HomeMy WebLinkAbout6043; PALOMAR AIRPORT ROAD WIDENING AT PASEO DEL NORTE; SUPPLEMENTAL GEOTECHNICAL INVESTIGATION - INFILTRATION TESTING; 2017-12-08
5710 Ruffin Road | San Diego, California 92123 | p. 858.576.1000 | www.ninyoandmoore.com
December 8, 2017
Project No. 108040005
Mr. Daniel Zimny
City of Carlsbad
1635 Faraday Avenue
Carlsbad, California 92008
Subject: Supplemental Geotechnical Evaluation of Infiltration Characteristics
Palomar Airport Road
Right Turn Lane at Paseo Del Norte
Carlsbad, California
Dear Mr. Zimny:
In accordance with your request and authorization, we have a performed supplemental geotechnical
evaluation of the infiltration/permeability characteristics for the Palomar Airport Road Right Turn Lane
to Paseo Del Norte Project in Carlsbad, California (Figure 1). Based on our discussions, we
understand that a dedicated right turn lane is proposed along the east bound lanes of Palomar
Airport Road leading to Paseo Del Norte in Carlsbad, California. In addition to new pavements,
concrete flatwork and infiltration devices will be constructed. To accommodate the new turn lane, the
roadway will be widened several feet to the south.
Our previous work for the project included an evaluation of the infiltration characteristics of
relatively shallow subsurface soils at the site (Ninyo & Moore, 2017). That evaluation indicated
relatively poor infiltration characteristics that were used in the initial project design. However, due
to site constraints and the relatively poor infiltration rates of the shallow subsurface soils,
alternative methods for implementing storm water Best Management Practices (BMP) are being
considered, specifically, the use of dry wells is being considered for the project. The purpose of
our supplemental study is to provide information regarding the infiltration/permeability
characteristics of the deeper subsurface soils at the site. This letter report presents the results of
our supplemental field exploration and laboratory testing, as well as our conclusions regarding
the feasibility for the implementation of dry wells at the site and our recommendations for the
design infiltration rates.
Ninyo & Moore | Right Turn Lane at Paseo Del Norte, Carlsbad, California | 108040005 | December 8, 2017 2
SCOPE OF SERVICES
Our scope of services for this supplemental evaluation included the following:
Reviewing background information including available utility plans and topographic maps.
Obtaining a boring permit from the County of San Diego Department of Environmental
Health (DEH) prior to drilling the exploratory boring.
Preparing and submitting a Right-of-Way permit for approval by the City of Carlsbad prior to the
performance of our fieldwork.
Siting and staking of the exploratory boring location for clearance by Underground Service Alert.
Implementing the City of Carlsbad approved traffic control plan during drilling of the exploratory
boring.
Drilling, logging, and sampling of one exploratory boring with a limited-access drill rig. The
boring was drilled to a depth of approximately 51 feet. Bulk and in-place samples of the
encountered soils were collected and transported to our in-house laboratory for testing.
Performing geotechnical laboratory testing of the subsurface soils to evaluate in-situ dry
density and moisture content, gradation (sieve) analysis, Atterberg Limits, and permeability
characteristics.
Preparing this letter report to provide our findings regarding the permeability characteristics of
the subsurface soils at depth, and our recommendations for infiltration rates to be used in the
design of dry wells.
SUBSURFACE EXPLORATION
Our subsurface exploration was conducted on October 26, 2017 and consisted of the drilling,
logging, and sampling one exploratory boring (B-1). The boring was drilled to a depth of
approximately 51 feet using a limited-access drill rig equipped with 6-inch diameter hollow-stem
augers. During the drilling operations, the boring was logged and sampled by Ninyo & Moore
personnel. Representative bulk and in-place soil samples were obtained from the boring. The
samples were then transported to our in-house geotechnical laboratory for testing. The
approximate location for the exploratory boring for this supplemental evaluation along with the
locations of the shallow infiltration test locations from the initial study (Ninyo & Moore, 2017) are
shown on Figure 2. The log of boring B-1 is included in Attachment A.
