. Permeable Pavement Width = ft. Permeable Pavement Length = ft. No.2 Stone Subbase = 1.50 ft. Sand Depth = 0.0 ft. Permeable Pavement Storage Volume = Perimeter = 0 ft. Total Required Permeable area = 14,417 ftsq. Void of Gravel = 40 Void of Sand = 25 (E Area x Depth x Void) = 8,650 cf Infiltration Trench 2 Required Cover = 1.00 ft. Trench Width = 5 ft. Perimeter = 180 ft. Trench Length = 85 ft. Area = 425 ftsq. Gravel Depth = 2.5 ft. Void of Gravel = 40 Sand Depth = 3.0 ft. Void of Sand = 25 Trench Storage Volume = Area x Depth x Void) = 425 cf JOB Pera Place Subdivision JOB NUMBER. SD099.001 DATE 11/22/2021 FILE: Total Above Surface Storage Volume = cf Total Subsurface Storage Volume = 9,075 cf Total Storage Volume = 9,075 cf > Required Volume, Dimensions Good! Required Storage Volume = 8,385 of Summary of Infiltration Areas Depth from Area (so Grade (f) Notes Infiltration at Bottom of Permeable Pavement 14417 2.0 Does not include area of sand window or trench Sidewall Infiltration (Includes Sand) 0 0 Area of Bottom of Trench = Width x Length Sand Window or Trench Area 425 3.5 Page ( LEAVITT 8 ASSOCIATES ENGINEERS, INC. JOB: Pera Place Subdivision 1324 1st Street South JOB NUMBER: SD099.001 Nampa, Idaho 83651 DATE: 11/22/2021 208/463-0333 FILE: 0 STORM RUNOFF CALCULATIONS - RATIONAL METHOD POST -DEVELOPMENT FLOW Storm Runoff for Effective Area 0.31 Design Runnoff Coefficient, C 0.50 Time of Concentration, Tc 10 min SwalefTrench Summary Infiltration at Pond Bottom Infiltration Area of Trench Sand Window or Trench Bottom Soil Profile Test Pit # 1 Area (so Depth ft I in/hr A x I 936 1.0 0.5 468.00 0 0.0 NA 0.00 0 0.0 0.5 0.00 'From Perk Test =rom Test pit #1 (Axt) = 468.00 sf x in/hr Qu = Discharge flow, if allowed, see predevelompenl fl 0.000 cfs Assume Constant for all storm durations after tc Qi = 468 sf x in/hr x 1 hr/ 3600 sec x 1f /12in = 0.011 cfs Assume Constant for all storm durations after tc Qs = 0 sf x 8 in/hr x 1 hr/ 3600sec x 1ft/12in = 0.00 cfs Assume Constant for all storm durations after tc JOV4 I. - SECONDARY RUNOFF EVENT FREQUENCY: 100 PRIMARY RUNOFF EVENT FREQUENCY: 25 Duration (Min) i (in./hr) Qd (cfs) Vnet (cf) 10 2.58 0.405 315.4 15 2.18 0.342 397.7 20 1.81 0.284 437.4 25 1.58 0.248 474.5 30 1.51 0.237 543.0 35 1.25 0.196 519.2 40 1.15 0.180 543.1 45 1.07 0.168 565.8 50 1.00 0.157 584.7 55 0.96 0.151 615.5 60 0.96 0,151 671.5 120 0.54 0.085 709.8 180 0.40 0.063 748.2 360 0.25 0.039 818.1 720 0.16 0.025 822.3 1440 0.10 0.016 559.2 SECONDARY CONVEYANCE FLOW RATE, Q100= PRIMARY CONVEYANCE FLOW RATE, Q25= REQUIRED STORAGE VOLUME (Add 15 For Sediment) = VOLUME OF SUBSURFACE STORAGE= REQUIRED ABOVE SURFACE STORAGE VOLUME= TIME OF INFILTRIATION INTO SUBSURFACE LAYER= TIME UNTIL NO VISIBLE WATER EXISTS AFTER PRIMARY STORM = TIME OF UNTIL NO VISIBLE WATER EXISTS AFTER SECONDARY STORM= Duration (Min) i (in./hr) Qd (cfs) Vnet (co 10 1.85 0.290 223.7 15 1.56 0.245 280.9 20 1.30 0.204 309.2 25 1.14 0.179 336.3 30 1.08 0.169 380.9 35 0.90 0.141 365.3 40 0.82 0.129 377.3 45 0.77 0.121 396.2 50 0.72 0.113 408.8 55 0.69 0.108 429.0 60 0.69 0.108 468.0 120 0.39 0.061 483.7 180 0.29 0.045 499.5 360 0.18 0.028 501.6 720 0.12 0.019 460.5 1440 0.08 0.013 197.5 0.40 cfs (at Tc) 0.29 cfs (at Tc) 772 cf 1484 cf 0 cf 136985 sec 53244 sec = 136985 sec = 14.79 hrs<48hrs O.K. 38.05 hrs <72hrs O.K. DEPTH FROM BOTTOM OF FACILITY TO GROUNDWATER = 6.10 ft ok DEPTH FROM BOTTOM OF FACILITY TO BEDROCK = 12.00 ft ok No Bed rock was encountered Page 12- LEAVITT 8 ASSOCIATES ENGINEERS, INC. 1324 1st Street South Nampa, Idaho 83651 208/463-0333 Infiltration Swale Size Area 4 Total Required Storage Volume = 772 cf Infiltration Ditch/Swale Total Pond Length = 250 ft. Total Pond Width = 20 ft. Water Depth = 0.50 ft. Side Slope = 8 : 1 Freeboard = 6 in. Top of Water Area = 5000 sf Bottom of Pond Area = 936 sf JOB. Pera Place Subdivision JOB NUMBER_ SD099.001 DATE: 11/22/2021 FILE: 0 Pond Storage Volume = (Top of Pond Area + Bottom of Pond Area)12 x Water Depth = 1,484 cf Total Above Surface Storage Volume = 1,484 cf Total Subsurface Storage Volume = cf Total Storage Volume = Required Storage Volume = Summary of Infiltration Areas Infiltration at Bottom of Swale Sidewall Infiltration (Includes Sand) Sand Window or Trench Area 1,484 cf > Required Volume, Dimensions Good! 772 cf Depth from Area (so Grade (ft) Notes 936 1.0 Does not include area of sand window or trench NA 0 Area = 2/3 (Wall Depth x Perimeter) 0 NA APPENDIX B Geotechnical Engineering report NOVEMBER 11, 2021 Page i 7, LEAVITT 6 ASSOCIATES ENGINEERS, INC. Permeable Paver Ratio Check ACHD Standards Maximum allowable run on (from adjacent impermeable surfaces to PICP surfaces) ratio is 3:1. Run on rates of up to 5:1 may be considered on a case by case basis. Rooftop and impermeable surface Rooftop: 3,000 sf Impermeable: 9,853 sf Total: 12,853 sf < 3 O.K. Permeable Area #2 35,510 sf Rooftop and impermeable surface Area Rooftop: 52,500 sf Impermeable: 127,529 sf Total: 180,029 sf Ratio 5.0 < 5 O.K. Permeable Area #2 14,417 sf Rooftop and impermeable surface Area Rooftop: 10,000 sf Impermeable: 33,251 sf Total: 43,251 sf Ratio 3.0 < 3 O.K. JOB: era Place Subdirivon GEOTECHNICAL EVALUATION FOR "PERA PLACE" — A 16.7+ ACRE RESIDENTIAL DEVELOPMENT LOCATED NORTH OF DAPHNE STREET AND EAST OF NORTH BLACK CAT ROAD, MERIDIAN, IDAHO July 27, 2021 GTI-Project No. 231 I -ID Prepared For: RICHMOND AMERICAN HOMES OF IDAHO 1804 N Middleton Boulevard Nampa, Idaho 83651 GeoTek, Inc. TABLE OF CONTENTS SCOPEOF SERVICES.......................................................................................................................................... SITEDESCRIPTION............................................................................................................................................. 2 PROPOSED DEVELOPMENT............................................................................................................................2 FIELDSTUDIES...................................................................................................................................................... 2 REGIONALGEOLOGY......................................................................................................................................2 SITESOILS.............................................................................................................................................................. 3 ArtificialFill...................................................................................................................................................... 3 NativeAlluvial Soils........................................................................................................................................ 3 SURFACE & GROUND WATER......................................................................................................................4 TECTONIC FAULTING AND REGIONAL SEISMICITY............................................................................4 Secondary Seismic Constraints.................................................................................................................... 4 Summary: .......................................................................................................................................................... 4 RESULTS OF LABORATORY TESTING......................................................................................................... 5 CONCLUSIONS................................................................................................................................................... 5 RECOMMENDATIONS - EARTHWORK CONSTRUCTION................................................................. 5 General............................................................................................................................................................. 5 Demolition....................................................................................................................................................... 5 Removals/Processing - General................................................................................................................... 6 TransitionalPads............................................................................................................................................. 