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HomeMy WebLinkAboutCC - Storm Drain Calcs 'AN EK ENGINEERING DRAINAGE CALCULATIONS FOR: Horse Meadows #3 Meridian,Ada County, Idaho April 09, 2025 ASS% NA L Fiyc o� �CENS£p /y 223 a 41-0 9-W162 0 FgTf 0 Y S. Fo Prepared for: KB Home Idaho, LLC Sabrina Durtschi 1299 N. Orchard St. Suite 210 Boise, ID 83702 (208)-250-6161 Prepared by: CK Engineering, P.C. Jeremy Foster, PE, ID 13oo E. State St. Ste 102 Eagle, ID 83616 (208)-639-1992 EK ENGINEERING 13oo E.State St Suite,102 Eagle,ID 83616 208.639.1992 CK ENGINEERING Drainage Narrative for Horse Meadows Subdivision Phase #3 Horse Meadows Subdivision #3 consists of 11 drainage areas that drain to 3 permanent seepage beds as well as to existing drainage facilities. The drainage areas #10 and #11 along Pine drains to existing facilities. Drainage area #9 drains is an existing drainage area that drains to a seepage bed built within Horse Meadows Subdivision #1. The public seepage beds will be owned and maintained by Ada County Highway District(ACHD) and built using ACHD's Best Management Practices (BMP's). The geotechnical report that was referenced for the design of the storm drain facilities within Horse Meadows #3 was created by Atlas Technical Consultants, LLC, B2402339 with additional groundwater letter and infiltration testing letter dated 2/19/25 and 4/5/24 respectively. Based on the Infiltration Test Addendum letter a design percolation rate of 2"per hour was used for seepage bed #1. Seepage Bed #2 used an average of the test pits closest to this facility and a design percolation rate of 3"per hour was used. Seepage bed #3 used a 5"/hr design percolation rate.All storm drain facilities will require onsite percolation testing at the location and depth of infiltration in order to verify these percolation rates. Over excavation may be required to reach material that meets the design infiltration rate. If over excavation is required, clean pit run may be used as a backfill to get back to grade. If the design percolation rate cannot be achieved, the facility will need to be redesigned. Seepage Trench #1 Seepage Trench #1 will be a permanent storm drain facility designed per ACHD BMP20. It will accept runoff from drainage areas #1-2. These combine for a total of 42,796 sf or o.98 acres. The too year storm intensity is 2.58 in/hr. The total weighted C value for drainage areas 1-2 is 0.50. These combined numbers give a too year flow of 1.27 CFS to Seepage Bed #1. The required too year storm volume for seepage bed #1 is 1,698 CF. Seepage Bed #1 is to be 1o'Wx8'Dx51'L. With a void ratio of 0.4 and design infiltration rate of 2"/hr, this bed will be sufficiently sized. Please see the attached calculations for Seepage Bed #1. Seepage Trench #2 Seepage Trench #2 will be a permanent storm drain facility designed per ACHD BMP20. It will accept runoff from drainage areas #3-6. These combine for a total of 118,292 SF or 2.72 acres. The too year storm intensity is 2.58 in/hr. The total weighted C value for drainage areas 3-6 is 0.50. These combined numbers give a too year flow of 2.92 CFS to Seepage Bed #2. The required too year storm volume for seepage bed #2 is 4,223 CF. Seepage Bed #2 is to be 1o'Wx1o'Dx113'L. With a void ratio of 0.4 and design infiltration rate of 3"/hr, this bed is sufficiently sized. Please see the attached calculations for Seepage Bed #2. CK ENGINEERING 13oo E.State St Suite,102 Eagle,ID 83616 208.639.1992 CK ENGINEERING Seepage Trench #3 Seepage Trench #3 will be a permanent storm drain facility designed per ACHD BMP20. It will accept runoff from drainage areas #7 and #8 which combines for a total of 99,330 SF or 2.28 acres. The loo year storm intensity is 2.58 in/hr. The C value for drainage areas 7 and 8 is 0.50. These combined numbers give a loo year flow of 2.94 CFS to Seepage Bed #3. The required loo year storm volume for seepage bed #3 is 3,940 CF. Seepage Bed #3 is to be 12'Wx10'Dx77'L. With a void ratio of 0.4 and design infiltration rate of 5"/hr, this bed will be sufficiently sized. Please see the attached calculations for Seepage Bed #3. Pine Ave Frontage As mentioned in the introduction, the drainage along Pine Ave frontage will drain to existing storm drain already in place. Due to Pine being superelevated along the frontage,but the portion directly east of Horse Meadows #3 is crowned, a small drain area exists, DA#10 which, which drains east along Pine to handle the tie in from a superelevated road to a crowned road. Attached: 1. Storm drain calculations for 2 private seepage beds. 2. 