HomeMy WebLinkAboutMS 16-06; CARLSBAD VILLAGE LOFTS; PROPOSED CARLSBAD VILLAGE LOFTS; 2019-05-22. I CI E ~IN(-Y Construction Testing & Engineering, Inc.
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' Inspection j Testing I Geotechnical I Environmental & Construction Engineering I Civil Engineering I Surveying
May 22, 2019 CTE Job No. 10-14798G
Wermers Properties
Attn: Austin Wermers
5080 Shoreham Place, Suite 105
San Diego California 92122
(858) 623-4958 Via Email: AustinW@wermerscompanies.com
Subject: Proposed Carlsbad Village Lofts
Percolation Testing and Limited Infiltration Evaluation
1044 Carlsbad Village Drive (APNs: 203-320-3200, -3900, & -4700)
Carlsbad, California
Mr. Wermers:
As requested, Construction Testing and Engineering, Inc. (CTE) provides percolation and
calculated infiltration rates pertinent to the proposed stormwater BMP's at the subject site. This
testing was performed in general accordance with the San Diego Region Model BMP (Best
Management Practice) Design Manual", Appendix C and Appendix D, dated February 2016.
The work included test hole excavation, percolation testing, and preparation of this summary
report. The attached Figure 1 shows the layout and approximate percolation test locations.
References are included in Appendix A.
1.0 PERCOLATION TESTING
The test locations and associated depths were determined by the civil engineer and from
evaluation of project plans provided by the general contractor. The test holes were excavated
with a drill rig as well as manually operated auger equipment to depths ranging from
approximately 1.7 to 5.6 feet below the ground surface. The evaluation was performed in
accordance with Appendix C of the San Diego Region Model BMP Design Manual
"Geotechnical and Groundwater Investigation Requirements", dated February 2016.
1.1 Field Exploration
Six percolation test holes were excavated with a truck-mounted drill rig equipped with eight-inch
diameter augers on December 24, 2015 and four supplemental manually augured six-inch
diameter test holes were excavated on May 12, 2019. The test holes were excavated such that
the percolation testing was performed in the areas of proposed BMP's and to characterize
representative infiltration conditions at the site.
1441 Montiel Road, Suite 115 1 Escondido, CA 92026 1 Ph (760) 746-4955 1 Fax (760) 746-9806 1 www.cte-inc.net
I
Percolation Testing and Limited Infiltration Evaluation Page 2
Proposed Carlsbad Village Lofts
1044 Carlsbad Village Drive (APNs: 203-320-3200, -3900, & -4700)
Carlsbad, California
May 22, 2019 CTE Job No. 10-14798G
1.2 Soil Materials
According to geologic mapping by Kennedy and Tan (2008), and as observed and described in
the referenced soils report, the site is generally underlain by Quaternary Undocumented Fill and
Old Paralic Deposits, Unit 6.
The percolation tests were performed in Quaternary Undocumented Fill (Qudf) and Quaternary
Old Paralic Deposits-Unit 6 (Qop6). The Qppf generally consisted of silty to clayey fine to
medium grained sand. The Qop6 consisted of silty fine to medium grained sand to poorly graded
fine to medium grained sand.
1.3 Percolation Test Methods
The percolation tests were performed in accordance with methods ,approved by the San Diego
BMP Design Manual approximately 18 to 21 hours after the. four-hour presoak period.
Percolation test results and calculated infiltration rates are presented below in Table 2.0. Field
Data and percolation to infiltration calculations are included in Appendix B.
2.0 CALCULATED INFILTRATION RATE
As per the San Diego Region BMP design documents (2016) infiltration rates are to be evaluated
using the Porchet Method. San Diego BMP design documents utilize the Porchet Method
through guidance of the County of Riverside (2011). The intent of calculating the infiltration
rate is to take into account bias inherent in percolation test borehole sidewall infiltration that
would not occur at a basin bottom where such sidewalls are not present.