6 ExcavationDifficulty ....................................................................................................................................... 6 FillPlacement................................................................................................................................................... 7 ImportMaterial............................................................................................................................................... 7 Observationand Testing............................................................................................................................... 7 GroundWater................................................................................................................................................ 7 EarthworkSettlements.................................................................................................................................. 7 RECOMMENDATIONS — FOUNDATIONS.................................................................................................8 General............................................................................................................................................................. 8 Conventional Foundation Recommendations..........................................................................................9 FoundationSettlement.................................................................................................................................. 9 PAVEMENTSECTIONS.................................................................................................................................... 10 Pavement Construction and Maintenance.............................................................................................. 10 OTHER RECOMMENDATIONS.................................................... SiteImprovements........................................................................ Landscape Maintenance and Planting ........................................ GeoTek, Inc. SoilCorrosion............................................................................................................................................... 12 TrenchExcavation........................................................................................................................................ 12 UtilityTrench Backfill.................................................................................................................................. 12 Drainage.......................................................................................................................................................... 12 PLANREVIEW..................................................................................................................................................... 13 LIMITATIONS...................................................................................................................................................... 13 Enclosures: Figure # 1, Site Vicinity Map Figure #2, Site Exploration Plan Appendix A, References Appendix B, Test Pit Logs Appendix C, Field Test Results Appendix D, Laboratory Test Results GeoTek, Inc. GeoTek, Inc. 320 East Corpor,,te Drive Suire 300 Mernd.an, ID 83642-351 1 (208) 888-7010 (208) 888-7924 w w -geotekusa.com July 27, 2021 Project No. 231 I -ID RICHMOND AMERICAN HOMES OF IDAHO 1804 N Midland Boulevard Nampa, Idaho 83651 Attention: Mr. Joe Austin Subject: GEOTECHNICAL EVALUATION for "Pera Place" — a 16.7± Acre Residential Development — Located North of Daphne Street and East of North Black Cat Road, Meridian, Idaho Dear Mr. Austin, In accordance with your request, GeoTek, Inc. (GTI) has completed a geotechnical evaluation of the subject property for the construction of a single-family residential development with associated improvements. The purpose of our study was to evaluate the soils underlying the site and to provide recommendations for project design and construction based on our findings. This report outlines the geologic and geotechnical conditions of the site based on current data and provides earthwork and construction recommendations with respect to those conditions. SCOPE OF SERVICES The scope of our services has included the following: Review of soils and geologic reports and maps for the site (Appendix A) 2. Site reconnaissance 3. Review of aerial photographs 4. Excavating and logging of ten (10) exploratory test pits (Appendix B) 5. Obtaining samples of representative soils, as the exploratory test pits were advanced 6. Performing laboratory testing on representative soil samples (Appendix D) 7. Assessment of potential geologic constraints 8. Engineering analysis regarding foundation settlement, determination of fill depth in lots, and the documentation of organic material in native subgrade 9. Preparation of this report GEOTECHNICAL I ENVIRONMENTAL I MATERIALS PERA PLACE JULY 27, 2021 RICHMOND AMERICAN HOMES OF IDAHO PAGE 2 PROJECT NO. 231 I -ID SITE DESCRIPTION The project site consists of an irregularly shaped parcel totaling approximately 16.7± acres that is generally bound by a single-family residential development to the north, a single-family residence and vacant agricultural land to the east, Daphne Street and a single-family residential development to the south, and North Black Cat Road and a single-family residential development to the west (Figures and 2). Two single-family residences with associated improvements exist at the southern portion of the site. Currently, the property consists primarily of agricultural land that has been corrugated/irrigated and cultivated for crop farming purposes and pasture over many years. Access to the site is currently possible from North Black Cat Road and Daphne Street. From topographic maps, the site's elevation is approximately 2,535± feet to 2,545± feet above mean sea level. Historically, topography generally directs surface water to the northwest. PROPOSED DEVELOPMENT It is our understanding that site development would consist of performing typical cut and fill earthwork to attain the desired graded configuration(s) for the construction of a residential subdivision of one- to two-story detached single-family residential structures with associated improvements. It is further assumed that final site grade will be within 5 feet of existing site grade. FIELD STUDIES Subsurface conditions at the site were explored by using a rubber -tired backhoe. Ten (10) test pits were advanced onsite. A log of each exploration is included within this report in Appendix B. Six (6) percolation tests were performed on the subject site as well as six (6) initial ground water measurements (Appendix C). Field studies were completed during July of 2021 by field personnel who conducted field excavation location mapping, logged the excavations, and obtained samples of representative soils for laboratory testing. The approximate locations of the explorations are indicated on the enclosed Site Exploration Plan (Figure 2). The Unified Soil Classification System (USCS) was used to visually classify the subgrade soils during the field exploration. REGIONAL GEOLOGY The subject site is situated within the Boise River Valley, which comprises the northwestern portion of the Snake River Plain physiographic province. The western portion of the Snake River Plain is aligned in a northwest -southeast direction and generally divides the Owyhee mountains to the south from the Central Idaho mountains toward the north (Wood and Clemens, 2004). The headwaters of the Boise River are located in the Central Idaho mountains east of Boise, Idaho. The river leaves the central mountains and enters the Snake River Plain near Barber and drains toward the west into the Snake River near Parma. The Owyhee mountains and the Central Idaho Mountains are composed predominantly of volcanic and igneous rocks. The western portion of the Snake River Plain is a northwest trending complex graben formed by extension and regional uplift along the northern boundary of the basin and range province (Wood and Clemens, 2004). The graben generally forms a GeoTek, Inc. PERA PLACE JULY 27, 2021 RICHMOND AMERICAN HOMES OF IDAHO PAGE 3 PROJECT NO. 231 I -ID basin which has been partially filled with younger sedimentary and volcanic rocks (Malde, 1991). The Boise River Valley is bounded on the northeast by the Boise Front, which is a northwest trending topographic high extending generally from Boise to