HomeMy WebLinkAboutCUP 2017-0008; OAKMONT OF CARLSBAD; TRANSMITTAL OF GEOTECHNICAL INFORMATION; 2017-09-25TRANSMITTAL OF
GEOTECHNICAL INFORMATION
CARLSBAD OAKS NORTH - LOT I
CARLSBAD, CALIFORNIA
'') q- i- . ,
-
MAR 18 2019
LAND flEVELOPMET
I- - -'
PREPARED FOR
OAKMONT SENIOR LIVING
WINDSOR, CALIFORNIA
SEPTEMBER 25, 2017
PROJECT NO. 06442-32-29
ot
GEOCON
INCORPORATED
GEOTECHNICAL a ENVIRONMENTAL a MATERIALS
Project No. 06442-32-29
September 25, 2017
Oakmont Senior Living
9240 Old Redwood Highway, Suite 200
Windsor, California 95492
Attention: Ms. Hannah Daugherty
Subject: TRANSMITTAL OF GEOTECIINTCAL INFORMATION
CARLSBAD OAKS NORTH - LOT 1
CARLSBAD, CALIFORNIA
References: 1. Final Report of Testing and Observation Services During Site Grading, Carlsbad
Oaks North Business Park, Phase 1, Lots 1 through 9, Carlsbad, California,
prepared by Geocon Incorporated, dated August 30, 2006.
Addendum to Final Report of Testing and Observation Services During Site
Grading, Carlsbad Oaks North Business Park - Phase 1, Lot 1, Carlsbad,
California, prepared by Geocon Incorporated, dated October 30, 2008.
Update Geotechnical Correspondence, Carlsbad Oaks North Lot 1, Carlsbad,
California, prepared by Geocon Incorporated, dated June 28, 2017 (Project
No. 06442-32-29).
Preliminary Grading and Drainage Plan, Oakmont of Carlsbad, Lot 1 of Tract
No. 14926, prepared by Alliance Land Planning & Engineering, Inc., dated
June 30, 2017.
Dear Ms. Daugherty:
In accDrdance with your request, Geocon Incorporated has provided geotechnical engineering services
on the subject project. Specifically, we have performed two in-situ permeability tests to aid in
evaluating the on-site storm water BMP design. The following information is provided to support
storm water BMP design in accordance with the 2016 City of Carlsbad Storm Water Standards.
STORM WATER MANAGEMENT INVESTIGATION
We understand storm water management devices are being proposed in accordance with the 2016 City
of Carlsbad Storm Water Standards. If not properly constructed, there is a potential for distress to
improvements and properties located hydrologically down gradient or adjacent to these devices.
6960 Flanders Drive 2 San Diego. California 92121-2974 a Telephone 858.55 B.6900 13 Fax 858.558.6159
Factors such as the amount of water to be detained, its residence time, and soil permeability have an
important effect on seepage transmission and the potential adverse impacts that may occur if the storm
water management features are not properly designed and constructed. We have not performed a
hydrogeological study at the site. If infiltration of storm water runoff occurs, downstream properties
may be subjected to seeps, springs, slope instability, raised groundwater, movement of foundations
and slabs, or other undesirable impacts as a result of water infiltration.
Hydrologic Soil Group
The United States Department of Agriculture (USDA), Natural Resources Conservation Services,
possesses general information regarding the existing soil conditions for areas within the United States.
The USDA website also provides the Hydrologic Soil Group. Table 1 presents the descriptions of the
hydrologic soil groups. If a soil is assigned to a dual hydrologic group (AID, BID, or C/D), the first
letter is for drained areas and the second is for undrained areas.
TABLE I
HYDROLOGIC SOIL GROUP DEFINITIONS
Soil Group Soil Group Definition
Soils having a high infiltration rate (low runoff potential) when thoroughly wet. These
A consist mainly of deep, well drained to excessively drained sands or gravelly sands. These
soils have a high rate of water transmission.
Soils having a moderate infiltration rate when thoroughly wet. These consist chiefly of
B moderately deep or deep, moderately well drained or well drained soils that have moderately
fine texture to moderately coarse texture. These soils have a moderate rate of water
transmission.