The infiltration rate (Ii) is derived by the equation:
it AH itr2 60 = AH 60 r
At(itr2 +2itrHavg) At(r+2Hav9)
Where:
It = tested infiltration rate, inches/hour
AH = change in head over the time interval, inches
At = time interval, minutes
* r = effective radius of test hole
Havg = average head over thetime interval, inches
Given the measured percolation rates, the calculated infiltration rates are presented with and
without a Factor of Safety applied in Table 2.0 below. The civil engineer of record completed
Form 1-9 of the San Diego Region Best Management Practice Design Manual, Appendix D and
determined that a factor of safety of 2.81 is appropriate for the site.
\\ESC_SERVERkProjects\10- 14798G\InfiItration\Revised Letter\Ltr Infiltration Evaluation Results (5-19) Revised May 17.doc
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Percolation Testing and Limited Infiltration Evaluation Page 3
Proposed Carlsbad Village Lofts
1044 Carlsbad Village Drive (APNs: 203-320-3200, -3900, & -4700)
Carlsbad, California
May 22, 2019 CTE Job No. 10-14798G
TABLE 2.0
RESULTS OF PERCOLATION TESTING WITH FACTOR OF SAFETY APPLIED
Test Depth Soil Type* Percolation Infiltration Infiltration Rate
Test Rate (inches Rate (inches with FOS of 2.81
Location per hour) per hour) Applied (inches
(USCS per hour)
(inches) Case Classification)
P-i 24 III Qop 3.500 5.895 2.098
P-2 20 III Qudf 0.500 0.421 0.150
P-3 27 III Qudf 2.500 3.636 1.294
P-4 25 III Qop 1.625 1.576 0.561
P-5 27 III Qop 0.625 0.122 0.044
P-6 59 III Qop 5.250 0.139 0.049
P-7 67 III Qop 2.000 0.333 0.119
P-8 67 III Qop 2.500 0.423 0.150
P-9 43 III Qop 4.125 0.731 0.260
P-10 38 III Qop 6.500 1.228 0.437
NOTES: Water level was measured from a fixed point at the top of the hole.
Weather was clear during the percolation testing.
Qudf = Quaternary Undocumented Fill
Quaternary Old Paralic Deposits
The test holes P-i to P-6 were eight inches in diameter.
The test holes P-7 to P- 10 were six inches in diameter.
3.0 CONCLUSIONS
The percolation test results were obtained in general accordance with regional standards.
However, it should be noted that percolation test results can significantly vary laterally and
vertically due to slight changes in soil type, degree of weathering, secondary mineralization, and
other physical and chemical variabilities. As such, the test results are considered to be an
estimate of percolation and converted infiltration rates for design purposes. No guarantee is
made based on the percolation testing related to the actual functionality or longevity of
associated infiltration basins or other BMP devices designed from the presented infiltration rates.
\\ESCSERVER\Projects\10- 14798G\Infi1tration\Revised Letter\Ltr Infiltration Evaluation Results (5-19) Revised May I7.doc
Percolation Testing and Limited Infiltration Evaluation Page 4
Proposed Carlsbad Village Lofts
1044 Carlsbad Village Drive (APNs: 203-320-3200, -3900, & -4700)
Carlsbad, California
May 22, 2019 GTE Job No. 10-14798G
Based on the analysis performed using Worksheet 1-8, a result of No Infiltration is recommended
for the site due to the designation on Geotracker as an open Cleanup Program (DEH Case #
DEH2019-LSAM-000529) and site history (former Chevron station with leaking underground
storage tanks). As such, it is recommended that all stormwater collection bioretention basins be
fully lined and connected to appropriate drains/subdrains that discharge to an appropriate off-site
location. Infiltrating through tree wells and permeable pavements is also not recommended.
Recent testing (AEC May 3, 2019) has only shown limited low-level contamination based on
nine shallow, gas-probes. However, based on previous site usage, noted LUST classification, and
recent analytical results showing some low-level contamination, there is a possibility/likelihood
that localized residual contaminated soils remain on site. As such, the no-infiltration
recommendation would appear to be appropriate.
4.0 LIMITATIONS
This letter is subject to the same limitations as previous GTE geotechnical documents issued for
the subject project. GTE's conclusions and recommendations are based on an analysis of the
observed conditions. If conditions different from those described in this report are encountered
during construction, this office should be notified and additional recommendations, if required,
will be provided.