Emmett, Idaho. The Boise Front consists of Cretaceous aged granitic and metamorphic rocks cut by Tertiary aged rhyolite and overlain with Miocene aged lake sediments (Wood and Clemens, 2004). These units have been cut by northwest trending faults which down drop these units toward the southwest. The faults also provide conduits for Quaternary aged basalt intrusions and flows (Malde, 1991). The depositional environment for the valley floor is dominantly lake laid deposits of sand, silt and clay. These materials were deposited during two periods of lake activity, one during the Miocene and the other during the Pleistocene. This valley infilling process has been subsequently truncated by down faulting within the valley ranging in height from a few feet to over 50 feet. Younger alluvium has been, and continues to be, transported dominantly by water and deposited on the basins gently sloping valley floor and within low-level flood plains. Portions of the alluvial deposits are being down cut by intermittent streams to the flood plain, and as a result stream terraces are being formed. ciTF cnn c Artificial Fill Based on our field studies, some spread fills were observed along the perimeter of the site. This fill is generally associated with the construction of adjacent roadways, nearby residences, and irrigation laterals. This spread fill shall be considered artificial fill. Trash, debris, and scrap metal was observed at a depth up to 2.5' in TP-6. The majority of the property has been cultivated for agricultural use, the upper 12 inches of material has been disturbed and consists primarily of sandy silts with a moderate amount of organics and roots. This shall be considered artificial fill. Deeper fills may be encountered onsite. The "Artificial Fills" are soft and contain organics/roots and are not considered suitable for support of foundations. All artificial fill material should be removed as described in the "Removals" section of this report. Native Alluvial Soils Alluvial soils encountered generally consist of surficial layers of sandy silts underlain by silty sands, weakly cemented silty sands, poorly graded sands, partially cemented silty sands and poorly graded gravels with varying amount of sand and silt. The moisture content within the alluvial materials was generally slightly moist to moist near surface and moist to saturated at depth. The consistency of these soils ranged from firm near surface and dense to moderately hard at depth. Partially cemented layers of material were encountered in one of our excavations; however, we anticipate that the onsite soils can be excavated with conventional earthwork equipment equivalent to CAT D9R dozers and CAT 235 excavators. Special excavation equipment and techniques may be necessary dependent upon if harder materials are encountered during construction. GeoTek, Inc. PERA PLACE JULY 27, 2021 RICHMOND AMERICAN HOMES OF IDAHO PAGE 4 PROJECT NO. 2311-ID SURFACE & GROUND WATER Ground water was encountered during our field investigation at a depths ranging from 4.4' (TP-4) to 7.1' (TP-9) below existing ground surface. Irrigation laterals exist adjacent to the site and they transmit water on a periodic basis. Generally, irrigation ditches and canals will locally influence ground water during the irrigation season (i.e., April through October). If encountered, wet materials should be spread out and air-dried or mixed with drier soils to reduce their moisture content as appropriate for fill placement. Ground water is not anticipated to adversely affect planned development, provided that earthwork construction methods comply with recommendations contained in this report or those made subsequent to review of the improvement plan(s). GTI assumes that the design civil engineer of record will evaluate the site for potential flooding and set grades such that the improvements are adequately protected. These observations reflect conditions at the time of this investigation and do not preclude changes in local ground water conditions in the future from natural causes, damaged structures (lines, pipes etc.), or heavy irrigation. The groundwater monitoring results obtained are depicted in a table format in Appendix C. TECTONIC FAULTING AND REGIONAL SEISMICITY The site is situated in an area of active as well as potentially active tectonic faults, however no faults were observed during our field evaluation. There are a number of faults in the regional area, which are considered active and would have an affect on the site in the form of ground shaking, should they be the source of an earthquake. It is reasonable to assume that structures built in this area will be subject to at least one seismic event during their life, therefore, it is recommended that all structures be designed and constructed in accordance with the International Building Code (IBC). Based on our experience in the general vicinity, references in our library, field evaluation of the site, a Seismic Design Site Class Designation of 'D' may be used for seismic design. Secondary Seismic Constraints The following list includes other potential seismic related hazards that have been evaluated with respect to the site, but in our opinion, the potential for these seismically related constraints to affect the site is considered negligible. * Liquefaction * Dynamic Settlements Surface Fault Rupture * Ground Lurching or Shallow Ground Rupture Summary: It is important to keep in perspective that if a seismic event were to occur on any major fault, intense ground shaking could be induced to this general area. Potential damage to any settlement sensitive structures would likely be greatestfrom the vibrations and impelling force caused by the inertia of the structures mass than that created from secondary seismic constraints. Considering the subsurface soil conditions and local seismicity, it is estimated that the site has a low risk associated with the potential for these phenomena to occur and adversely affect surface improvements. These potential risks are no greater at this site than they are for other structures and improvements developed on the alluvial materials in this vicinity. GeoTek, Inc. PERA PLACE JULY 27, 2021 RICHMOND AMERICAN HOMES OF IDAHO PAGE 5 PROJECT NO. 231 I -ID RESULTS OF LABORATORY TESTING Laboratory tests were performed on representative samples of the onsite earth materials in order to evaluate their physical and chemical characteristics. The tests performed, and the results obtained are presented in Appendix D. CONCLUSIONS Based on our field exploration, laboratory testing and engineering analyses, it is our opinion that the subject site is suited for development from a geotechnical engineering viewpoint. The recommendations presented herein should be incorporated into the final design, grading, and construction phases of development. The engineering analyses performed concerning site preparation and the recommendations presented below have been completed using the information provided to us regarding site development. In the event that the information concerning proposed development is not correct, the conclusion and recommendations contained in this report shall not be considered valid unless the changes are reviewed, and conclusions of this report are modified or approved in writing by this office. RECOMMENDATIONS - EARTHWORK CONSTRUCTION General All grading should conform to the International Building Code (IBC) and the requirements of the City of Meridian, except where specifically superseded in the text of this report. During earthwork construction all removals, drain systems, slopes, and the general grading procedures of the contractor should be observed and the fill selectively tested. If unusual or unexpected conditions are exposed in the field, they should be reviewed by this office and, if warranted, modified and/or additional recommendations will be offered. It is recommended that the earthwork contractor(s) perform their own independent reconnaissance of the site to observe field conditions firsthand. If the contractor(s) should have any questions regarding site conditions, site preparation, or the remedial recommendations provided, they should contact an engineer at GeoTek for any necessary clarifications prior to submitting earthwork bids. All applicable requirements of local and national construction and general industry safety orders, the Occupational Safety and Health Act, and the Construction Safety Act should be met. Demolition The following recommendations are provided as guidelines in the event that structures are encountered that are not intended to remain. 