HomeMy WebLinkAboutCC - Drain CalcCalcs_09-10-25 ENGINEERING P. C .
Civil Engineering * Project Management
DRAINAGE CALCULATIONS FOR:
Gramercy Subdivision
Meridian, Idaho
September 10, 2025
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Submitted For:
Phoenix Commercial Construction
Shannon Robnett
1307 N. 39th St. Suite 102
Nampa ID, 83687
208.284.7889
CK Engineering
13oo E.State St Suite 102 Eagle,ID 83616
208.639.1992 office
ENGINEERING P . C .
Civil Engineering * Project Management
Gramercy Subdivision - Meridian, Idaho
Drainage Calculation Narrative
Gramercy Subdivision is located southwest at 1925 Wells Ave Meridian. The
roads surrounding Gramercy Subdivision are private roads and all internal roads
are private roads. The storm drain system has been designed per ACHD
Standards and Specifications. All seepage beds have been designed to handle the
ioo-year storm event per BMP 20 in the ACHD Stormwater Design Manual —
Section 8200.
Private Storm Drain System:
Gramercy Subdivision has 15 drainage areas. Drainage Areas 1-3 drain to private Seepage
Bed #1. Drainage Areas 4-9 drain to private Seepage Bed #2. Drainage Areas 10-14 drain
to private Seepage Bed#3. Drainage Area#15 is self contained and is in the middle of the
common space in lot 42. There is one existing drainage area near the intersection of
Existing Private Drive 1, Existing Private Drive 2 and E. Ainsley Ln (Pvt.). This drainage
area drains to an existing catch basin and drainage facility. Please see the attached
Drainage Exhibit.
Private Seepage Bed#1:
Private Seepage Bed #1 will be a private permanent storm drain facility designed per
ACHD BMP20. It will accept runoff from Drainage Areas 1-3. These areas combine for a
total of 69,236 SF or 1.59 Acres. A 10 minute time of concentration was used for this
drainage area. The too year storm intensity is 2.58 in/hr. The C value for this area is
o.75. The total too year flow is 3.o8 CFS to Private Seepage Bed #1. The too year storm
volume is 4,120 CF. Private Seepage Bed #1 is 12.5'Wx5.5'Dx136'L. With a void ratio of
0.4 and a design infiltration rate of 5"/hr this bed will be sufficiently sized. With the too
year flow of 3.o8 CFS, one — l000 Gallon sand and grease trap will be needed for pre-
treatment. Please see the attached calculations for Private Seepage Bed #1 and Sand and
Grease Trap #1. Due to the proximity of Private Seepage Bed#1 to the water main in
Private Seepage Bed#2:
Private Seepage Bed #2 will be a private permanent storm drain facility designed per
ACHD BMP20. It will accept runoff from Drainage Areas 4-9. These areas combine for a
total of 139,959 SF or 3.21 Acres. A to minute time of concentration was used for this
drainage area. The too year storm intensity is 2.58 in/hr. The C value for this area is
o.75. The total too year flow is 6.22 CFS to Private Seepage Bed #2. The too year storm
volume is 8,328 CF. Private Seepage Bed #2 is 25'Wx5.o'Dx114'L. With a void ratio of
0.4 and a design infiltration rate of 3"/hr this bed will be sufficiently sized. With the too
year flow of 6.22 CFS, two — l000 Gallon sand and grease traps will be needed for pre-
treatment. Please see the attached calculations for Private Seepage Bed #2 and Sand and
Grease Trap #2.
CK Engineering
13oo E.State St Suite 102
Eagle,ID 83616
208.639.1992 office
ENGINEERING PECE
Civil Engineering * Project Management
Private Seepage Bed#3:
Private Seepage Bed #3 will be a private permanent storm drain facility designed per
ACHD BMP20. It will accept runoff from Drainage Areas 10-14.These areas combine for
a total of 48,424 SF or 1.11 Acres. A to minute time of concentration was used for this
drainage area. The ioo year storm intensity is 2.58 in/hr. The C value for this area is
o.75. The total ioo year flow is 2.15 CFS to Private Seepage Bed #3. The loo year storm
volume is 2,881 CF. Private Seepage Bed #3 is 15'Wx7.5'Dx57'L. With a void ratio of 0.4
and a design infiltration rate of 8"/hr this bed will be sufficiently sized.With the ioo year
flow of 2.15 CFS, one — l000 Gallon sand and grease trap will be needed for pre-
treatment. Please see the attached calculations for Private Seepage Bed #3 and Sand and
Grease Trap #3.
Attached:
1. Storm Drain Calculations for 3 Private Seepage Beds.
2. 11"x17"colored drainage exhibit.
3. Pipe Sizing Calculations.
4. Geotechnical Reports and GW Monitoring from Allwest
End Narrative
CK Engineering
13oo E.State St Suite 102
Eagle,ID 83616
208.639.1992 office
If-6- ENGINEERING P . C .
Civil Engineering * Project Management
DRAINAGE CALCULATIONS
CK Engineering 130o E.State St Suite 102 Eagle,ID 83616
208.639-1992 office
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 Gramercy Seepage Bed no.1
2 Is area drainage basin map provided? YES
(mop 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 Subbaslns F 1.
Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin
1 Subbasin 2 3 4 5 6 7 8 9 10
5 Area of Drainage Subbasin(SF or Acres) SF 16,858 26,775 25,603
Acres 1.59
6 Determine the Weighted Runoff Coefficient(C) 0.75 0.75 0.75
C=((C1xA1)+(C2xA2)+(CnxAn))/A Weighted Avgl 0.75
7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 user calculate
min [10 Min. Estimated Runoff_Coefficients for Various Surfac.
Type of Surface Runoff Coefficients"I
8 Determine the average rainfall Intensity(1)from IDF Curve based on Tc 1 2.58 in r Business
Downtown areas 0.70.0.95
9 Calculate the Post-Development peak discharge(QPeak) QpeA 3.09 cis _Urban neighborhoods 0.50-0,70
Residential
10 Calculate total runoff vol(V)(for sizing primary storage) V 4,120 ft Single Family 0.35-0.50 Multi-family0.60-0.75
V=CI(Tc=60)Ax3600 Residential rural 0.25-0.40
11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70
Enter Percentile Storm I(95th percentile=0.60 in) 95th Industrlal and Commercial
0.60 in Light areas 0.80
Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) V„ 2,575 ft' -Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cfs Parks,Cemeteries 0.10.0.25
Playgrounds 0.20.0.35
Railroad yard areas 0.20.0.40
13 Volume Summary Unimproved areas 0.10-0.30
Surface Storage:Basin Streets
Basin Forebay V 412 h' Asphalt 0.95
Concrete 0.95
Primary Treatment/StorageBasin V 3,708 It' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 4,120 W Gravel 0.75
Fields:Sandy soil soil Type
Slope A B C D
Flat:O-276 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:\SHANNON ROBNETT\2024 Grammercy Commons Multi Condos\Documents\DRAINAGE CALCS\SEEPAGE BED q1-08-11-2025 9/5/2025,2:29 PM
Version 10.0,May 2018
ACHD Calculation Sheet for Sand/Grease Traps
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.
User input in yellow cells.
1 Project Name Gramercy Seepage Bed no. 1
2 Enter number of Sand/Grease Traps(25 max) 1
Number of Peak Flow Baffle Throat Velocity Is the
Vault Size Spacing width Area(ft2) 0.5 fps Velocity
S/G Traps Q-cfs inch inch max. ok?
1000 G 1 3.08 20 48 6.67 0.46
Reference for Throat widths(inch)
Boise ADS
Vault Lar-ken WQU,
BMP 16
1000 G 48.0 50.5 n/a
1500 G 60.0 61.5 n/a
QU1000 n/a n/a 60
QU1500 n/a n/a 60
D:\SHANNON ROBNETT\2024 Grammercy Commons Multi Condos\Documents\DRAINAGE CALCS\SEEPAGE BED#1-08%T4ZM,2:29 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 ACHO 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 Gramercy Seepage Bed no.1
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.75 Unk to: [Qv��
5 Area A(Acres) 1.59 acres QV TRSS
6 Approved discharge rate(if applicable) 0.00 cfs
7 Is Seepage Bed in Common Lot? Yes V 4,120 It3 0%Sediment
8 Set Total Design Width of All Drain Rock W 12.5 ft
9 Set Total Design Depth of All Drain Rock D 5.5 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"dram rock and 3/4"Chips
11 Design Infiltration Rate(8 in/hr max) Perc 5.00 in/hr
12 Size of WQ Perf Pipe(Pert 180°) Dia pipe 18 in
13 Size of Overflow Perf Pipe(Perfs 3600),REQD if Q300>3 3 cfs in
14 Calculate Total Storage per Foot Spf 303 It,/ft
15 Calculate Design Length L 136 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 136 ft
17 Variable Infiltration Window W SWW 125 ft
18 Time to Drain 5.2 hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 116 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Ctperf=CdxAxV(2xgxH)
O tional Stara a Chambe►s
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 ft,
9 Volume Infiltration Vperc 0 ft3/hr
10 Time to Drain hours
90%volume in 48-hours minimum
D:\SHANNON ROBNETT\2024 Grammercy Commons Multi Condos\Documents\DRAINAGE CALCS\SEEPAGE BED#1-08-11-2025 9/5/2025,2:35 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(forpre-development flows,Increase number of storage facilities to create new tab)
User input in yellow cells.