\\ESC_SERVER\Projects\IO- 14798G\Infiltration\Revised Letter\Ltr_Infiltration Evaluation Results (5-19) Revised May I 7.doc
I) 0
Percolation Testing and Limited Infiltration Evaluation Page 5
Proposed Carlsbad Village Lofts
1044 Carlsbad Village Drive (APNs: 203-320-3200, -3900, & -4700)
Carlsbad, California
May 22,2019 CTE Job No. 10- 1 4798G
The opportunity to be of service on this project is appreciated. If you have any questions
regarding this report, please do not hesitate to contact the undersigned.
Respectfully submitted,
CONSTRUCTION TESTING & ENGINEERING, INC. A L
No.1890 C'
ENGINEERING
GEOLOGIST
Jay F. Lynch, CEG# 2665 QFC
Principal Engineering Geologist
No.2603 - CER11RED 9 ENGINEERING I -
* GEOLOGIST *
Exp. 3/31/2
CM2'
Aaron J. Beeby, CEG #2603
Project Geologist
Z-- o NO6
EXP. 9/30/19
CoimJ. Kenny, RCE #84406
Senior Engineer 4 OFC
Attachments:
Figure 1 Percolation Test Location Map
Appendix A References
Appendix B Percolation to Infiltration Calculations and Field Data
Appendix C Worksheet 1-8
Appendix D Form 1-9
\\ESC_SERVER\Projects\1O- 14798G\Infi1tration\Revised Letter\Ltr_Infi1tration Evaluation Results (5-19) Revised May 17.doc
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APPP1IflTY A
REFERENCES
Construction Testing & Engineering, Inc. (CTE), 2019, Grading Plan Review, Proposed
Carlsbad Village Lofts, 1044 Carlsbad Village Drive (APN: 203-320-3200, & -4700)
Carlsbad, California, Job No. 10-14798G. dated April 9.
Construction Testing & Engineering, Inc. (CTE), 2019, Response to the City of Carlsbad
Review Comment, Proposed Carlsbad Village Lofts, 1044 Carlsbad Village Drive (APN:
203-320-3200, & -4700) Carlsbad, California, Job No. 10-14798G, dated March 22.
Construction Testing & Engineering, Inc. (CTE), 2019, Updated Preliminary
Geotechnical Recommendations and Grading Plan Review, Proposed Carlsbad Village
Lofts, 1044 Carlsbad Village Drive (APN: 203-320-3200, & -4700) Carlsbad, California,
Job No. 10-14798G, dated February 28.
Construction Testing & Engineering, Inc. (CTE), 2015, Geotechnical Investigation,
Proposed Carlsbad Village Lofts, 1044 Carlsbad Village Drive (APN: 203-320-3200, & -
4700) Carlsbad, California, Job No. 10-12371G, dated January 27.
Kennedy, M.P. and Tan, S.S., 2008, "Geologic Map of the Oceanside 30' x 60'
Quadrangle, California", California Geological Survey, Map No. 2, Plate 1 of 2.
Riverside, County of (rev. 9/2011) "Low Impact Development Design Handbook."
San Diego, County of, January 2016, "BMP Design Manual, Appendix C and Appendix
D."
SB&O, Inc., 2019, Precise Grading Plans for: Carlsbad Village Lofts, GR 2018-0050,
Drawing No. 515-5A, Project No. MS 16-06.
San Diego, County of, July 2014, "Low Impact Development Handbook: Stormwater
Management Strategies."