Ninyo & Moore | Right Turn Lane at Paseo Del Norte, Carlsbad, California | 108040005 | December 8, 2017 3
GEOTECHNICAL LABORATORY TESTING
Geotechnical laboratory testing was performed on representative soil samples collected during our
subsurface exploration. Testing included an evaluation of in-situ dry density and moisture content,
gradation (sieve) analysis, Atterberg Limits, and permeability characteristics. The results of the in-situ dry
density and moisture content tests are presented at the corresponding sample depths on the boring log in
Attachment A. The results of the other laboratory tests performed are presented in Attachment B.
As a means of evaluating the infiltration characteristics of the subsurface material at depth, a
laboratory permeability test was performed on a soil sample obtained at a depth of approximately
40 feet in boring B-1. The permeability test indicated a rate of 13 feet per year (ft/yr).
GEOLOGIC SUBSURFACE CONDITIONS
Geologic units encountered during our subsurface exploration for this study included fill materials,
old paralic deposits, and materials of the Santiago Formation (Kennedy and Tan, 2008).
Generalized descriptions of the earth units encountered during our subsurface exploration are
provided in the subsequent sections. Additional descriptions of the subsurface units are provided
on the boring log in Attachment A.
Fill
Fill materials were encountered in our boring B-1 at the ground surface and extending to a depth of
approximately 3 feet. The fill materials encountered during our subsurface exploration generally
consisted of brown, moist, medium dense, clayey sand. Scattered asphalt concrete (AC) fragments,
roots, and chunks of sandy clay were encountered in the fill materials.
Old Paralic Deposits
Materials mapped as old paralic deposits (Kennedy and Tan, 2008) were encountered in our boring
B-1 underlying the fill materials and extending to a depth of approximately 29 feet. As encountered,
these materials generally consisted of various shades of gray, brown, and olive, moist, medium
dense, silty and clayey sand, and very stiff, sandy clay.
Santiago Formation
Materials mapped as the Santiago Formation (Kennedy and Tan, 2008) were encountered in our
boring B-1 underlying the old paralic deposits and extending to the total depth explored of
approximately 51 feet. As encountered, these materials generally consisted of various shades of
olive, brown, and white, moist, moderately indurated, silty claystone and moderately to strongly
cemented, silty sandstone.
Ninyo & Moore | Right Turn Lane at Paseo Del Norte, Carlsbad, California | 108040005 | December 8, 2017 4
Groundwater
Groundwater was not encountered in the boring performed as part of our subsurface exploration
that extended to a depth of approximately 51 feet. However, perched water was encountered at a
depth of approximately 29 feet overlying a claystone layer within the Santiago Formation. A
petroleum like odor was also noted at this depth. Sampling for analytical testing of soil or
groundwater was outside the scope of this evaluation. Fluctuations in the groundwater level and
perched conditions may occur due to variations in ground surface topography, subsurface geologic
conditions and structure, rainfall, irrigation, and other factors.
CONCLUSIONS AND RECOMMENDATIONS
As presented above, laboratory testing on a soil sample obtained from boring B-1 at a depth of
approximately 40 feet indicated a permeability rate of 13 ft/yr, which corresponds to a rate of
approximately 0.02 inches per hour (in/hr). Although these rates do not specifically correlate to infiltration
rates into subsurface soils, they are general indicators of the potential for infiltration. Additionally, suitability
assessment factors-of-safety (FOS) for the design of dry well infiltration devices are presented on the
attached Worksheet I-8, which were calculated based on the guidelines presented in Appendix I of the
City of Carlsbad BMP Design Manual (2016). Also attached is the San Diego Categorization of Infiltration
Feasibility worksheet (Worksheet I-9) with responses to the suitability assessment questions. The design
safety factor shall be determined by the design engineer.
Relatively poor infiltration characteristics have been encountered in both the shallow and deeper
subsurface soils as discussed in this report and the initial site evaluation (Ninyo & Moore, 2017).
