HomeMy WebLinkAboutPIP 05-25x1A; HCP Bressi Ranch PA 2; Planned Industrial Permit (PIP) (5)BRESS/ RANCH PlANNING AREA 2
HYDROMODIFICATION MANAGEMENT STUDY
1 . PROJECT DESCRIPTION
October 20 7 7
This Hydromodification Management Study analyzes the potential hydromodification impacts of Bressi
Ranch Planning Area 2 project, and has been prepared based on the requirements set forth in the Final
Hydromodification Management Plan (HMP) for the County of San Diego, prepared by Brown and Caldwell
and dated March 2011.
This 23.09± acre project site consists of eight (8) existing, mass-graded, undeveloped lots which will be
graded to accommodate the construction of eight (8) new two-story buildings with a parking structure,
associated on-grade parking and site improvements.
The project site is bordered on the north by Gateway Road, to the east by Alicante Road, to the south
by Town Garden Road and west by El Camino Real. The immediate surrounding area is comprised
primarily of industrial and commercial uses as well as some single family residential as planned for in the
Bressi Ranch master plan. Interstate 5 is approximately 3.5 miles to the west of the project site along
Palomar Airport Road. The project site is currently located in the zone designated as P-M, planned
industrial.
2. SITE INFORMATION
The following sections summarize the site conditions which relate to drainage and hydromodification,
including the geotechnical conditions, drainage basins, and the low flow threshold determination.
2.1 Geotechnical Conditions
A Geotechnical Update Study was completed by Leighton and Associates, Inc. dated April 12, 2011
(Project No. 971 009-065) which details the subsurface conditions for the project. Selected excerpts
from the report are as follows:
Site Location and As-Graded Description:
"The Bressi Ranch Industrial Planning Area 2 site is located south of Palomar Airport Road and east of
El Camino Real Road in Carlsbad, California (Figure 7 ). The mass grading operations for the site were
performed between June 2003 and January 2004 (Leighton, 2004b). The mass grading of the site
resulted in three terraced sheet-graded pads separated by south-and west-facing slopes
approximately 5 to 8 feet in height and three desilting basins along Town Garden Road, the southern
boundary of the site. In addition, along Town Garden Road there is a south-to southeast facing 2 to 7
fill slope, which ranges from 5 to 15 feet in height. In general, the mass grading of the site included: 7)
the removal of potentially compressible desiccated older fill soils, undocumented fill soils, topsoil,
colluvium, alluvium, landslide deposits, and weathered formational material; 2) preparation of areas to
receive fill; 3) the placement of a subdrain system in the canyon bottom; 4) excavation of formational
material; 5) the placement of compacted fill soils, and 6) excavation of stability fill keys. Up to
approximately 15 feet of cut was excavated and a maximum of approximately 90 feet of fill was placed
during the mass grading operations within the limits of the site.
"The sheet-graded pads of Planning Areas 2 consist of both cut and fills. The cut/fill transition
conditions on the sheet-graded pads were not mitigated during the mass grading operations. As
""""" reported, once the site improvements on the pads of the planning areas are determined, specific
""-"' recommendations concerning the cut/fill transition conditions were to be provided in an update report
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BRESS/ RANCH PLANNING AREA 2
HYDROMOD/F/CATION MANAGEMENT STUDY
October 20 11
for the site. In general, the cut/fill transition conditions can be mitigated by the overexcavation of the
cut portion of the pad or by designing deep foundations that extend through the fill."
Geologic Setting:
"The subject site is located in the coastal section of the Peninsular Range Province, a geomorphic
province with a long and active geologic history throughout Southern California. Throughout the last
54 million years, the area known as the "San Diego Embayment" has undergone several episodes of
marine inundation and subsequent marine regression, resulting in the deposition of a thick sequence of
marine and nonmarine sedimentary rocks on the basement rock of the Southern California batholith.
Gradual emergence of the region from the sea occurred in Pleistocene time, and numerous wave-cut
platforms, most of which were covered by relatively thin marine and nonmarine terrace deposits,
formed as the sea receded from the land. Accelerated fluvial erosion during periods of heavy rainfall,
coupled with the lowering of the base sea level during Quaternary time, resulted in the rolling hills,
mesas, and deeply incised canyons which characterize the landforms we see in the general site area
today."
Geologic Units:
"The geologic units encountered during our update study included both recent artificial fill and the
Tertiary-aged Santiago Formation. The artificial fill (Af) was placed during the mass grading operations
and generally consist of silty sands to sandy silts/clays. The approximate limits of the artificial fill soils
are presented on the Geotechnical Map (Plate 1 ). In addition to the fill limits, the elevations of the
bottom of the fill are provided on the geotechnical map so that potential fill differentials across the site
can be identified."
"In accordance with the project geotechnical recommendations, the fill soils in the lower portions of the
deep fill areas (i.e. fill areas generally deeper than approximately 40 feet below the proposed finish
grade elevations of the sheet-graded pads) were compacted to at least 95 percent of the maximum dry
density in accordance with ASTM Test Method D 1557. Fill soils placed within 40 feet of the finish
grade surface were compacted to a minimum 90 percent relative compaction (based on with ASTM
Test Method D 1557)."