S
APPENDIX B
PERCOLATION TO INFILTRATION CALCULATIONS AND FIELD DATA
Project: Carlsbad Apartments
Project No.: 10-14798G Tables P-i
Percolation Field Data and Calculated Rates
P-i Total Depth: 24 inches
Test Water Water Incremental Percolation Percolation Time Interval Test Refill Level Level Water Level Rate Rate Time Initial/Start End/Final Change
(minutes) Depth /Inches Depth finches Depth finches (inches) inches/minute inches/hour
8:55:00 Initial None 23.63 initial -
9:25:00 30 24.25 23.63 26.50 2.88 0.096 5.750
9:55:00 30 12.0625 24.25 26.00 1.75 0.058 3.500
10:25:00 30 23.9375 12.06 25.63 13.56 0.452 27.125
10:55:00 30 23.8125 23.94 25.50 1.56 0.052 3.125
11:25:00 30 23.3125 23.81 25.25 1.44 0.048 2.875
11:55:00 30 23.5 23.31 25.19 1.88 0.063 3.750
12:25:00 30 23.5625 23.50 25.25 1.75 0.058 3.500
12:55:00 30 12 23.56 25.31 1.75 0.058 3.500
P-2 Total Depth: 20 inches
Test Water Water Incremental Percolation Percolation Time Interval Test Refill Level Level Water Level Rate Rate Time Initial/Start End/Final Change
(minutes) Depth finches Depth /Inches Depth finches (inches) inches/minute inches/hour
8:50:00 Initial None 19.63 initial -
9:20:00 30 19.625 19.63 19.88 0.250 0.008 0.500
9:50:00 30 19.4375 19.63 19.63 0.000 0.000 0.000
10:20:00 30 19.375 19.44 19.75 0.313 0.010 0.625
10:50:00 30 19.125 19.38 19.63 0.250 0.008 0.500
11:20:00 30 19.0625 19.13 19.38 0.250 0.008 0.500
11:50:00 30 19.25 19.06 19.25 0.188 0.006 0.375
12:20:00 30 19.125 19.25 19.56 0.313 0.010 0.625
12:50:00 30 NO 19.13 19.38 0.250 0.008 0.500
I P-3 Total Depth: 27 inches I
Water Water
Test Refill Level Level
Initial/Start End/Final
Depth /Inches Depth /Inches Depth /Inches
None 27.56 initial
27.75 27.56 29.19
27.625 27.75 29.00
27.75 27.63 28.88
27.1875 27.75 29.00
26.0625 27.19 28.38
27.0625 26.06 28.31
26.9375 27.06 28.44
NO 26.94 28.19
Water Water
Test Refill Level Level
Initial/Start End/Final
Depth /Inches Depth /Inches Depth /Inches
None 24.56 initial
24.125 24.56 26.38
23.9375 24.13 25.31
24.1875 23.94 25.00
24.3125 24.19 25.06
23.75 24.31 25.31
23.4375 23.75 24.63
24.125 23.44 24.38
NO 24.13 24.94
Incremental Percolation Percolation Water Level Rate Rate Change
(inches) inches/minute inches/hour
1.63 0.054 3.250
1.25 0.042 2.500
1.25 0.042 2.500
1.25 0.042 2.500
1.19 0.040 2.375
2.25 0.075 4.500
1.38 0.046 2.750
1.25 0.042 2.500
Fotal Deoth: 25 inches
Incremental Percolation Percolation Water Level Rate Rate Change
(inches) inches/minute inches/hour
1.81 0.060 3.625
1.19 0.040 2.375
1.06 0.035 2.125
0.88 0.029 1.750
1.00 0.033 2.000
0.88 0.029 1.750
0.94 0.031 1.875
0.81 0.027 1.625
Time
9:15:00
9:45:00
10:15:00
10:45:00
11:15:00
11:45:00
12:15:00
12:45:00
P-4
Time
8:40:00
9:10:00
9:40:00
10:10:00
10:40:00
11:10:00
11:40:00
12:10:00
12:40:00
Test
Interval
Time
(minutes)
30
30
30
30
30
30
30
30
Test
Interval
Time
(minutes)
Initial
30
30
30
30
30
30
30
30
Test Water Water
Interval Test Refill Level Level
Time Initial/Start End/Final
(minutes) Depth /Inches Depth /Inches Depth finches
Initial None 19.13 initial
30 19.1875 19.13 19.69
30 18.6875 19.19 19.69
30 18.6875 18.69 19.19
30 18.875 18.69 19.13
30 18.8125 18.88 19.38
30 18.75 18.81 19.25
30 18.875 18.75 19.13
30 NO 18.88 19.19
Test Water Water
Interval Test Refill Level Level