Accordingly, the use of infiltration devices such as pervious pavements, bioretention swales, or dry
wells will result in lateral migration of subsurface water and potentially adverse effects to adjacent
site improvements. For infiltration into shallower soils, these adverse effects may include
settlement of trench backfill and yielding subgrade conditions beneath pavements. For infiltration
into deeper subsurface soils, these effects may include the transport of materials generating the
petroleum odor that was noted at a depth of approximately 29 feet in boring B-1. Therefore, if
infiltration devices are to be used on the project, we recommend that the bottom and sides of the
gravel reservoirs for these infiltration devices be lined with an impermeable liner. In addition, the
site design may consider the use of pavement edge drains and cutoff curbs to reduce the potential
for lateral migration of irrigation and runoff both into the trench backfill, subgrade soils, or
aggregate base materials beneath adjacent improvements.
The proposed site improvements should be constructed in accordance with the requirements of the
applicable governing agencies and the recommendations of this report.
Ninyo & Moore | Right Turn Lane at Paseo Del Norte, Carlsbad, California | 108040005 | December 8, 2017
REFERENCES
City of Carlsbad, 2016, Engineering Standards, Volume 5: Carlsbad BMP Design Manual for Post
Construction Treatment BMPs: dated February.
County of San Diego, 1963, Topographic Survey, Sheet 346-1671, Scale 1:2,400: dated
September.
County of San Diego, 1975, Topographic Survey, Sheet 346-1671, Scale 1:2,400: dated
September 17.
Google, Inc., 2017, www.googleearth.com: accessed in October.
Kennedy, M.P., and Tan, S.S., 2008, Geologic Map of the Oceanside 30x60-Minute Quadrangle,
California, Scale 1:100,000.
Ninyo & Moore, In-House Proprietary Data.
Ninyo & Moore, 2017, Infiltration Testing Results, Palomar Airport Road Right Turn Lane to Paseo
Del Norte, Carlsbad, California, Project No. 108040005: dated January 31.
Ninyo & Moore | Right Turn Lane at Paseo Del Norte, Carlsbad, California | 108040005 | December 8, 2017
FIGURES
SITE
0 1,500 3,000
FEET
MAP INDEX
San Dieg oCounty
1_108040005_SL.mxd 12/7/2017 AOBNOTE: DIRECTIONS, DIMENSIONS AND LOCATIONS ARE APPROXIMATE. | SOURCE: ESRI WORLD TOPO, 2017
SITE LOCATION
108040005 | 12/17
FIGURE 1
PALOMAR AIRPORT ROAD
RIGHT TURN LANE AT PASEO DEL NORTE, CARLSBAD, CALIFORNIA
LEGEND
IT-2
TD=5.0
PALOMAR AIRPORT ROAD
INFILTRATION TEST (2017)
TD=TOTAL DEPTH IN FEET
IT-2
TD=5.0
IT-1
TD=5.0
PASEO DEL NORTE0 80 160
FEET
2_108040005_EL.mxd 12/7/2017 AOBNOTE: DIRECTIONS, DIMENSIONS AND LOCATIONS ARE APPROXIMATE. | SOURCE: GOOGLE EARTH, 2017
EXPLORATION LOCATIONS
108040005 | 12/17
FIGURE 2
PALOMAR AIRPORT ROAD
RIGHT TURN LANE AT PASEO DEL NORTE, CARLSBAD, CALIFORNIA
B-1
TD=50.9
B-1
TD=50.9
SOIL BORING
TD=TOTAL DEPTH IN FEET
Ninyo & Moore | Right Turn Lane at Paseo Del Norte, Carlsbad, California | 108040005 | December 8, 2017
ATTACHMENT A
Boring Log
Soil Classification Chart Per ASTM D 2488
Primary Divisions Secondary Divisions
Group Symbol Group Name
COARSE-
GRAINED