11"x17" colored drainage area exhibit. 3. Geotechnical reports from Atlas Technical Consultants, LLC. End of Narrative CK ENGINEERING 130o E.State St Suite,102 Eagle,ID 83616 208.639•1992 C K E N G I N E E R I N G DRAINAGE CALCULATIONS CK ENGINEERING 13oo E.State St Suite,102 Eagle,ID 83616 208.639•1992 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology.These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name PIVOT POINTE-SEEPAGE BED#1-DRAIN AREAS#1-2 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 21,365 21,431 Acres 0.98 6 Determine the Weighted Runoff Coefficient(C) 0.50 0.50 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avgl 0.50 7 User Calculate Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 min 10 Min. Estimated Runoff Coefficients for Various Surface Type of Surface Runoff Coefficients"t Business Downtown areas 0.70-0.95 Hydraulic Urban neighborhoods 0.50-0.70 Radius Flow Residential Intercept A/Wet Velocity V Flow Time Single Family 0.35-0.50 Multi-family 0.60-0.75 ID Pipe Size(in) Slope(ft/ft) Coeff. Length Manning n Perm (fps) (min) Residential(rural) 0.25-0.40 Segment 1:Pipe Flow Apartment Dwelling Areas 0.70 a 12 0.0022 29 0.012 0.25 2.3 0.2 Industrial and Commercial Light areas 90 0.80 Segment 2:Gutter Shallow Concentrated Flow Heavy areas 0. Parks,Cemeteries 0.1010-0.25 b 0.018 0.619 120 2.7 0.7 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 Segment 3:Overland Sheet Flow By TR-55,<300-ft c 0.010 115 0.240 3.3 34.4 Computed Tc= 35.3 User-Entered Tc= 30.0 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 1.51 in/hr 9 Calculate the Post-Development peak discharge(OPeak) Opeak 0.74 cfs 10 Calculate total runoff vol(V)(for sizing primary storage) V 1,698 ft V=Ci(Tc=60)Ax3600 11 Calculate Volume of Runoff Reduction Vrr Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 1,061 ft' 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 0.95 Basin Forebay V 170 ft' Concrete 0.95 Primary Treatment/StorageBasin V 1,528 ft' Brick 0.95 Subsurface Storage Roofs 0. Gravel 0.75 5 Volume Without Sediment Factor(See BMP 20 Tab) V 1,698 ft' Fields:Sandysoil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0.. Steep:>6% 0.13 0.18 0.23 0.. Adapted from ASCE D:\KB Homes\PIVOT POINTE-MERIDIAN\DOCUMENTS\DRAINAGE CALCS\PP-SEEPAGE BED#13-19-25.xlsm 4/9/2025,3:46 PM Version 10.0,May 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology.These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak Q,V"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name PIVOT POINTE-SEEPAGE BED#1-DRAIN AREAS 111-2 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.50 Unk to: �Qv-� QV TRSS 5 Area A(Acres) 0.98 acres 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? Yes V 1,698 It` 0%Sediment 8 Set Total Design Width of All Dram Rock W 10.0 It 9 Set Total Design Depth of All Drain Rock D 8.0 It Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"Z'drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 2.00 in/hr 12 Size of WQ Perf Pipe(Pert 1800) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 3600),REQD if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 33.0 ft,/ft 15 Calculate Design Length L 51 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 51 ft 17 Variable Infiltration Window W SWW 10.0 ft 18 Time to Drain 17.8 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 51 261 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxV(2xgxH) O tional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ftz 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum D:\KB Homes\PIVOT POINTE MERIDIAN\DOCUMENTS\DRAINAGE CALCS\PP-SEEPAGE BED#1 3-19-25 3/25/2025,12:01 PM Version 10.0,May 2018 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology.These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name PIVOT POINTE-SEEPAGE BED#2-DRAIN AREA#3-6 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 30,959 72,677 5,817 8,839 Acres 2.72 6 Determine the Weighted Runoff Coefficient(C) 0.50 0.50 0.50 0.50 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avgl 0.50 7 User Calculate Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 min 10 Min. Estimated Runoff Coefficients for Various Surface Type of Surface Runoff Coefficients"t Business Downtown areas 0.70-0.95 Hydraulic Urban neighborhoods 0.50-0.70 Radius Flow Residential Intercept A/Wet