Time Initial/Start End/Final
(minutes) Depth /Inches Depth finches Depth finches
Initial None 22.56 initial
30 20.25 22.56 28.19
30 20.1875 20.25 24.63
30 20.4375 20.19 23.81
30 20.875 20.44 23.50
30 21 20.88 23.63
30 20.8125 21.00 23.69
30 20.9375 20.81 23.63
30 NO 20.94 23.56
Total Depth: 27.25 inches
Incremental Percolation Percolation Water Level Rate Rate Change
(inches) inches/minute inches/hour
0.56 0.019 1.125
0.50 0.017 1.000
0.50 0.017 1.000
0.44 0.015 0.875
0.50 0.017 1.000
0.44 0.015 0.875
0.38 0.013 0.750
0.31 0.010 0.625
Total Depth: 59 inches
Incremental Percolation Percolation Water Level Rate Rate Change
(inches) inches/minute inches/hour
5.63 0.188 11.250
4.38 0.146 8.750
3.63 0.121 7.250
3.06 0.102 6.125
2.75 0.092 5.500
2.69 0.090 5.375
2.81 0.094 5.625
2.63 0.088 5.250
p-s
Time
9:05:00
9:35:00
10:05:00
10:35:00
11:05:00
11:35:00
12:05:00
12:35;00
Time
9:00:00
9:30:00
10:00:00
10:30:00
11:00:00
11:30:00
12:00:00
12:30:00
13:00:00
67 inches
Water Water
Test Refill Level Level
Initial/Start End/Final
Depth /Inches Depth finches Depth /Inches
None 58.50 initial
58.5 58.50 60.00
NO 58.50 59.50
58.875 59.50 60.38
NO 58.88 59.88
58.625 59.88 60.63
58 58.63 60.00
NO 58.00 59.00
NO 59.00 60.00
Water Water
Test Refill Level Level
Initial/Start End/Final
Depth finches Depth finches Depth /Inches
None 59.00 initial
NO 59.00 59.63
58.875 59.63 60.25
NO 58.88 59.75
58.875 59.75 60.13
59 58.88 60.00
59 59.00 60.13
59 59.00 60.38
NO 59.00 60.25
Incremental Percolation Percolation Water Level Rate Rate Change
(inches) inches/minute inches/hour
1.50 0.050 3.000
1.00 0.033 2.000
0.88 0.029 1.750
1.00 0.033 2.000
0.75 0.025 1.500
1.38 0.046 2.750
1.00 0.033 2.000
1.00 0.033 2.000
Total Depth: 67 inches
Incremental Percolation Percolation Water Level Rate Rate Change
(inches) inches/minute inches/hour
0.63 0.021 1.250
0.63 0.021 1.250
0.88 0.029 1.750
0.38 0.013 0.750
1.13 0.038 2.250
1.13 0.038 2.250
1.38 0.046 2.750
1.25 0.042 2.500
Test
Time Interval
Time
(minutes)
Initial
8:30:00 30
9:00:00 30
9:30:00 30
10:00:00 30
10:30:00 30
11:00:00 30
11:30:00 30
12:00:00 30
P-8
Test
Time Interval
Time
(minutes)
8:02:00 Initial
8:32:00 30
9:02:00 30
9:32:00 30
10:02:00 30
10:32:00 30
11:02:00 30
11:32:00 30
12:02:00 30
rA
Test Water Water
Interval Test Refill Level Level
Time Initial/Start End/Final
(minutes) Depth /Inches Depth /Inches Depth /inches
Initial None 34.63 initial
30 33.5 34.63 38.13
30 34.875 33.50 36.75
30 35 34.88 37.75
30 34.75 35.00 37.88
30 35 34.75 37.88
30 35 35.00 37.50
30 35 35.00 37.19
30 NO 35.00 37.06
Total Depth: 43 inches
Incremental Percolation Percolation Water Level Rate Rate Change
(inches) inches/minute inches/hour
3.50 0.117 7.000
3.25 0.108 6.500
2.88 0.096 5.750
2.88 0.096 5.750
3.13 0.104 6.250
2.50 0.083 5.000
2.19 0.073 4.375
2.06 0.069 4.125
T,,i Q .,-krn
F-9
Time
8:04:00
8:34:00
9:04:00
9:34:00
10:04:00
10:34:00
11:04:00
11:34:00
12:04:00
p-b
Test Water Water
Interval Test Refill Level Level
Time Initial/Start End/Final
(minutes) Depth finches Depth /Inches Depth /Inches
Initial None 29.63 initial
30 29.25 29.63 32.63
30 30 29.25 32.88
30 29.875 30.00 34.25
30 29.875 29.88 34.50
30 30 29.88 33.75
30 30 30.00 33.88
30 29.9375 30.00 33.13
30 NO 29.94 33.19