SOILS
more than
50% retained
on No. 200
sieve
GRAVEL more than 50% of coarse fraction
retained on No. 4 sieve
CLEAN GRAVEL
less than 5% fines
GW well-graded GRAVEL
GP poorly graded GRAVEL
GRAVEL with DUAL CLASSIFICATIONS 5% to 12% fines
GW-GM well-graded GRAVEL with silt
GP-GM poorly graded GRAVEL with silt
GW-GC well-graded GRAVEL with clay
GP-GC poorly graded GRAVEL with
GRAVEL with FINES more than
12% fines
GM silty GRAVEL
GC clayey GRAVEL
GC-GM silty, clayey GRAVEL
SAND 50% or more of coarse fraction passes No. 4 sieve
CLEAN SAND less than 5% fines
SW well-graded SAND
SP poorly graded SAND
SAND with DUAL CLASSIFICATIONS 5% to 12% fines
SW-SM well-graded SAND with silt
SP-SM poorly graded SAND with silt
SW-SC well-graded SAND with clay
SP-SC poorly graded SAND with clay
SAND with FINES more than 12% fines
SM silty SAND
SC clayey SAND
SC-SM silty, clayey SAND
FINE-
GRAINED
SOILS
50% or
more passes
No. 200 sieve
SILT and CLAY
liquid limit less than 50%
INORGANIC
CL lean CLAY
ML SILT
CL-ML silty CLAY
ORGANIC OL (PI > 4)organic CLAY
OL (PI < 4)organic SILT
SILT and CLAY liquid limit 50% or more
INORGANIC CH fat CLAY
MH elastic SILT
ORGANIC
OH (plots on or above “A”-line)organic CLAY
OH (plots below “A”-line)organic SILT
Highly Organic Soils PT Peat
USCS METHOD OF SOIL CLASSIFICATION
Apparent Density - Coarse-Grained Soil
Apparent Density
Spooling Cable or Cathead Automatic Trip Hammer
SPT (blows/foot)
Modified Split Barrel (blows/foot)
SPT (blows/foot)
Modified Split Barrel (blows/foot)
Very Loose < 4 < 8 < 3 < 5
Loose 5 - 10 9 - 21 4 - 7 6 - 14
Medium
Dense 11 - 30 22 - 63 8 - 20 15 - 42
Dense 31 - 50 64 - 105 21 - 33 43 - 70
Very Dense > 50 > 105 > 33 > 70
Consistency - Fine-Grained Soil
Consis-tency
Spooling Cable or Cathead Automatic Trip Hammer
SPT (blows/foot)
Modified Split Barrel (blows/foot)
SPT (blows/foot)
Modified Split Barrel (blows/foot)
Very Soft < 2 < 3 < 1 < 2
Soft 2 - 4 3 - 5 1 - 3 2 - 3
Firm 5 - 8 6 - 10 4 - 5 4 - 6
Stiff 9 - 15 11 - 20 6 - 10 7 - 13
Very Stiff 16 - 30 21 - 39 11 - 20 14 - 26
Hard > 30 > 39 > 20 > 26
LIQUID LIMIT (LL), %PLASTICITY INDEX (PI), %0 10
107
4
20
30
40
50
60
70
0 20 30 40 50 60 70 80 90 100
MH or OH
ML or OLCL - ML
Plasticity Chart
Grain Size
Description Sieve Size Grain Size Approximate Size
Boulders > 12”> 12”Larger than basketball-sized
Cobbles 3 - 12”3 - 12”Fist-sized to basketball-sized
Gravel
Coarse 3/4 - 3”3/4 - 3”Thumb-sized to fist-sized
Fine #4 - 3/4”0.19 - 0.75”Pea-sized to thumb-sized
Sand
Coarse #10 - #4 0.079 - 0.19”Rock-salt-sized to
pea-sized
Medium #40 - #10 0.017 - 0.079”Sugar-sized to rock-salt-sized
Fine #200 - #40 0.0029 - 0.017”Flour-sized to sugar-sized
Fines Passing #200 < 0.0029”Flour-sized and smaller
CH or OH
CL or OL
0
5
10
15
20
XX/XX
SM
CL
Bulk sample.
Modified split-barrel drive sampler.
No recovery with modified split-barrel drive sampler.
Sample retained by others.
Standard Penetration Test (SPT).
No recovery with a SPT.
Shelby tube sample. Distance pushed in inches/length of sample recovered in inches.
No recovery with Shelby tube sampler.
Continuous Push Sample.
Seepage.
Groundwater encountered during drilling.