1. All existing surface or subsurface structures (not intended to remain), within the area to be developed, should be razed and moved off site. 2. If a septic tank (to be abandoned or below a proposed improvement) is located within the project site, it is recommended that it be pumped out and, with few exceptions, likely removed. Any leach lines, seepage pits, or other pipes associated with this structure should also be removed or properly abandoned. GeoTek, Inc. PERA PLACE RICHMOND AMERICAN HOMES OF IDAHO PROJECT NO. 231 1-ID JULY 27, 2021 PAGE 6 3. If any wells are encountered, an attempt should be made to identify the owner and purpose of the well. Well abandonment should adhere to the recommendations provided by the Idaho Department of Water Resources, the Public Health Department, or any other government agencies. If the well is located in the area of a proposed structure, these recommendations should be reviewed by GTI and, if warranted, additional geotechnical recommendations will be offered. Removals/Processing - General Presented below are removal/processing recommendations for the various soils encountered on the project. Debris, vegetation, and other deleterious material should be stripped/removed from areas proposed for structural improvements. Based on a review of the exploratory logs and our site reconnaissance, after the artificial fill and deleterious material are removed (approximately 12 inches across majority of site and 30 inches as observed in TP-6), a minimum removal/processing depth of 12 inches into alluvial materials should be accomplished across the site. If the left in place soils can be scarified to encounter a competent layer below; they may be processed in place; otherwise, they should be removed to competent material. Locally deeper removals/processing may be necessary based on the field conditions exposed. Since much of has been disturbed, it should be anticipated that deeper fills may be encountered onsite. Beneath foundations and slab areas, the exposed ground surface should be moisture conditioned and compacted a minimum of 12 inches to provide a more uniform foundation support. A minimum relative compaction of 90 percent of the laboratory maximum modified density (ASTM D 1557) at moisture content of optimum or above is necessary to generate any near surface settlements. Locally deeper removals/processing may be necessary based on the conditions exposed. Removal bottoms should be checked by a representative of GeoTek, Inc. to see if deeper removals are necessary. If existing improvements or property line restrictions limit removals, condition specific recommendations would be provided on a case -by -case basis. During earthwork construction, care should be taken by the contractor so that adverse ground movements or settlements are not generated affecting existing improvements. Transitional Pads Transitional pads are defined in this report as pads which are partially cut and partially fill. To mitigate some of the differential settlement which will occur on transitional pads, the cut side should be over- excavated/processed to a minimum depth equal to 2 feet below the bottom of the footings or to the depth of the fill, whichever is less. On transitional pads with more than 7.5 feet of fill, plans need to be reviewed by GTI and site -specific recommendations will be provided. Excavation Difficulty We anticipate that the onsite soils can be excavated with conventional earthwork equipment. Seasonal conditions could cause wet soil conditions to occur onsite. Depending on the depth of cuts, it should be expected that special excavation and fill placement measures may be necessary. Wet materials should be spread out and air-dried or mixed with drier soils to reduce their moisture content to the appropriate level for fill placement. Frozen soils, if encountered, should be removed and allowed to thaw prior to any fill placement or construction. Removal bottoms should be checked by a representative of GTI to see if deeper removals are necessary. GeoTek, Inc. PERA PLACE JULY 27, 2021 RICHMOND AMERICAN HOMES OF IDAHO PAGE 7 PROJECT NO. 231 I -ID Fill Placement Subsequent to completing removals/processing and ground preparation, the excavated onsite and/or imported soils may be placed in relatively thin lifts (less than 8 inches thick), cleaned of vegetation and debris, brought to at least optimum moisture content, and compacted to a minimum relative compaction of 90 percent of the laboratory standard (ASTM D 1557). Import Material Potentially, soils will be imported to the site for earthwork construction purposes. A sample of any intended import material should first be submitted to GTI so that, if necessary, additional laboratory or chemical testing can be performed to verify that the intended import material is compatible with onsite soils. In general, import material should be within the following minimum guidelines: Free of organic matter and debris * Maintain less than 0.2 percent sulfate content Maintain less than 3.0 percent soluble material * Maintain less than 0.02 percent soluble chlorides * Maintain less than 0.2 percent sodium sulfate content * Maintain a Plasticity Index less than 12 (i.e., low expansive) -r. One hundred percent passing the six-inch screen * At least seventy-five percent passing a three-inch screen Maintain at least 20 percent on No. 4 screen Maintain between 5 and 30 percent passing the No. 200 screen Observation and Testing During earthwork construction all removal/processing and the general grading procedures should be observed, and the fill selectively tested by a representative(s) of GTI. If unusual or unexpected conditions are exposed in the field, they should be reviewed by GTI and if warranted, modified and/or additional recommendations will be offered. Ground Water Ground water was encountered during our field investigation at a depths ranging from 4.4' (TP-4) to 7.1' (TP-9) below existing ground surface. Based on site conditions in the future, a transient high ground water condition could develop over a clay or less permeable layer and this condition could generate down gradient seepage. The possible effect these layers could have on this and adjacent sites should be considered and can best be evaluated in the field during grading. If warranted by exposed field conditions, it may be recommended that a drainage system be established to collect and convey any subsurface water to an appropriate location for drainage. Typically, potential areas of seepage are difficult to identify prior to their occurrence; therefore, it is often best to adopt a "wait and see" approach to determine if any seepage conditions do develop, at which time specific recommendation to mitigate an identified condition can be provided. Earthwork Settlements Ground settlement should be anticipated due to primary consolidation and secondary compression. The total amount of settlement and time over which it occurs is dependent upon various factors, including material type, depth of fill, depth of removals, initial and final moisture content, and in -place density of subsurface materials. Compacted fills, to the heights anticipated, are not generally prone to GeoTek, Inc. PERA PLACE JULY 27, 2021 RICHMOND AMERICAN HOMES OF IDAHO PAGE 8 PROJECT NO. 231 I -ID excessive settlement. However, some settlement of the left -in -place alluvium is expected, and the majority of this settlement is anticipated to occur during grading. Slope Stability No significantly high (greater than ten feet) slopes are anticipated to be constructed onsite. All slopes should be designed at gradients of 2 to I (Horizontal to Vertical) or flatter. All slopes should be constructed in accordance with the minimum requirements of the City of Meridian and the International Building Code. Cut and fill slopes are anticipated to perform adequately in the future with respect to gross and surficial stability if the soil materials are maintained in a solid to semi -solid state (as defined by the soils Atterberg Limits) and are limited to the heights prescribed herein. The importance of proper compaction to the face of a slope cannot be overemphasized. In order to achieve proper compaction, one or more of the three following methods should be employed by