Incremental Percolation Percolation Water Level Rate Rate Change
(inches) inches/minute inches/hour
3.00 0.100 6.000
3.63 0.121 7.250
4.25 0.142 8.500
4.63 0.154 9.250
3.88 0.129 7.750
3.88 0.129 7.750
3.13 0.104 6.250
3.25 0.108 6.500
Time
8:06:00
8:36:00
9:06:00
9:36:00
10:06:00
10:36:00
11:06:00
11:36:00
12:06:00
11 [IJ
Percolation Rate Conversion P-i [ Percolation Rate Conversion P-2
Inches Inches -
Time Interval, At= 30 Time Interval, At= 30
Final Depth of Water, Df= 25.31 Final Depth of Water, Df= 19.38
Test Hole Radius, r = 4 Test Hole Radius, r = 4
Initial Depth to Water, Do= 23.56 Initial Depth to Water, Do= 19.13
Total Depth of Test Hole, Di = 23.625 Total Depth of Test Hole, Di 19.625
Ho= 0.0625 in Ho 0.5 in
Hf= -1.6875 in Hf= 0.25 in
AH = AD = 1.75 in AH = AD = 0.25 in
Havg -0.8125 in Havg 0.375 in
It j 5.89jin/hr It= 0.42
Percolation Percolation Rate Conversion P-3 Percolation Rate Conversion P-4
Inches Inches
Time Interval, At= 30 Time Interval, At= 30
Final Depth of Water, Df= 28.19 Final Depth of Water, Df= 24.94
Test Hole Radius, r = 4 Test Hole Radius, r = 4
Initial Depth to Water, Do = 26.94 Initial Depth to Water, Do = 24.13
Total Depth of Test Hole, Di 27.25 Total Depth of Test Hole, Di = 24.5625
Ho 0.3125 in Ho 0.4375 in
Hf= -0.9375 in Hi -0.375 in
AH = AD = 1.25 in AH = AD 0.8125 in
Havg -0.3125 in Havg = 0.03125 in
It= [ 2.9631in/hr It= 1.600lin/hr
Percolation Rate Conversion P-5 Percolation Rate Conversion P-6
Inches Inches
Time Interval, At= 30 Time Interval, At= 30
Final Depth of Water, Df= 19.19 Final Depth of Water, Df= 23.56
Test Hole Radius, r = 4 Test Hole Radius, r = 4
Initial Depth to Water, Do= 18.88 Initial Depth to Water, Do = 20.94
Total Depth of Test Hole, Di = 27.25 Total Depth of Test Hole, Di = 59
Ho= 8.375 in Ho= 38.0625 in
Hf= 8.0625 in Hf= 35.4375 in
AH=AD= 0.3125 in AH=AD= 2.625 in
Havg 8.21875 in Havg = 36.75 in
It= J 0.1221in/hr It= 0.271in/hr
Percolation Rate Conversion P-7 Percolation Rate Conversion P-8
- Inches Inches
Time Interval, At= 30 Time Interval, At= 30
Final Depth of Water, Df= 60.00 Final Depth of Water, Df= 60.25
Test Hole Radius, r = 3 Test Hole Radius, r = 3
Initial Depth to Water, Do = 59.00 Initial Depth to Water, Do = 59.00
Total Depth of Test Hole, Di = 67 Total Depth of Test Hole, DT = 67
Ho= 8 i Ho= 8 i
Hf= 7 in Hf= 6.75 in
AH =AD = 1 in AH =AD = 1.25 in
Havg 7.5 in Havg 7.375 in
It= [ 0jin/hr It= [0.423]in/hr
Percolation Rate Conversion P-9 Percolation Rate Conversion P-10
Inches Inches
Time Interval, At= 30 Time Interval, At= 30
Final Depth of Water, Df= 37.06 Final Depth of Water, Df= 33.19
Test Hole Radius, r = 3 Test Hole Radius, r = 3
Initial Depth to Water, Do= 35.00 Initial Depth to Water, Do= 29.94
Total Depth of Test Hole, Di = 43 Total Depth of Test Hole, Di = 38
Ho= 8 in Ho 8.0625 in
Hf= 5.9375 in Hf= 4.8125 in
AH=AD= 2.0625 in AH =AD 3.25 in
Havg zz 6.96875 in Havg 6.4375 in
It= L 0.7311in/hr It= [__1jin/hr
APPENDIX C
WORKSHEET 1-8
Worksheet 1-8 Categorization of Infiltration Feasibility Condition
____comftft (thTftIM
I
Part 1 - Full Infiltration Feasibility Screening Criteria
Would infiltration of the full design volume be feasible from a physical perspective without any undesirable
consequences that cannot be reasonablymitigated?