Groundwater measured after drilling.
MAJOR MATERIAL TYPE (SOIL):
Solid line denotes unit change.
Dashed line denotes material change.
Attitudes: Strike/Dipb: Bedding
c: Contactj: Joint
f: FractureF: Fault
cs: Clay Seams: Shear
bss: Basal Slide Surfacesf: Shear Fracture
sz: Shear Zonesbs: Shear Bedding Surface
The total depth line is a solid line that is drawn at the bottom of the boring.
BORING LOG
Explanation of Boring Log Symbols
PROJECT NO.DATE FIGUREDEPTH (feet)BulkSAMPLESDrivenBLOWS/FOOTMOISTURE (%)DRY DENSITY (PCF)SYMBOLCLASSIFICATIONU.S.C.S.BORING LOG EXPLANATION SHEET
Updated Nov. 2011
BORING LOG
20
0
10
20
30
40
14
16
50/6"
50/5"11.1 111.5
SC
SM
SC
CL
SM
SC
FILL:Brown, moist, medium dense, clayey fine to medium SAND; scattered AC
fragments; scattered roots.Few chunks of sandy clay.
OLD PARALIC DEPOSITS:Gray, moist, medium dense, silty fine to medium SAND; trace clay.
Olive, moist, medium dense, clayey fine SAND; slight organic odor.
Mottled grayish brown and brown, moist, very stiff, fine sandy CLAY.
Gray, moist, medium dense, silty fine SAND; cohesionless; slightly micaceous.
Gray, moist, medium dense, clayey fine to medium SAND.
Strong petroleum odor.
SANTIAGO FORMATION:Olive, moist, moderately indurated, silty CLAYSTONE.
Yellowish brown, moist, moderately to strongly cemented, silty fine-grained
SANDSTONE.
Grades to light brown to white.
Trace medium-grained; slightly micaceous.
FIGURE A- 1
PALOMAR AIRPORT ROAD RIGHT TURN LANE AT PASEO DEL NORTE
CARLSBAD, CALIFORNIA
108040005 |12/17DEPTH (feet)BulkSAMPLESDrivenBLOWS/FOOTMOISTURE (%)DRY DENSITY (PCF)SYMBOLCLASSIFICATIONU.S.C.S.DESCRIPTION/INTERPRETATION
DATE DRILLED 10/26/17 BORING NO.B-1
GROUND ELEVATION 78' (MSL)SHEET 1 OF
METHOD OF DRILLING 6" Diameter Hollow Stem Auger (Fraste) (Pac Drill)
DRIVE WEIGHT 140 lbs. (Auto-Trip)DROP 30"
SAMPLED BY CAT LOGGED BY CAT REVIEWED BY CAT
2
40
50
60
70
80
256/6"
50/5"
SANTIAGO FORMATION: (Continued)Light brown to white, moist, moderately to strongly cemented, fine-grained
SANDSTONE; trace clay.
Fine- to medium-grained.
Total Depth = 50.9 feet.
Perched water encountered at approximately 29 feet during drilling.
Backfilled with approximately 16 cubic feet of bentonite grout shortly after drilling
on 10/26/17.
Note: Groundwater may rise to a level higher than that measured in borehole due
to seasonal variations in precipitation and several other factors as discussed in
the report.
The ground elevation shown above is an estimation only. It is based on our
interpretations of published maps and other documents reviewed for the purposes
of this evaluation. It is not sufficiently accurate for preparing construction bids and
design documents.