Velocity V Flow Time Single Family 0.35-0.50 Multi-family 0.60-0.75 ID Pipe Size(in) Slope(ft/ft) Coeff. Length Manning n Perm (fps) (min) Residential(rural) 0.25-0.40 Segment 1:Pipe Flow Apartment Dwelling Areas 0.70 a 12 0.0022 29 0.012 0.25 2.3 0.2 Industrial and Commercial Light areas 90 0.80 Segment 2:Gutter Shallow Concentrated Flow Heavy areas 0. Parks,Cemeteries 0.1010-0.25 b 0.009 0.619 416 1.9 3.6 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 Segment 3:Overland Sheet Flow By TR-55,<300-ft c 0.010 113 0.240 3.3 33.9 Computed Tc= 37.7 User-Entered Tc= 30.0 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 1.51 in/hr 9 Calculate the Post-Development peak discharge(OPeak) Opeak 2.05 cfs 10 Calculate total runoff vol(V)(for sizing primary storage) V 4,693 ft V=Ci(Tc=60)Ax3600 11 Calculate Volume of Runoff Reduction Vrr Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 2,933 ft' 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 0.95 Basin Forebay V 469 ft' Concrete 0.95 Primary Treatment/StorageBasin V 4,223 ft' Brick 0.95 Subsurface Storage Roofs 0. Gravel 0.75 5 Volume Without Sediment Factor(See BMP 20 Tab) V 4,693 ft' Fields:Sandysoil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0.. Steep:>6% 0.13 0.18 0.23 0.. Adapted from ASCE D:\KB Homes\PIVOT POINTE-MERIDIAN\DOCUMENTS\DRAINAGE CALCS\PP-SEEPAGE BED#24-09-25.xlsm 4/9/2025,3:55 PM Version 10.0,May 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name PIVOT POINTE-SEEPAGE BED#2-DRAIN AREA#3-6 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.50 Unkto: LQV J QV TR55 5 Area A(Acres) 2.72 acres 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? Yes V 4,693 ft3 o%Sediment 8 Set Total Design Width of All Drain Rock W 10.0 ft 9 Set Total Design Depth of All Drain Rock D 10.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 3.00 in/hr 12 Size of WC.Perf Pipe(Pert 180°) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 360°),REQD if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 41.4 Oft 15 Calculate Design Length L 113 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 113 ft 17 Variable Infiltration Window W SWW 10.0 ft 18 Time to Drain 14.9 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 113 261 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxy(2xgxH) Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum D:\KB Homes\PIVOT POINTE-MERIDIAN\DOCUMENTS\DRAINAGE CALCS\PP-SEEPAGE BED#2 4-09-25 4/9/2025,2:41 PM Version 10.0,May 2018 ACHD Calculation Sheet for Finding Peak Discharge/Volume-Rational Method NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology.These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name PIVOT POINTE-SEEPAGE BED#3-DRAIN AREA#7 AND#8 2 Is area drainage basin map provided? YES (map must be included with stormwater calculations) 3 Enter Design Storm(100-Year or 25-Year With 100-Year Flood Route) 100 4 Enter number of storage facilities(25 max) Click to Show More Subbasins ❑ Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin 1 Subbasin 2 3 4 5 Subbasin 6 7 8 9 10 5 Area of Drainage Subbasin(SF or Acres) SF 81,254 18,076 Acres 2.28 6 Determine the Weighted Runoff Coefficient(C) 0.50 0.50 C=[(C1xA1)+(C2xA2)+(CnxAn)]/A Weighted Avgl 0.50 7 User Calculate Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 min 10 Min. Estimated Runoff Coefficients for Various Surface Type of Surface Runoff Coefficients"t Business Downtown areas 0.70-0.95 Hydraulic Urban neighborhoods 0.50-0.70 Radius Flow Residential Intercept A/Wet Velocity V Flow Time Single Family 0.35-0.50 Multi-family 0.60-0.75 ID Pipe Size(in) Slope(ft/ft) Coeff. Length Manning n Perm (fps) (min) Residential(rural) 0.25-0.40 Segment 1:Pipe Flow Apartment Dwelling Areas 0.70 a 12 0.0022 35 0.012 0.25 2.3 0.3 Industrial and Commercial Light areas 90 0.80 Segment 2:Gutter Shallow Concentrated Flow Heavy areas 0. Parks,Cemeteries 0.1010-0.25 b 0.005 0.619 380 1.5 4.4 Playgrounds 0.20-0.35 Railroad yard areas 0.20-0.40 Segment 3:Overland Sheet Flow By TR-55,<300-ft c 0.010 114 0.240 3.3 34.1 Computed Tc= 38.8 User-Entered Tc= 30.0 8 Determine the average rainfall intensity(i)from IDF Curve based on Tc i 1.51 in/hr 9 Calculate the Post-Development peak discharge(OPeak) Opeak 1.72 cfs 10 Calculate total runoff vol(V)(for sizing primary storage) V 3,940 ft V=Ci(Tc=60)Ax3600 11 Calculate Volume of Runoff Reduction Vrr Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) Vrr 2,463 ft' 