"The Tertiary-aged Santiago Formation, as encountered during the mass grading operations, consisted
primarily of massively bedded sandstones and claystones/siltstones. The sandstone generally consisted
of orange-brown (iron oxide staining) to light brown, damp to moist, dense to very dense, silty very fine
to medium grained sandstone. The siltstones and claystones were generally olive-green to gray
(unweathered), damp to moist, stiff to hard, moderately weathered, and occasionally fractured and
moderately sheared. Several well cemented fossiliferous sandstone beds were encountered during the
mass grading operations. It should be noted that high to very high expansive formational claystones
and siltstones are present at the existing finish grade elevation of the sheet-graded pad in the eastern
portion of Planning Area 2 (see Geotechnical Map -Plate 1 ). "
Ground Water:
"During the original site grading, perched ground water was encountered in the alluvial soils located in
the lower portions of the main canyon and in some of the lower tributary canyons on the east side of
Planning Area 2. In addition, several seepage zones were also encountered along the base of a
number of the relatively permeable sandstone units in the lower portion of the canyon on the southwest
3
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BRESS/ RANCH PLANNING AREA 2
HYDROMODIFICA.TION MANAGEMENT STUDY
October 20 11
Grading by Project Design Consultants, dated October, 2004 on file with the City of Carlsbad under
CT 00-06, DWG 400-SA, 400-SC and 400-80.
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BRESS/ RANCH PlANNING AREA 2
HYDROMODIFICATION MANAGEMENT STUDY
2.3 Drainage Basins
October 20 7 7
The site currently does not have any storm drain infrastructure installed on-site, but public storm drain
infrastructure is located in the adjacent public rights-of-way along Town Garden Road and Alicante
Road. Storm drain laterals have been installed during the previous mass-grading operation to serve
the temporary desilting basins located on site. These storm drain laterals will be used for the new
private storm drain systems associated with the project's development.
Presently, the site sheet flows to temporary desilting basins located on each lot. The site generally
drains to the south and to the east toward the public storm drain infrastructure located in Town
Garden Road and Alicante Road. Runoff from the project site enters the public storm drain system
through the existing storm drain laterals, and flows to two storm drain outfalls south of the project in
an unnamed canyon.
The westerly outfall discharges through a concrete energy dissipater and over a rip rap apron. The
easterly outfall discharges into a detention basin and flow continues to the south after existing the
detention basin through a concrete energy dissipater and rip rap apron. The two flows confluence
after this point and continue to flow to the south in swales through the future Alga Norte Community
Park site. The runoff then crosses under Poinsettia Lane, flows across the La Costa Resort golf course,
crosses under Alga Road, continues to flow through the La Costa Resort golf course and enters San
Marcos Creek near the intersection of El Camino Real and La Costa Avenue. Near this intersection,
San Marcos Creek drains to the west and discharges into Batiquitos Lagoon and ultimately the Pacific
Ocean.
A detailed description of the drainage patterns and flows onsite are discussed in the report titled
Drainage Study for Bressi Ranch Planning Area 2 prepared by Fuscoe Engineering, dated October
2011. Additional information on the downstream storm drain system and detention facility is
contained in the Drainage Report for Bressi Ranch Mass Grading & Backbone Improvements by Project
Design Consultants, dated February, 2003 and Addendum to Drainage Report for Bressi Ranch Mass
Grading by Project Design Consultants, dated October, 2004 on file with the City of Carlsbad under
CT 00-06, DWG 400-8A, 400-8C and 400-8D.
2.4 Hydromodification Applicability
The Bressi Ranch Planning Area 2 project does not qualify for any exemptions listed in the Final
Hydromodification Management Plan, and ~ therefore subject to hydromodification mitigation
requirements.
2.5 Domain of Analysis
A Hydromodification Screening assessment was completed by Chang Consultants dated October 18,
2011 which analyzes the project's point of compliance, domain of analysis and low flow threshold for
the project. Selected excerpts from the report are as follows:
"The downstream domain of analysis for the study area has been determined by assessing and
comparing the four bullet items above. The proiect runoff will discharge into the natural canyon at the
easterly and westerly points of compliance (POC). The downstream domain of analysis will be below
these POCs."
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BRESS I RANCH PLANNING AREA 2
HYOROMODIFICATION MANAGEMENT STUDY
October 20 11
"Per the first bullet item, the first permanent grade control below the discharge location is at 72-inch
RCP at the north end of Alga Norte Community Park. Since the storm drain containing this RCP
continues for over a thousand feet south, one reach (656 feet) downstream of the grade control will be
within a non-erodible pipe. Therefore, the downstream domain of analysis based on the first bullet item
will be the grade control created by the 72-inch RCP entrance. 11
"The second bullet item is the tidal backwater or lentic (still) waterbody location. The nearest tidal
backwater or lentic waterbody is Batiquitos Lagoon, which is over 2 miles south of the POCs."