1 Project Name Gramercy Seepage Bed q2
2 Is area drainage basin map provided? YES
(map must be included with stormwoter 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 Subbasms l
Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin
1 Subbasin 2 3 4 5 6 7 8 9 10
5 Area of Drainage Subbasin(SF or Acres) SF 18,878 13,162 22,665 46,349 21,356 17,549
Acres 3.21
6 Determine the Weighted Runoff Coefficient(C) 0.75 0.75 0.75 0.75 0.75 0.7S
C=[(C1xA1)+(C2xA2)+(CnxAn))/A Weighted Avg1 0.75
7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 user calculate
min [10 min. Estimated Runoff Coefficients for Various Surface
Type of Surface Runoff Coefficients"t
Determine the average rainfall Intensity(1)from IDF Curve based on Tc I 2.S8 In r Business
9 Calculate the Post-Development peak discharge(QPeak) Downtown areas 0.70-0.95
Qpeak 6.22 cfs Urban neighborhoods 0.50-0.70
Residential
30 Calculate total runoff vol(V)(for sizing primary storage) V 8 Single Family 0.35.0.50 328 Ft Multi-famll 0.60.0.75
V=CI(Tc=60)Ax3600 Residential rural 0.25.0.40
11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70
Enter Percentile Storm I(95th percentile=0.60 in) 95th 0.60 in Industrial and Commercial
Light areas 0.80
Enter Runoff Reduction Vol(95th Percentile=0.60-in x Area x C) V, 5,20S ft Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) cis Parks.Cemeteries 0.10.0.25
Playgrounds 0.20.0.35
Railroad yard areas 0.20.0.40
13 Volume Summary Unimproved areas 0.10-0.30
Surface Storage:Basin Streets
Basin Forebay V 833 ft Asphalt 0.95
Concrete 0.95
Primary Treatment/StorageBasin V 7,495 ft' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20Tab) V 8,328 ft' Gravel 0.75
Fields:Sandy soil 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.
Stee :>6% 0.13 0.18
Adapted from ASCE
D:\SHANNON ROBNETT\2024 Grammercy Commons Multi Condos\Documents\DRAINAGE CALCS\SEEPAGE BED#2 9-05-25 9/5/2025,2:30 PM
Version 10.0,May 2018
ACHD Calculation Sheet for Sand/Grease Traps
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.
User input in yellow cells.
1 Project Name Gramercy Seepage Bed no.2
2 Enter number of Sand/Grease Traps(25 max) 1
Number of Peak Flow Baffle Throat Velocity Is the
Vault Size P20
cing width Area(ftz) 0.5 fps Velocity
S/G Traps Q-cfsin
inch max. ok?
1000 G 2 6.22 48 13.33 0.47
Reference for Throat widths(inch)
Boise ADS
Vault Lar-ken WQU,
BMP 16
1000 G 48.0 50.5 n/a
1500 G 60.0 61.5 n/a
QU1000 n/a n/a 60
QU1500 n/a n/a 60
D:\SHANNON ROBNETT\2024 Grammercy Commons Multi Condos\Documents\DRAINAGE CALCS\SEEPAGE BED#2 9.09/V2025,2:30 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 CL,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 Gramercy Seepage Bed#2
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 075 Unk to: [Qv�
QV TR55
5 Area A(Acres) 3.21 acres
6 Approved discharge rate(if applicable) 0.00 cfs
7 Is Seepage Bed in Common Lot? Yes V 8,328 it, 0%Sediment
8 Set Total Design Width of All Drain Rock W 25.0 ft
9 Set Total Design Depth of All Drain Rock D 7.0 ft
Rock Only,Do Not Include Filter Sand Depth or Cover
10 Void Ratio of Drain Rock Voids 0.4
0.4 for 1.5"-2"drain rock and 3/4"Chips
11 Design Infiltration Rate(8 in/hr max) Perc 3.00 in/hr
12 Size of WQ Perf Pipe(Pert 1801) 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 73.3 ft'Ift
15 Calculate Design Length L 114 0 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 0 116.0 ft
17 Variable Infiltration Window W SWW 25.0 25.0 ft
18 Time to Drain 0.0 hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 0 116 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxV(2xgxH)
Optlonal Storage Chemtieis
Note:This assumes chambers are organized in a rectangular layout.
1-StormTech,
1 Type of Chambers SC740
2 Volume to Store V 8,328 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 112 ea
8 Area of Infiltration Aperc ft,
9 Volume Infiltration Vperc 0 ft3/hr
10 Time to Drain hours
90%volume in 48-hours minimum
D:\SHANNON ROBNETT\2024 Grammercy Commons Multi Condos\Documents\DRAINAGE CALCS\SEEPAGE BED#2 9-05-25 9/5/2025,2:30 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 Gramercy Seepage Bed#3
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 Subbasim
Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin Subbasin
1 Subbasin 2 3 4 5 6 7 8 9 10
5 Area of Drainage Subbasin(SF or Acres) SF 7,574 17,487 6,610 5,170 11,583
Acres 1.11
6 Determine the Weighted Runoff Coefficient(C) 0.75 0.75 0.75 0.75 0.75
C=[(C1xA1)+(C2xA2)+(CnxAn)(/A Weighted Avg1 0.75
7 Calculate Overland Flow Time of Concentration in Minutes(Tc)or use default 10 Fluser Calculate
min [10 ruin. Estimated Runoff Coefficients for Various Surface
Type of Surface Runoff Coefficients"(
8 Determine the average rainfall Intensity(1)from IDF Curve based on Tc 1 2.58 InJhr Business
Downtown areas 0.70.0.95
V Calculate the Post-Development peak discharge(QPeak) Qxax 2.15 cis Urban neighborhoods 0.50-0.70
Residential
Single Family 0.35-0.50
10 Calculate total runoff vol(V)(for sizing primary storage) V 2,881 ft Multl-famll 0.60.0.75
V=Cl(Tc=60)Ax3600 Residential rural 0.25.0.40
11 Calculate Volume of Runoff Reduction Vrr Apartment Dwelling Areas 0.70
Enter Percentile Storm 1(95th percentile=0.60 In) 95th 0.60 In Industrial and Commercial
Light areas 0.80
Enter Runoff Reduction Vol(95th Percentile=0.6134n x Area x C) V.. 2,801 ft Heavy areas 0.90
12 Detention:Approved Discharge Rate to Surface Waters(if applicable) rfs Parks,Cemeteries 0.10.0.25
Pla rounds 0.20.0.35
Rellroad yard areas 0.20.0.40
13 Volume Summary Unimproved areas 0.10-0.30
Surface Storage:Basin Streets
Basin Forebay V 288 h' Asphalt o 95
Concrete 0.95
Primary Treatment/Storage Basin V 2,593 ft' Brick 0.95
Subsurface Storage Roofs 0.95
Volume Without Sediment Factor(See BMP 20 Tab) V 2,881 it Gravel _ 0.75
Fields:Sandy soil Soil Type
Slope A B io
Flat:0.2% 0.04 0.07 Average:2-6% 0.09 0.12 Stet :>6% 0.13 0.18
Adapted from ASCE
D:\SHANNON ROBNETT\2024 Grammercy Commons Multi Condos\Documents\D RAI NAGE CALCS\SEEPAGE BED#3 9-05.25 9/5/2025,2:31 PM
Version 10.0,May 2018
ACHD Calculation Sheet for Sand/Grease Traps
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.
User input in yellow cells.
1 Project Name Gramercy Seepage Bed no.3
2 Enter number of Sand/Grease Traps(25 max) 1
Number of Peak Flow Baffle Throat Velocity Is the
Vault Size Spacing width Area(ftz) 0.5 fps Velocity
S/G Traps Q-cfs inch inch max. ok?