FIGURE A- 2
PALOMAR AIRPORT ROAD RIGHT TURN LANE AT PASEO DEL NORTE
CARLSBAD, CALIFORNIA
108040005 |12/17DEPTH (feet)BulkSAMPLESDrivenBLOWS/FOOTMOISTURE (%)DRY DENSITY (PCF)SYMBOLCLASSIFICATIONU.S.C.S.DESCRIPTION/INTERPRETATION
DATE DRILLED 10/26/17 BORING NO.B-1
GROUND ELEVATION 78' (MSL)SHEET 2 OF
METHOD OF DRILLING 6" Diameter Hollow Stem Auger (Fraste) (Pac Drill)
DRIVE WEIGHT 140 lbs. (Auto-Trip)DROP 30"
SAMPLED BY CAT LOGGED BY CAT REVIEWED BY CAT
2
Ninyo & Moore | Right Turn Lane at Paseo Del Norte, Carlsbad, California | 108040005 | December 8, 2017
ATTACHMENT B
Laboratory Testing
Coarse Fine Coarse Medium SILT CLAY
3" 2"¾"½" ⅜"4 8 30 50
PERFORMED IN GENERAL ACCORDANCE WITH ASTM D 422
B-1 35.0-35.4 -- -- -- -- -- SM-- -- -- 15
Sample
Location
100
D10
16 200
Passing
No. 200
(percent)
Cc
GRAVEL SAND FINES
Symbol Plasticity
Index
Plastic
Limit
Liquid
Limit
1½" 1"
Depth
(ft)D30 Cu
Equivalent
USCSD60
Fine
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.00010.0010.010.1110100PERCENT FINER BY WEIGHTGRAIN SIZE IN MILLIMETERS
U.S. STANDARD SIEVE
NUMBERS HYDROMETER
GRADATION TEST RESULTS
PALOMAR AIRPORT ROAD RIGHT TURN LANE AT PASEO DEL NORTE
CARLSBAD, CALIFORNIA
108040005 | 12/17
FIGURE B-1
108040005 SIEVE B-1 @ 35.0-35.4 (Dry Well).xlsx
Coarse Fine Coarse Medium SILT CLAY
3" 2"¾"½" ⅜"4 8 30 50
PERFORMED IN GENERAL ACCORDANCE WITH ASTM D 422
B-1 50.0-50.9 -- -- -- -- -- SM-- -- -- 20
Sample
Location
100
D10
16 200
Passing
No. 200
(percent)
Cc
GRAVEL SAND FINES
Symbol Plasticity
Index
Plastic
Limit
Liquid
Limit
1½" 1"
Depth
(ft)D30 Cu
Equivalent
USCSD60
Fine
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
0.00010.0010.010.1110100PERCENT FINER BY WEIGHTGRAIN SIZE IN MILLIMETERS
U.S. STANDARD SIEVE
NUMBERS HYDROMETER
GRADATION TEST RESULTS
PALOMAR AIRPORT ROAD RIGHT TURN LANE AT PASEO DEL NORTE
CARLSBAD, CALIFORNIA
108040005 | 12/17
FIGURE B-2
108040005 SIEVE B-1 @ 50.0-50.9 (Dry Well).xlsx
NP - INDICATES NON-PLASTIC
PERFORMED IN GENERAL ACCORDANCE WITH ASTM D 4318
SYMBOL LOCATION DEPTH (ft)
LIQUID
LIMIT
PLASTIC
LIMIT
CLCL
19
No. 40 Sieve)
PLASTICITY
INDEX
CLASSIFICATION
30.0-31.0 1736
EQUIVALENT
USCS
B-1
USCS
(Fraction Finer Than
CH or OH
CL or OL MH or OH
ML or OLCL - ML
0
10
20
30
40
50
60
0 102030405060708090100110120PLASTICITY INDEX, PI LIQUID LIMIT, LL
FIGURE B-3
ATTERBERG LIMITS TEST RESULTS
PALOMAR AIRPORT ROAD RIGHT TURN LANE AT PASEO DEL NORTE
CARLSBAD, CALIFORNIA
108040005 | 12/17
108040005 ATTERBERG Page 1 (Dry Well).xlsx
PERFORMED IN GENERAL ACCORDANCE WITH ASTM D 5084
B-1 10.7
SAMPLE
LOCATION
40.0-41.0
SAMPLE
DEPTH
(ft)
INITIAL
MOISTURE
(percent)
DRY DENSITY
(pcf)
PERMEABILITY
(ft/yr)
110.9 13
PERMEABILITY TEST RESULTS
PALOMAR AIRPORT ROAD RIGHT TURN LANE AT PASEO DEL NORTE
CARLSBAD, CALIFORNIA
108040005 | 12/17
FIGURE B-4
108040005 PERMEABILITY Page 1 (Dry Well).xlsx
Ninyo & Moore | Right Turn Lane at Paseo Del Norte, Carlsbad, California | 108040005 | December 8, 2017
ATTACHMENT C
Forms I-8 and I-9
Appendix I: Forms and Checklists
I-3 February 2016
Categorization of Infiltration Feasibility
Condition
Form I-8
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 reasonably mitigated?