the contractor following implementation of typical slope construction guidelines: 1) track walk the slopes at grade, 2) use a combination of sheep's -foot roller and track walking, or 3) overfill the slope 3 to 5 feet laterally and cut it back to grade. Random testing will be performed to verify compaction to the face of the slope. If the tests do not meet the minimum recommendation of 90 percent relative compaction, the contractor will be informed and additional compactive efforts recommended. A final evaluation of cut slopes during grading will be necessary in order to identify any areas of adverse conditions. The need for remedial stabilization measures should be based on observations made during grading by a representative of this office. Based on our observations, and if warranted, specific remedial recommendations will be offered for stabilization. The setback from the face of a structure and the toe of the graded slope should be at least the smaller of H/2 or 15 feet, where "H" is the height of the slope. RECOMMENDATIONS — FOUNDATIONS General Foundation design and construction recommendations are based on preliminary laboratory testing and engineering analysis performed on near surface soils. The proposed foundation systems should be designed and constructed in accordance with the guidelines contained herein and in the International Building Code. Based on our experience in the area, the soils onsite should have a negligible corrosive potential to concrete and metal, materials selected for construction purposes should be resistant to corrosion. Where permitted by building code, PVC pipe should be utilized. All concrete should be designed, mixed, placed, finished, and cured in accordance with the guidelines presented by the Portland Cement Association (PCA) and the American Concrete Institute (ACI). Based on our grading recommendations, the soils beneath the foundations are anticipated to have low expansion potential. Therefore, foundation recommendations for low expansive soil conditions are provided below. If more expansive soils are encountered, the pad(s) will either need to be regraded and the more expansive soils removed by the contractor — or increased foundation recommendations will need to be provided. GeoTek, Inc. PERA PLACE JULY 27, 2021 RICHMOND AMERICAN HOMES OF IDAHO PAGE 9 PROJECT NO. 231 1-ID Conventional Foundation Recommendations Column loads are anticipated to be 50 kips or less while wall loads are expected to be 3 kips per lineal foot or less. The conventional recommendations provided are from a geotechnical engineering perspective (i.e., for expansive conditions) and are not meant to supersede the design by the project's structural engineer. Preliminary recommendations for foundation design and construction are presented below. The specific criteria to be used should be verified on evaluation of the proposed buildings, structural loads, and expansion and chemical testing performed after grading is complete. The bearing values indicated are for the total dead, plus frequently applied, live loads and may be increased by one third for short duration loading which includes the effects of wind or seismic forces. When combining passive pressure and friction for lateral resistance, the passive component should be reduced by one-third. A grade beam, reinforced as below and at least 12 inches wide, should be utilized across all large entrances. The base of the grade beam should be at the same elevation as the bottom of the adjacent footings. Footings should be founded at a minimum depth of 24 inches below lowest adjacent ground surface as required by local codes to extend below the frost line. Reinforcement for spread footings should be designed by the project's structural engineer. For foundations systems including a crawl space, it is recommended that it be designed so that water is not allowed to penetrate the crawl space. Proper grading and backfill for the foundations are critical and should adhere to the "fill placement" and "drainage" recommendations of this evaluation as well as local building codes. Minimum Allowable Passive Maximum Footing Soil Footing Bearing Coefficient Earth Earth Type Expansion Depth Pressure of Friction Pressure Pressure Classification (inches) (psf) (psf/ft) (psf) Strip/Spread Low 24 2,000 0.35 250 3,000 The coefficient of friction and passive earth pressure values recommended are working values. Strip footings should have a minimum width of one foot and spread footings should have a minimum soil to concrete area of four -square feet. Increases are allowed for the bearing capacity of the footings at a rate of 250 pounds per square foot for each additional foot of width and 250 pounds per square foot for each additional foot of depth into the recommended bearing material, up to a maximum outlined. If the bearing value exceeds 3,000 psf, an additional review by GTI is recommended. As mentioned earlier, the exposed ground surface should be moisture conditioned and compacted a minimum depth of 12 inches below bottom of footings. Foundation Settlement Provided that the recommendations contained in this report are incorporated into final design and construction phase of development, total settlement is estimated to be less than one inch and differential settlement is estimated to be less than 0.75 inches for a 25-foot span. Two-way angular GeoTek, Inc. PERA PLACE JULY 27, 2021 RICHMOND AMERICAN HOMES OF IDAHO PAGE 10 PROJECT NO. 231 I -ID distortions due to settlements are not estimated to exceed 1/400. The structures should be loaded uniformly so as to avoid any localized settlements. PAVEMENT SECTIONS Pavement sections presented in the following table are based on an R-value result of 15, Ada County Highway District Development (ACHD) pre -assigned traffic index(s) for residential construction and estimated traffic index(s) for commercial construction, and the guidelines presented in the latest edition of the ACHD Development Policy Manual. These pavement sections are presented for planning purposes only and should be verified based on specific laboratory testing performed subsequent to rough grading of the site. Pavement Construction and Maintenance All section changes should be properly transitioned. If adverse conditions are encountered during the preparation of subgrade materials, special construction methods may need to be employed. All subgrade materials should be processed to a minimum depth of 12 inches and compacted to a minimum relative compaction of 90 percent near optimum moisture content. All aggregate base should be compacted to a minimum relative compaction of 95 percent at optimum moisture content. The recommended pavement sections provided are meant as minimums. If thinner or highly variable pavement sections are constructed, increased maintenance and repair should be expected. If the ADT (average daily traffic) or ADTT (average daily truck traffic) increases beyond that intended, as reflected by the traffic index(s) used for design, increased maintenance and repair could be required for the pavement section. Positive site drainage should be maintained at all times. Water should not be allowed to pond or seep into the ground. If planters or landscaping are adjacent to paved areas, measures should be taken to minimize the potential for water to enter the pavement section. MINIMUM MINIMUM AGGREGATE ASPHALT THICKNESS (in.) ASSUMED TRAFFIC SUBGRADE CONCRETE Aggregate Subbase RIGHT -OF -AWAY R-VALUE THICKNESS Base (3/4" (Uncrushed (in.) minus)* Aggregate)" Residential Normal Traffic 15 2.5 4.0 11.0 TI = 6.0 Collector Normal Traffic 15 3.0 6.0 14.0 TI = 8.0 "Aggregate Base and Subbase gradation specification requirement per the current edition of the Idaho Standards for Public Works Construction (ISPWC) Manual. Asphalt mix design shall meet the requirements of ISPWC, Section 810 Class III Plant mix. Materials shall be placed in accordance with ISPWC Standard Specifications for Highway Construction. GeoTek, Inc. PERA PLACE JULY 27, 2021 RICHMOND AMERICAN HOMES OF IDAHO PAGE I I PROJECT NO. 231 I -ID OTHER RECOMMENDATIONS Site Improvements As is commonly known, expansive soils are problematic with respect to the design, construction, and long-term performance of concrete flatwork. Due to the nature of concrete flatwork, it is essentially impossible to totally mitigate the effects of soil expansion. Typical measures to control soil expansion for structures