12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs 13 Volume Summary Unimproved areas 0.10-0.30 Surface Storage:Basin Streets Asphalt 0.95 Basin Forebay V 394 ft' Concrete 0.95 Primary Treatment/StorageBasin V 3,546 ft' Brick 0.95 Subsurface Storage Roofs 0. Gravel 0.75 5 Volume Without Sediment Factor(See BMP 20 Tab) V 3,940 ft' Fields:Sandysoil Soil Type Slope A B C D Flat:0-2% 0.04 0.07 0.11 0. Average:2-6% 0.09 0.12 0.15 0.. Steep:>6% 0.13 0.18 0.23 0.. Adapted from ASCE D:\KB Homes\PIVOT POINTE-MERIDIAN\DOCUMENTS\DRAINAGE CALCS\PP-SEEPAGE BED#34-09-25.xlsm 4/9/2025,3:57 PM Version 10.0,May 2018 ACHD Calculation Sheet for Sizing Seepage Bed With Optional Chambers NOTE:This worksheet is intended to be a guideline to standardize ACHD checking of drainage calculations and shall not replace the Engineer's calculation methodology. These calculations shall establish a minimum requirement.The Engineer's methodology must result in facilities that meet or exceed these calculations in order to be accepted. Note this spreadsheet pulls information from the"Peak QV"tab Calculate Post-Development Flows(for pre-development flows,increase number of storage facilities to create new tab) User input in yellow cells. 1 Project Name PIVOT POINTE-SEEPAGE BED#3-DRAIN AREA#7 AND#8 2 Enter number of Seepage Beds(25 max) 1 3 Design Storm 100 4 Weighted Runoff Coefficient C 0.50 Link to: LQV J QV TR55 5 Area A(Acres) 2.28 acres 6 Approved discharge rate(if applicable) 0.00 cfs 7 Is Seepage Bed in Common Lot? Yes V 3,940 ft3 0%Sediment 8 Set Total Design Width of All Drain Rock W 12.0 ft 9 Set Total Design Depth of All Drain Rock D 10.0 ft Rock Only,Do Not Include Filter Sand Depth or Cover 10 Void Ratio of Drain Rock Voids 0.4 0.4 for 1.5"-2"drain rock and 3/4"Chips 11 Design Infiltration Rate(8 in/hr max) Perc 5.90 in/hr 12 Size of WC.Perf Pipe(Pert 180°) Dia pipe 18 in 13 Size of Overflow Perf Pipe(Perfs 360°),REQD if Q100>3.3 cfs in 14 Calculate Total Storage per Foot Spf 51.1 Oft 15 Calculate Design Length L 77 ft Override Value Required for Chambers 16 Variable Infiltration Window L SWL 77 ft 17 Variable Infiltration Window W SWW 12.0 ft 18 Time to Drain 77 hours 90%volume in 48-hours minimum 19 Length of WQ&Overflow Perf Pipes 77 261 ft 20 Perf Pipe Checks.Qperf>=Qpeak; where Qperf=CdxAxV(2xgxH) Optional Storage Chambers Note:This assumes chambers are organized in a rectangular layout. 1-StormTech, 1 Type of Chambers SC740 2 Volume to Store V 0 ft3 3 Installed Chamber Width Cw 4.25 ft Installed Chamber Depth Cd 2.50 ft Installed Chamber Height Ch 7.12 ft 4 Chamber Void Factor 5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft3/Unit 6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft3/Unit 7 Total Number of Units Required 0 ea 8 Area of Infiltration Aperc ft2 9 Volume Infiltration Vperc 0 ft3/hr 10 Time to Drain hours 90%volume in 48-hours minimum D:\KB Homes\PIVOT POINTE-MERIDIAN\DOCUMENTS\DRAINAGE CALCS\PP-SEEPAGE BED#3 4-09-25 4/9/2025,2:44 PM Version 10.0,May 2018 TIME OF CONCENTRATION PROJECT. Pivot Point Subdivision BASIN: Seepage Bed #1 (D.A.s#1-2) OVERLAND SHEET FLOW(TI): 0.007(nL) OR , WHERE: n = 0.24 T, _ �,.:; 0.4 L1= 115 P2= 1.2 where: s= 0.01 T, = travel time(hr), n = Manning's roughness coefficient T1 (hrs)= 0.573 L = flow length(ft) P•, = 2-year,24-hour rainfall(in) T1 (min)= 34.39 s = slope of hydrattlic grade hne (land slope,ft/ft) GUTTER CONCENTRATED FLOW: s2= 0.0175 V 20.'32S(s)°;, , WHERE: V2= 2.69 L2= 120 T2= L2N2 T2 (s)= 44.6239 T2(min)= 0.74 CHANNEL/PIPE FLOW: (T3) Pipe D(in)= 12 V_ 1.49r 1 ,WHERE: Ac(ft)= 0.79 ►t PW(ft)= 3.14 where: r= 0.25 V = average velocity(ft/s) s= 0.0022 r= hydraulic radios(ft)and is equal to a/p,, n= 0.012 a= cross sectional flow area(W) V3= 2.30 1),= wetted perimeter(ft) s= slope of the hydraulic grade line(channel L3= 29 slope,ft/ft) n= Manning's roughness coefficient for open channel flow. T3(s)= 12.61 T3(min)= 0.21 T3 = L3/\/3 TOTAL TIME OF CONCENTRATION (Tl+T2+T3) TC= 35.34 min TIME I in hr TIME I in hr TIME I in hr 10 min 2.58 50 min 1 12 hr 0.16 15 min 2.18 1 hr 0.96 24 hr 0.1 20 min 1.81 2 hr 0.54 30 min 1.51 3 hr 0.4 40 min 1.15 6 hr 0.25 100 YR STORM INTENSITY GIVEN WITH TIME OF CONCENTRATION 30 MIN 1.51 (IN/HR) WEIGHTED RUNOFF COEFFICIANT PEAK DESIGN STORM RUNOFF C= 0.5 Q=c(I)(A) DRAIN AREA SIZE SF SIZE AC INTENSITY C BASIN PEAK RUNOFF CATCH BASIN DA#1 21365 0.490 1.51 0.5 0.37 cfs CB#1 DA#2 21431 0.492 1.51 0.5 0.37 cfs CB#2 TOTAL: 42796 0.982 1.51 0.5 0.74 cfs 