1000 G 1 2.15 20 48 6.67 0.32
Reference for Throat widths(inch)
Boise ADS
Vault Lar-ken WQU,
BMP 16
1000 G 48.0 50.5 n/a
1500 G 60.0 61.5 n/a
QU1000 n/a n/a 60
QU1500 n/a n/a 60
D:\SHANNON ROBNETT\2024 Grammercy Commons Multi Condos\Documents\DRAINAGE CALCS\SEEPAGE BED#3 9-09,/V2025,2:32 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 Gramercy Seepage Bed q3
2 Enter number of Seepage Beds(25 max) 1
3 Design Storm 100
4 Weighted Runoff Coefficient C 0.75 Unk to: [Q•v—�
5 Area A(Acres) 1.11 acres QV TR55
6 Approved discharge rate(if applicable) 0.00 cfs
7 Is Seepage Bed in Common Lot? Yes V 2,881 It, 0%Sediment
8 Set Total Design Width of All Dram Rock W 15.0 ft
9 Set Total Design Depth of All Drain Rock D 7.5 ft
Rock Only,Do Not Include Filter Sand Depth or Cover
30 Void Ratio of Drain Rock Voids 0.4
0.4 for 1.5"-2"dram rock and 3/4"Chips
11 Design Infiltration Rate(8 in/hr max) Perc 8.00 in/hr
12 Size of WQ Perf Pipe(Pert 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 50.2 ft'/ft
15 Calculate Design Length L 57 ft
Override Value Required for Chambers
16 Variable Infiltration Window L SWL 57 45.0 ft
17 Variable Infiltration Window W SWW 15.0 ft
18 Time to Drain 5.8 hours
90%volume in 48-hours minimum
19 Length of WQ&Overflow Perf Pipes 57 ft
20 Perf Pipe Checks.Qperf>=Qpeak;
where Qperf=CdxAxJ(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 ft'
3 Installed Chamber Width Cw 4.25 ft
Installed Chamber Depth Cd 2.50 ft
Installed Chamber Height Ch 7.12 ft
4 Chamber Void Factor
5 Chamber Storage Volume,Without Rock,Per Manuf 45.90 ft'/Unit
6 Chamber Storage Volume,With Rock,Per Manuf 74.90 ft'/Unit
7 Total Number of Units Required 0 ea
8 Area of Infiltration Aperc ftz
9 Volume Infiltration Vperc 0 ft'/hr
10 Time to Drain hours
90%volume in 48•hours minimum
D:\SHANNON ROBNETT\2024 Grammercy Commons Multi Condos\Documents\DRAINAGE CALCS\SEEPAGE BED k3 9-05-25 9/5/2025,2.33 PM
Version 10.0,May 2018
PRIVATE SEEPAGE BED 1
STORM INTENSITY GIVEN WITH TIME OF CONCENTRATION
10 min 2.58 (IN/HR)
RUNOFF COEFFICIANT PEAK DESIGN STORM RUNOFF
C= 0.75 Q= c(I)(A)
DRAIN AREA SIZE SF SIZE AC INTENSITY C BASIN PEAK RUNOFF CATCH BASIN
DA#1 16858 0.387 2.58 0.75 0.75 cfs CB#1
DA#2 26775 0.615 2.58 0.75 1.19 cfs CB#2
DA#3 25603 0.588 2.58 0.75 1.14 cfs CB#3
DA#4 0 0.000 2.58 0.75 0.00 cfs
DA#5 0 0.000 2.58 0.75 0.00 cfs
DA#6 0 0.000 2.58 0.75 0.00 cfs
DA#7 0 0.000 2.58 0.75 0.00 cfs
DA#8 0 0.000 2.58 0.75 0.00 cfs
DA#9 0 0.000 2.58 0.75 0.00 cfs
TOTAL: 69236 1.589 2.58 0.75 3.08 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 3.08 0.5 48" 60"
1000 gal 1500 gal
V=Q/A
Vprovided= 0.46
Vprovided<Vma. YES
GREASE TRAPS NEEDED= 1 1000 gal
Private Seepage Bed 2
STORM INTENSITY GIVEN WITH TIME OF CONCENTRATION
10 min 2.58 (IN/HR)
RUNOFF COEFFICIANT PEAK DESIGN STORM RUNOFF
C= 0.75 Q= c(I)(A)
DRAIN AREA SIZE SF SIZE AC INTENSITY C BASIN PEAK RUNOFF CATCH BASIN
DA#4 18878 0.433 2.58 0.75 0.84 cfs CB#4
DA#5 13162 0.302 2.58 0.75 0.58 cfs CB#5
DA#6 22665 0.520 2.58 0.75 1.01 cfs CB#6
DA#7 46349 1.064 2.58 0.75 2.06 cfs CB#7
DA#8 21356 0.490 2.58 0.75 0.95 cfs CB#8
DA#9 17549 0.403 2.58 0.75 0.78 cfs CB#9
TOTAL: 139959 3.213 2.58 0.75 6.22 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 6.22 0.5 48" 60"
1000 gal 1500 gal
V=Q/A
Vprovided= 0.93
Vprovided<Vma. NO
GREASE TRAPS NEEDED= 1 1000 gal
Private Seepage Bed 3
STORM INTENSITY GIVEN WITH TIME OF CONCENTRATION
10 min 2.58 (IN/HR)
RUNOFF COEFFICIANT PEAK DESIGN STORM RUNOFF
C= 0.75 Q= c(I)(A)
DRAIN AREA SIZE SF SIZE AC INTENSITY C BASIN PEAK RUNOFF CATCH BASIN
DA#10 11583 0.266 2.58 0.75 0.51 cfs CB#10
DA#11 7574 0.174 2.58 0.75 0.34 cfs CB#11
DA#12 17487 0.401 2.58 0.75 0.78 cfs CB#12
DA#13 6610 0.152 2.58 0.75 0.29 cfs CB#13
DA#14 5170 0.119 2.58 0.75 0.23 cfs CB#14
TOTAL: 48424 1.112 2.58 0.75 2.15 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 2.15 0.5 48" 60"
1000 gal 1500 gal
V=Q/A
Vprovided= 0.32
Vprovided<Vma YES
GREASE TRAPS NEEDED= 1 1000 gal
Channel Report
Hydraflow Express Extension for Autodesk®Civil 3130 by Autodesk,Inc. Thursday,Aug 212025
CB #1 to S&G Trap 1
Circular Highlighted
Diameter(ft) = 1.00 Depth (ft) = 0.68
Q (cfs) = 3.080
Area (sqft) = 0.57
Invert Elev (ft) = 2644.51 Velocity (ft/s) = 5.41
Slope (%) = 1.00 Wetted Perim (ft) = 1.94
N-Value = 0.012 Crit Depth, Yc (ft) = 0.76
Top Width (ft) = 0.93
Calculations EGL (ft) = 1.14
Compute by: Known Q
Known Q (cfs) = 3.08
Elev (ft) Section
2646.00
2645.50
2645.00
2644.50
2644.00 - - -
0 1 2 3
Reach (ft)
Channel Report
Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk, Inc. Friday,Sep 5 2025
PIPE FROM CB#6-S&G TRAP 2
Circular Highlighted
Diameter (ft) = 1.33 Depth (ft) = 1.06
Q (cfs) = 6.220
Area (sqft) = 1.19
Invert Elev (ft) = 2644.99 Velocity (ft/s) = 5.23
Slope (%) = 0.60 Wetted Perim (ft) = 2.94
N-Value = 0.012 Crit Depth, Yc (ft) = 1.00
Top Width (ft) = 1.07
Calculations EGL (ft) = 1.49
Compute by: Known Q
Known Q (cfs) = 6.22
Elev (ft) Section
2647.00
2646.50
lrz� v
2646.00
2645.50 'oo/
2645.00 Li
2644.50
2644.00
0 1 2 3 4
Reach (ft)
Channel Report
Hydraflow Express Extension for Autodesk®Civil 3D®by Autodesk,Inc. Friday,Sep 5 2025
PIPE FROM CB14 TO S&G TRAP 3
Circular Highlighted
Diameter (ft) = 1.00 Depth (ft) = 0.84
Q (cfs) = 2.150
Area (sqft) = 0.70
Invert Elev (ft) = 2646.36 Velocity (ft/s) = 3.05
Slope (%) = 0.30 Wetted Perim (ft) = 2.32
N-Value = 0.012 Crit Depth, Yc (ft) = 0.63
Top Width (ft) = 0.73
Calculations EGL (ft) = 0.98
Compute by: Known Q
Known Q (cfs) = 2.15
Elev (ft) Section Depth
2648.00 1.64
2647.50 1.14
v
2647.00 0.64
2646.50 0.14
2646.00 -0.36
2645.50 -0.86
0 1 2 3
Reach (ft)
ticENGINEERING P . C .
Civil Engineering * Project Management
DRAINAGE EXHIBIT
CK Engineering 130o E.State St Suite 102 Eagle,ID 83616
208.639-1992 office
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ticENGINEERING P . C .
Civil Engineering * Project Management
GEOTECHNICAL REPORT
CK Engineering 130o E.State St Suite 102 Eagle,ID 83616
208.639-1992 office
I ENVIRONMENTAL
TECHNICAL
ALLWEST MATERIALS OTESTING I SPECIAL INSPECTION
AN EMPLOYEE-OWNED COMPANY
February 12, 2021
Mike Chidester
Intermountain Pacific, LLC
2541 East Gala Street, Suite 310
Meridian, Idaho 83642
mikeRbristol-company c..
RE: Geotechnical Evaluation
Wells Avenue Multifamily Development
Meridian, Idaho
ALLWEST Project No. 520-448G
Mr. Chidester:
ALLWEST has completed the authorized geotechnical evaluation for the proposed Wells
Avenue Multifamily Development to be developed approximately 700 feet southwest of the
East Gala Street and South Wells Avenue intersection in Meridian, Idaho. The purpose of
this evaluation was to characterize subsurface soil conditions at the site and provide
geotechnical recommendations to assist planning, design, and construction of the proposed
development. Based on our evaluation,the site is suitable for the planned development. The
attached report presents the results of our field evaluation, laboratory testing, and our
recommendations.
Once final structural and development plans are provided for our review, we can provide
foundation-related recommendations in an addendum to this report. This additional service
will be provided on a time-and-expense basis.
We appreciate the opportunity to be of service to Intermountain Pacific, LLC. If you have
any questions or need additional information, please contact us at (208) 895-7898.