include low expansive soil caps, deepened foundation system, increased structural design, and soil pre -saturation. As they are generally not cost effective, these measures are very seldom utilized for flatwork because it's less costly to simply replace any damaged or distressed sections than to "structurally" design them. Even if "structural" design parameters are applied to flatwork construction, there would still be relative movements between adjoining types of structures and other improvements (e.g., curb and sidewalk). This is particularly true as the level of care during construction of flatwork is often not as meticulous as that for structures. Unfortunately, it is fairly common practice for flatwork to be poured on subgrade soils, which have been allowed to dry out since site grading. Generally, after flatwork construction is completed, landscape irrigation begins, utility lines are pressurized, and drainage systems are utilized; presenting the potential for water to enter the dry subgrade soils, causing the soil to expand. Recommendations for exterior concrete flatwork design and construction can be provided upon request. If, in the future, any additional improvements are planned for the site, recommendations concerning the geological or geotechnical aspects of design and construction of said improvements could be provided upon request. This office should be notified in advance of any fill placement, grading, or trench backfilling after rough grading has been completed. This includes any grading, utility trench and retaining wall backfills. Landscape Maintenance and Planting Water has been shown to weaken the inherent strength of all earth materials. Slope stability is significantly reduced by overly wet conditions. Graded slopes constructed within and utilizing onsite materials would be erosive. Eroded debris may be minimized, and surficial slope stability enhanced by establishing and maintaining a suitable vegetation cover as soon as possible after construction. Compaction to the face of fill slopes would tend to minimize short-term erosion until vegetation is established. Plants selected for landscaping should be lightweight, deep-rooted types, which require little water and are capable of surviving the prevailing climate. From a geotechnical standpoint leaching is not recommended for establishing landscaping. If the surface soils are processed for the purpose of adding amendments, they should be recompacted to 90 percent compaction. Only the amount of irrigation necessary to sustain plant life should be provided. Over watering the landscape areas could adversely affect proposed site improvements. We recommend that any proposed open bottom planter areas adjacent to proposed structures, be eliminated for a minimum distance of 5 feet and desert landscape using xeriscape technology be used outside of this buffer zone. As an alternative, closed bottom type planter could be utilized. An outlet, placed in the bottom of the planter, could be installed to direct drainage away from structures or any exterior concrete flatwork. Irrigation timers should be adjusted on a monthly basis. GeoTek, Inc. PERA PLACE JULY 27, 2021 RICHMOND AMERICAN HOMES OF IDAHO PAGE 12 PROJECT NO. 231 1-ID Soil Corrosion Based on our experience in the area, the soils onsite should have a negligible corrosive potential to concrete and metal, materials selected for construction purposes should be resistant to corrosion. Where permitted by building code, PVC pipe should be utilized. All concrete should be designed, mixed, placed, finished, and cured in accordance with the guidelines presented by the Portland Cement Association (PCA) and the American Concrete Institute (ACI). Trench Excavation All footing trench excavations should be observed by a representative of this office prior to placing reinforcement. Footing trench spoil and any excess soils generated from utility trench excavations should be compacted to a minimum relative compaction of 90 percent if not removed from the site. Considering the nature of the onsite soils, it should be anticipated that caving or sloughing could be a factor in excavations. Shoring or excavating the trench walls and slopes to the angle of repose (typically 25 to 45 degrees) may be necessary and should be anticipated in non -cemented soils. All excavations should be observed by one of our representatives and conform to national and local safety codes. Utility Trench Backfill Considering the overall nature of the soil encountered onsite, it should be anticipated that materials will need to be imported to the site for use as pipe bedding and pipe zone material. Onsite utility trench backfill should be brought to near optimum moisture content and then compacted to obtain a minimum relative compaction of 90 percent of the laboratory standard. Sand backfill, unless excavated from the trench, should not be used adjacent to perimeter footings or in trenches on slopes. Offsite utility trenches should also be compacted to a minimum relative compaction of 90 percent. Compaction testing and observation, along with probing should be performed to verify the desired results. Drainage Positive site drainage should be maintained at all times in accordance with the IBC. Drainage should not flow uncontrolled down any descending slope. Water should be directed away from foundations and not allowed to pond and/or seep into the ground. Pad drainage should be directed toward the street or other approved area. The ground immediately adjacent to the foundation shall be sloped away from the building at a minimum of 5-percent for a minimum distance of 10 feet measured perpendicularly to the face of the wall. If physical obstructions prohibit 10 feet of horizontal distance, a 5-percent slope shall be provided to an approved alternate method of diverting water away from the foundation. Swales used for this purpose shall be sloped a minimum of 2-percent where located within 10 feet of the building foundation. Impervious surfaces within 10 feet of the building foundation shall be sloped a minimum of 2-percent away from the building. Roof gutters and down spouts should be utilized to control roof drainage. Down spouts should outlet onto paved areas or a minimum of five feet from proposed structures or into a subsurface drainage system. Areas of seepage may develop due to irrigation or heavy rainfall. Minimizing irrigation will lessen this potential. If areas of seepage develop, recommendations for minimizing this effect could be provided upon request. GeoTek, Inc. PERA PLACE JULY 27, 2021 RICHMOND AMERICAN HOMES OF IDAHO PAGE 13 PROJECT NO. 231 1-ID PLAN REVIEW Final grading, foundation, and improvement plans should be submitted to this office for review and comment as they become available, to minimize any misunderstandings between the plans and recommendations presented herein. In addition, foundation excavations and earthwork construction performed on the site should be observed and tested by this office. If conditions are found to differ substantially from those stated, appropriate recommendations would be offered at that time. LIMITATIONS The materials encountered on the project site and utilized in our laboratory study are believed representative of the area; however, soil materials vary in character between excavations and conditions exposed during mass grading. Site conditions may vary due to seasonal changes or other factors. GeoTek, Inc. assumes no responsibility or liability for work, testing, or recommendations performed or provided by others. Since our study is based upon the site materials observed, selective laboratory testing and engineering analysis, the conclusions and recommendations are professional opinions. These opinions have been derived in accordance with current standards of practice and no warranty is expressed or implied. Standards of practice are subject to change with time. The opportunity to be of service is greatly appreciated. If you have any questions concerning this report or if we may be of further assistance, please do not hesitate to contact the undersigned. Respectfully submitted, GeoTek, Inc. Tyler S. Lydeen, El Staff Professional �S1pNAL F�\ �G1SSTTEo O 1'. David C. Waite, PE Senior Engineer GeoTek, Inc. I:t•r-�2r,-, "l:a (:cmirc) Whr le%;& 9 Roger' Tire Pros ?. Alilo Cw4P APPROXIMATE SITE LOCATION N Source: Google Maps 2021, GeoTek Field Observations, 2021. Not to Scale FIGURE I SITEVICINITY