25 YR STORM INTENSITY GIVEN WITH TIME OF CONCENTRATION 30 MIN 1.08 (IN/HR) WEIGHTED RUNOFF COEFFICIANT PEAK DESIGN STORM RUNOFF C= 0.5 Q=c(I)(A) DRAIN AREA SIZE SF SIZE AC INTENSITY C BASIN PEAK RUNOFF CATCH BASIN DA#1 21365 0.490 1.08 0.5 0.26 cfs CB#1 DA#2 21431 0.492 1.08 0.5 0.27 cfs CB#2 TOTAL: 42796 0.982 1.08 0.5 0.53 cfs Sand and Grease Traps Check: Given: Baffel Baffel Spacing(in) Width(in) 1#of traps jQp (cfs-100Y) jVmax (fps) Baffel Widths: 20 48 1 0.742 0.5 48" 60" 1000 gal 1500 gal V=Q/A Vprovided= 0.11 Vprovided<Vma YES GREASE TRAPS NEEDED= 1 1000 gal TIME OF CONCENTRATION PROJECT. Pivot Point Subdivision BASIN: Seepage Bed#2 (D.A.s#3-6) OVERLAND SHEET FLOW(T1): _ 0.007(nL) 0� , WHERE: n = 0.24 Tt o� L1= 113 o� P2= 1.2 where: s= 0.01 Tt = travel time(hr), n = Manning's roughness coefficient T1 (hrs)= 0.565 L = flow length(ft) P, = 2-year,24-hour rainfall(in) T1 (min)= 33.91 s = slope of hydraulic grade line (land slope,ft/ft) GUTTER CONCENTRATED FLOW: s2= 0.0091 WHERE: V2= 1.94 L2= 413 Tz= L2/U2 T2 (s)= 212.978 T2(min)= 3.55 CHANNEL/PIPE FLOW: (T3) t Pipe D(in)= 12 V 1.49r ;S2 WHERE: Ac (ft)= 0.79 n PW (ft)= 3.14 where: r= 0.25 V = average velocity(ft/s) s= 0.0022 r= hydraulic radius(ft)and is equal to a/p, n= 0.012 a= cross sectional flow area(ft2) V3= 2.30 p,= wetted perimeter(ft) s= slope of the hydraulic grade line(charnel L3= 29 slope,ft/ft) n= Manning's roughness coefficient for open channel flow. T3(s)= 12.61 T3(min)= 0.21 T3 = L3/V3 TOTAL TIME OF CONCENTRATION (T1+T2+T3) TC = 37.67 min TIME I in hr TIME I in hr TIME I in hr 10 min 2.58 50 min 1 12 hr 0.16 15 min 2.18 1 hr 0.96 24 hr 0.1 20 min 1.81 2 hr 0.54 30 min 1.51 3 hr 0.4 40 min 1.15 6 hr 0.25 100 YR STORM INTENSITY GIVEN WITH TIME OF CONCENTRATION 30 MIN 1.51 (IN/HR) WEIGHTED RUNOFF COEFFICIANT PEAK DESIGN STORM RUNOFF C= 0.5 Q= c(I)(A) DRAIN AREA SIZE SF SIZE AC INTENSITY C BASIN PEAK RUNOFF CATCH BASIN DA#3 30959 0.711 1.51 0.5 0.54 cfs CB#3 DA#4 72677 1.668 1.51 0.5 1.26 cfs CB#4 DA#5 5817 0.134 1.51 0.5 0.10 cfs CB#5 DA#6 8839 0.203 1.51 0.5 0.15 cfs CB#6 TOTAL: 118292 2.716 1.51 0.5 2.05 cfs 25 YR STORM INTENSITY GIVEN WITH TIME OF CONCENTRATION 30 MIN 1.08 (IN/HR) WEIGHTED RUNOFF COEFFICIANT PEAK DESIGN STORM RUNOFF C= 0.5 Q= c(I)(A) DRAIN AREA SIZE SF SIZE AC INTENSITY C BASIN PEAK RUNOFF CATCH BASIN DA#3 30959 0.711 1.08 0.5 0.38 cfs CB#3 DA#4 72677 1.668 1.08 0.5 0.90 cfs CB#4 DA#5 5817 0.134 1.08 0.5 0.07 cfs CB#5 DA#6 8839 0.203 1.08 0.5 0.11 cfs CB#6 TOTAL: 118292 2.716 1.08 0.5 1.47 cfs Sand and Grease Traps Check: Given: Baffel Baffel Spacing (in) I Width(in) 1#of traps jQp (cfs-100Y) jVmax (fps) Baffel Widths: 20 48 1 2.050 0.5 48" 60" 1000 gal 1500 gal V=Q/A Vprovided= 0.31 Vprovided<Vma YES GREASE TRAPS NEEDED= 1 1000 gal TIME OF CONCENTRATION PROJECT. Pivot Point Subdivision BASIN: Seepage Bed#3 (D.A.s#7-#8) OVERLAND SHEET FLOW(T1): _ 0.007(nL) 0� , WHERE: n = 0.24 Tt o� L1= 114 o� P2= 1.2 where: s= 0.01 Tt = travel time(hr), n = Manning's roughness coefficient T1 (hrs)= 0.569 L = flow length(ft) P, = 2-year,24-hour rainfall(in) T1 (min)= 34.15 s = slope of hydraulic grade line (land slope,ft/ft) GUTTER CONCENTRATED FLOW: s2= 0.0051 WHERE: V2= 1.45 L2= 380 T2= L2N2 T2 (s)= 261.7603 T2(min)= 4.36 CHANNEL/PIPE FLOW: (T3) t Pipe D(in)= 12 V 1.49r ;S2 WHERE: Ac (ft)= 0.79 n PW (ft)= 3.14 where: r= 0.25 V = average velocity(ft/s) s= 0.0022 r= hydraulic radius(ft)and is equal to a/p, n= 0.012 a= cross sectional flow area(ft2) V3= 2.30 p,= wetted perimeter(ft) s= slope of the hydraulic grade line(charnel L3= 35 slope,ft/ft) n= Manning's roughness coefficient for open channel flow. T3(s)= 15.21 T3(min)= 0.25 T3 = L3/V3 TOTAL TIME OF CONCENTRATION (T1+T2+T3) TC = 38.76 min TIME I in hr TIME I in hr TIME I in hr 10 min 2.58 50 min 1 12 hr 0.16 15 min 2.18 1 hr 0.96 24 hr 0.1 20 min 1.81 2 hr 0.54 30 min 1.51 3 hr 0.4 40 min 1.15 6 hr 0.25 100 YR STORM INTENSITY GIVEN WITH TIME OF CONCENTRATION 30 MIN 1.51 (IN/HR) WEIGHTED RUNOFF COEFFICIANT PEAK DESIGN STORM RUNOFF C= 0.5 Q= c(I)(A) DRAIN AREA SIZE SF SIZE AC INTENSITY C BASIN PEAK RUNOFF CATCH BASIN DA#7 81254 1.865 1.51 0.5 1.41 cfs CB#7 DA#8 18076 0.415 1.51 0.5 0.31 CB#8 TOTAL: 99330 2.280 1.51 0.5 1.72 cfs 25 YR STORM INTENSITY GIVEN WITH TIME OF CONCENTRATION 30 MIN 1.08 (IN/HR) WEIGHTED RUNOFF COEFFICIANT PEAK DESIGN STORM RUNOFF C= 0.5 Q= c(I)(A) DRAIN AREA SIZE SF SIZE AC INTENSITY C BASIN PEAK RUNOFF CATCH BASIN DA#7 81254 1.865 1.08 0.5 1.01 cfs CB#7 DA#8 18076 0.415 1.08 0.5 0.22 cfs CB#8 TOTAL: 118980 2.731 1.08 0.5 1.47 cfs Given: Baffel Baffel Spacing (in) I Width(in) 1#of traps jQp (cfs-100Y) jVmax (fps) Baffel Widths: 20 48 1 1.408 0.5 48" 60" 1000 gal 1500 gal V=Q/A Vprovided= 0.21 Vprovided<Vma YES GREASE TRAPS NEEDED= 1 1000 gal C K ENGINEERING DRAINAGE AREA EXHIBIT CK ENGINEERING 13oo E.State St Suite,102 Eagle,ID 83616 208.639•1992 N W E S 0 100' 200' — — — PINE SEEPAGE BED #3 DA#10 ........ ........ . DA#11 , SCALE 1' = 100' 'n, I �s FNNFDy CB#1v: I I - i �-�-7_ CB#7 �4TF'Q9l SEEPAGE BED 1 CB#2 SEEPAGE BED #1 � \ # �z/ e DA#1 = 21,365 SF - CB#1 - DA#2 I DA#1 DA#2 = 21,431 SF - CB#2 i DA#. -. ` TOTAL = 42,796 SF MEADOWPINE SEEPAGE BED #2 CB#8 14 DA#3 = 30,959 SF - CB#3 DA#8 DA#4 = 72,677 SF - CB#4 EXISTING DA#5 = 5,817 SF - CB#5 6 SEEPAGE BED #1 Ip— DA16 = 8,839 SF - CB#6 24 I I I r 1 31 DA#6 TOTAL = 118,292 SF — I—J SEEPAGE BED #2 , — 12 m _ a DA#4 DA#3 SEEPAGE BED #3 41 k o n fa 5 DA#7 = 81,254 SF - CB#7 EXISTING D I''''� I r-- ~� — DA#8 = 18.076 SF - CB#8 HORSE \ GI DA#9 I 1E- J� _ Ib �I�_ ' CB#6 v CB#4 a TOTAL 99,330 SF MEADOWS -7- r b EXISTING FACILITIES =SUBDIVISION 1 I I I I DA#9 = 142,293 SF - EXISTING SEEPAGE BED #1 CB#3 W. QUARTERHORSE DR. a DA#10 = 34,464 SF - EXISTING -- , — DA#5 DA#11 = 3,472 SF - EXISTING ��— —=_= CB#5 m Ir" a I 8 I I O I Q I EXISTING ° ALEXANDER —-- SLOCK, LANDING C2D HORSE MEADOWS SUB #3 REVISIONS: DRAWN BY: AKB CHECKED BY: CSK CK ENGINEERING KB HOMES D R A I V A G E EXHIBIT DATE: 03/25/25 1300 E. STATE ST., SUITE 102 FILE: DRAINAGE EX.DWG EAGLE, ID 83616 CITY OF M ER D AN ADA COUNTY DAH 0 DIR: o-AKB 9wPmm—wsmowncK—°wGs\B4G PHONE 208-639-1992 C K ENGINEERING GEOTECHNICAL REPORTS CK ENGINEERING 13oo E.State St Suite,102 Eagle,ID 83616 208.639•1992 ■ �► 2/19/2025 �T B240233_GWIetter 2791 S.Victory View Way Boise, ID 83709 (208)376-4748 1 oneatlas.com Sabrina Durtschi KB Home Idaho, LLC 1414 West Bannock Street Boise, ID 83702 (208) 340-8305 Re: Groundwater Letter Pivot Point Subdivision 4600 West Quarter Horse Lane Meridian, ID 83641 Dear Sabrina Durtschi: This letter has been prepared to verify seasonal high groundwater as determined through regular monitoring unavailable at the time of the previously issued Atlas Geotechnical Engineering Report (B240233g). Descriptions of general site characteristics and the proposed project are available in the previous report. Unless otherwise noted in this letter, all initial recommendations, limitations, and warranties expressed in the previous report must be adhered to. The following table represents groundwater data collected for the site. It should be noted that these levels will fluctuate from year to year, and are limited to the data collected. Atlas will continue to monitor these wells on a monthly basis. Atlas appreciates this opportunity to be of service to you and looks forward to working with you in the future. If you have questions, please call (208) 376-4748. Respectfully Submitted, Atlas Technical Consultants Sydney Shockley Reviewed by. Gavin Marron, El Staff Geologist Staff Engineer Enclosures: Groundwater Data T ■ �► 2/19/2025 �T B240233_GWletter 2791 S.Victory View Way Boise, ID 83709 (208)376-4748 1 oneatlas.com Groundwater Depth (Feet bgs) Date Monitored TP-1 TP-2 TP-3 TP-4 2/19/2025 15.58 Dry 15.36 Dry arm I �lrT—G7T�� April 5, 2024 Atlas No. B240233g Sabrina Durtschi KB Home Idaho, LLC 1414 West Bannock Street Boise, ID 83702 Subject: Addendum #1 — Infiltration Testing Pivot Point Subdivision 4600 West Quarter Horse Lane Meridian, ID Dear Sabrina Durtschi: This addendum report presents test results unavailable at the time of the previously issued Atlas Geotechnical Engineering Report (B240233g). During the initial geotechnical investigation, the infiltration testing locations were unable to be accessed with the water tank due to wet conditions. Descriptions of general site characteristics and the proposed project are available in the previous report. Unless otherwise noted in this addendum, all initial recommendations, limitations, and warranties expressed in the previous report must be adhered to. INFILTRATION TESTING Infiltration tests were performed in test pits 1, 2 and 3. Test pit 4 was unable to be tested due to homeowner's equipment blocking access to the test location. Infiltration testing was conducted using an open test pit method. The test location was presoaked prior to testing. Pre-soaking increases soil moistures, which allows