Sincerely,
ALLWEST y��CNs
F
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14253
OF IOt��
Adrian Mascorro, P.E. ' �y�
Area Manager
255 N. Linder Rd., Suite#100, Meridian, ID 83642
Phone: 208.895.7898 • Fax: 208.898.3959
Hayden, ID•Lewiston, ID•Meridian, ID•Spokane Valley,WA• Missoula, MT
www.allwesttesting.com
GEOTECHNICAL EVALUATION
WELLS AVENUE MULTIFAMILY DEVELOPMENT
MERIDIAN, IDAHO
ALLWEST PROJECT NO. 520-448G
February 12, 2021
Prepared for:
Intermountain Pacific, LLC
2541 East Gala Street, Suite 310
Meridian, Idaho 83642
Prepared By:
ALLWEST
255 North Linder Road, Suite 100
Meridian, Idaho 83642
A LWE T
WWW.ALLWESTTESTING.COM
TABLE OF CONTENTS
ALLWEST Project No. 520-448G
Wells Avenue Multifamily Development
Meridian, Idaho
Page
1.0 SCOPE OF SERVICES ........................................................................................2
2.0 PROJECT UNDERSTANDING.............................................................................2
3.0 FIELD EVALUATION PROCEDURES.................................................................3
4.0 SITE CONDITIONS ..............................................................................................3
4.1 General Geologic Conditions............................................................................. 3
4.2 General Soil Conditions.....................................................................................4
5.0 EXPLORATION AND SAMPLING .......................................................................4
5.1 Subsurface Soil Conditions ...............................................................................4
5.2 Subsurface Water.............................................................................................. 5
6.0 LABORATORY TESTING ....................................................................................5
7.0 CONCLUSIONS AND RECOMMENDATIONS ....................................................6
7.1 Grading and Drainage....................................................................................... 6
7.2 Site Preparation.................................................................................................6
7.3 Subgrade Stabilization ...................................................................................... 7
7.4 Excavation......................................................................................................... 8
7.5 Materials............................................................................................................ 8
7.6 Fill Placement and Compaction......................................................................... 9
7.7 Utility Trenches.................................................................................................. 9
7.8 Wet Weather Construction ................................................................................ 9
7.9 Cold Weather Construction ............................................................................. 10
7.10 Stormwater Disposal ..................................................................................... 10
7.11 Asphalt Pavements ....................................................................................... 11
8.0 ADDITIONAL RECOMMENDED SERVICES..................................................... 12
9.0 EVALUATION LIMITATIONS............................................................................. 13
Appendix A— Site Vicinity Map, Exploration Location Plan
Appendix B —Test Pit Logs, Unified Soil Classification System
Appendix C— Laboratory Test Results
GEOTECHNICAL I ENVIRONMENTAL
ALLWESTMATERIALS TESTING I SPECIAL INSPECTION
AN EMPLOYEE-OWNED COMPANY
Geotechnical Evaluation
Wells Avenue Multifamily Development
Meridian, Idaho
ALLWEST has completed the geotechnical evaluation for the proposed Wells Avenue
Multifamily Development planned approximately 700 feet southwest of the East Gala
Street and South Wells Avenue intersection in Meridian, Idaho. The general location
of the site is shown on Figure A-1 — Site Vicinity Map in Appendix A of this report. The
purpose of this evaluation was to identify subsurface soil conditions at the site, and
provide opinions and recommendations for the proposed development, relative to
earthwork, utilities, stormwater disposal, and pavement section design. This report
details the results of our field evaluation and presents recommendations to assist
planning, design, and construction.
1.0 SCOPE OF SERVICES
Our scope of services for the project included the following:
1) Prior to subsurface exploration, we visited the site to observe site accessibility
and to pre-mark exploration locations, as required by Idaho Digline.
2) Notified Idaho Digline to locate on-site utilities, as required by Idaho state law.
3) Subcontracted a backhoe and operator to observe the excavation of 8 test pits
throughout the site.
4) Visually described and classified the soils encountered within test pits in general
accordance with ASTM D 2487 and ASTM D 2488, which utilizes the Unified
Soil Classification System (USCS), and we logged the subsurface profiles. We
obtained soil samples within select test pits.
5) Performed seepage tests within select test pits to evaluate subsurface seepage.
We installed PVC pipes within select test pits for future groundwater monitoring.
6) Performed laboratory tests on select soil samples to assess some of the soil
engineering properties and characteristics.
7) Reviewed the results of the field evaluation and laboratory testing, performed
engineering analyses, and prepared this report with our field evaluation results,
subsurface logs, and geotechnical-related opinions and recommendations.
We provided our services for the project in general accordance with our geotechnical
proposal (520-448P) dated November 16, 2020.
2.0 PROJECT UNDERSTANDING
Based on electronic communication with you, which included an aerial image of the
project location comprising of three parcels, we understand the project will consist of
an approximate 7-acre multifamily development with associated infrastructure,
GEOTECHNICAL I ENVIRONMENTAL
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Wells Avenue Multifamily Development Page 3
Meridian, Idaho
stormwater disposal facilities, and asphalt-paved parking and drive-lanes. The
development will consist of multiple 3- or 4-story-tall apartment buildings with
elevators; as such, elevator pits will be required.
Final structural and development plans were not available at the time of this report. As
such, foundation-related recommendations are not included as a part of this
evaluation. Once final plans are developed for our review, we can provide foundation-
related recommendations for final construction, to assist structural design. Final
foundation-related recommendations can be provided as an addendum to this
geotechnical evaluation. Providing foundation-related recommendations were not a
part of the scope of services for this report; once requested, we can provide this
information on a time-and-expense basis. Depending on the final type and size of the
structures, this may require additional exploration, testing, and evaluation to provide
structure-specific foundation-construction recommendations. The need for additional
evaluation will be determined once final structural plans are provided for our review.
3.0 FIELD EVALUATION PROCEDURES
To complete this evaluation, on January 20, 2021 we observed the excavation of 8 test
pits to a maximum depth of 14 feet. We did observe excavation refusal within two of
the test pits within strongly cemented soils. We identified subsurface soil conditions,
logged the subsurface soil profiles, and obtained soil samples for laboratory testing.
We performed field seepage testing within select test pits to help evaluate subsurface
soil seepage. At completion of exploration, the test pits were loosely backfilled with
excavated soil approximately level with existing ground surfaces. The approximate test
pit locations are shown on Figure A-2 — Exploration Location Plan in Appendix A.
4.0 SITE CONDITIONS
At the time of our field exploration, the site consisted of undeveloped dirt lots with
sparse surficial vegetation. The site was bordered by residential apartment buildings
to the south, Mountain View High School baseball fields to the west, and commercial
developments to the north and east.
4.1 General Geologic Conditions
The geologic conditions at the site are mapped as Gravel of Sunrise terrace (Qsg) on
the "Geologic Map of the Boise Valley and Adjoining Area, Western Snake River Plain,
Idaho" (by Othberg and Stanford, 1992). Surficial soils consist of 3 to 6 feet of loess
overlying sandy pebble and cobble gravel approximately 44 feet thick. This area
consists of the third terrace above the floodplain.
The soils encountered within test pits are generally consistent with geologic mapping.
GEOTECHNICAL I ENVIRONMENTAL
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4.2 General Soil Conditions
The USDA Natural Resources Conservation Service (NRCS), which represents the
upper 5 feet of soil profile, has mapped the soils on the site as Elijah silt loam and Abo
silt loam. The parent materials are lacustrine deposits, loess, and/or alluvium
consisting of loam, silt loam, clay loam, silty clay loam, fine gravelly coarse sandy loam,
gravelly sand, and cemented material.
The soils encountered within test pits are generally consistent with NRCS mapping.
5.0 EXPLORATION AND SAMPLING
We observed the excavation of the test pits using a Case 580C backhoe with a 3-foot-
wide bucket. We obtained soil samples at select depths within test pits for further
identification and laboratory testing. We performed seepage testing within select test
pits throughout the site. The test pit locations were identified on-site with flagged-
stakes or white PVC pipes.
We obtained Google Earth latitude and longitude coordinates of test pit locations with
a hand-held cellular device; these coordinates can be found on individual test pit logs
in the Appendix B, and should be considered accurate to the degree implied by the
method used.
5.1 Subsurface Soil Conditions
At the time of exploration, the site was mainly bare of vegetation and contained sparse
areas with surficial vegetation. Significant roots and vegetation were not observed
within the test pits. In general, the subsurface soils within the observed test pits
consisted of surficial lean clay, underlain by silts and silty sands with varying
thicknesses and levels of cementation, overlying silty gravels and poorly-graded
gravels with varying amounts of silt.
Specific descriptions of soils observed throughout our field exploration follow:
Poorly-graded gravel with silt and sand (filly — At the ground surface in test pits TP-1
and -2, we observed undocumented fill soils consisting of poorly-graded gravel with silt
and sand down to depths of/z to 1'/2 feet below ground. We described fill poorly-graded
gravel with silt and sand as tan, medium dense, and moist.
Lean clay with sand (CL) (native) — Underlying undocumented fill gravels within test
pits TP-1 and -2, and at the ground surface within the other test pits, we observed
native lean clay with sand (with no sand in test pits TP-7 and -8) down to depths of 1'/2
to 3 feet below ground. We described lean clays as brown, stiff, and moist.