MAP Pera Place Northeast of N Black Cat Rd and Daphne St Intersection G E a T E K Meridian, Idaho GEOTECHNICAL I ENVIRONMENTAL I MATERIALS Prepare for: Richmond Homes Project No: Report Date: Drawn By: 320 E. Corporate Dr, Suite 300, Meridian, ID 83642 231 1-ID July 2021 JJK (208) 888-7010 (phone) 1 (208) 888-7924 (FAX) + APPROXIMATETEST PIT LOCATIONS JV Source: Google Earth 2018, GeoTek Field Observations, 2021. Not to Scale GEOTEK GEOTECHNICAL I ENVIRONMENTAL I MATERIALS 320 E. Corporate Dr, Suite 300, Meridian, ID 83642 (208) 888-7010 (phone) / (208) 888-7924 (FAX) FIGURE 2 SITE EXPLORATION PLAN Pera Place Northeast of N Black Cat Rd and Daphne St Intersection Meridian, Idaho Prepare for: Richmond Homes ct No: Report Date: Drawn By: 231 1-I1D I July 2021 JJK APPENDIX A GeoTek, Inc. REFERENCES Ada County Highway District Development Policy Manual, Revised by Resolution No. 690, October 2003 ASTM, 200, "Soil and Rock: American Society for Testing and Materials," vol. 4.08 for ASTM test methods D-420 to D-4914, 153 standards, 1,026 pages; and vol. 4.09 for ASTM test method D- 4943 to highest number. Breckinridge, R.M., Lewis, R.S., Adema, G.W., Weisz, D.W., 2003, Map of Miocene and Younger Faults in Idaho, Idaho Geological Survey, University of Idaho Collett, Russell A., 1980, Soil Survey of Ada County, Eastern Part, United States Department of Agriculture Soil Conversation Service, United States Department of the Interior Bureau of Land Management, Idaho Soil Conservation Commission, University of Idaho College of Agriculture. Day, Robert W., 1999, Geotechnical and Foundation Engineering — Design and Construction Day, Robert W., 2002, Geotechnical Earthquake Engineering Handbook GeoTek, Inc., In-house proprietary information. Idaho Department of Water Resources, Treasure Valley Hydrology — Geology, January 2003 Idaho Department of Water Resources, Well Information, Well Driller Reports, 2002 Idaho Transportation Department CD-ROM Publications, September 2003 Johnson, Bruce R. and Raines, Gary L., 1995, Digital representation of the Idaho state geologic map: a contribution to the Interior Columbia Basin Ecosystem Management Project. USGS Open -File Report 95-690 Malde, H.E., 1991. Quaternary geology and structural history of the Snake River Plain, Idaho and Oregon. In: The Geology of North America, Quaternary Nonglacial Geology: Conterminous U.S., Vol. K-2, 252-281 pp. Othberg, K.L., 1994. Geology and geomorphology of the Boise Valley and adjoining areas, western Snake River Plain, Idaho. Idaho Geological Survey Bulletin 29: 54 pp. USGS, Cloverdale Quadrangle, 7.5-Minute Series Topographic Map, 1979. USGS, 2003, Seismic Hazard Map of Idaho, Peak Acceleration (%g) with 2% Probability of Exceedance in 50 years. GeoTek, Inc. APPENDIX B GeoTek, Inc. LOG GENERAL NOTES CONSISTENCY OF FINE-GRAINED SOILS Unconfined Compressive Strength, Qu, psf Standard Penetration or N- Value (SS) Blows/Ft Consistency < 500 <2 Very Soft 500 - 1,000 2 - 3 Soft 1,001 - 2,000 4-7 Firm 2,001 - 4,000 8 - 16 Stiff 4,001 - 8,000 17 - 32 Very Stiff > 8,001 32+ Hard RELATIVE DENSITY OF COARSE -GRAINED SOILS Standard Penetration (SPT) or N. Value (SS) Blows/Ft Relative Density 0 - 3 Very Loose 4-9 Loose 10 - 29 Medium Dense 30 - 49 Dense 50+ Very Dense SPT penetration test using 140 pound hammer, with 30 inch free fall on 2 inch outside diameter(I-3/8 ID) sampler For ring sampler using 140 lb hammer, with a 30 inch free fall on 3 inch outside diameter (2-1/2 ID) sample, use N-value x 0.7 to get Standard N-value For fine grained soil consistency, thumb penetration used per ASTM D-2488 RELATIVE PROPORTIONS OF SAND & GRAVEL Descriptive Term of other constituents Percent of Dry Weight Trace < 15 With IS - 29 Modifier > 30 GRAIN SIZE TERMINOLOGY Major Component of Sample Particle Size Boulders Over 12 inches Cobbles 3 inches to 12 inches Gravel #4 Sieve to 3 inches Sand #200 Sieve to #4 Sieve Silt or Clay Passing #200 Sieve RELATIVE HARDNESS OF CEMENTED SOILS (CALICHE) Description General Characteristics Very Dense to Moderately Hard Partially Cemented Granular Soil - Can be carved with a knife and broken with force by hand. Very Stiff to Moderately Hard Partially Cemented Fine -Grained Soil - Can be carved with a knife and broken with force by hand. Moderately Hard Moderate hammer blow required to break a sample Hard Heavy hammer blow required to break a sample Very Hard Repeated heavy hammer blow required to break a sample LOG LEGEND MATERIAL DESCRIPTION Soil Pattern USCS Symbol USCS Classification - = FILL Artificial Fill GP or GW Poorly/Well graded GRAVEL GM Silty GRAVEL GC Clayey GRAVEL GP -GM or GW-GM Poorly/Well graded GRAVEL with Silt GP -GC or GW-GC Poorly/Well graded GRAVEL with Clay SP or SW Poorly/Well graded SAND SM Silty SAND SC Clayey SAND SP-SM or SW-SM Poorly/Well graded SAND with Silt SP-SC or SW -SC Poorly/Well graded SAND with Clay SC-SM Silty Clayey SAND ML SILT MH CL-ML Elastic SILT Silty CLAY CL Lean CLAY CH Fat CLAY PCEM CEM BDR PARTIALLY CEMENTED CEMENTED BEDROCK SAMPLING SPT Ring Sample No Recovery Bulk Sample Water Table NR CONSISTENCY Cohesionless Soils Cohesive Soils Cementation VL Very Loose So Soft MH Moderately Hard L Loose F Firm H Hard MD Medium Dense S Stiff VH Very Hard D Dense VS Very Stiff VD Very Dense TEST PIT LOG LOGGED BY: TSL PROJECT #: 231 1-ID METHOD: Backhoe PROJECT: Pera Place EXCAVATOR: Just Dig It CLIENT: Richmond American Homes of Idaho DATE: 7114/21 G E O T E K LOCATION: Northeast of N Black Cat Rd and Daphne St ELEVATION: SAMPLES n c 10 v E TEST PIT NUMBER: TP-I c a a N REMARKS o o o N o CIO 7 U MATERIAL DESCRIPTION AND COMMENTS == FILL Brown to Dk. Brown, Artificial Fill Sandy SILT, Moist So Roots/Organics to 1.0' ML Brown to Dk. Brown, Sandy SILT, Moist F 2 3 4 SM Brown to Dk. Brown, Silty SAND, Moist D Percolation Test Conducted at 4.0' 5 6 Groundwater Depth at 6.3' 7/ 1 S/21 Measurement 7-per GP Lt. Brown to Brown, Poorly graded GRAVEL w/ sand and silt, Moist to D B Saturated 9 10 II END OF TEST PIT @ 10.0' 12 13 14 15 16 17 18 19 20 320 E. Corporate Drive, Suite 300, Meridian, Idaho 83642 1 Office: (208) 888-7010 1 Fax: (208) 888-7924 TEST PIT LOG LOGGED BY: TSL AE;Z.." PROJECT#: 2311-ID METHOD: Backhoe PROJECT: Pera Place EXCAVATOR: Just Dig It CLIENT: Richmond American Homes of Idaho DATE: 7/14/21 G E O T C r K LOCATION: Northeast of N Black Cat Rd and Daphne St ELEVATION: SAMPLES O � TEST PIT NUMBER: TP-2 N a REMARKS a a D a c 0 (AU 0 m MATERIAL DESCRIPTION AND COMMENTS -- =- FILL Brown to Dk. Brown, Artificial Fill Sandy SILT, Moist So Roots/Organics to 1.0' . ML Brown to Dk. Brown, Sandy SILT, Moist F 2 III 3 ii 4 SM Brown to Dk. Brown, Silty SAND, Moist to Saturated D 5 GP Lt. Brown to Brown, Poorly graded GRAVEL w/ sand and silt, Saturated D 6 7 Groundwater Depth Observed at 7.5' 8 END OF TEST PIT @ 8.0' 9 10 II 12 13 14 15 16 17 18 19 20 320 E. Corporate Drive, Suite 300, Meridian, Idaho 83642 1 Office: (208) 888-7010 1 Fax: (208) 888-7924 TEST PIT LOG LOGGED BY: TSL PROJECT #: 231 I -ID METHOD: Backhoe PROJECT: Pera Place EXCAVATOR: Just Dig It CLIENT: Richmond American Homes of Idaho DATE: 7/14/21 GE O T E K LOCATION: Northeast of N Black Cat Rd and Daphne St ELEVATION: SAMPLES O N N TEST PIT NUMBER: TP-3 V V I'll o REMARKS 2 CL o V o 1° Co O U MATERIAL DESCRIPTION AND COMMENTS - - FILL Dk. Brown, Artificial Fill Sandy SILT, Slightly Moist to Moist So Roots/Organics to 1.0' ML Dk. Brown, Sandy SILT, Slightly Moist to Moist F 2 SM Brown, Weakly Cemented Silty SAND, Moist to Saturated VD 3 4 5 GP Lt. Brown to Brown, Poorly graded GRAVEL w/ silt and sand, Moist to D Percolation Test Conducted 6 Saturated at 5.0' Groundwater Depth at 6.5' 7 per 7/15/21 Measurement 8 9 END OF TEST PIT @ 9.0' 10 II 12 13 14 15 16 17 18 19 20 320 E. Corporate Drive, Suite 300, Meridian, Idaho 83642 1 Office: (208) 888-7010 1 Fax: (208) 888-7924 TEST PIT LOG LOGGED BY: TSL PROJECT #: 231 I -ID METHOD: Backhoe PROJECT: Pera Place EXCAVATOR: Just Dig It CLIENT: Richmond American Homes of Idaho DATE: 7/14/21 GE O T E K LOCATION: Northeast of N Black Cat Rd and Daphne St ELEVATION: SAMPLES a u a F � r i > TEST PIT NUMBER: TP-4 REMARKS a o N o n. o N � y o U MATERIAL DESCRIPTION AND COMMENTS m FILL Brown to Dk. Brown, Artificial Fill Sandy SILT, Slightly Moist to Moist So Roots/Organics to 1.0' ML Brown to Dk. Brown, Sandy SILT, Slightly Moist to Moist F 2 —X 3 SM Brown, Silty SAND, Moist D 4 Groundwater Depth at 