"The final two bullet items are related to the tributary drainage area. According to Project Design
Consultants' February 2003, Drainage Report, Bressi Ranch Mass Grading & Backbone Improvements,
the areas tributary to the easterly and westerly POCs are 749.7 and 23.7 acres, respectively (the
proposed project will generally maintain these drainage areas). The equal order tributary is the point
below the easterly and westerly POC's with the same drainage area as the POCs. For the easterly
POC, the equal order tributary will be beyond Alga Norte Community Park. For the westerly POC, the
equal order tributary will be within the natural canyon. Since the natural canyon is not a stream system
or urban conveyance system, the fourth bullet point does not apply."
"Based on the above information, the 72-inch RCP was selected as the downstream domain of analysis
point for both POCs. The downstream domain of analysis for the westerly POC could have been
selected as the point in the natural canyon with a tributary area of 23. 1 acres, but since the easterly
POC analysis point is at the 72-inch RCP, this was chosen for the westerly POC as we//. Per the first
bullet item, the downstream domain of analysis begins one reach below the 72-inch RCP grade
control. As discussed above, a reach is not to exceed 200 meters (656 feet). Since the storm drain
system containing this RCP continues for over a thousand feet, one reach downstream of the grade
control will be within a non-erodible pipe. Therefore, the downstream domain of analysis based on the
first bullet item will be the grade control created at the 72-inch RCP entrance. 11
"Upstream Domain of Analysis
The area upstream of the RCP outlet of each POC is an existing graded 2: 1 fill slope with landscaping.
The only storm runoff on the slope is from direct precipitation. Consequently, the slope is not
anticipated to erode (erosion was not observed during a recent site visit) and the upstream domain of
analysis for both POCs will be at each RCP outlet, i.e., the 42-inch RCP outlet and its D-41 establishes
the upstream domain of analysis for the westerly POC, and the 24/30-inch RCP outlets and their D-41
establish the upstream domain of analysis for the easterly POC."
"Study Reaches within Domain of Analysis
The entire domain of analysis extends from each of the POCs to the 72-inch RCP at the north end of
Alga Norte Community Park. The total domain of analysis covers approximately 2,300 feet. The
domain of analysis was subdivided into three study reaches with similar characteristics (see the Study
Area Exhibit). Reach 7 {upper reach) extends from the westerly POC to the easterly POC. Reach 2
(middle reach) continues from the easterly POC downstream to a large existing berm crossing the
lower third of the natural canyon. The berm is earthen and the center portion was breached sometime
in the past. The canyon runoff currently flows through the breach. Reach 3 (lower reach) extends from
the earthen berm to the 72-inch RCP."
"Each reach is longer than the 656 feet maximum reach length specified by SCCWRP. Review of
topographic mapping, aerial photographs, and field conditions reveals that the physical (channel
geometry and longitudinal slope), vegetative, hydraulic, and soil conditions within each reach are
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BRESS/ RANCH PlANNING AREA 2
HYDROMODIF/CATION MANAGEMENT STUDY
October 20 11
relatively uniform. Subdividing the reaches into smaller subreaches of less than 656 feet will not yield
significantly varying results within a reach. Although the screening tool was applied across the entire
·..........-length of each of the three reaches, the results will be similar for shorter subreaches within each
reach."
2.6 low Flow Threshold Determination
"The SCCWRP channel screening tools were used to assess the downstream channel susceptibility for
the Bressi Ranch project. The project runoH will discharge into a natural canyon south of the site at an
easterly and westerly point of compliance. Each POC contains RCP discharging through D-41 concrete
energy dissipaters. The assessment was made for the natural canyon from the POCs to Alga Norte
Community Park, which is just under 0.5 miles south of the site (domain of analysis). The assessment
was performed based on oflice analyses and field work. The results indicate a low threshold for vertical
and lateral susceptibilities."
"The HMP requires that these results be compared with the critical stress calculator results incorporated
in the County of San Diego's BMP Sizing Calculator. The BMP Sizing Calculator critical stress results
are included in Appendix B for Reach 1, 2, and 3. Based on these values, the critical stress results
returned a low threshold. Therefore, the SCCWRP analyses and critical stress calculator demonstrate
that the project can be designed assuming a low susceptibility, i.e., 0.502."
"The SCCWRP results are consistent with the physical condition of the natural canyon within the
domain of analysis, which is densely vegetated environmental preserve. None of the three study
reaches nor D-41 outlets exhibit signs of extensive, ongoing erosion."
Based upon the information provided above and the full study performed for the project by Chang
Consultants, the low-flow threshold for the project shall be 0.5Q2• Please see the study
Hydromodification Screening for Bressi Ranch Planning Area 2 by Chang Consultants, dated October
18, 2011 under separate cover for the full study which is also on file with the City of Carlsbad.