Silt with sand, sandy silt (ML) — Underlying lean clay soils, we observed silt with sand
or sandy silt down to depths of 4 to 5 feet below ground. We described silt soils as
brown, medium dense, and moist.
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Silty sand (SM) — Underlying the silt soils, we observed silty sand down to depths of 6
to 10 feet below ground. We described silty sand as tan to brown, dense to very dense,
and moist. The silty sand soils contained varying amounts and thicknesses of weak to
very strong cementation. Within test pits TP-1, -5, -6, and -8, we observed sandy silts
or silts with sand underlying silty sand soils.
Silty gravel with sand (GM), poorly-graded gravel with silt and sand (GP-GM) —
Underlying silty sands, sandy silts, or silts with sand, we typically observed silty gravel
with sand and/or poorly-graded gravel with silt and sand down 11'/2 to maximum
excavation depths of up to 14 feet below ground. We described "dirty" gravels as
brown, medium dense, and moist.
Poorly-graded gravel with sand (GP) — Underlying the poorly-graded gravels with silt
and sand within test pits TP-2 and -4, we observed poorly-graded gravel with sand to
maximum excavation depths of up to 14 feet below ground. We described "clean"
gravels as tan, medium dense, and moist.
Detailed soil descriptions, depths, and notes are presented on individual test pit logs
in Appendix B. The descriptive soil terms used on the test pit logs, and in this report,
can be referenced by the USCS. A copy of the USCS is included in Appendix B.
Subsurface conditions may vary between exploration locations. Such changes in
subsurface conditions may not be apparent until construction, and if they change
significantly from those observed, then accordingly, construction timing, plans, and
costs may change.
5.2 Subsurface Water
At the time of exploration, we did not encounter groundwater within test pits down to a
maximum depth of 14 feet. Groundwater in the area may be influenced by irrigation,
precipitation, on-site construction, and development to adjacent sites. Subsurface
water will fluctuate throughout the different seasons of the year, but will most likely be
affected during seasonal snow melt and irrigation seasons (March to October).
We installed PVC pipes within 4 test pits for future groundwater monitoring.
Groundwater monitoring should be accomplished throughout snowmelt and irrigation
seasons to verify the presence or absence of groundwater on-site.
6.0 LABORATORY TESTING
We performed laboratory testing to supplement field classifications and to assess
some of the soil engineering properties and parameters. The laboratory tests
conducted included moisture content (ASTM D 2216), gradation (ASTM D 1140),
Atterberg limits (ASTM D 4318), and California bearing ratio (CBR) (ASTM D 1883).
Laboratory test results are summarized in Appendix C, and are also presented on test
pit logs in Appendix B.
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7.0 CONCLUSIONS AND RECOMMENDATIONS
Based on our observations, testing, and evaluation, in our opinion the site is suitable
for the planned development, provided our recommendations are adhered to. The
following recommendations are presented to assist with planning, design, and
construction of the development, relative to earthwork, infrastructure, stormwater
disposal, and asphalt pavements.
These recommendations are based on our understanding of the proposed
development, the conditions observed within exploration locations, laboratory test
results, and engineering analysis. If the scope of construction changes, or if conditions
are encountered during construction that differ from those described herein, we should
be notified so we can review our recommendations and provide revisions, if necessary.
Foundation-related recommendations are not provided as part of this evaluation, but
can be provided as an addendum to this report, once final structural/development plans
are provided for our review.
7.1 Grading and Drainage
We did not review final grading plans for this development, but we anticipate site
grading will consist of cuts and fills of up to 2 feet or less. We should be notified if actual
site grading varies significantly from this stated information, as it may affect our
recommendations herein.
Final site grading should be such that surfaces slope away from development areas.
7.2 Site Preparation
• Prior to conducting site grading, surficial soil containing vegetation, roots, and
organics (if vegetation growth occurs prior to development) should be removed
below proposed site grading fill areas, pavement areas, and any other
development areas.
• Loose test pit backfill will settle with time, so where any test pits are located
below proposed structures or any development areas, the loose test pit backfill
soil must be re-excavated its entire depth and replaced with suitably moisture-
conditioned and compacted fill soil. Existing over-excavated soils can be reused
to backfill the test pits, provided the soils are not overly saturated, and they can
achieve the required compaction criteria, as required in section 7.6 Fill
Placement and Compaction. We recommend test pit areas be accurately
surveyed so that they may be located and remediated, prior to earthwork
construction and development.
• After site stripping, any over-excavations, loose test pit remediation, and prior
to site grading, utility backfill, or roadway construction, the exposed subgrades
should be proof-rolled with a minimum of 5-ton vibratory roller, or with a vibratory
GEOTECHNICAL I ENVIRONMENTAL
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hoe-pack, to confirm subgrade stability. This will also assist in identifying any
soil associated with loose test pit backfills or wet/soft soils due to precipitation.
If native subgrade soil is observed to significantly deflect or pump, it should be
over-excavated and replaced with properly compacted fills, or stabilized to firm,
non-yielding soil as recommended in section 7.3 Subgrade Stabilization.
7.3 Subgrade Stabilization
If the subgrade soils are observed to pump or deflect significantly during grading, the
subgrades should be stabilized prior to fill placement. Subgrades may be stabilized
using geosynthetic reinforcement in conjunction with imported granular structural fill.
The required thicknesses of granular structural fill (used in conjunction with
geosynthetic reinforcement)will be dependent on the construction traffic loading, which
is unknown at this time. Therefore, a certain degree of trial and error may be required
during construction to verify recommended stabilization section thicknesses.
Geosynthetic reinforcement should consist of Tensar TX-160 or equivalent.
Alternatives to Tensar TX-160 must be approved by the geotechnical engineer prior to
use on site. The following recommendations are provided for subgrade stabilization
using geosynthetic reinforcement.
• Geosynthetic reinforcement materials should be placed on a non-disturbed
subgrade with smooth surface. Loose and disturbed soil should be removed
prior to placement of geosynthetic reinforcement materials.
• A minimum weight 4-ounce, non-woven filter fabric should be placed on the
undisturbed subgrade. The geosynthetic reinforcement should be placed
directly on top of the filter fabric. The filter fabric and geosynthetic reinforcement
should be unrolled in the primary direction of fill placement and should be over-
lapped at least 3 feet, or follow manufacturer's recommendations.
• The geosynthetic materials should be pulled taut to remove slack.
• Construction equipment should not be operated directly on the geosynthetic
materials. Fill should be placed from outside the excavation to create a pad to
operate equipment on. We recommend a minimum of 12 to 18 inches of
granular structural fill be placed over the geosynthetic reinforcement before
operating construction equipment on the fill. Low-pressure, track-mounted
equipment should be used to place fill over the geosynthetic reinforcement.
• Granular structural fill placed directly over geosynthetic reinforcement should be
properly moisture-conditioned prior to placement, and once placed, be statically
rolled. This section is the "bridge" section over soft subgrades.
GEOTECHNICAL I ENVIRONMENTAL
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• After the first "bridge" lift has been placed, the remaining fill material above the
"bridge" section should be compacted to structural fill criteria in section 7.6 Fill
Placement and Compaction, utilizing vibratory compaction methods.
• Vibration should be discontinued if it reduces the subgrade stability. If
compaction criterion is not met within the fill lift above the "bridge" section, the
"bridge" section thickness is not enough, and subgrade stabilization must be
attempted again with a greater "bridge" section.
The geotechnical engineer or a representative of the geotechnical engineer must be
on-site during subgrade stabilization to verify our recommendations are followed, and
to provide additional recommendations, as needed.
7.4 Excavation
Generally, excavation of on-site soil can be accomplished with typical excavation
equipment. Where strong cementation is encountered, excavation may require larger
excavation equipment. We recommend excavations greater than 4 feet deep be sloped
no steeper than 1.5H:1 V (horizontal to vertical). Alternatively, deeper excavations may
be shored or braced in accordance with Occupational Safety and Health Administration
(OSHA) specifications and local codes. Regarding trench wall support, the site soil is
considered Type C soil according to OSHA guidelines. Ultimately, the contractor is
responsible for site safety, excavation configurations and following OSHA guidelines.
7.5 Materials
Stripped soils and soils containing vegetation or debris are only suitable for use in non-
structural landscape areas. Existing on-site soils may be reused as site grading fill,
provided they are stockpiled separately, they meet the criteria below, and they are
compacted as required in this report. Imported granular soils should be free of
organics, debris and other deleterious material and meet the following criteria. Import
materials should be approved by ALLWEST prior to delivery to the site.
Fill Type Criteria
Site Grading Fill Maximum size <_ 6 inches; 0
Retained on /4 inch sieve < 30o ; Liquid limit < 50/o
Maximum size <_ 6 inches;
Granular Structural Fill, Retained on 3/4-inch sieve < 30%;
Granular Subbase Passing No. 200 sieve <_ 15%; Non-plastic
Alternatively, meet ISPWC section 801 6 inches
Maximum size <_ 1 inch;
Crushed Base Course Retained on 3/4-inch sieve < 10%;
Passing No. 200 sieve < 10%; Non-plastic
Alternatively, meet ISPWC section 802 (Type I
Maximum size 5 2 inches;
Utility Trench Backfill Retained on 3/4-inch sieve < 30%;
Passing No. 200 sieve <_ 10%; Non-plastic
Alternatively, meet ISPWC section 305 (Type 1)
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7.6 Fill Placement and Compaction
Fill should be placed in lift thicknesses which are appropriate for the compaction
equipment used. Typically, 8- to 12-inch-thick loose-lifts are appropriate for typical
rubber-tire and steel-drum compaction equipment. Lift thicknesses should be reduced
to 4 inches for hand-operated compaction equipment. Fill should be moisture-
conditioned to within 2% of the optimum moisture content prior to placement to facilitate
compaction. Fill should be compacted to the following percentages of the maximum
dry density as determined by ASTM D 1557 (modified Proctor).