Criteria Screening Question Yes No
Is the estimated reliable infiltration rate below proposed facility locations
1 greater than 0.5 inches per hour? The response to this Screening Question shall
be based on a comprehensive evaluation of the factors presented in Appendix X
C.2 and Appendix D.
Provide basis: The NRCS soils across the site are all Type B soils with medium surface runoff. The site soils are
generally consistent with the NRCS mapped soil types based on site explorations and percolation
testing. Two soil types were present in the area of the proposed development, Quaternary
Undocumented Fill and Old Paralic Deposits.
Ten percolation tests were completed with two performed in Undocumented Fill and eight in the
Old Paralic Deposits. The calculated infiltration rates (with an applied factor of safety of 2.81)
ranged from approximately to 0.044 to 2.098 inch per hour. Three of the ten tests meet full
infiltration criteria. These tests were performed in Undocumented Fill soils and the upper two to
three feet of weathered Old Paralic Deposits which are recommended to be removed during
grading. Therefore, site conditions following grading are not anticipated to support full infiltration
due to removal of full infiltration soils and limited capacity.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide
narrative discussion of study/data source applicability.
Can infiltration greater than 0.5 inches per hour be allowed without increasing
risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or
2 other factors) that cannot be mitigated to an acceptable level? The response to X
this Screening Question shall be based on a comprehensive evaluation of the
factors presented in Appendix C.2.
Provide basis: Provided the basins are constructed with impermeable liners and focused infiltration not being
recommended due to the no infiltration condition, risk of geotechnical hazards will not be
significantly increased.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide
narrative discussion of study/data source applicability.
C-il
S
Criteria Screening Question Yes No
Can infiltration greater than 0.5 inches per hour be allowed without increasing
risk of groundwater contamination (shallow water table, storm water pollutants
3 or other factors) that cannot be mitigated to an acceptable level? The response X
to this Screening Question shall be based on a comprehensive evaluation of the
factors presented in Appendix C.3.
Provide basis: According to Geotracker, an Open" Cleanup Program (DEH Case # DEH20 19-LSAM-000529)
and site history (former Chevron station with leaking underground storage tanks), therefore
infiltrating water could potentially increase the risk of groundwater contamination.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide
narrative discussion of study/data source applicability.
Can infiltration greater than 0.5 inches per hour be allowed without causing
potential water balance issues such as change of seasonality of ephemeral
4 streams or increased discharge of contaminated groundwater to surface waters? X
The response to this Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.3.
Provide basis: The nearest down gradient surface waters consist of Buena Vista Lagoon which is over 2,800 feet
from the proposed improvement area. Due to the distance and topography to the lagoon it is
unlikely to be impacted by infiltrating site water.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide
narrative discussion of study/data source applicability.
If all answers to rows I - 4 are "Yes" a full infiltration design is potentially feasible. The
feasibility screening category is Full Infiltration
Part No Full Result* If any answer from row 1-4 is "No", infiltration may be possible to some extent but
would not generally be feasible or desirable to achieve a "full infiltration" design.
Proceed to Part 2
*To be completed using gathered Site information and best professional judgment considering the definition of MEP in
the MS4 Permit. Additional testing and/or studies may be required by City Engineer to substantiate findings.