the tested soils to reach a saturated condition more readily during testing. Saturation of the tested soils is desirable in order to isolate the vertical component of infiltration by inhibiting horizontal seepage during testing. Infiltration testing was conducted using an open test pit method. Test locations were presoaked prior to testing. Pre-soaking increases soil moistures, which allows the tested soils to reach a saturated condition more readily during testing. Saturation of the tested soils is desirable in order to isolate the vertical component of infiltration by inhibiting horizontal seepage during testing. Testing was conducted on March 19, 2024. Details and results of testing are as follows: Atlas No. B240233g Page11 Copyright©2024 Atlas Technical Consultants �TrT-G7T-�. Table 1 — Infiltration Test Results Test Test Depth Stabilized Infiltration Location (feet bgs) Soil Type Rate TP-1 6.0 Poorly Graded Sand 11.8 TP-2 7.0 Poorly Graded Sand with 3.7 Silt TP-3 6.7 Poorly Graded Sand with 9.4 Silt and Gravel Appropriate factors of safety have been applied to the stabilized infiltration rates achieved during testing to obtain the design infiltration rates listed below. Table 2 — Infiltration Test Results Test Test Dep sign Infiltration Rate Location (feet . . jj WSTII MTYWII (inches/hour) TP-1 6.0 Poorly Graded Sand 5.9 TP-2 7.0 Poorly Graded Sand with 1.9 Silt TP-3 6.7 Poorly Graded Sand with 4.7 Silt and Gravel The reason for the decreased infiltration rate is to account for long term saturation of the soils and the potential for less permeable soils to settle into the bottom of the infiltration facilities. Atlas recommends that all infiltration facilities be constructed in accordance with the local municipality requirements. If you have any questions, please call us at (208) 376-4748. Respectfully submitted, Max Kasberger, PE Jacob Schlador, PE Geotechnical Engineer Geotechnical Practice Manager- Northwest Attachments: Site Map Geotechnical Investigation Test Pit Logs Geotechnical General Notes Atlas No. B240233g Page12 Copyright©2024 Atlas Technical Consultants Site Map Figure 2 NOTES: N •Not to Scale A w z LU LU a LEGEND Approximate Site 00 Boundary Approximate Atlas Test PINE AVENUE _ Pit Location with Piezometer TP-1 '-�, kFNN�DyIgT MIMI Pivot Point Subdivision NMI _ TP 3 4600 West Quarter Horse Lane TP 2 ® Meridian,ID QUARTER HORSE LANE ® _ Modified by:MPK February 26,2024 Drawing:B240233g ' �r'1rmomrC'1t—�� ' 2791 S.Victory View Way Phone: (208)376-4748 Boise,ID 83709 Fax: (208)322-6515 o Web: oneatlas.com �TrT-G7T_� APPENDIX IV GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log#: TP-1 Latitude: 43.611893 Date Advanced: February 15, 2024 Longitude: -116.451283 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 15.8 feet bgs Depth Field Description and USCS Soil and Sample Sample Depth Lab h . . . • • • • . Test I Lean Clay with Sand (CL): Light brown to 0.0-1.2 brown,slightly moist,stiff to very stiff,with fine- 2.0 grained sand. --Organics noted to 0.3 foot bgs. Sandy Lean Clay(CL): Brown, dry, stiff to very 1.2-5.1 stiff, with fine to medium-grained sand. --Weak to moderate induration encountered throughout. Poorly Graded Sand with Gravel (SP): Light 5.1-15.8 brown,dry, medium dense,with fine to coarse- grained sand and fine to coarse gravel. --Minor clay content noted throughout. Notes:See Site Map for test pit location. Piezometer installed to a depth of 15.8 feet bgs. Atlas No. B240237g Page 122 Copyright©2024 Atlas Technical Consultants �TrT-G7T_�. GEOTECHNICAL INVESTIGATION TF Test Pit Log #: TP-2 Latitude: 43.611179 Date Advanced: February 15, 2024 Longitude: -116.451009 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 13.4 feet bgs V. Depth eld Description and USCS Soil and Sample Sample Depth 11 !