Fill Area Compaction
(0
Sub grade Proof-roll'
Site Grading Fill / Granular Structural Fill / Pavements 95
Granular Subbase/ Crushed Base Course 95
Utility Trench Backfill 92
'Subgrade stability must be verified and approved by a representative of the geotechnical engineer prior
to any fill placement or construction.
7.7 Utility Trenches
Support soils for underground utilities will most likely consist of lean clays, sandy silts
and/or silty sands. These soils should provide adequate support for utilities, provided
utility subgrades are compacted utilizing vibratory methods, such as with a large
vibratory hoe-pack. If utility pipe subgrades are soft, yielding, and/or saturated at the
time of construction, subgrade over-excavation and replacement with competent
structural fill may be required below utilities. If support soils yield and/or are saturated
at the time of construction, we should be notified to observe these soils and provide
additional recommendations, as necessary.
We strongly recommend backfilling trench excavations with fill soils which meet criteria
in section 7.5 Materials, as on-site fine-grained soils (silts and clays) may be difficult to
moisture-condition and compact in utility trenches.
7.8 Wet Weather Construction
We recommend earthwork for this site be scheduled for the drier seasons of the year.
If construction is undertaken in wet periods of the year, it will be important to slope the
ground surface to provide drainage away from construction. If construction occurs
during or immediately after excessive precipitation, it may be necessary to over-
excavate and replace saturated subgrade soil, which might otherwise be suitable.
The on-site soils are sensitive to disturbance when wet. If these soils become wet and
unstable, we recommend construction traffic is minimized where these soils are
exposed. Low ground-pressure (tracked) equipment should be used to minimize
disturbance. Soft and disturbed subgrade areas should be excavated to undisturbed
soil and backfilled with structural fill.
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In addition, it should be noted the on-site soils tend to have notable adhesion when
wet and may be easily transported off-site by construction traffic.
7.9 Cold Weather Construction
The on-site soils are frost susceptible. If site grading and construction are anticipated
during cold weather, we recommend good winter construction practices be observed.
Snow and ice should be removed from excavated and fill areas prior to additional
earthwork or construction. Pavement and flatwork portions of the construction should
not be placed on frozen ground, nor should the supporting soils be permitted to freeze
during or after construction. Frozen soils must not be used as fill.
If native subgrades, or suitably moisture-conditioned and compacted fill lifts, will be left
exposed to freezing temperatures overnight, those areas should be protected with a
minimum of 12 inches of loose soil, or covered with heated construction blankets, so
construction subgrades do not freeze. Any frozen soils should be removed prior to
additional fill placement or construction of any kind.
Earthwork construction during cold inclement weather will require a higher level of
attention and detail to achieve required earthwork construction and compaction criteria
and may lead to additional earthwork requirements and extended construction
schedules.
7.10 Stormwater Disposal
During our field exploration we performed seepage testing within test pits TP-1 at 12
feet, TP-4 at 11'/2 feet, and TP-6 at 10 feet, within "dirty" poorly-graded gravel with silt
and sand, "clean" poorly-graded gravel with sand, and silt with sand soils, respectively.
We obtained field-measured seepage rates of 5 inches per hour(in/hr) in "dirty" gravel,
greater than 15 in/hr in "clean" gravel, and 3 in/hr in silt with sand.
Due to the variability and strong nature of calcium carbonate cementation (as observed
within silty sand soils) and induration (as observed within silt with sand in TP-5), we do
not recommend stormwater disposal be planned within or above silt with sand, sandy
silt, or silty sand soils, as cemented and indurated soils will exhibit very poor and
inconsistent soil seepage.
Stormwater disposal facilities must be constructed below the previously mentioned soil
types, and into non-cemented gravel-type soils. Refer to individual test pit logs in
Appendix B to verify depths and contacts of cemented and indurated soils, as well as
contact depths of gravel-type soils.
Based on our evaluation and experience with similar soils, the following recommended
and allowable seepage rates should be utilized for on-site stormwater disposal.
• Silty gravel with sand, poorly-graded gravel with silt and sand ......... 2 in/hr
• "Clean" poorly-graded gravel with sand ....................................... 8 in/hr
GEOTECHNICAL I ENVIRONMENTAL
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Wells Avenue Multifamily Development Page 11
Meridian, Idaho
Stormwater disposal facilities should be constructed a minimum of 1 foot into the
receiving soil. Where "clean" gravels with sand soils were not encountered during our
field exploration (due to excavation refusal on cemented soils or due to maximum
backhoe equipment reach), we anticipate "clean" gravels with sand will be encountered
with depth. "Clean" gravel with sand depths may be determined by utilizing a large
track-mounted excavator capable of reaching excavation depths of up to 20 feet. This
can be accomplished prior to site construction, to assist civil design, or it can be
determined at the time of construction. We remain available to assist with this
endeavor, if requested.
Seepage beds should be "burrito wrapped" or otherwise maintain a separation/filter
fabric between native fine-grained soils and drain rock/filter sand to help prevent fine-
soil migration into drainable/filtering media. During construction, ALLWEST should
observe stormwater disposal facility subgrades to establish if the suitable receiving soil
is encountered, to confirm the allowable seepage rate, and to ensure the
separation/filter fabric has been properly installed.
The proper separation from bottom of stormwater disposal facilities and seasonal high
groundwater should be maintained. At the time of exploration, we did not observe
groundwater within test pits to a maximum exploration depth of up to 14 feet below
existing ground surfaces.
We installed slotted PVC pipes within 4 test pits throughout the site for future
groundwater monitoring. At a minimum, these pipes should be monitored during
seasonal snow melt and irrigation seasons (March to October), or as required by
governing jurisdictions, to confirm the presence or absence of seasonal high
groundwater throughout the site. We can provide monthly groundwater monitoring
services, at your request.
7.11 Asphalt Pavements
Prior to pavement section construction, the pavement subgrade should be proof-rolled
as recommended in section 7.2 Site Preparation. Parking and access lanes should be
designed for a 20-year Equivalent Single Axle Load (ESAL) of 33,000, which is
equivalent to a traffic index (TI) of 6. If actual traffic conditions are different than what
is stated, we should be notified so that we may modify our pavement section design.
The pavement subgrades consisted of lean clays with sand, or silts with sand. As such,
we performed California bearing ratio (CBR) testing on a lean clay with sand soil to
assist pavement section design. Based on laboratory testing, we obtained a CBR of
12.7 for the lean clay with sand, which is equivalent to an R-value of 32. We observed
lean clay soils that did not contain much sand content; due to that and based our
experience with clay-type soils and performance of asphalt pavements, we utilized an
R-value of 15 for lean clay for pavement section design.
GEOTECHNICAL I ENVIRONMENTAL
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AN EMPLOYEE-OWNED COMPANY
Geotechnical Evaluation ALLWEST Project No. 520-448G
Wells Avenue Multifamily Development Page 12
Meridian, Idaho
The following flexible asphalt pavement section design is provided adhering to the
Idaho Transportation Department (ITD), which utilizes the AASHTO pavement design
methodology. Based on subgrade preparation requirements, design assumptions, and
frost-depth considerations, we recommend the following pavement sections be utilized
for subdivision roadway construction for local and collector roadways.
Asphalt Crushed Granular
Pavement Application Concrete Base Course Subbase
inches (inches) (inches)
Parking and Access Lanes 2.5 4 11
Base course and subbase should conform to the material recommendations as noted
in this report and should be placed over a properly prepared subgrade. The subgrade,
subbase, and base course surfaces should slope at no less than 2% away from the
crown of the roadway to help reduce the potential for surface water infiltration into the
underlying pavement subgrade.
Asphalt concrete pavement should be compacted to minimum of 92% of the Rice
density. Crack maintenance on pavements should be performed at a minimum of every
3 years, or when cracking is evident. Crack sealing will help reduce surface water
infiltration into the supporting soils.
8.0 ADDITIONAL RECOMMENDED SERVICES
To maintain continuity and efficiency, we recommend ALLWEST be retained to provide
observations and testing throughout construction. As an independent testing company,
ALLWEST can document the recommendations included in this report are properly
implemented, provide quality control testing, and observe earthwork for conformance
to project specifications. As a minimum, we recommend the following testing and
observations be provided by ALLWEST:
• Observe site stripping, any over-excavations, compaction of test pit backfill, and
any other soil backfills.
• Observe subgrade proof-rolling and approve subgrades prior to fill construction,
materials placement, or pavement section construction.
• Observe removal of disturbed soil and subgrade stabilization, if required.
• Observe seepage bed subgrades, confirm subsurface seepage rates by
performing seepage testing within stormwater disposal facility locations, and
observe overall construction.