" ;\ .,/',
C-12
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4flTI1 (kJ ftw gwa
Part 2 - Partial Infiltration vs. No Infiltration Feasibility Screening Criteria
Would infiltration of water in any appreciable amount be physically feasible without any negative
consequences that cannot be reasonably mitigated?
Criteria Screening Question Yes No
Do soil and geologic conditions allow for infiltration in any appreciable rate or
5 volume? The response to this Screening Question shall be based on a
comprehensive evaluation of the factors presented in Appendix C.2 and
Appendix D.
Provide basis: Based on infiltration testing throughout the site, the site soils adequately support partial
infiltration.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide
narrative discussion of study/data source applicability and why it was not feasible to mitigate low
infiltration rates.
Can Infiltration in any appreciable quantity be allowed without increasing risk
of geotechnical hazards (slope stability, groundwater mounding, utilities, or
6 other factors) that cannot be mitigated to an acceptable level? The response to X
this Screening Question shall be based on a comprehensive evaluation of the
factors presented in Appendix C.2.
Provide basis: Provided the basins are constructed with impermeable liners and focused infiltration not being
recommended due to the no infiltration condition, risk of geotechnical hazards will not be
significantly increased.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide
narrative discussion of study/data source applicability and why it was not feasible to mitigate low
infiltration rates.
C-13
S
Criteria Screening Question Yes No
Can Infiltration in any appreciable quantity be allowed without posing
significant risk for groundwater related concerns (shallow water table, storm
7 water pollutants or other factors)? The response to this Screening Question X
shall be based on a comprehensive evaluation of the factors presented in
Appendix C.3.
Provide basis: According to Geotracker, an "Open" Cleanup Program (DEH Case # DEH20 19-LSAM-000529)
and site history (former Chevron station with leaking underground storage tanks), therefore
infiltrating water could potentially increase the risk of groundwater contamination.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide
narrative discussion of study/data source applicability and why it was not feasible to mitigate low
infiltration rates.
Can infiltration be allowed without violating downstream water rights? The
8 response to this Screening Question shall be based on a comprehensive x
evaluation of the factors presented in Appendix C.3.
Provide basis: The nearest down gradient surface waters consist of Buena Vista Lagoon which is over 2,800 feet
from the proposed improvement area. Due to the distance and topography to the lagoon it is
unlikely to be impacted by infiltrating site water.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide
narrative discussion of study/data source applicability and why it was not feasible to mitigate low
infiltration rates.
If all answers from row 1-4 are yes then partial infiltration design is potentially feasible.
Part 2 The feasibility screening category is Partial Infiltration. No In f. f . Result* If any answer from row 5-8 is no, then infiltration of any volume is considered to be
infeasible within the drainage area. The feasibility screening category is No Infiltration.
*To be completed using gathered site information and best professional judgment considering the definition of MEP in
the MS4 Permit. Additional testing and/or studies may be required by City Engineer to substantiate findings
C-14
APPENDIX C
Appendix I: Forms and Checklists
eiJ alsobb MM
Assigned Factor Product (p) Factor Category Factor Description Weight Value p = w x
Soil assessment methods 0.25 1 0.25
Predominant soil texture 0.25 1 0.25
Suitability Site soil variability 0.25 1 0.25 A Assessment Depth to groundwater / impervious 2 0.50
layer 0.25
Suitability Assessment Safety Factor, SA = p 1.25
Level of pretreatment/ expected
0.51 sediment loads 2 1.0
B Design Redundancy /resiliency 0.25 2 0.50
Compaction during construction 0.25 3 0.75
Design Safety Factor, SB = Ep 2.25
Combined Safety Factor, S,~,i= SAX SB 2.81
Observed Infiltration Rate, inch/hr, Kobserved Varies by test
(corrected for test-speciiië bias) location.
Design Infiltration Rate, in/hr, I<&sigss = Kobservcd / Stotai
Supporting Data
Briefly describe infiltration test and provide reference to test forms:
A. Soil assessment based upon field & infiltration testing.
Soil texture is loamy soils
Limited variability of site soils.
Historic groundwater less than 15 feet.
B No Pre-treatment, but limited sediment load expected.
Not easily restored / not redundant (assumes basin).
Redevelopment of site and proximity to building indicates high degree of
compaction is likely.
1-7 February 2016