4.4' per 7/15/21 Measurement 5 GP Brown, Poorly graded GRAVEL w/ silt and sand, Saturated D Percolation Test Conducted at 5.0' 6 7 8 9 END OF TEST PIT @ 9.0' 10 11 12 13 14 15 16 17 18 19 20 320 E. Corporate Drive, Suite 300, Meridian, Idaho 83642 1 Office: (208) 888-7010 1 Fax: (208) 888-7924 TEST PIT LOG LOGGED BY: TSL PROJECT#: 2311-ID METHOD: Backhoe PROJECT: Pera Place EXCAVATOR: Just Dig It CLIENT: Richmond American Homes of Idaho DATE: 7/14/21 G E O T E K LOCATION: Northeast of N Black Cat Rd and Daphne St ELEVATION: SAMPLES v TEST PIT NUMBER: TP-5 C REMARKS a O v H o a U (A o N m to D V MATERIAL DESCRIPTION AND COMMENTS FILL Brown to Dk. Brown, Artificial Fill Sandy SILT, Slightly Moist So Roots/Organics to 1.0' 1 ML Brown to Dk. Brown, Sandy SILT, Slightly Moist F 2 SM Lt. Brown to Dk. Brown, Silty SAND, Moist to Saturated F 3 -X 4 GP Lt- Brown to Brown, Poorly graded GRAVEL, Saturated D S 6 7 8 Groundwater Depth Observed 9 at 8.0' END OF TEST PIT @ 9.0' 10 II 12 13 14 IS 16 17 18 19 20 320 E. Corporate Drive, Suite 300, Meridian, Idaho 83642 1 Office: (208) 888-7010 1 Fax: (208) 888-7924 TEST PIT LOG LOGGED BY: TSL PROJECT#: 2311-ID METHOD: Backhoe PROJECT: Pera Place EXCAVATOR: Just Dig It CLIENT: Richmond American Homes of Idaho DATE: 7114/21 G E O T E K LOCATION: Northeast of N Black Cat Rd and Daphne St ELEVATION: SAMPLES N a TEST PIT NUMBER: TP-6 V N a REMARKS o a E o N 0 y m N u MATERIAL DESCRIPTION AND COMMENTS Hansa FILL Brown to Dk. Brown, Artificial Fill Sandy SILT, Slightly Moist So Roots/Organics to 1.0' Trash, Debris, and Scrap Metal Observed up to 2.5' 2 3 Brown to Dk. Brown, Sandy SILT, Moist to Saturated F 4 i 5 GP Reddish Brown, Poorly graded GRAVEL w/ sand and silt, Saturated D 6 7 Groundwater Depth Observed 8 at 7.0' 9 END OF TEST PIT @ 8.5' 10 II 12 13 14 15 16 17 18 19 20 320 E. Corporate Drive, Suite 300, Meridian, Idaho 83642 1 Office: (208) 888-7010 1 Fax: (208) 888-7924 TEST PIT LOG LOGGED BY: TSL PROJECT #: 231 I -ID METHOD: Backhoe PROJECT: Pera Place EXCAVATOR: Just Dig It CLIENT: Richmond American Homes of Idaho DATE: 7/14/21 G E O T E K LOCATION: Northeast of N Black Cat Rd and Daphne St ELEVATION: SAMPLES a c y TEST PIT NUMBER: TP-7 c ao a N N REMARKS r7 E c o N o V rn m D U MATERIAL DESCRIPTION AND COMMENTS _ FILL Lt. Brown, Artificial Fill Sandy SILT, Slightly Moist So Roots/Organics to 1.0' I ML Lt. Brown, Sandy SILT, Slightly Moist F 2 SM Lt. Brown to Brown, Weakly Cemented Silty SAND, Moist VD 3 4 5 SM Brown, Silty SAND, Moist to Saturated D Percolation Test Conducted 6 at 5.5' — Groundwater Depth at 5.6' 7 GP Brown, Poorly graded GRAVEL w/ sand and silt, Saturated D per 7/15/21 Measurement 8 9 10 END OF TEST PIT @ 9.S' II 12 13 14 15 16 17 18 19 20 320 E. Corporate Drive, Suite 300, Meridian, Idaho 83642 1 Office: (208) 888-7010 1 Fax: (208) 888-7924 TEST PIT LOG LOGGED BY: TSL PROJECT #: 231 I -ID METHOD: Backhoe PROJECT: Pera Place EXCAVATOR: Just Dig It CLIENT: Richmond American Homes of Idaho DATE: 7114/21 GE O T E K LOCATION: Northeast of N Black Cat Rd and Daphne St ELEVATION: SAMPLES o >, N TEST PIT NUMBER: TP-8 aN N REMARKS v DE c c 0 (Am V D U MATERIAL DESCRIPTION AND COMMENTS FILL Brown to Dk. Brown, Artificial Fill Sandy SILT, Slightly Moist So Roots/Organics to 1.0' 1 ML Tan to Lt. Brown, Sandy SILT w/ some cementation, Slightly Moist S 2 i ,'::i �;I 3 GP Brown, Poorly graded GRAVEL w/ sand, Slightly Moist D 4 SP Brown, Poorly graded SAND, Slightly Moist D S Moist 6 GP Brown, Poorly graded GRAVEL, Moist to Saturated D 7 Groundwater Depth Observed at 7.0' 8 9 10 END OF TEST PIT @ 9.S' II 12 13 14 15 16 17 18 19 20 320 E. Corporate Drive, Suite 300, Meridian, Idaho 83642 1 Office: (208) 888-7010 1 Fax: (208) 888-7924 TEST PIT LOG LOGGED BY: TSL PROJECT#: 2311-ID METHOD: Backhoe PROJECT: Pera Place EXCAVATOR: Just Dig It CLIENT: Richmond American Homes of Idaho DATE: 7/14/21 G E O T E K LOCATION: Northeast of N Black Cat Rd and Daphne St ELEVATION: SAMPLES d � s i b d N TEST PIT NUMBER: TP-9 u N REMARKS 0 c a m N (Ao 7 U MATERIAL DESCRIPTION AND COMMENTS _ = FILL Dk. Brown, Artificial Fill Sandy SILT, Slightly Moist So Roots/Organics to 1.0' 1 ML Tan to Lt. Brown, Sandy SILT, Slightly Moist F 3 4 PCEM Brown to Dk. Brown, PARTIALLY CEMENTED Silty Sand, Moist MH 5 -- 6 - — Groundwater Depth at 7.1' 7 GP Brown, Poorly graded GRAVEL w/ sand and silt, Saturated D per 7/15/21 Measurement 8 Percolation Test Conducted _ at 7.5' 9 10 END OF TEST PIT @ 9.5' 11 12 13 14 15 16 17 18 19 20 320 E. Corporate Drive, Suite 300, Meridian, Idaho 83642 1 Office: (208) 888-7010 1 Fax: (208) 888-7924 TEST PIT LOG LOGGED BY: TSL PROJECT #: 231 1-ID METHOD: Backhoe PROJECT: Pera Place EXCAVATOR: just Dig It CLIENT: Richmond American Homes of Idaho DATE: 7/14/21 GE O T E K LOCATION: Northeast of N Black Cat Rd and Daphne St ELEVATION: SAMPLES o aN aV1 TEST PIT NUMBER: TP-10 N REMARKS o o N 2 m N V 7 U MATERIAL DESCRIPTION AND COMMENTS - FILL Brown, Artificial Fill Sandy SILT, Moist So Roots/Organics to 1.0' ML Brown, Sandy SILT, Moist F 2 SM Brown, Silty SAND w/ some cement, Moist VD 3 4 5 SP Brown, Poorly graded SAND, Saturated D Percolation Test Conducted 6 at 5.5' Groundwater Depth at 6.5' 7 GP Brown, Poorly graded GRAVEL w/ sand and silt, Saturated D per 7l15/21 8 9 10 II END OF TEST PIT @ 10.0- 12 13 14 15 16 17 18 19 20 320 E. Corporate Drive, Suite 300, Meridian, Idaho 83642 1 Office: (208) 888-7010 1 Fax: (208) 888-7924 APPENDIX C GeoTek, Inc. FIELD TESTS AND OBSERVATIONS (231 1-ID) PERCOLATION TESTS The infiltration rate was determined by conducting percolation tests for onsite earth materials. The infiltration rate was determined in inches per hour in general accordance with the City of Meridian requirements. Infiltration rate results are presented below. The infiltration rates provided below should be used for design and not exceeded. LOCATION USCS Soil Classification Symbol INFILTRATION RATE (Inches/Hour) TP- I @ 4.0' SM 3.1 TP-3 @ 3.0' GP 24.0 TP-4 @ 5.0' GP 2.8 TP-7 @ 5.5' SM 2.1 TP-9 @ 7.5' GP 2.6 TP-10 @ 5.S' SP 6.2 GROUND WATER MONITORING RESULTS Ground water monitoring results are presented below. Ground water elevation results are recorded in feet below existing grade. STAND- PIPE TP-I TP-3 TP-4 TP-7 TP-9 TP-10 PIEZOM ETER # 7-15-21 6.3' 6.5' 4.4' 5.6' 7.1' 6.5' "+" Indicates a dry reading at the bottom of the piezometer "n/a" Indicates that the piezometer was damaged/missing in the field and no measurements were obtained. GeoTek, Inc. APPENDIX D GeoTek, Inc. LABORATORY TESTS RESULTS( 311-ID) ATTERBERG LIMITS Atterberg limits were performed on representative samples in general accordance with ASTM D 4318. The results are shown in the following plates. PARTICLE SIZE ANALYSIS Sieve analyses were performed in general accordance with ASTM test method C 136 and ASTM C 117. Test results are presented in the following plates. RESISTANCE R-VALUE AND EXPANSION PRESSURE OF COMPACTED SOILS Tests were conducted on representative soil samples, in general accordance with Idaho test method T-8 and AASHTO T-190, to determine the soil's performance when placed in the base, subbase, or subgrade of a road subjected to traffic. LOCATION R-VALUE @ 200 psi TP-4 @ 1.0'-2.0' 15 GeoTek, Inc. GeoTek - Idaho 320 Corporate Drive, Ste #300 7950 Meadowlark Way, Ste E Meridian, ID 83642 Coeur d'Alene, ID 83815 Phone: (208)888-7010 (208)888-7924 Fax: (208) 904-2980 (208) 904-2981 Material Test Report Client: Richmond American Homes of Idaho CC: 849 W. LeVoy Drive Taylorsville UT 84123 Project: 2311-I D Pera Place Report No: MAT:21-00556-S01 II THIS DOCUMENT SHALL NOT BE REPRODUCED EXCEPT IN FULL Sample Details Sample ID 21-00556-S01 Date Sampled 7/14/2021 Specification General Sieve Set Sampled By Tyler Lydeen Location TP-4. 1.0'-2.0' Particle Size Distribution sc 3o i — r .... ........ ................................ ............ o -- R 8 z z z' d i z z z Sieve COBBLES GRAVEL SAND FINES (61.8%) Coarse Fine Coarse Medium Fine Silt Clay (0.0%) (0.0%) (0.4%) (1.2%) (11.1%) (25.4%) Sample Description: ML, Sandy SILT Atterberg Limit: Liquid Limit: 34 Plastic Limit: 25 Plasticity Index: 9 Grading: ASTM C 136, ASTM C 117 Date Tested: 7/16/2021 Tested By: Sieve Size % Passing Limits 3/8in 100 No.4 100 No.8 99 No.16 97 No.30 92 No.50 83 No.100 72 No.200 62 D85: 0.3500 D60: N/A D50: N/A D30: N/A D15: N/A D10: N/A Form No: 18909, Report No: MAT:21-00556-S01 © 2000-2021 QESTLab by SpectraQEST.com Page 1 of 2