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BRESS/ RANCH PlANNING AREA 2
HYDROMODIF/CA.TION MANAGEMENT STUDY
3. METHODOLOGY
October 20 11
The hydromodification analysis for Bressi Ranch Planning Area 2 project has been done in
accordance with the Final Hydromodification Management Plan, dated March 2011.
3.1 Drainage Management Strategy
The drainage management strategy for the project utilizes Low Impact Development principles and
practices to provide water quality treatment and hydromodification mitigation. Portions of the site
which consist of almost entirely pervious surfaces will be identified as self-treating areas. Where
possible, the majority of the project's impervious surfaces, including roofs and hardscape, will drain to
flow-through planters. Depending on site constraints, some drainage areas may drain to permeable
pavers underlain by a gravel storage layer and sand filter layer which serves as an inverted flow-
through planter. The following sections will provide detailed descriptions of each of the BMPs utilized.
To size the BMPs, the tributary areas to each BMP were delineated into Drainage Management Areas
(DMAs). The DMAs were further broken down into proposed impervious areas, such as roofs and
pavement, and proposed pervious areas, including landscaping and slopes. Refer to the
Hydromodification Management Exhibit in Appendix 2.
The San Diego Hydromodification Sizing Calculator Version 3.0, developed by Brown and Caldwell,
was utilized to size the BMPs. As the proposed BMPs are low-impact development features, the "LID
Sizer" feature of the calculator was used. The BMPs were sized for "Treatment + Flow Control". The
prevalent hydrologic soil group for the project is Group D, and the project site is located within the
Oceanside rainfall basin. The calculator's Point of Compliance screen was utilized and the vertical
and lateral susceptibility were entered as "low". This allowed the BMPs to be sized using the correct
low-flow threshold of 0.5Q2. The existing site slopes are flat (0-5%) for all the project basins. The
output from the calculator can be found in Appendix 5.
3.2 Flow-Through Planters
Flow-through planters are proposed in the majority of the project's DMAs throughout the site. The
flow-through planters will receive runoff from building downspouts, pavement areas, hardscape and
adjacent landscaped areas. The majority flow-through planters have been placed and sized to
provide water quality treatment and hydromodification flow control for their respective DMAs. A few
flow-through planter IMPs will required subsurface detention to meet hydromodification orifice flows,
which are modeled in the Calculator as bioretention plus vault.
Runoff from small storm events will pond up on the surface of the planter, being treated by vegetative
update and biofiltration as it percolates through a 24" soil layer. An overflow catch basin will be
located 1 0" above the bottom of the planting area to allow for up to 1 0" of pending. Then runoff will
enter an 18" deep storage reservoir consisting of #57 stone with 40% void space. Treated water will
be collected by a subdrain at the bottom the planter. Outflow through the subdrain will be controlled
by a galvanized steel plate with a drilled orifice placed at the outfall of the subdrain pipe when it
enters a downstream storm drain structure. The system's orifice has been sized per the San Diego
Hydromodification Calculator.
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BRESS/ RANCH PLANNING AREA 2
HYDROMODIFICAT/ON MANAGEMENT STUDY
4. CALCULATIONS/RESULTS
4.1 Flow-Through Planters
October 20 7 7
As described in Section 3.2, the flow-through planters were sized using the BMP Calculator. The table
below summarizes each of the DMAs which flow to the flow-through planters, as well as the required
and provided area for each BMP. As noted in Section 3.5 above, the orifice size produced by the
Calculator is applicable to these BMPs, and is also listed in the table.
FLOW-THROUGH PLANTERS
BMP
Drainage Management Areas (DMAs) Sizing Factor Calculations (0.5 Q 2) Size
Provided
Impervious Pervious Total Area Low Flow Orifice Area
Basin DMA Area Required Threshold Diameter Provided
(s.f.) (s.f.) (s.f.) (s .f.) (cfs) (in.) (s.f.)
1 47 13,736 2,910 14,030 975 0.028 0.8 990
1 49 6,580 818 6,670 457 0.013 0.6 470
1 50 7,187 1,547 7,350 518 0.014 0.6 520
1 51 10,060 4,209 10,490 731 0.021 0.7 800
1 52 8,003 4,404 8,450 579 0.016 0.6 600
2 34 44,741 13,862 46,130 3,232 0.092 2.0 3,300
2 35 21,012 2,423 21,260 1,494 0.042 1.0 1,500
2 39 17,378 7,545 18,140 1,280 0.036 1.0 1,280
2 40 11,315 6,798 12,000 853 0.024 0.8 900
2 41 13A64 4,056 13,870 975 0.028 0.8 1,000
2" 42 7,682 ---7,690 548 0.015 0.6 600
3 1 17,380 4,020 17,790 1,250 0.035 1.0 1,300
3 23 13,186 ---13,190 1,768 0.050 1.0 1,800
3 24 3,827 1,136 3,950 274 0.007 0.4 300
3 25 7,059 1,029 7,170 487 0.014 0.6 600
3 26 3,084 1,013 3,190 213 0.006 0.4 300
3 27 1,430 831 1,520 91 0.002 0.2 110
3 29 6,170 ---6,170 426 0.012 0.5 440
3 30 8,627 ---8,630 609 0.017 0.7 700
3 31 6,562 ---6,570 457 0.013 0.6 500
3 32 8,872 3,793 9,260 640 0.018 0.7 700
3 33 10,473 1,142 10,590 731 0.021 0.7 750
3 54 2,809 996 3,000 213 0.006 0.4 300
4 2 13,307 ---13,310 945 0.027 0.8 1,000
4 3 13,186 ---13,190 914 0.026 0.8 1,000
4 5 4,803 2,373 5,050 365 0.010 0.5 400
4 9 11,965 ---11,970 823 0.023 0.8 920
4 10 12,949 ---12,950 914 0.026 0.8 1,000
4 20 7,044 ---7,050 487 0.014 0.6 500
4 8 13,035 ---13,040 914 0.026 0.8 1,000
5 13 10,754 3,328 11,090 762 0.021 0.7 800
5 14 13,229 4,062 13,640 945 0.027 0.8 1,000
5 15 6,806 ---6,810 487 0.014 0.6 500
5 16 10,901 2,471 11,150 792 0.022 0.8 500
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BRESS/ RANCH PLANNING AREA 2
HYDROMODIFICATION MANAGEMENT STUDY
5.0 MAINTENANCE
Designated Responsible Party: HCP LS Carlsbad, LLC
c/o Project Management Advisors
462 Stevens Avenue, Suite 1 06
Solana Beach, CA 92075
(858) 704-1980
October 20 11
Below are the suggested maintenance activities for the underground storage systems; these are
minimum requirements only. The frequency and/or scope may be increased, if necessary, to meet
and/or maintain the level of storm water quality treatment and flow control required of this project.
For additional information on maintenance of the various storm water treatment control BMPs, please
refer to the project's Storm Water Management Plan for the Bressi Ranch Planning Area 2 project
prepared by Fuscoe Engineering under separate cover.
Underground Storage Systems
Safety: Before entering into any storm sewer or underground storage system, check to make sure that
all OSHA and local safety regulations and guidelines are observed during the maintenance process.
Hard hats, steel-toed boots and any other appropriate personal protective equipment shall be worn at
all times.
Inspection Frequency: Inspections are recommended at a mm1mum on an annual basis. The first
year of operation may require more frequent inspections. Frequency of inspections will vary
significantly on the local site weather and site conditions. An inspection schedule should be
established for each installation.
Inspections: Inspection is the key to effective maintenance and is easily performed. The entire storm
water treatment train should be inspected and maintained beginning with the upstream device and
continuing downstream to the discharge orifice located immediately downstream of the underground
storage system.
Maintenance: The underground storage systems are accessed through manholes above each system.
Underground storage systems should be inspected at regular intervals and maintained when necessary
to ensure optimum performance. The rate at which the system accumulates silt and sediment will
depend on the local site weather and site conditions or the configuration of the system. Silt and
sediment should be removed, especially it accumulated materials are interfering with the operation of
the system (i.e. blocking outlet orifices, pipes or reducing the storage capacity).
It is easiest to maintain a system when there is no flow entering. For this reason,
cleanout/maintenance of the system should be scheduled during dry weather. The maintenance of
this system should be coordinated with the maintenance of the other storm water treatment control
BMPs on site to limit the potential for pollutants to be flushed downstream inadvertently.
A vector truck or similar device can be used to remove silt and sediment from the underground
storage system. High pressure water jets can be used to dislodge and remove any accumulated
sediment or debris and the vacuum truck will collect and properly dispose of the resulting runoff.
Once maintenance is complete, replace all manhole rims and access covers as necessary.
15
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BRESS/ RANCH PLANNING AREA 2
HYDROMODIF/CA.TION MANAGEMENT STUDY
6. SUMMARY AND CONCLUSION
October 20 7 7
As demonstrated in this report, the hydromodification mitigation measures proposed for the Bressi
Ranch Planning Area 2 project will satisfy the requirements of the Final Hydromodification
Management Plan. This will be achieved through the use of flow-through planter, permeable paver
and underground storage BMPs which will reduce peak runoff flows and increase durations from the
developed areas of the project to below pre-project levels for the flow range of 0.502 to Q 10• The
BMPs have been designed using the San Diego Hydromodification Sizing Calculator. Maintenance of
the BMPs will be performed by the owner/developer or their agents. Please refer to the project's
Storm Water Management Plan and Drainage Study for further information regarding the water quality
and hydrology aspects of the proposed project.
16
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Appendix3
c Underground Storage Basin Map1
Appendix5
Calculator Output
R~Result (
Project Summary
ProjectN...,. Breaai Ranch Ptanning Area 2
Project Appllc.t HCP LS Car1abad, LLC
Jurlodlcllon City ol Ca~sbad
Porcei(APN)
Hydrologic Unit Ca~sbad
Compliance Basin Summary
B•elnName: Basin 1
Receiving War: Weeterty SO Outfall into existing canyon south of project
blnf•IIB•In Oceanside
Mean Annuol P...:lpltollon (lnchn) 13.3
Project B•ln Ar .. (oc,..): 4.30
Warohed Aroo (oc,.o): 186.00
SCCWRP Larlll Chonnel SuecepUbllty (H, II, L): Low (Lateral)
SCCWRP Verllftclll Channel SuocepUbllty (H, II, L): Low(Vertical)
Overall Channel SuocepUblllty (H, II, L): LOW
Low.r Flow Th,.ohold (%of 2·Y•or Flow): 0.5
Drainage Management Area Summary
ID Type BIIPID Description A,.a(oc) P,..Project Cover Poat Surf.:• Type
11449 Drains to LID BMP1 DMA43 0.54 Pervious (Pre) Concrete or asphalt
-..
11451 Drains to LID BMP2 DMA44 1.01 Pervioua (Pre) Concrete or asphalt
-------------------
11453 Drains to LID BMP3 DMA45 0.46 Pervious (Pre) Concrete or asphalt
11455 Drains to LID BMP4 DMA46 0.36 Pervious (Pre) Concrete or asphalt
11457 Drains to LID BMP5 DMA47 0.32 Pervious (Pre) Concrete or aaphatt
--i ------------------------------
11459 Drains to LID BMP6 DMA46 0.14 Pervious (Pre) Concrete or asphalt
---------r----------r--------------
11461 Drains to LID BMP7 DMA49 0.15 Pervious (Pre) Concrete or asphalt
----------
11463 Draine to LID BMP8 DMA50 0.17 Pervious (Pre) Concrete or asphalt
11465 Drains to LID BMP9 DMA51 0.24 Pervklus (Pre) Concrete or asphalt
11467 Drains to LID BMP10 DMA52 0.19 Pervk>ua (Pre) Concrete or asphalt
LID Facility Summary
Drlllnoge Soli
TypeD (high runoff-clay
sol...
. -------------------------------
TypeD (high runoff-clay
sol ...
Slope
Flal-slope (1888 ..
Flal-slope (leoo ..
-------------------------·---------------------
TypeD (high runoff-clay
soL.
TypeD (high runoff-clay
eeL
Type D (high runoff-clay
sol ...
Flal· slope (1888 ..
Flal-slope (leoo ..
---
Flal-slope (lees ..
-------------+---------!
TypeD (high runoff-clay
eeL. Flal-slope (leoo ...
-+--------------~-----------
TypeD (high runoff-clay
eeL. Flat-slope (leoo ...
---~--------+-----------------
Type D (high runoff· cley
eeL
TypeD (high runoff-clay
soL.
TypeD (high runoff-clay
sol ...
Fial-slope (lees ..
Flat· slope (lees ...
Flat· slope (lees ...
Par)of2
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Project Summary
Project Name Bressi Ranch Planning Area 2
Project Applicant HCP LS Car1sbad, LLC
Jurisdiction City of Carlsbad
Parcel (APN)
Hydrologic Unit Car1sbad
Compliance Basin Summary
Basin Name: Basin 3
Receiving Water: Wester1y SD Outfall into existing canyon south of project
Rainfall Basin Oceanside
Mean Annual Precipitation (inches) 13.3
Project Basin Area (acres): 4.10
Watershed Area (acres): 186.00
SCCWRP Lateral Channel Susceptiblity (H, M, L): Low (Lateral)
SCCWRP Vertlfical Channel Susceptiblity (H, M, L): Low (Ver1ical)
Overall Channel Susceptibility (H, M, L): LOW
Lower Flow Threshold (%of 2-Year Flow): 0.5
Drainage Management Area Summary
ID Type BMPID Description Area (ac) Pre-Project Cover Post Surface Type Drainage Soil Slope
11489 Drains to LID BMP 1 DMA1 0.41 Pervious (Pre) Concrete or asphalt Type D (high runoff-clay Flat-slope (less ... soi...
11490 Drains to LID BMP 2 DMA4 0.22 Pervious (Pre) Concrete or asphalt Type D (high runoff-clay Flat -slope (less ... soi. ..
11491 Drains to LID BMP3 DMA19 0.45 Pervious (Pre) Concrete or asphalt Type D (high runoff. clay Flat-slope (less ... soi...
11492 Drains to LID BMP4 DMA21 0.08 Pervious (Pre) Concrete or asphalt TypeD (high runoff-clay Flat -slope (less ... soi. ..
11493 Drains to LID BMP 5 DMA22 0.21 Pervious (Pre) Concrete or asphalt Type D (high runoff-clay Flat-slope (less ... soi ...
11494 Drains to LID BMP6 DMA23 0.58 Pervious (Pre) Concrete or asphalt Type D (high runoff-clay Flat-slope (less ... soi. ..
11495 Drains to LID BMP7 DMA24 0.09 Pervious (Pre) Concrete or asphalt Type D (high runoff-clay Flat-slope (less ... soi. ..
11496 Drains to LID BMP8 DMA25 0.16 Pervious (Pre) Concrete or asphalt TypeD (high runoff-clay Flat-slope (less ... soi. ..
··-----------------
11497 Drains to LID BMP9 DMA26 0.07 Pervious (Pre) Concrete or asphalt TypeD (high runoff-clay Flat-slope (less ... soi. ..
11498 Drains to LID BMP10 DMA27 0.03 Pervious (Pre) Concrete or asphalt TypeD (high runoff-clay Flat -slope (less ... soi. ..
11499 Drains to LID BMP11 DMA28 0.6 Pervious (Pre) Concrete or asphalt Type D (high runoff-clay Flat-slope (less ... soi ...
11500 Drains to LID BMP 12 DMA29 0.14 Pervious (Pre) Concrete or asphalt Type D (high runoff-clay Flat-slope (less ... soi...
11501 Drains to LID BMP13 DMA30 0.2 Pervious (Pre) Concrete or asphalt Type D (high runoff-clay Flat-slope (less ... soi. ..
11502 Drains to LID BMP14 DMA31 0.15 Pervious (Pre) Concrete or asphalt Type D (high runoff-clay Flat-slope (less ... soi. ..
11503 Drains to LID BMP15 DMA32 0.21 Pervious (Pre) Concrete or asphalt TypeD (high runoff-clay Flat -slope (less ... soi ...
11504 Drains to LID BMP16 DMA33 0.24 Pervious (Pre) Concrete or asphalt Type D (high runoff-clay Flat-slope (less ... soi. ..
11505 Drains to LID BMP17 DMA54 0.07 Pervious (Pre) Concrete or asphalt Type D (high runoff-clay Flat-slope (less ... soi. ..
LID Facility Summary
BMPID Type Description Plan Area (sqft) Volume 1(cft) Volume 2(cft) Orifice Flow (cfs) Orifice Size (inch)
BMP1 Flow-Through Planter IMP 1 1250 1041 750 0.035 1.00
BMP2 Bioretention + Cistern IMP 4 335 1150 0.00 0.019 0.6
BMP3 Bioretention + Cistern IMP 19 686 2352 0.00 0.039 0.8
BMP4 Bioretention + Cistern IMP21 121 418 0.00 0.007 0.3
BMP5 Bioretention + Cistern IMP 22 320 1097 0.00 0.018 0.5
BMP6 Flow-Through Planter IMP 23 1768 1472 1061 0.050 1.00
BMP7 Flow-Through Planter IMP 24 274 228 164 0.007 0.4
BMP8 Flow-Through Planter IMP 25 487 406 292 0.014 0.6
BMP9 Flow-Through Planter IMP 26 213 177 128 0.006 0.4
BMP10 Flow-Through Planter IMP 27 91 76 54 0.002 0.2
BMP 11 Bioretention + Vault IMP28 1045 3659 0.00 0.052 1.00
( )
BMP12 Flow-Through Planter IMP 29 426 355 256 0.012 0.5
BMP13 Flow-Through Planter IMP30 609 507 365 0.017 0.7
BMP14 Flow-Through Planter IMP31 457 380 274 0.013 0.6
BMP15 Flow-Through Planter IMP 32 640 533 384 0.018 0.7
BMP16 Flow-Through Planter IMP33 731 609 439 0.021 0.7
BMP17 Flow-Through Planter IMP 54 213 177 128 0.006 0.4
R~Result ( P~of1
Project Summary
ProjectN.,.. Breasi Ranch Planning Area 2
Project Appllc.nt HCP LS Carlsbad, LLC
Jurladlctlon City of Carlsbad
Porc:ei(APN)
Hydrologic Unit Carlsbad
Compliance Basin Summary
Baaln Name: BasinG
Receiving WNr: Eaatarly SO outfall into existing canyon aoulh of project
Rainfall a .. tn Oceanakte
Meon Annuol Proclpltollon (lnchea) 13.3
Project a .. tn Araa (ocraa): 0.70
Warahed Araa (ocraa): 209.00
SCCWRP Larol Channa! Suacaptlbllty (H, M, L): Low (Lateral)
SCCWRP Vertlftcol Channa! Suaceptlbllty (H, M, L): Low(Veo1ical)
Overall Channel SuacepUblllty (H, M, L): LOW
Lower Flow Thraahold (%of 2·Yeer Flow): 0.5
Drainage Management Area Summary
ID Type BMP ID DeacrlpUon Arao(oc) Pre-Project Cover Poat Surface Type Drolnaga Soli Slope
BMP 7 DMA 7 0.27 Pervious (Pre) Concrete or asphalt Type 0 (high runoff-clay Flat-slope (leas ... eoi... 11412 Drains to LID
r-. ·-·-~·-·--·-. ---... ----·----~~-~---··-----~-~~~~~-
0.16 Pervious (Pre) Concrete or asphalt TypeD (high runoff-clay Flat-slope (leas .. sol ... 11414 Drains to LID BMP 18 DMA 18
LID Facility Summary
BMPID Type O.acrlptlon Plan Araa (aqft) Volume t(cft) Volume 2(cft) Orifice Flow (cfo) Orifice Stza (Inch)
BMP7 Flow-Through Planter IMP7 823 685 493 0.023 0.8
-· .. ---~-··----~--~ ------------------~----~ f----
BMP18 Flow-Through Planter IMP18 487 406 292 0.014 0.6
http:/ /uknow .brwncald.com/wastewater/Toolkits/W atershed/SiteToolkit/ReportResult.aspx?pid= 138617 &bid=SDC-0001 &sic=... 10/14/2011
Appendix6
I
· · :Penneable Paver Orifice Sizing
Bressi Ranch Planning Area 2
Permeable Paver Flow Control Orifice Sizing
,r""'
Fuscoe Engineering, Inc.
Job No. 02722-001-01
'--"' Size of flow control orifice under variable head conditions due variable gravel storage layer depths
Q = Co Ao (2gH0) A 0.5 from Equation 6.12 of the San Diego County Drainage Design Manual
Where:
Q = Discharge through orifice in cubic feet per second (cfs)
Co = Orifice Coefficient = 0.6 for a sharp, clean edge orifice
A0 = Cross-sectional area of orifice in square feet
g = gravitational constant = 32.2 ftlsec2
H0 = head acting on the orifice
Solving for the orifice area gives:
Ao = Q I [Co (2gH0) A 0.5]
The cross-sectional area of the orifice is given as:
A0 =IT* (d214)
Where:
d = Orifice diameter in feet
,_ Combining the equations and solving for the diameter of the orifice gives:
'"-d = (4Q I [IT Co (2gH0) A 0.5]) A 0.5
Basin:
Imp:
AProvided =
VProvided =
d=
Hydromodification
Management Study
1
45
1 ,785 s.f.
2,856 cu.ft.
0.042 cfs
4 feet
0.07 feet
0.9 inches
from County Calculator output
depth of gravel storage
Appendix 6 Page 1 of 4
,.....
f ' '-'
--
Bressi Ranch Planning Area 2
Permeable Paver Flow Control Orifice Sizing
Basin:
Imp:
AProvided =
YProvided =
Q=
H = 0
d=
Basin:
Imp:
AProvided =
YProvided =
Q=
H = 0
d=
Basin:
Imp:
AProvided =
YProvided =
Q=
H = 0
d=
Hydromodification
Management Study
1
46
1,339 s.f.
2,142 cu. ft.
0.042 cfs from County Calculator output
4 feet depth of gravel storage
0.07 feet
0.9 inches
1
48
595 s.f.
833 cu.ft.
0.031 cfs from County Calculator output
3.5 feet depth of gravel storage
0.07 feet
0.8 inches
2
36
2,529 s.f.
3,540 cu.ft.
0.057 cfs from County Calculator output
3.5 feet depth of gravel storage
0.09 feet
1.1 inches
Appendix 6
Fuscoe Engineering, Inc.
Job No. 02722-001-01
Page 2 of 4
~
~
-' "--'
Bressi Ranch Planning Area 2
Permeable Paver Flow Control Orifice Sizing
Basin:
Imp:
AProvided =
VProvided =
Q=
H = 0
d=
Basin:
Imp:
AProvided =
VProvided =
Q=
H = 0
d=
Basin:
Imp:
AProvided =
VProvided =
Q=
H = 0
d=
Hydromodification
Management Study
2
37
1,488 s.f.
2,083 cu.ft.
0.032 cfs from County Calculator output
3.5 feet depth of gravel storage
0.07 feet
0.8 inches
3
4
893 s.f.
1 ,250 cu.ft.
0.019 cfs from County Calculator output
3.5 feet depth of gravel storage
0.05 feet
0.6 inches
3
19
1 ,785 s.f.
2,499 cu.ft.
0.039 cfs from County Calculator output
3.5 feet depth of gravel storage
0.07 feet
0.9 inches
Appendix 6
Fuscoe Engineering, Inc.
Job No. 02722-001-01
Page 3 of 4
,.....,
"-"
'·~,
Bressi Ranch Planning Area 2
Permeable Paver Flow Control Orifice Sizing
Basin:
Imp:
AProvided =
VProvided =
Q=
H = 0
d=
Basin:
Imp:
AProvided =
VProvided =
Q=
H = 0
d=
Basin:
Imp:
AProvided =
VProvided =
Q=
H = 0
d=
Hydromodification
Management Study
3
21
446 s.f.
625 cu.ft.
0.007 cfs from County Calculator output
3.5 feet depth of gravel storage
0.03 feet
0.4 inches
3
22
893 s.f.
1,250 cu.ft.
0.018 cfs from County Calculator output
3.5 feet depth of gravel storage
0.05 feet
0.6 inches
4
53
1,041 s.f.
2,083 cu.ft.
0.032 cfs from County Calculator output
5 feet depth of gravel storage
0.06 feet
0.7 inches
Appendix 6
Fuscoe Engineering, Inc.
Job No. 02722-001-01
Page 4 of 4