• Conduct compaction testing of fill for general site grading, utilities, and
pavement areas.
• Observe placement of/test asphalt for compaction, oil content and gradation.
GEOTECHNICAL I ENVIRONMENTAL
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AN EMPLOYEE-OWNED COMPANY
Geotechnical Evaluation ALLWEST Project No. 520-448G
Wells Avenue Multifamily Development Page 13
Meridian, Idaho
If we are not retained to provide the recommended construction observation and
testing services, we shall not be held responsible for earthwork-related construction
errors or omissions.
9.0 EVALUATION LIMITATIONS
This report has been prepared to assist planning, design, and construction of the
proposed Wells Avenue Multifamily Development in Meridian, Idaho. Our services
consist of professional opinions and conclusions made in accordance with generally
accepted geotechnical engineering principles and practices in our local area at the time
this report was prepared. This acknowledgement is in lieu of all warranties either
expressed or implied.
Once final structural plans are provided for our review, we can provide foundation-
related construction recommendations as an addendum to this report.
The following plates complete this report:
Appendix A— Site Vicinity Map, Exploration Location Plan
Appendix B — Test Pit Logs, Unified Soil Classification System
Appendix C — Laboratory Test Results
GEOTECHNICAL I ENVIRONMENTAL
ALLWESTMATERIALS TESTING I SPECIAL INSPECTION
AN EMPLOYEE-OWNED COMPANY
Appendix A
A-1 — Site Vicinity Map
A-2 — Exploration Location Plan
ALLWEST
Y
f • -
I +
1 � \
�i.
T ws
C.
1 Y • 2.
�l W
LIU
1 m i
Figure A-1 - Site Vicinity Map
Geotechnical Evaluation
Wells - Multifamily Development
Meridain, Idaho
Linder255 N. Road, Suite 100 -nt: Intermountian
Meridian, •. • 83642 ProjectNo.: 1 44:
• - 1: :• :•Ti
: 1: :•: • • �. - -• 1
! 4 }
r
LJ Tp-
■ s. 4 y
slp
Or
r f
■ :gyp o
r
i
Legend
0 Approximate location of test pit observed by ALLWEST.
Slotted PVC pipe installed in test pit.
Figure A-2 - Exploration Location Plan
ALLWEST Geotechnical Evaluation
Wells Ave Multifamily Development
Meridain, Idaho
255 N. Linder Road, Suite 100 Client: Intermountian Pacific, LLC
Meridian, Idaho 83642 Project No.: 520-448G
Phone: (208) 895-7898 Fax: (208) 898-3959 Date: February 2021
Appendix B
Test Pit Logs
Unified Soil Classification System (USCS)
ALLWEST
ALLWEST DATE STARTED: 1/20/2021 TP - 1
DATE FINISHED: 1/20/2021 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Anish Pathak
TEST PIT LOG WEATHER:Sunny
PROJECT:520-448G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Wells Avenue Multifamily Development
LATITUDE(DEGREES):N 43°35'17.6388"(43.588233°)
= LONGITUDE(DEGREES):W-116°21'52.0704" (-116.364464°) W
H U U a
o- j TOTAL DEPTH: 13.5' Q
0CL
DESCRIPTION W `� NOTES
Poorly-graded GRAVEL with silt and sand(Fill);tan, medium
dense,moist
00<
FILL00<
100<
Lean CLAY with sand(Native);brown,stiff, moist
2
CL
3 SILT with sand;brown,medium dense, moist
4 ML
5 Silty SAND;tan to brown,dense,moist T.
6 sM ... moderate cementation observed from 5 to 7 feet
7 Sandy SILT; brown, medium dense, moist
8 BG Passing No.200 sieve=56%
ML Moisture content=22%
9
1 Silty GRAVEL with sand;brown,medium dense, moist
°
GM
1 °
Poorly-graded GRAVEL with silt and sand; brown, medium
dense,moist °
1 o Field seepage test performed at 12 feet.
Field seepage rate=5 in/hr.
GP-GM
oflc
O
1
°
Test pit terminated at 13-1/2 feet.
Slotted PVC pipe installed to 13-1/2 feet.
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 1/20/2021 TP - 2
DATE FINISHED: 1/20/2021 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Anish Pathak
TEST PIT LOG WEATHER:Sunny
PROJECT:520-448G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Wells Avenue Multifamily Development
LATITUDE(DEGREES):N 43°35'17.664"(43.58824°)
= LONGITUDE(DEGREES):W-116°21'48.0492" (-116.363347°) Lu
H U U a
o- j TOTAL DEPTH: 14' Q
0CL
DESCRIPTION W `o NOTES
Poorly-graded GRAVEL with silt and sand(Fill);tan, medium
FILL dense,moist
Lean CLAY with sand(Native);brown,stiff, moist
1
CL
2 SILT with sand;brown,medium dense, moist
3—
ML
4 Silty SAND;tan to brown,dense,moist
5 ... moderate cementation observed from 4 to 6 feet
6
SM
7
9 Silty GRAVEL with sand;brown,medium dense, moist
°
1 GM °
0
1 Poorly-graded GRAVEL with silt and sand; brown, medium
dense,moist
0
1 GP-GM
0
O
0
1 Poorly-graded GRAVEL with sand,tan,medium dense, moist
GP
O
Q
14— Test pit terminated at 14 feet.
Slotted PVC pipe installed to 14 feet.
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 1/20/2021 TP - 3
DATE FINISHED: 1/20/2021 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Anish Pathak
TEST PIT LOG WEATHER:Sunny
PROJECT:520-448G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Wells Avenue Multifamily Development
LATITUDE(DEGREES):N 43°35'15.1368"(43.587538°)
= LONGITUDE(DEGREES):W-116°21'52.1244" (-116.364479°) W
H U) U a
o j TOTAL DEPTH:6' Q
0CL
DESCRIPTION W `o NOTES
Lean CLAY with sand(Native);brown,stiff, moist
CL
1
SILT with sand;brown,medium dense, moist
2-
3— ML
4
Silty SAND;tan to brown,very dense,moist
5
sM .strong to very strong cementation observed from 4-1/2 to 6
feet
6 Test pit terminated at 6 feet due to refusal on strong cementation.
7
8
9
1
1
1
1
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 1/20/2021 TP - 4
DATE FINISHED: 1/20/2021 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Anish Pathak
TEST PIT LOG WEATHER:Sunny
PROJECT:520-448G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Wells Avenue Multifamily Development
LATITUDE(DEGREES):N 43°35'14.8668"(43.587463°)
= LONGITUDE(DEGREES):W-116°21'47.4336" (-116.363176°) W
H U U a
o j TOTAL DEPTH: 12.5'
CL Q
0
DESCRIPTION W `� NOTES
Lean CLAY with sand(Native);brown,stiff, moist
1
Passing No.200 sieve=80%
cL BK LL=42, PL=24,PI= 18
CBR=12.7
2
3 Sandy SILT; brown, medium dense, moist BG Passing No.200 sieve=54%
Moisture content=31%
4 ML
5 Silty SAND;tan to brown,dense,moist
6 ... moderate cementation observed from 5 to 7 feet
7 BG Passing No.200 sieve=44%
sM Moisture content=20%
8
9
1 Poorly-graded GRAVEL with silt and sand; brown, medium
dense,moist
GP-GM G
1 0
0
Poorly-graded GRAVEL with sand;tan,medium dense, moist Field seepage test performed at 11-1/2 feet.
0 Field seepage rate=>15 in/hr.
1 GP p
Q
Test pit terminated at 12-1/2 feet.
Slotted PVC pipe installed to 12-1/2 feet.
1
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 1/20/2021 TP - 5
DATE FINISHED: 1/20/2021 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Anish Pathak
TEST PIT LOG WEATHER:Sunny
PROJECT:520-448G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Wells Avenue Multifamily Development
LATITUDE(DEGREES):N 43°35'12.5952"(43.586832°) (0
= LONGITUDE(DEGREES):W-116°21'52.1064" (-116.364474°) Lu
H U) U a
o j TOTAL DEPTH: 13' Q
0CL
DESCRIPTION W `o NOTES
Lean CLAY with sand(Native);brown,stiff, moist
1 cL
2 SILT with sand;brown,medium dense, moist
3
ML
4
Silty SAND;tan to brown,dense,moist
5
6 ...weak to moderate cementation observed from 4-1/2 to 8 feet
SM
7
9 SILT with sand;brown,medium dense, moist
1
1 ML ... induration observed from 9 to 13 feet
BG
1
13-- Test pit terminated at 13 feet.
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 1/20/2021 TP - 6
DATE FINISHED: 1/20/2021 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Anish Pathak
TEST PIT LOG WEATHER:Sunny
PROJECT:520-448G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Wells Avenue Multifamily Development
LATITUDE(DEGREES):N 43°35'12.4764"(43.586799°) (0
= LONGITUDE(DEGREES):W-116°21'46.8792" (-116.363022°) Lu
H U) U a
o j TOTAL DEPTH: 12' Q
0CL
DESCRIPTION W `o NOTES
Lean CLAY with sand(Native);brown,stiff, moist
1 cL
2 Sandy SILT; brown, medium dense, moist
3 ML
4 Silty SAND;tan to brown,dense,moist
5
... moderate cementation observed from 4 to 7 feet
6
SM
7
g SILT with sand;brown,medium dense, moist
BG Passing No.200 sieve=72%
Moisture content=25%
1 Field seepage test performed at 10 feet.
ML Field seepage rate=3 in/hr.