Soils having a slow infiltration rate when thoroughly wet. These consist chiefly of soils
C having a layer that impedes the downward movement of water or soils of moderately fine
texture or fine texture. These soils have a slow rate of water transmission.
Soils having a very slow infiltration rate (high runoff potential) when thoroughly wet. These
D consist chiefly of clays that have a high shrink-swell potential, soils that have a high water
table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow
over nearly impervious material. These soils have a very slow rate of water transmission.
The subject sheet-graded pad is underlain by compacted fill placed above the Point Loma formation.
After completion of the proposed grading operations, the property would consist of compacted fill
over Pont Loma Formation. The compacted fill and formational materials should be classified as Soil
Group D. In addition, the USDA website also provides an estimated saturated hydraulic conductivity
for the existing soil. Table 2 presents the information from the USDA website. The Hydrologic Soil
Group Map presents output from the USDA website showing the limits of the soil units. The USDA
information is presented in Appendix B.
Project No. 06442-32-29 - 2 - September 25, 2017
TABLE 2
USDA WEB SOIL SURVEY - HYDROLOGIC SOIL GROUP
Map Unit Approximate Hydrologic kSAT of Most
Map Unit Name Symbol Percentage Soil Group Limiting Layer
of Property (Inches! Hour)
Cieneba coarse sandy loam CiG2 44 D 1.98-5.95
Huerhuero loam7T7 HrD 56 D 0.00 -0.0
In-Situ Testing
We performed two Soil Moisture, Inc. Aardvark Penneameter tests at the locations shown on the
attached Site Plan, Figure 1. Test P-i was located in the bottom of an existing basin. Some standing
water was observed in a portion of this basin. Test P-2 was hand augered until practical refusal was
encountered on the Point Loma Formation contact. The test borings were 4 inches in diameter. The
results of the tests provide parameters regarding the saturated hydraulic conductivity and infiltration
characteristics of on-site soil and geologic units. Table 3 presents the results of the field saturated
hydraulic conductivity/infiltration rates obtained from the Aardvark Permeameter tests. The data
sheets are presented in Appendix A. We applied a feasibility factor of safety of 2 to the test results.
Soil infiltration rates from in-situ tests can vary significantly from one location to another due to the
non-homogeneous characteristics inherent to most soil.
TABLE 3
FIELD PERMEAMETER INFILTRATION TEST RESULTS
Geologic Test Depth Field-Saturated Field
Test No. Unit (feet, below grade) Hydraulic Conductivity, Infiltration Rate
ksat (inch/hour) (inch/hour)
P-i Qcf 2.4 0.0002 0.0001
P-2 Kp 3.75 0.002 0.001
STORM WATER MANAGEMENT CONCLUSIONS
The Site Plan, Figure 1, presents the existing property and the locations of the in-situ infiltration test
locations.
Soil Types
Compacted Fill - Compacted fill exists across the property. The proposed storm water BMP's will be
founded in compacted fill placed above very dense formational materials. The compacted fill is
comprised of sandy/clayey silt. The fill has been or will be compacted to a dry density of at least 90
percent of the laboratory maximum dry density. In our experience, compacted fill does not possess
Project No. 06442-32-29 - 3 - September 25, 2017
i
infiltration rates appropriate for infiltration BMP's, as demonstrated by the in-situ testing. Hazards that
occur as a result of fill soil saturation include a potential for hydro-consolidation of the granular fill
soils and/or swelling of the expansive soils, long-term fill settlement, differential fill settlement, and
lateral movement associated with saturated fill relaxation. The potential for lateral water migration to
adversely impact existing or proposed structures, foundations, utilities, and roadways, is high.
Therefore, full and partial infiltration should be considered infeasible.
Section D.4.2 of the 2016 Storm Water Standards (SWS) provides a discussion regarding fill materials
used for infiltration. The SWS states:
For engineered fills, infiltration rates may still- be quite uncertain due to layering and
heterogeneities introduced as part of construction that cannot be precisely controlled. Due to
these uncertainties, full and partial infiltration should be considered geotechnically infeasible
and liners and subdrains should be used in areas where infiltration BMP's are founded in
compacted fill.