� • ••s)I& Sediment Classification • •• Lean Clay with Sand (CL): Light brown to 0.0-2.9 brown,slightly moist, stiff to very stiff,with fine- 1.75-2.0 grained sand. --Organics noted to 0.4 foot bgs. Sandy Lean Clay(CL): Brown, dry, stiff to very 2.9-5.4 stiff, with fine to medium-grained sand. --Weak to moderate induration encountered from 3.2 to 4.0 feet bgs. Poorly Graded Sand with Gravel (SP): Light brown to brown, dry, medium dense, with fine 5.4-13.4 to coarse-grained sand and fine to coarse gravel. --Minor clay content noted throughout. Notes:See Site Map for test pit location. Piezometer installed to a depth of 13.4 feet bgs. Atlas No. 13240237g Page 123 Copyright©2024 Atlas Technical Consultants �TrT-G7T_�. GEOTECHNICAL INVESTIGATION TF Test Pit Log #: TP-3 Latitude: 43.611101 Date Advanced: February 15, 2024 Longitude: -116.449103 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 14.8 feet bgs V. Depth eld Description and USCS Soil and Sample Sample Depth sla 11 I& � • •• • • • •• rTe t Lean Clay with Sand (CL): Light brown to 0.0-1.4 brown,slightly moist, stiff to very stiff,with fine- grained sand. --Organics noted to 0.4 foot bgs. 1.4-5.5 Sandy Lean Clay(CL): Brown, dry, stiff to very stiff, with fine to medium-grained sand. Poorly Graded Sand with Gravel (SP): Light brown to brown, dry, medium dense, with fine 5.5-14.8 to coarse-grained sand and fine to coarse gravel. --Minor clay content noted throughout. Notes:See Site Map for test pit location. Piezometer installed to a depth of 14.8 feet bgs. Atlas No. 13240237g Page 124 Copyright©2024 Atlas Technical Consultants �TrT-G7T-�. GEOTECHNICAL INVESTIGATION TEST PIT LOG Test Pit Log#: TP-4 Latitude: 43.611955 Date Advanced: February 15, 2024 Longitude: -116.448880 Excavated by: Turn of the Century Homes Depth to Water Table: Not Encountered Logged by: Wyatt Wolfe, El Total Depth: 13.5 feet bgs Depth _.Field Description and USCS Soil and Sample Sample Depth Qp Lab •• •iment Classification • bgs) Test ID mmmim Lean Clay with Sand (CL): Light brown to 0.0-1.5 brown, slightly moist, stiff, with fine-grained GS 1.0-1.5 1.5 A sand. --Organics noted to 0.3 foot bgs. Sandy Lean Clay(CL): Brown, dry, stiff to very 1.5-5.0 stiff, with fine to medium-grained sand. --Weak to moderate induration encountered throughout. Poorly Graded Sand with Gravel (SP): Light brown to brown, dry, medium dense, with fine 5.0-13.5 to coarse-grained sand and fine to coarse gravel. --Minor clay content noted throughout. Notes:See Site Map for test pit location. Piezometer installed to a depth of 13.5 feet bgs. • Test ID Moisture N A 25.9 39 21 100 99 94 1 87 82.4 Atlas No. B240237g Page 125 Copyright©2024 Atlas Technical Consultants �TrT-G7Tdr-W� APPENDIX V GEOTECHNICAL GENERAL NOTES Unified Soil Classification System Major Divisions Symbol Soil Descriptions Gravel & GW Well-graded ravels; ravel/sand mixtures with little or no fines Coarse- Gravelly Soils GP Poorl - raded ravels; ravel/sand mixtures with little or no fines Grained < 50% GM Silty gravels; poorly-graded ravel/sand/silt mixtures Soils < coarse GC Clayey gravels; poorly-graded gravel/sand/clay mixtures 50% Sand & Sandy SW Well-graded sands; gravelly sands with little or no fines passes Soils > 50% SP Poorl - raded sands; gravelly sands with little or no fines No.200 coarse SM Silty sands; poorly-graded sand/gravel/silt mixtures sieve fraction Sc Clayey sands; poorly-graded sand/gravel/clay mixtures Fine- ML Inorganic silts; sandy, gravellyor clayey silts Grained Silts & Clays CL Lean clays; inorganic, gravelly, sandy, or silty, low to medium- Soils > LL < 50 plasticity clays 50% OL Organic, low-plasticity clays and silts passes MH Inorganic, elastic silts; sand ravel) or clayey elastic silts No.200 Silts &Clays CH Fat clays high-plasticity, inorganic clays sieve LL > 50 OH Organic, medium to high-plasticity clays and silts Highly Organic Soils PT Peat, humus, h dric soils with high organic content Relative Density • Consistency • • and Cementation • • Coarse-Grained Soils SPT Blow Counts N Description Field Test VeryLoose: <4 Dr Absence of moisture, dryto touch Loose: 4-10 Slightly Moist Damp, but no visible moisture Medium Dense: 10-30 Moist Visible moisture Dense: 30-50 Wet Visible free water VeryDense: >50 Saturated Soil is usual) below water table Fine-Grained Soils SPT Blow Counts N Description Field Test Very Soft: <2 Weak Crumbles or breaks with handling or Soft: 2-4 slight finger pressure Medium Stiff: 4-8 Moderate Crumbles or breaks with Stiff: 8-15 considerable finger pressure Very Stiff: 15-30 Strong Will not crumble or break with finger Hard: >30 pressure Particle Size& ]�� Acronym List Boulders: > 12 in. GS grab sample Cobbles: 12 to 3 in. LL Liquid Limit Gravel: 3 in. to 5 mm M moisture content Coarse-Grained Sand: 5 to 0.6 mm NP non-plastic Medium-Grained Sand: 0.6 to 0.2 mm PI Plasticity Index Fine-Grained Sand: 0.2 to 0.075 mm QP penetrometer value, unconfined compressive Silts: 0.075 to 0.005 mm strength, tsf Clays: < 0.005 mm V vane value, ultimate shearing strength, tsf Atlas No. B240237g Page 126 Copyright©2024 Atlas Technical Consultants