1
1 Test pit terminated at 12 feet.
1
1
—75 WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 1/20/2021 TP - 7
DATE FINISHED: 1/20/2021 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Anish Pathak
TEST PIT LOG WEATHER:Sunny
PROJECT:520-448G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Wells Avenue Multifamily Development
LATITUDE(DEGREES):N 43°35'10.1076"(43.586141°) (0
= LONGITUDE(DEGREES):W-116°21'52.1244" (-116.364479°) W
H U) U a
0- j TOTAL DEPTH:8' Q
0CL
DESCRIPTION W `o NOTES
Lean CLAY(Native); brown,stiff, moist
1 cL Passing No.200 sieve=88%
BG Moisture content=23%
ILL=34, PL=21,PI= 13
2 SILT with sand;brown,medium dense, moist
BG Passing No.200 sieve=83%
Moisture content=20%
3
ML
4
5 Silty SAND;tan to brown,dense to very dense,moist
6
sM ... moderate to very strong cementation observed from 5 to 8 feet BG Passing No.200 sieve=23%
Moisture content=28%
7
8 Test pit terminated at 8 feet due to refusal on strong cementation.
9
1
1
1
1
1
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
ALLWEST DATE STARTED: 1/20/2021 TP - 8
DATE FINISHED: 1/20/2021 EXCAVATOR: CASE 580C
MERIDIAN,IDAHO OPERATOR:Steve Just
EXCAVATION METHOD:3-ft wide bucket
GEOTECHNICAL SECTION COMPANY:Just Dig'It Exc.
LOGGER:Anish Pathak
TEST PIT LOG WEATHER:Sunny
PROJECT:520-448G NOTES:See Figure A-2 in Appendix A for approximate test pit location.
Wells Avenue Multifamily Development
LATITUDE(DEGREES):N 43°35'10.2156"(43.586171°) (0
= LONGITUDE(DEGREES):W-116°21'46.8432" (-116.363012°) Lu
H U) U a
o j TOTAL DEPTH: 14' Q
0CL
DESCRIPTION W `o NOTES
Lean CLAY(Native); brown,stiff, moist
1 cL
2 Sandy SILT; brown, medium dense, moist
3 ML
4 Silty SAND;tan to brown,dense to very dense,moist
5
...weak to moderate cementation observed from 5 to 6-1/2 feet
6
7 SM
...strong cementation observed from 6-1/2 to 9 feet
8
9
1 SILT with sand;brown,medium dense, moist
BG
1
ML
1
Silty GRAVEL with sand;brown,medium dense, moist
0
1
GM
0
14— Test pit terminated at 14 feet.
Slotted PVC pipe installed to 14 feet.
WATER LEVELS
a WHILE EXCAVATING
Y AT COMPLETION
1 AFTER EXCAVATING Sheet 1 of 1
Unified Soil Classification System
MAJOR DIVISIONS SYMBOL TYPICAL NAMES
Well-Graded Gravel,
CLEAN GW Gravel-Sand Mixtures.
GRAVELS GP Poorly-Graded Gravel,
GRAVELS Gravel-Sand Mixtures.
Silty Gravel,
COARSE GRAVELS GM Gravel-Sand-Silt Mixtures.
GRAINED WITH FINES GC Clayey Gravel,
SOILS Gravel-Sand-Clay Mixtures.
Well-Graded Sand,
CLEAN SW Gravelly Sand.
SANDS SP Poorly-Graded Sand,
SANDS Gravelly Sand.
Silty Sand,
SANDS L SM Sand-Silt Mixtures.
WITH FINES Sc Clayey Sand,
Sand-Clay Mixtures.
ML Inorganic Silt,
SILTS AND CLAYS Silty or Clayey Fine Sand.
Inorganic Clay of Low to
LIQUID LIMIT CL Medium Plasticity,
LESS THAN 50% Sandy or Silty Clay.
FINE OL Organic Silt and Clay of Low
GRAINED Plasticity.
SOILS Inorganic Silt, Elastic Silt,
SILTS AND CLAYS MH Micaceous Silt,
Fine Sand or Silt.
LIQUID LIMIT CH Inorganic Clay of High Plasticity,
GREATER THAN 50% Fat Clay.
OH Organic Clay of Medium to High
Plasticity.
Highly Organic Soils PT Peat, Muck and Other Highly
Organic Soils.
ALLWEST
Appendix C
Laboratory Test Results
ALLWEST
Summary of Laboratory Test Results
Moisture Gradation Atterberg Limits
Test Pit Depth Content Liquid Plasticity CBR Sample Classification
No. (Feet) (%) Gravel Sand Silt/Clay Limit Index (USCS)
N N N M) N
TP-1 8 - 8.5 22 44 56 Sandy SILT (ML)
TP-4 1 - 2 20 80 42 18 12.7 Lean CLAY with sand (CL)
TP-4 3 - 3.5 31 46 54 Sandy SILT (ML)
TP-4 7 - 7.5 20 56 44 Silty SAND (SM)
TP-6 9.5 - 10 25 28 72 SILT with sand (ML)
TP-7 1 - 1.5 23 12 88 34 13 Lean CLAY(CL)
TP-7 2.5 - 3 20 17 83 SILT with sand (ML)
TP-7 6.5- 7 28 77 23 Silty SAND (SM)
Table C-1
255 N. Linder Road, Suite 100 • Meridian, Idaho 83642 • (208) 895-7895 • Fax (208) 898-3959
www.allwesttesting.com
This report may not be reproduced, except in full, without the permission of ALLWEST.
LIQUID AND PLASTIC LIMITS TEST REPORT
60
Dashed line indicates the approximate
upper limit boundary for natural soils
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LIQUID LIMIT
0 MATERIAL DESCRIPTION LL PL PI %<#40 %<#200 USCS
• Lean Clay with sand 42 24 18 80% CL
c■ Lean Clay 34 21 13 88% CL
CD
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` Project No. 520-448G Client: Intermountain Pacific,LLC Remarks:
aD Project: Wells Avenue Multifamily Development
c *Location: TP-4 Depth: F-2'
■Location: TP-7 Depth: F-1.5'
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ALLWEST
E
Figure C-1
Tested By: C. Downes Checked By:J.Varozza
California Bearing Ratio
ASTM D 1883
Project: Wells Avenue Multifamily Development Project No.: 520-448G
Client: Intermountain Pacific, LLC Location: TP-4 @ 1 - 2 ft
Date Tested: 2/8/2021 Compaction Method: ASTM D1557
Tested By: C. Downes Classification: Lean Clay with sand (CL)
275
250
225
200
a
175
c
150
'a
c
125
VI
L PSI @ 0.1 inch penetration= 127
N 100
75
50
25
0
0 0.1 0.2 0.3 0.4 0.5
Penetration(inches)
CBR @ 0.1 Inch Penetration: 12.7 Maximum Dry Unit Weight (pcf): 106.3
Swell (%): 2.4 Optimum Water Content (%): 17.4
Dry Unit Weight Before Soak(pcf): 95.8 Remold of Max. Dry Unt Wgt(%): 90
Water Content Before Soak (%): 19.3
Water Content After Soak, Top 1 Inch (%): 33.6
Surcharge (psf): 50
Immersion Period (hrs): 96
Reviewed By: James Varozza
Figure: C-2
►LL1 EST
255 N Linder Rd,Suite 100•Meridian,ID 83642•(208)895-7898•Fax(208)898-3959
www.allwesttesting.com
This report shall not be reproduced except in full without the permission of ALLW EST.
Test Pit: TP-1 TP-2 TP-4 TP-8
Feet Below Ground Surface
Date
3/15/2021 >11.8 >13 >11.2 >13.8
4/12/2021 >11.8 >13 >11.2 >13.8
5/19/2021 >11.8 >13 >11.2 >13.8
6/15/2021 >11.8 >13 >11.2 >13.8
7/19/2021 >11.8 >13 >11.2 >13.8
8/16/2021 >11.8 >13 >11.2 >13.8
9/16/2021 >11.8 >13 >11.2 >13.8
10/19/2021 >11.8 >13 >11.2 >13.8
11/23/2021 >11.8 >13 >11.2 >13.8
3/25/2022 >11.8 >13 >11.2 >13.8
Table 1
ALLWEST Ground Water Monitoring
Gramercy Commons (Wells Avenue Multifamily)
Meridian, Idaho
255 N. Linder Road, Suite 100 Client Name: Intermountain Pacific, LLC
Meridian, Idaho 83642 Project No.: 520-448G
Phone: 208-895-7898 Fax: 208-898-3959 Date: March 2022
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p Approximate location of test pit observed by ALLWEST.
Slotted PVC pipe installed in test pit.
Figure A-2 - Exploration Location Plan
ALLWEST Geotechnical Evaluation
Wells Ave Multifamily Development
Meridain, Idaho
255 N. Linder Road, Suite 100 Client: Intermountian Pacific, LLC
Meridian, Idaho 83642 Project No.: 520-448G
Phone: (208) 895-7898 Fax: (208) 898-3959 Date: February 2021