Where possible, infiltration BMPs on fill material should be designed such that their
infiltrating surface extends into native soils. The underlying formation below the compacted
fill is expected between 5 to 10 feet below proposed finish grades after remedial grading is
performed. Full and partial infiltration should be considered geotechnically infeasible within
the compacted fill and liners and subdrains should be used. If the infiltration BMP's extended
below the compacted fill, partial infiltration may be feasible.
Because of the uncertainty of fill parameters as well as potential compaction of the native
soils, an infiltration BMP may not be feasible. Therefore, full and partial infiltration should be
considered geotechnically infeasible and liners and subdrains should be used in the fill areas.
If the source offill material is defined and this material is known to be of a granular nature
and that the native soils below are permeable and will not be highly compacted, infiltration
through compacted fill materials may still be feasible. In this case, a project phasing
approach could be used including the following general steps, (1) collect samples from areas
expected to be used for fill, (2) remold samples to approximately the proposed degree of
compaction and measure the saturated hydraulic conductivity of remolded samples using
laboratory methods, (3) if infiltration rates appear adequate for infiltration, then apply an
appropriate factor of safety and use the initial rates for preliminary design. (4) following
placement of fill, conduct in-situ testing to refine design infiltration rates and adjust the
design as needed. However, based on the discussion above, it is our opinion that infiltrating
into compacted fill should be considered geotechnically infeasible and liners and subdrains
should be used.
Infiltration Rates
The results of the unfactored infiltration rates (i.e. field saturated hydraulic conductivity) for Tests P-i
and P-2 were 0.0002 inches per hour (iph) and 0.002 iph, respectively. After applying a feasibility
factor of safety of 2.0, the infiltration rates obtained for P-i and P-2 are 0.0001 and 0.001 iph,
respectively. The infiltration test results show the on-site soil permeability is variable across the site. A
Project No. 06442-32-29 - 4 - September 25, 2017
single design rate for an area could not be accurate based on the variability. Therefore, based on the
results of the field infiltration tests, anticipated grading, and our experience, full and partial infiltration
should be considered infeasible. The results of the permeability testing are presented in Appendix A.
Groundwater Elevations
Groundwater is expected to be encountered at depths greater than 100 feet below the site, therefore
groundwater is not expected to be a factor. Groundwater mounding is caused when infiltration is
allowed and the lateral hydraulic conductivity is relatively low causing an increase in the groundwater
table. Groundwater mounding is not likely.
Soil or Groundwater Contamination
Based on review of the Geotracker website, no active cleanup sites exist on or adjacent to the subject
site. In addition, we are not aware of any contaminated soils or shallow groundwater on the site that
would preclude storm water infiltration. An environmental assessment was not part of our scope of
work.
Slopes
Existing slopes exist on the perimeter of the property. Infiltration of storm water adjacent to cut or fill
slopes should be avoided. Fill slopes will exhibit instability if water is allowed to saturate the
compacted fill. Cut slopes may exhibit daylight seepage.
Storm Water Management Devices
Based on the discussion above, both infiltration tests did not meet the minimum feasibility criteria for
full or partial infiltration. To limit the adverse impacts of storm water infiltration, i.e. lateral water
migration, daylight water seepage, etc., the design should include liners and subdrains. The
impermeable liners should consist of a high-density polyethylene, HDPE, with a thickness of about 30
mil or equivalent Polyvinyl Chloride, PVC. The liner should surround the bottom and sides of the
infiltrating surface and should extend slightly above the high water elevation. The subdrain should be
perforated, installed near the base of the excavation, be at least 4-inches in diameter and consist of
Schedule 40 PVC pipe. The final segment of the subdrain outside the limits of the storm water BMP
should consist of solid pipe and connected to a proper outlet. Any penetration of the liner should be
properly waterproofed. The devices should also be installed in accordance with the manufacturer's
recommendations.
Project No. 06442-32-29 - 5 - September 25, 2017
Storm Water Standard Worksheets
The Storm Water Standard manual stipulates the geotechnical engineer complete the Categorization of
Infiltration Feasibility Condition (Worksheet C.4-1 or Form 1-8) worksheet information to help
evaluate the potential for infiltration on the property. A completed Form 1-8 is presented in
Appendix B.
The regional storm water standards also have a worksheet (Worksheet D.5-1 or Form 1-9) that helps
the project civil engineer estimate the factor of safety based on several factors. Table 4 describes the
suitability assessment input parameters related to the geotechnical engineering aspects for the factor of
safety determination.
TABLE 4
SUITABILITY ASSESSMENT RELATED CONSIDERATIONS FOR INFILTRATION FACILITY
SAFETY FACTORS
Consideration High Medium Low
Concern —3 Points Concern —2 Points Concern - 1 Point
Use of soil survey maps or Use of well permeameter
or simple texture analysis to borehole methods with Direct measurement with
estimate short-term
.g accompanying continuous boring log, localized (i.e. small-
infiltration rates. Use of Direct measurement of scale) infiltration testing
Assessment Methods well permeameter or infiltration area with methods at relatively high
borehole methods without localized infiltration resolution or use of
accompanying continuous measurement methods extensive test pit
boring log. Relatively (e.g., infiltrometer). infiltration measurement
sparse testing with direct Moderate spatial
methods.
infiltration methods resolution
Predominant Soil Silty and clayey soils Loamy soils Granular to slightly
Texture with significant fines loamy soils
Highly variable soils
indicated from site Soil boring/test pits Soil boring/test pits
Site Soil Variability assessment or unknown indicate moderately indicate relatively
variability homogenous soils homogenous soils
Depth to Groundwater! <5 feet below 5-15 feet below >15 feet below
Impervious Layer I facility bottom facility bottom facility bottom
Based on our geotechnical investigation and the previous table, Table 5 presents the estimated factor
values for the evaluation of the factor of safety. This table only presents the suitability assessment
safety factor (Part A) of the worksheet. The project civil engineer should evaluate the safety factor for
design (Part B) and use the combined safety factor for the design infiltration rate.
Project No. 06442-32-29 - 6 - September 25, 2017
TABLE 5
FACTOR OF SAFETY WORKSHEET DESIGN VALUES - PART A1
Suitability Assessment Factor Category Assigned
(w)
Factor
Value (v)
Product
Weight (p = w x v)
Assessment Methods 0.25 3 0.75
Predominant Soil Texture 0.25 3 0.75
Site Soil Variability 0.25 3 0.75
Depth to Groundwater! Impervious Layer 0.25 1 0.25
Suitability Assessment Safety Factor, SA = p 2.5
1 The project civil engineer should complete Worksheet D.5-1 or Form-I-9 using the data provided above.
Additional information is required to evaluate the design factor of safety. -
If you have questions, or if we may be of further service, please contact the undersigned at your
convenience.
Very truly yours,
GEOCON iNCORPORATED
Trevor E. Myers
ID CE 63773
TEM:DBE:dmc
(4) Addressee
David B. Evans
CEG 1860
(k DAVID B.
Of EVANS
NO. 1860
* CERTIFIED
cP\ ENGINEERING
GEOLOGIST
Project No. 06442-32-29 - 7 - September 25, 2017
CARLSBAD OAKS NORTH - LOT 1
CARLSBAD, CALIFORNIA
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P-2 4- ........ APPROX. LOCATION OF PERMEABILITY TEST
GEOCON
INCORPORATED
GEOTECHNICALU ENVIRONMENTAL U MATERIALS
ttwtf) H ANI)l-PS flIlVF -SAN I)II-(fl (Al ll-()I/MA 92121- 29/4
PHONE 858 558-6900 - FAX 858 558-6159
PROJECT NO. 06442 32 29
SITE PLAN FIGURE 1
plotted:09I2512011624AM I Uy:JONAIHAN WILKINS I File L0catuon:Y:Wt-<OJLlIS\Ub44-J-Z9 CarlsbAD 0300 North lot 1\SHEhIS(Ub440-3-3oItet-9ar1.OWg
APPENDIX A
AARDVARK TEST RESULTS
FOR
CARLSBAD OAKS NORTH - LOT I
CARLSBAD, CALIFORNIA
PROJECT NO. 06442-32-29
Aardvark Permeameter Data Analysis
Project Name: Oakmont Senior Living Date: 9/15/2017
Project Number: 06442-32-29 By: DG
Test Number: P-i
Borehole Diameter, d (in.): 4.00 Ref. EL (feet, MSL): 238.0
Borehole Depth, H (in): 29.00 Bottom EL (feet, MSL): 235.6
Distance Between Reservoir & Top of Borehole (in.): 28.00
Estimated Depth to Water Table, S (feet): 100.00
Height APM Raised from Bottom (in.): 2.00
Pressure Reducer Used: No
Distance Between Resevoir and APM Float, D (in.): 47.75
Head Height Calculated, h (in.): 5.66
Head Height Measured, h (in.): 57.00
Distance Between Constant Head and Water Table, I (in.): 1228.00
0.03
0.02
0.011
0 10 20 30 40 50 60
Time (mm)
Soil Matric Flux Potential, Ct,.
0.00004 Iin2/min
Field-Saturated Hydraulic Conductivity (Infiltration Rate)
Ksat = I 407E-06 In/mn 1 0.0002 In/hr
E
C
j 'I
)GEocoN
Aardvark Permeameter Data Analysis
Project Name: Oakmont Senior Living
Project Number: 06442-32-29
Test Number: P-2
Date: 9/15/2017
By: DG
Ref. EL (feet, MSL): 253.0
Bottom EL (feet, MSL): 249.3
Borehole Diameter, d (in.):4.00
Borehole Depth, H (in): 45.00
Distance Between Reservoir & Top of Borehole (in.) 28.00
Estimated Depth to Water Table, S (feet): 100.00
Height APM Raised from Bottom (in.): 2.00
Pressure Reducer Used: _No
Distance Between Resevoir and APM Float, D (in.): 63.75
Head Height Calculated, h (in.): 5.71
Head Height Measured, h (in.): 73.00
Distance Between Constant Head and Water Table, L (in.): 1228.00
Time Elapsed Water Weight Water Volume
Q (in3/min) Reading (mm) Consummed (Ibs) Consumed (in 3)
1 0.00 0.000 0.00 0.00
2 1 10.00 0.110 3.05 0.305
3 10.00 0.160 4.43 0.443
4 15.00 0.180 4.98 0.332
5 5.00 0.025 0.69 0.138
6 5.00 0.035 0.97 0.194
7 5.00 0.030 0.83 0.166
8 5.00 0.040 1.11 0.222
9 5.00 0.040 1.11 0.222
10 5.00 0.040 1.11 0.222
11 5.00 0.050 1.38 0.277
12 5.00 1 0.050 1 1.38 0.277
Steady Flow Rate, Q (in 3/min): 0.277
Cr
0.1
0 10 20 30 40 50 60 70 80
Time (mm)
Soil Matric Flux Potential, cI...
0.0003 Iin2/min
Field-Saturated Hydraulic Conductivity _(infiltration Rate )
Ks~t = 2.72E-05 In/mn 1 0.002In/hr
APPENDIX
FORM 1-8
FOR
CARLSBAD OAKS NORTH - LOT I
CARLSBAD, CALIFORNIA
PROJECT NO. 06442-32-29
RV"111AINkI Hair
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
Is the estimated reliable infiltration rate below proposed facility locations greater than
1 0.5 inches per hour? The response to this Screening Question shall be based on a X
comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D.
Provide basis: Based on the results of permeability testing in two locations at the site, the unfactored infiltration
rates were measured to be 0.0002 inches/hour (iph), and 0.002 iph using a constant head borehole permeameter
placed inside a 4-inch diameter boring between 2 and 4 feet below existing grades. If applying a feasibility
factor of safety of 2.0, the infiltration rates would be 0.0001 iph and 0.001 iph. Based on the USDA Web Soil
Survey website, the underlying soils are classified as Cieneba sandy loam and Huerhuero loam and belong to
Hydrologic Soil Group D, which are generally not considered suitable for infiltration BMP's. The existing
compacted fill should be classified as Hydrologic Soil Group D, which is not suitable for infiltration BMP's.
Informa:ion collected from the USDA website is attached. The Aardvark Permeameter test results are presented
in Appendix A. In accordance with the Riverside County storm water procedures, which reference the United
States Bureau of Reclamation Well Permeameter Method (USBR 7300), the saturated hydraulic conductivity is
equal to the unfactored infiltration rate.
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 other factors)
2 that cannot be mitigated to an acceptable level? The response to this Screening X
Question shall be based on a comprehensive evaluation of the factors presented in
Appendix C.2.
Provide basis: Natural slopes and fill slopes surround the property. Full infiltration adjacent to descending slopes
is not recommended due to slope instability and daylight water seepage issues. The landslide potential is very
low to negligible. Groundwater mounding is not likely to occur. Existing and proposed utilities would be in
close proximity to the proposed BMP's. The potential for lateral water migration and distress to the public and
private roadway improvements and proposed buildings is high.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussion of study/data source applicability.
1 4 JT
Criteria Screening Question -, Y7SN
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
3 factors) that cannot be mitigated to an acceptable level? The response to this Screening X
Question shall be based on a comprehensive evaluation of the factors presented in
Appendix C.3.
Provide basis: Groundwater is not located within 10 feet from the proposed infiltration BMP.
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 streams or increased
4 discharge of contaminated groundwater to surface waters? The response to this X
Screening Question shall be based on a comprehensive evaluation of the factors
presented in Appendix C.3.
Provide basis: It is our opinion there are no adverse impacts to water balance impacts to stream flow, or impacts
on any downstream water rights. It should be noted that researching downstream water rights or evaluating
water balance issues to stream flows is beyond the scope of the geotechnical consultant.
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
Part 1 feasibility screening category is Full Infiltration No.
Result* If any answer from row 1-4 is "No". infiltration may be possible to some extent but would not
See
Part 2 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.
71 L'i _MM J;1 W;I1WUU
Part 2,7 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 volume?
5 The response to this Screening Question shall be based on a comprehensive evaluation X
of the factors presented in Appendix C.2 and Appendix D.
Provide basis: The infiltration test results did not meet the minimum threshold of 0.01 iph for partial infiltration.
Saturating compacted fill may result in settlement and distress to nearby public roadway improvements and
proposed private improvements and structures.
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 other factors)
6 that cannot be mitigated to an acceptable level? The response to this Screening X
Question shall be based on a comprehensive evaluation of the factors presented in
Appendix C.2.
Provide basis: The adverse impacts of partial infiltration could be reasonably mitigated to acceptable levels using
side liners and a subdrain. However, infiltrating into compacted fill is not recommended. Any infiltration BMP's
should be founded in the formational materials and side liners should be used to prevent lateral water migration
and daylight water seepage from adversely impacting the compacted fill and slopes.
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.
ScreeningQuestion 7Y7esNOCriteria
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: Groundwater is not located within approximately 10 feet from the bottom of the proposed basins.
Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative
discussior of study/data source applicability and why it was not feasible to mitigate low infiltration rates.
I Can infiltration be allowed without violating downstream water rights? The response to
8 this Screening Question shall be based on a comprehensive evaluation of the factors X
presented in Appendix C.3.
Provide basis: Geocon is not aware of any downstream water rights that would be affected by incidental
infiltration of storm water. Researching downstream water rights is beyond the scope of the geotechnical
consultant.
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
Result* If any answer from row 5-8 is no, then infiltration of any volume is considered to be Infiltration
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
4 'I
Soil Map—San Diego County Area, California
(Carlsbad Oaks North - Lot 1)
33 820"N 33 & 2(r N
C
33' 8'11"N 338'11'N
475550 47-5,5W 475630 475670 475710 475750 475~
Map Scale: 1:1,900 ff printed on A landscape (lix 8.5") sheet
—Meters N 0 25 50 180 150 A Feet-
0 50 100 200 3:0
Map projection: Web Mercator Comer coordirebes:WG584 edge tics: UTM Zone uN WGS84
VsQA Natural Resources Web Soil Survoy
Conservation Service National Cooperative Soil Survey
4750 477O 4710 4750
a
5,
9/201201 /
Page 1 of 3
Soil Map—San Diego County Area, California
(Carlsbad Oaks North - Lot 1)
MAP LEGEND MAP INFORMATION
Area of Interest (AOl)
Area of Interest (AOl)
Soils
Soil Map Unit Polygons
, Soil Map Unit Lines
• Soil Map Unit Points
Special Point Features
wo Blowout
10 Borrow Pit
* Clay Spot
Closed Depression
Gravel Pit
Gravelly Spot
O Landfill
A. Lava Flow
Marsh or swamp
* Mine or Quarry
Miscellaneous Water
o Perennial Water
Rock Outcrop
+ Saline Spot
Sandy Spot
Severely Frnded Spot
Ciiklk
Slide or Slip
fif Sodic Spot
The soil surveys that comprise your AOl were mapped at
1:24,000.
Warning: Soil Map may not be valid at this scale.
Enlargement of maps beyond the scale of mapping can cause
misunderstanding of the detail of mapping and accuracy of soil
line placement. The maps do not show the small areas of
contrasting soils that could have been shown at a more detailed
scale.
Please rely on the bar scale on each map sheet for map
measurements.
Source of Map: Natural Resources Conservation Service
Web Soil Survey URL.
Coordinate System: Web Mercator (EPSG:3857)
Maps from the Web Soil Survey are based on the Web Mercator
projection, which preserves direction and shape but distorts
distance and area. A projection that preserves area, such as the
Albers equal-area conic projection, should be used if more
accurate calculations of distance or area are required.
This product is generated from the USDA-NRCS certified data as
of the version date(s) listed below.
Soil Survey Area: San Diego County Area, California
Survey Area Data: Version 10, Sep 12, 2016
Soil map units are labeled (as space allows) for map scales
1:50,000 or larger.
Date(s) aerial images were photographed: Nov 3, 2014—Nov
22, 2014
The orthophoto or other base map on which the soil lines were
compiled and digitized probably differs from the background
imagery displayed on these maps. As a result, some minor
shifting of map unit boundaries may be evident.
Spoil Area
, Stony Spot
s Very Stony Spot
i' Wet Spot
, Other
Special line Features
Water Features
Streams and Canals
Transportation
4-I-I Rails
Interstate Highways
US Routes
Major Roads
Local Roads
Background
Aerial Photography
LISUA Natural Resources Web Soil Survey 9120/2017
Conservation Service National Cooperative Soil Survey Page 2 of 3
(
Soil Map—San Diego County Area, California Carlsbad Oaks North - Lot 1
Map Unit Legend
San Diego County Area, California (CA638)
Map Unit Symbol Map Unit Name Acres in AOl Percent of AOl
ClG2 Cieneba coarse sandy loam,
30 to 65 percent slopes, ero
ded
3.1 43.7%
HrD Huerhuero loam, 9 to 15
percent slopes
4.0 56.3%
Totals for Area of Interest 7.2 100.0%
LISDA Natural Resources Web Soil Survey 9/20/2017
Conservation Service National Cooperative Soil Survey Page 3 of 3
Map Unit Description: Cieneba coarse sandy loam, 30 to 65 percent slopes, ero ded --- San Carlsbad Oaks North - Lot 1
Diego County Area, California
San Diego County Area, California
C1G2—Cieneba coarse sandy loam, 30 to 65 percent slopes,
ero ded
Map Unit Setting
National map unit symbol: hb9s
Elevation: 500 to 4,000 feet
Mean annual precipitation: 12 to 35 inches
Mean annual air temperature: 57 to 64 degrees F
Frost-free period: 200 to 300 days
Farmland classification: Not prime farmland
Map Unit Composition
Cieneba and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Cieneba
Setting
Landform: Hills
Landform position (two-dimensional): Backslope
Landform position (three-dimensional): Side slope
Down-slope shape: Convex
Across-slope shape: Convex
Parent material: Residuum weathered from granite and
granodiorite
Typical profile
HI - 0 to 10 inches: coarse sandy loam
H2 - 10 to 14 inches: weathered bedrock
Properties and qualities
Slope: 30 to 65 percent
Depth to restrictive feature: 4 to 20 inches to paralithic bedrock
Natural drainage class: Somewhat excessively drained
Runoff class: Medium
Capacity of the most limiting layer to transmit water (Ksat): High
(1.98 to 5.95 in/hr)
Depth to water table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Available water storage in profile: Very low (about 1.0 inches)
Interpretive groups
Land capability classification (irrigated): 7e
Land capability classification (nonirrigated): 7e
Hydrologic Soil Group: 0
Ecological site: SHALLOW LOAMY (1975) (R019XD060CA)
Hydric soil rating: No
usnk Natural Resources Web Soil Survey 9/20/2017
Conservation Service National Cooperative Soil Survey Page 1 of 2
Map Unit Description: Huerhuero loam, 9 to 15 percent slopes---San Diego County Area, Carlsbad Oaks North - Lot 1
California
Ecological site: CLAYPAN (1975) (R019XD061 CA)
Hydric soil rating: No
Minor Components
Las flores
Percent of map unit: 10 percent
Hydric soil rating: No
Oliventain
Percent of map unit: 3 percent
Hydric soil rating: No
Unnamed
Percent of map unit: 2 percent
Hydric soil rating: No
Data Source Information
Soil Survey Area: San Diego County Area, California
Survey Area Data: Version 10, Sep 12, 2016
usDA Natural Resources Web Soil Survey 9/20/2017
Conservation Service National Cooperative Soil Survey Page 2 of 2
Map Unit Description: Cieneba coarse sandy loam, 30 to 65 percent slopes, ero ded --- San Carlsbad Oaks North - Lot 1
Diego County Area, California
Minor Components
Vista
Percent of map unit: 10 percent
Hydric soil rating: No
Las posas
Percent of map unit: 5 percent
Hydric soil rating: No
Data Source Information
Soil Survey Area: San Diego County Area, California
Survey Area Data: Version 10, Sep 12, 2016
usm Natural Resources Web Soil Survey 9/20/2017
Conservation Service National Cooperative Soil Survey Page 2 of 2
Map Unit Description: Huerhuero loam, 9 to 15 percent slopes---San Diego County Area, Carlsbad Oaks North - Lot 1
California
San Diego County Area, California
HrD—Huerhuero loam, 9 to 15 percent slopes
Map Unit Setting
National map unit symbol: hbcp
Elevation: 1,100 feet
Mean annual precipitation: 12 to 20 inches
Mean annual air temperature: 57 degrees F
Frost-free period: 260 days
Farmland classification: Not prime farmland
Map Unit Composition
Huerhuero and similar soils: 85 percent
Minor components: 15 percent
Estimates are based on observations, descriptions, and transects of
the mapunit.
Description of Huerhuero
Setting
Landform: Marine terraces
Down-slope shape: Concave
Across-slope shape: Concave
Parent material: Calcareous alluvium derived from sedimentary
rock
Typical profile
HI - 0 to 12 inches: loam
H2 - 12 to 55 inches: clay loam, clay
H2 - 12 to 55 inches: stratified sand to sandy loam
H3 - 55 to 72 inches:
Properties and qualities
Slope: 9 to 15 percent
Depth to restrictive feature: More than 80 inches
Natural drainage class: Moderately well drained
Runoff class: Very high
Capacity of the most limiting layer to transmit water (Ksat): Very
low to moderately low (0.00 to 0.06 in/hr)
Depth to wafer table: More than 80 inches
Frequency of flooding: None
Frequency of ponding: None
Salinity, maximum in profile: Nonsaline to very slightly saline (0.0
to 2.0 mmhos/cm)
Sodium adsorption ratio, maximum in profile: 25.0
Available water storage in profile: Moderate (about 6.6 inches)
Interpretive groups
Land capability classification (irrigated): 4e
Land capability classification (nonirrigatod): 4e
Hydrologic Soil Group: D
usa Natural Resources Web Soil Survey 9/20/2017
Conservation Service National Cooperative Soil Survey Page 1 of 2