Criteria Screening Question Yes No
1
Is the estimated reliable infiltration rate below proposed
facility locations 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 C.2 and Appendix
D.
Provide basis:
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
2
Can infiltration greater than 0.5 inches per hour be allowed
without increasing risk of geotechnical hazards (slope stability,
groundwater mounding, utilities, or other factors) that cannot
be mitigated to an acceptable level? The response to this
Screening Question shall be based on a comprehensive evaluation of
the factors presented in Appendix C.2.
Provide basis:
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
Appendix I: Forms and Checklists
I-4 February 2016
Form I-8 Page 2 of 4
Criteri
a Screening Question Yes No
3
Can infiltration greater than 0.5 inches per hour be allowed
without increasing risk of groundwater contamination (shallow
water table, storm water pollutants or other factors) that cannot
be mitigated to an acceptable level? The response to this
Screening Question shall be based on a comprehensive evaluation of
the factors presented in Appendix C.3.
Provide basis:
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
4
Can infiltration greater than 0.5 inches per hour be allowed
without causing potential water balance issues such as change
of seasonality of ephemeral streams or increased discharge of
contaminated groundwater to surface waters? The response to
this Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.3.
Provide basis:
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
Part 1
Result
*
If all answers to rows 1 - 4 are “Yes” a full infiltration design is potentially feasible.
The feasibility screening category is Full Infiltration
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 the City to substantiate findings.
Appendix I: Forms and Checklists
I-5 February 2016
Form I-8 Page 3 of 4
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
5
Do soil and geologic conditions allow for infiltration in any
appreciable rate or 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:
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.
6
Can Infiltration in any appreciable quantity be allowed
without increasing risk of geotechnical hazards (slope
stability, groundwater mounding, utilities, or other factors)
that cannot be mitigated to an acceptable level? The response
to this Screening Question shall be based on a comprehensive
evaluation of the factors presented in Appendix C.2.
Provide basis:
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.
Appendix I: Forms and Checklists
I-6 February 2016
Form I-8 Page 4 of 4
Criteria Screening Question Yes No
7
Can Infiltration in any appreciable quantity be allowed
without posing significant risk for groundwater related
concerns (shallow water table, storm water pollutants or other
factors)? The response to this Screening Question shall be based
on a comprehensive evaluation of the factors presented in
Appendix C.3.
Provide basis:
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.
8
Can infiltration be allowed without violating downstream
water rights? The response to this Screening Question shall be
based on a comprehensive evaluation of the factors presented in
Appendix C.3.
Provide basis:
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.
Part 2
Result*
If all answers from row 5-8 are yes then partial infiltration design is potentially feasible.
The feasibility screening category is Partial Infiltration.
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 the City to substantiate findings.
Appendix I: Forms and Checklists
I-7 February 2016
Factor of Safety and Design Infiltration Rate
Worksheet Form I-9
Factor Category Factor Description Assigned
Weight (w)
Factor
Value (v)
Product (p)
p = w x v
A Suitability
Assessment
Soil assessment methods 0.25
Predominant soil texture 0.25
Site soil variability 0.25
Depth to groundwater / impervious
layer 0.25
Suitability Assessment Safety Factor, SA = p
B Design
Level of pretreatment/ expected
sediment loads 0.5
Redundancy/resiliency 0.25
Compaction during construction 0.25
Design Safety Factor, SB = p
Combined Safety Factor, Stotal= SA x SB
Observed Infiltration Rate, inch/hr, Kobserved
(corrected for test-specific bias)
Design Infiltration Rate, in/hr, Kdesign = Kobserved / Stotal
Supporting Data
Briefly describe infiltration test and provide reference to test forms: