HomeMy WebLinkAboutSDP 03-07; LA COSTA OAKS SOUTH NEIGHBORHOODS 3.08 & 3.09; ADDENDUM TO STORM WATER MANAGEMENT PLAN; 2003-07-24ADDENDUM TO STORM WATER
MANAGEMENT PLAN
for
LA COSTA OAKS SOUTH
NEIGHBORHOODS 3.08 & 3.09
PLANNING
ENGINEERING
SURVEYING
IRVINE
LOS ANGELES
RIVERSIDE
SAN DIEGO
City of Carlsbad, California
Prepared for:
Real Estate Collateral Management Company
do Morrow Development
1903 Wright Place, Suite 180
Carlsbad, CA 92008
RECEIV
W.O. 2352-39 SEP 05 200
ENGINEERING
DEPARTMW
July 24, 2003
DAVE HAMMAR
LEX WhItMAN
ALISA V1ALPANDO
OFESS,0\
fc M
° ((( NO. 62O14im Eric Mosolgo, R. .E. \ %Exp. 09/30/05/
A Water Resources Department Manager
Hunsaker & Associates San Diego, Inc.CAOf
10179 Huennekens St.
San Diego, CA 92121
(858) 558-4500 PH
(858) 558-1414 FX
www.HunsakerSO.com
Inlo@HunsakerSD.com EM:smm h:\sw quaIit2352\39\3.08&3.09title.doc
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La Costa Oaks South (Neighborhoods 3.08.7 3.15)
Storm Water Management Plan
TABLE OF CONTENTS
CHAPTER 1 - Executive Summary
1.1 Introduction
1.2 Summary of Pre-Developed Conditions
1.3 Summary of Proposed Development
1.4 Results and Recommendations
CHAPTER 2— Storm Water Criteria
2.1 Regional Water Quality Control Board Criteria
2.2 City of Carlsbad SUSMP Criteria
CHAPTER 3- Identification of Typical Pollutants
3.1 Anticipated Pollutants from Project Site
3.2 Sediment
3.3 Nutrients
3.4 Trash & Debris
3.5 Oxygen-Demanding Substances
3.6 Oil & Grease
CHAPTER 4— Conditions of Concern
4.1 Receiving Watershed Descriptions .
4.2 Pollutants of Concern in Receiving Watersheds
4.3 Peak Flow Attenuation (Regional Detention Facility)
CHAPTER 5— Volume-Based Best Management Practices (BMPs)
5.1 Design Criteria
5.2 Extended Detention Basins
5.3 Pollutant Removal
5.4 Maintenance Requirements
CHAPTER 6— Flow-Based BMPs
6.1 Design Criteria
6.2 Vortechs Treatment Units
6.3 Pollutant Removal Efficiency Table
6.4 Maintenance Requirements
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La Costa Oaks South (Neighborhoods 3.08.— 3.15)
Storm Water Management Plan
CHAPTER 7— Source Control BMPs
7.1 Landscaping
7.2 Urban Housekeeping
7.3 Automobile Use
CHAPTER 8— Site BMP Design (Extended Detention Basin)
8.1 BMP Location
8.2 Determination of Treatment Volume
8.3 Water Quality Basin Design
CHAPTER 9— Site BMP Design (Vortechs Treatment Units)
9.1 BMP Locations
9.2 Determination of Treatment Flows
9.3 Vortechs Treatment Unit Selections
CHAPTER 10 - References•
List of Tables and Figures
Chapter 1 -Watershed Map .
Chapter 1 - BMP Location Map
Chapter 3— Pollutant Category Table
Chapter 4— San Diego Region Hydrologic Divisions
Chapter 4— Combined 1998 and Draft 2002 Section 303(d) Update
Chapter 4— Beneficial Uses of Inland Surface Waters
Chapter 4— Water Quality Objectives
Chapter 5— Pollutant Removal Efficiency Table (Volume-Based BMPs)
Chapter 6— Pollutant Removal Efficiency Table (Flow-Based BMPs)
Chapter 8— Extended Detention Basin Location Map
Chapter 8— Water Quality Basin Schematic (Profile)
Chapter 8— Stage-Storage Data
Chapter 8— Stage-Discharge Data for Water Quality Basin Dewatering
Chapter 8— 85th Percentile Rainfall Isopluvial Map
Chapter 9— Neighborhood 3.9 West BMP Location Map
Chapter 9— Neighborhood 3.9 East BMP Location Map
Chapter 9— Neighborhood 3.12 BMP Location Map
Chapter 9— Neighborhood 3.15 BMP Location Map
Chapter 9 - Design Runoff Determination Summary Table
Chapter 9— Vortechs Unit Treatment Capacity Table
Chapter 9— Vortechs System Data
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La Costa Oaks South (Neighborhoods 3.08&.3.09)
Addendum to Storm Water Management Plan•
Chapter 1 - EXECUTIVE SUMMARY
This report is an addendum to the "Storm Water Management Plan for La Costa
Oaks South", specifically addressing treatment of 85th percentile runoff from
Neighborhoods 3.08 and 3.09. A portion of the runoff from Neighborhoods 3.08 and
3.09 drains to the regional water quality basin located at the downstream end of
Neighborhood 3.12 (see Watershed Map on the following page) while the remainder
of the runoff drains to one of two Vortechs treatment units located within the property
boundary.
Per the "Hydrology Study, for La Costa Oaks Neighborhoods 3.08 and 3.09", dated
January 8, 2002, the storm drain systems from the two neighborhoods had the
following drainage parameters. upon their discharge to the public storm drain system.
Discharge to New Rancho Sante Fe Storm Drain System (Northern Outlet)
Drainage Area = 62 acres
Developed Area = 16 acres
Impervious Area = 4 acres
85th Percentile Runoff Volume = .0.2 acre-feet
Runoff treated in Regional Water Quality Basin in Neighborhood 3.12
Discharge to New Rancho Sante Fe Storm Drain System (Southern Outlet)
Drainage Area = 14 acres
Developed Area = 14 acres
85th Percentile Design Flow = 1.3 cfs
Runoff treated in Vortechs Model 1000
Discharge to Old Rancho Sante Fe Storm Drain System (@Paseo Conifera)
Drainage Area =24 acres
Developed Area = 24 acres
85th Percentile Design Flow = 2.3 cfs
Runoff treated in Vortechs Model 2000
As shown in the ensuing text from the "Storm Water Management Plan for La Costa
Oaks South", the water quality basin at the downstream end of Neighborhood 3.12
has a treatment capacity of 3.0 acre-feet. The combined 85 th percentile runoff volume
from Neighborhoods 3.08 and 3.09 totals 0.2 acre-feet,which is less than the 3.0
acre-feet of treatment storage provided in the water quality basin downstream.
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La Costa Oaks South (Neighborhoods 3.08 $3.09)
Addendum to Storm Water Management Plan
85th percentile design runoff volume calculations are provided in Chapter 8 of this
report. Since the downstream treatment facility is a volume-based BMP, hydrograph
methods were used to determine the corresponding 85th percentile runoff volume to
the regional water quality basin from Neighborhoods 3.08 and 3.09.
Both proposed Vortechs units are offline precast treatment units. The 85th percentile
design flow rate is forced into the treatment area by a diversion weir built in the -
upstream junction. Flows in excess of the design flow rate pass over the weir and
proceed downstream.
The following table shows the treatment capacities of each of the proposed Vortechs
units. Supporting calculations are located in Chapter 9 of this report.
VORTECHS UNIT TREATMENT CAPACITY TABLE
85th Pct. Recommended
Treatment Unit Design Flow Vortechs Treatment Capacity
(cfs) Model (cfs)
Paseo Conifera 2.3 2000 2.8
Neigh. 3.09 1.3 1000 1.6
Calculations contained within this report show that the regional water quality basin
and the two Vortechs treatment units effectively treat 85th percentile design runoff
from Neighborhoods 3.08 and 3.09 to the maximum extent practicable.
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La Costa Oaks South (Neighborhoods 3.08-3.15)
Storm Water Management Plan
Chapter 1 - EXECUTIVE SUMMARY
1.1 - Introduction
The La Costa Oaks South development is located east of the existing alignment of
Rancho Santa Fe Road, north of the existing extension of La Costa Avenue, and
south of the Stanley Mahr Reservoir in the City of Carlsbad, California (see
Watershed Map on the following page). Neighborhoods 3.08 through 3.15 comprise
the Oaks South portion of the larger La Costa Oaks development.
Per the City of Carlsbad SUSMP, the La Costa Oaks South project is classified as a
Priority Project and subject to the City's Permanent Storm Water BMPRequirements.
This Storm Water Management Plan (SWMP) has been prepared pursuant 1d
requirements set forth in the City of Carlsbad's "Standard Urban Storm Water
Mitigation Plan (SUSMP)." All calculations are consistent with criteria set forth by the
Regional Water Quality Control Board's Order No. 2001-01, and the City of Carlsbad
SUSMP.
This SWMP recommends the location and sizing of site Best Management Practices
(BMPs) which include one water quality extended detention basin and four Vortechs
treatment units (see BMP Location Map in this chapter).
Furthermore, this report determines anticipated project pollutants, pollutants of
concern in the receiving watershed, peak flow mitigation, recommended source
control BMPs, and methodology used for the design of flow-based and volume-based
BMPs.
1.2 - Summary of Pre-Developed Conditions
As shown in the watershed map on the following page, the majority of the pre-
developed La Costa Oaks South site drained to the Encinitas Creek watershed. The
remainder of the site (portions of Neighborhoods 3.08 and 3.09) drained to the San
Marcos Creek watershed via an existing inlet to the old Rancho Santa Fe storm drain
system.
The Regional Water Quality Control Board has identified both Encinitas Creek and
San Marcos Creek as part of the Carlsbad Hydrologic Unit, San Marcos Hydrologic
Area, and the Batiquitos Hydrologic Subarea (basin number 4.51).
1.3 - Summary of Proposed Development
Development of the La Costa Oaks South site will include the construction of single-
famliy homes as well as the associated streets, sidewalks, landscaping and utilities.
As part of the development, a regional detention basin was constructed at the
downstream end of the project in Neighborhood 3.12.
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La Costa Oaks South (Neighborhoods 3.08_73.15)
Storm Water Management Plan
The "Addendum to Preliminary Hydrology Study for Villages of La Costa - The Ridge
& The Oaks", prepared by Hunsaker & Associates and dated October 23, 2001,
details the design of the regional detention facility.
As shown in the referenced report, the regional detention facility mitigates design
peak flow increases below pre-development levels. In addition to peak flow
attenuation, this basin also serves as a regional water quality basin.
A riser extends from the basin bottom elevation of 285 feet to a top-elevation of 293
feet. Storm water treatment occurs in this bottom 8 feet of the basin while peak flow
attenuation is provided in the basin above elevation 293 feet.
Four flow-based BMPs will be located at other site discharge locations. 85th
percentile runoff will be treated in the proposed Vortechs systems at Paseo Conifera,
Neighborhood 3.09, Avenida Junipero, and La Costa Avenue prior-to discharging into
the receiving drainage system.
1.4— Results and Recommendations
The water. quality. / regional detention facility is located at the downstream (south) end
of Neighborhood 3.12 (see BMP Location Map on the following page). Runoff from
Neighborhoods 3.08, 3.10, 3.11, 3.12, 3.13, 3.14 and 3.15 drains to this location.
Additionally, runoff from a large offsite area will also drain to the basin area. The
combined. watershed area draining the basin was determined to be 401 acres.
Using the 85' percentile rainfall of 0.68 inches (see Ispoluvial Map at the end of this
chapter) and assuming 20 percent imperviousness in the contributing watershed,
HEC-HMS calculations predicted an 85th percentile runoff volume of roughly 3.0 acre-
feet.
The basin's stage-storage data shows that the water quality basin area has a peak
storage volume of 3.0-acre-feet at the riser top elevation of293 feet. The total basin
storage volume for detention (above elevation 293 feet) is 7.6 acre-feet. Since the
basin storage volume in the water quality portion of the basin equals the projected
85th percentile runoff volume, the BMP meets SUSMP criteria.
Each of the proposed Vortechs units is an offline precast treatment unit. The 85th
percentile design flow rate is forced into the treatment area by a diversion weir built in
the upstream junction. Flows in excess of the design flow rate pass over the weir and
proceed downstream.
Vortechs Model 1000 units, with a treatment flow capacity of 1.6 cfs, are
recommended for the treatment units at Neighborhood 3.09, La Costa Avenue and
Avenida Junipero while a Model 2000 is recommended at Paseo Conifera.
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La Costa Oaks South (Neighborhoods 3.08-3.15)
Storm Water Management Plan
Chapter 2— STORM WATER CRITERIA
2.1 - Regional Water Quality Control Board Criteria
All runoff conveyed in the proposed storm drain systems will be treated in compliance
with Regional Water Quality Control Board regulations and NPDES criteria prior to
discharging to natural watercourses. California Regional Water Quality Control Board
Order No. 2001-01, dated February 21, 2001, sets waste discharge requirements for
discharges of urban runoff from municipal storm separate drainage systems draining
the watersheds of San Diego County.
Per the RWQCB Order, post-development runoff from a site shall not contain
pollutant loads which cause or contribute to an exceedance of receiving water quality
objectives or which have not been reduced to the maximum extent practicable. Post-
construction Best Management Practices (BMPs), which refer to specific storm water
management techniques that are applied to manage construction and post-
constniction site runoff and minimize erosion, include source control -- aimed at
reducing the amount of sediment and other pollutants - and treatment controls that.
keep soil and other pollutants onsite once they have been loosened by storm water
erosion.
Post construction pollutants are a result of the urban development of the property
and the effects of automobile use. Runoff from paved surfaces can contain both
sediment (in the form of silt and sand) as well as a variety of pollutants transported by
the sediment. Landscape activities by homeowners are an additional source of
sediment. . '. .
All structural BMPs shall be located to infiltrate, filter, or treat the required runoff
volume or flow (based on the 85th percentile rainfall) prior to its discharge to any
receiving watercourse supporting beneficial uses.
2.2 - City of Carlsbad SUSMP Criteria
Per the City of Carlsbad SUSMP, the La Costa Oaks South project is classified as a
Priority Project and subject to the City's Permanent Storm Water BMP Requirements.
These requirements required the preparation of this Storm Water Management Plan.
The Storm Water Applicability Checklist, which must be included along with Grading
Plan applications, is included on the following page.
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Storm Water Standards
4/03/03
tVI -RESOURCES:&RERERENCEL
APPENDIX A
STORM WATER REQUIREMENTS APPLICABILITY CHECKLIST
Complete Sections 1 and 2 of the following checklist to determine your project's
permanent and construction storm water best management practices requirements.
This form must be. completed and submitted with your permit application.
Section 1. Permanent Storm Water BMP Requirements:
If any answers to Part A are answered "Yes," your project is subject to the "Priority
Project Permanent Storm Water BMP. Requirements," and "Standard Permanent Storm
Water BMP Requirements" in Section III, "Permanent Storm Water BMP Selection
Procedure" in the Storm Water Standards manual.
If all answers to Part A are "No," and any answers to Part B are "Yes," your project is
only subject to the "Standard Permanent Storm Water BMP Requirements". If every
question in Part A and B is answered "No," your project is exempt from permanent
storm water requirements.
Part A fltrmlna Priority Prolect Permanent Storm Water BMP Reaulrements.
Does the project meet the definition of one or more of the priority project
categories? V es N0
Detached residential development of 10 or more units
Attached residential development of 10 or more units -
Commercial development greater than 10,000 square feet -
Automotive repair shop -
S. Restaurant
Steep hillside development greater than 5,000 square feet
Project discharging to receiving waters within Environmentally Sensitive Areas -
Parking lots greater than or equal to 5,000 ft' or with at least 15 parking spaces, and
potentially exposed to urban runoff
Streets, roads, highways, and freeways which would create a new paved surface that is
5,000 square feet or greater
* Refer to the definitions section in the Storm Wafer Standards for expanded definitions of the priority
project categories.
Limited Exclusion: Trenching and resurfacing work associated with utility projects are not considered
priority projects. Parking lots, buildings and other structures associated with utility projects are
priority projects if one or more of the criteria In Part A Is met. If all answers to Part A are "No",
continue to Part B.
30
La Costa Oaks South (Neighborhoods 3.08- 3.15)
Storm Water Management Plan
3.2 - Sediment
Soils or other surface materials eroded and then transported or deposited by the
action of wind, water, ice, or gravity. Sediments can increase turbidity, clog fish gills,
reduce spawning habitat, smother bottom dwelling organisms, and suppress aquatic
vegetative growth.
3.3 - Nutrients
Inorganic substances, such as nitrogen and phosphorous, that commonly exist in the
form of mineral salts that are either dissolved or suspended in water. Primary sources
of nutrients in urban runoff are fertilizers and eroded soils. Excessive discharge of
nutrients to water bodies and streams can cause excessive aquatic algae and plant •
growth. Such excessive production, referred to as cultural eutrophication, may lead to
excessive decay of organic matter in the water body, loss of oxygen in the water,
release of toxins in sediment, and the eventual death of aquatic organisms.
3.4 - Trash & Debris
Examples include paper, plastic, leaves, grass cuttings, and food waste, which may
have a significant impact on the recreational value of a water body and aquatic
habitat. Excess organic matter can create a high biochemical oxygen demand in a
stream and thereby lower its water quality. In areas where stagnant water is present,
the presence of excess organic matter can promote septic conditions resulting in the
growth of undesirable organisms and the release of odorous and hazardous
compounds such as hydrogen sulfide.
3.5 - Oxygen-Demanding Substances
Biodegradable organic material as well as chemicals that react with dissolved oxygen
in water to form other compounds. Compounds such as ammonia and hydrogen
sulfide are examples of oxygen-demanding compounds. The oxygen demand of a
substance can lead to depletion of dissolved oxygen in a water body and possibly the
development of septic conditions -
3.6 - Oil & Grease
Characterized as high high-molecular weight organic compounds. Primary sources of
oil and grease are petroleum hydrocarbon products, motor products from leaking
vehicles, oils, waxes, and high-molecular weight fatty acids. Elevated oil and grease
content can decrease the aesthetic value of the water body, as well as the water
quality.
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La Costa Oaks South (Neighborhoods 3.08.-3.15)
Storm Water Management Plan
Chapter 4— CONDITIONS OF CONCERN
4.1 - Receiving Watershed Descriptions
As shown in the watershed map on the following page, the majorityof the pre-
developed La Costa Oaks South site drained to the Encinitas Creek watershed. In
developed conditions, runoff from a 401-acre watershed drains through the regional detention facility near La Costa Avenue (in Neighborhood 3.12) and then discharges
to a tributary of Encinitas Creek.
Runoff from Neighborhood 3.09 discharges to a storm drain system constructed
along with the new alignment of Rancho Santa Fe Road. This runoff, along with
runoff from Rancho Santa Fe Road confluences with the aforementioned 401-acre
watershed around the location of the La Costa Avenue - Camino De Los Coches intersection.
At the southeast corner of the Oaks South site, a 5-acre watershed discharges to a
side canyon near Avenida Junipero (in the headwater regions of Encinitas Creek). In
developed conditions, the total drainage area from the site area (including offsite
areas draining through the site) to the Encinitas Creek watershed is roughly 422
acres.
Portions of Neighborhood 3.08 drain to the San Marcos Creek watershed via an
existing inlet to the old Rancho Santa Fe storm drain system. In developed
- conditions, the developed condition drainage area from the site area to the San
Marcos Creek watershed is roughly 24 acres.
The Regional Water Quality Control Board has identified both Encinitas Creek and
San Marcos Creek as part of the Carlsbad Hydrologic Unit, San Marcos Hydrologic : Area, and the Batiquitos Hydrologic Subarea (basin number 4.51).
4.2 - Pollutants of Concern in Receiving Watersheds
Neither Encinitas Creek nor San Marcos Creek are listed on the EPA's 303(d) List of
endangered waterways (included in this Chapter). Per the "Water Quality Plan for the
San Diego Basin", the beneficial uses for both waterways include agricultural supply,
contact water recreation, non-contact recreation, warm freshwater habitat, and
wildlife habitat.
Table 3-2 from the "Water Quality Plan for the San Diego Basin" (included at the end
of this Chapter) lists-water quality objectives for a variety of potential pollutants
required to sustain the beneficial uses of the San Marcos hydrologic area.
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La Costa Oaks South (Neighborhoods 3.08.-.3..15)
Storm Water Management Plan
4.3 -Peak Flow Attenuation (Regional Detention Facility)
The "Addendum to Preliminary Hydrology Study for Villages of La Costa - The Ridge
& The Oaks", prepared by Hunsaker & Associates and dated October 23, 2001,
details the design of the regional detention facility located near La Costa Avenue in
Neighborhood 3.12.
As shown in-the referenced report, the regional detention facility mitigates design
peak flow increases below pre-development levels. In addition to peak flow
attenuation, this basin also serves as a regional water quality basin.
A riser extends from the basin bottom elevation of 285 feet.to a top elevation of 293
feet. Storm water treatment occurs in this bottom 8 feet of the basin while peak flow
attenuation is provided in the basin above elevation 293 feet.
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TABLE 1
SAN DIEGO REGION HYDROLOGIC DIVISIONS
BASIN
NUMBER HYDROLOGIC BASIN BASIN
NUMBER HYDROLOGIC BASIN
1.00 SAN JUAN HYDROLOGIC UNIT 2.74 Burnt NSA 1.10 Laguna HA 2.80 Aguanga HA 1.11 San Joaquin Hills NSA 2.81 Vail NSA 1.12 Lagtrna Beach NSA 2.82 DevIls Hale NSA 1.13 MaO NSA 2.83 Rodeo NSA 1.14 Dana Point NSA 2.84 TUIeCreek NSA 1.20 Mission Viejo NA 2.90 oalcgcve HA - 1.21 One NSA 2.91 Lower-Culp NSA 1.22 Upper flibuco NSA 2.92 Prevltt Canyon NSA 1.2a Middle Tabuco NSA 2.93 Dodge NSA 124 Gobernadora NSA 2.94 ChIhuahua NSA 125 upper San ivan NSA
1.26 Middle San Juan NSA 3.00 SAN LUIS REY HYDROLOGIC UNIT 127 Lower San jua, NSA 3.10 Leer San Luis HA' 1.28 Ortega NSA 3.11 Mission NSA J 1.30 San Clement. HA 3.12 Bonsall NSA 1.31 Prima Deshecha NSA 3.13 Moosa NSA. 1.32 SegwidaDeshacha NSA • 3.14 Valley Center .NSA 1.40 San Mateo Cairjon HA 3.15 Woods NSA 1.50 San On*9 HA 3.18 Rlncon NSA 1.51 San Onafre Valley NSA 3.20 Monserata 1.52 Las Pulgas NSA 3.21 Pala . HA 1.53 Stuart NSA 3.22. Plums NSA 323 La Jolla Anwga NSA 2.00 SANTA MARGARITA HYDROLOGIC UNIT 3.30 Wanier Valley . NA 2.10 Yskkn NA 3.31 Warner .. NSA 2.11 LoweryaJdora NSA 3.32 Combs NSA 2.12 Chappo NSA 2.13 Upper ysldora NSA 4.00 CARLSBAD HYDROLOGIC UNIT 2.20 DeLuz HA 4.10 Lam Alta HA 221 DeLuzCreek NSA 4.20 Buena Vista Creek • HA 2.22 Gavltan NSA 421 El Salta NSA 2.23 Vailealtas NSA 422 VIsta - NSA 2.30 MUrTIeta HA 4.30 AguaHedlonda HA 2.31 Wlldomar NSA 4.31 Los Manes NSA 2.32 Miirrteta NSA 4.32 Buena NSA 2.33 French NSA 4.40 Elnpj HA 2.34 LawerDomenlgonl 'NSA 1anMarcos 2.35 0OiTneilgonl NSA 1 4.51 4J.lftos - 2.36 DIamond NSA Richlai NSA 2.40 Auld HA 4.53 Thin Oaks NSA 2.41 Bachelor Mountain NSA 4.60 Escondldo Creek HA 2.42 Gertrudis NSA 4.61 San ElUo NSA 2.43 Lcv,j ru? NSA 4.62 Escandldo NSA 2.44 TucaIota NSA 4.63 Lake WOhiford NSA 2.50 echanga HA 2.51 Pauba NSA 5.00 SAN DIEGUITO HYDROLOGIC UNIT 2.52 Wolf NSA 5.10 Solana Beach HA 2.50 WIlson HA 5.11 Rancho Santa Fe NSA 2.81 Lancaster Valley NSA 5.12 Le Jolla NSA 2.82 Lewis NSA 5.20 Hodges HA 2.83 Reed Valley NSA 521 Del Olos NSA 2.70 Cave Rocks HA 5.22 Green NSA 2.71 Lower Coahuila NSA 823 Felldta NSA 2.72 Upper Coahulla NSA 524 Bear NSA 2.73 Anza NSA
¼
Table 4 - Combined 1998" and Draft 2002 Section 303(d) Update
Hydrologic
Pollutant! Waterbody
-
Segment I Area Stor
Descriptor Extent of Year
21 Loma Alta HA
Bacterial (904.10) Pacific Ocean Shoreline at Loma Alta Creek Mouth
lndlCatorsE I mile 1998 22 Loma Ma HA Loma Ma Slough Bacterial (904.10)
IndicatorsE 8 acres 1998
Eutrophic 23 Buena Vista Creek at Buena Vista Creek
Bacterial 0.65 miles 1998 HA (904.20) Pacific Ocean Shoreline Carlsbad City Beach at Carlsbad
Indicator sE Village Drive
Carlsbad State Beach at Pine
Avenue 24 El Salto HSA
Bacterial
(904.21)
Buena Vista Lagoon
1998 IndicatorsE 350 acres
Sedimentation / 350 acres 1998 Siltation
Nutrients 150 acres 1998 25 Los Monos HSA
(904.31)
Agua Hedlonda Lagoon Bacterial
IndicatorsE 5 acres 1998
Sedimentation /
Siltation 26 Los Monos HSA lower portion Diazinon lower 2 miles 2002 (904.31) Agua Hedionda Creek Total Dissolved* lower 8 miles 2002 Solids 27 San Marcos HA
IOflA rn Pacific Ocean Shoreline at Moonlight State Beach Bacterial
_.i.a......E 0.4 miles 1998 28 Escondido Creek Pacific at San Elijo Lagoon uacienai 0.8 miles 1998 HA904.60) Ocean Shoreline at Solana Beach
IndicatorsE
-- .IuI I_IIJd I
(904.61) San Elijo Lagoon
IndicatorsE 150 acres 1998
Eutrophic 330 acres
Sedimentation I 150 acres Siltation 30 San Dieguito HU at San Dieguito Lagoon Mouth Bacterial 0.8 miles 1998 (905.00) Pacific Ocean Shoreline Torrey Pines State Beach at Del lndicatorsE - ... Mar. (Anderson Canyon) 31 Del Dios HSA
Green Valley Creek Sulfate I mile 2002 (905.21)
32 Del Dios HSA Hodges Reservoir Entire Reservoir Color Entire
Reservoir
2002 (905.21) Nitrogen
Phosphorus
Total Dissolved
Solids 33 Felicita HSA
Felicita Creek Total Dissolved lower 2 miles 2002 (905.231 Solids 34 Felicita HSA Kit Carson Creek Total Dissolved I mile 2002
2002 (905.31) Cloverdale Creek Total Dissolved
Solids 36 Sutherland HSA
Entire (905.53)
Reservoir
Sutherland Reservoir Entire Reservoir • Color 2002
it tçdatid 7l2O3
&S%.3O3dUstSD Staff Rspott.20O22CO2 tht3O3d watt
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Table 2-2. BENEFICIAL USES OF INLAND SURFACE WATERS
" Surface Waters 1,2 Inland
V
Hydrologic
Unit Basin
Number
BENEFICIAL USE
M
U
N
A
G
R
I
N
0
P
R
0
C
G
W
R
F
R
S
H
P
0
W
R
E
C
1
R
E
C
2
B
I
0
L
W
A
R
M
C
0
L
DD
W
I
L
R
A
R
E
S
P
W
N
San Diego County Coastal Streams -continued
Buena Vista Lagoon 4.21 See Coastal Waters- Table 2-3
Buena Vista Creek 4.22 + • • • •
Buena Vista Creek 4.21 + 1 .0 • • • • S
Agua Hedlonda 4.31 See Coastal Waters- Table 2-3
Agua Hedlonda Creek 4.32 • • • • S S
Buena Creek 4.32 S • • • • f
Agua Hedionda Creek 4.31 • • • .. 0 • S • •
Letterbox canyon 4.31 • • • • S 0 •
Canyon de las Encinas • 4.40 + 0 • S
San Marcos Creek Watershed
Batiquitos Lagoon 4.51 See Coastal Waters- Table 2-3
San Marcos Creek 4.52 + • • • S S
unnamed Intermittent streams 4.53 + • • .5 5 .
San Marcos Creek Watershed
an Marcos + !. . - - - - - - f ncinitas Creek 4.51J + • . . 5 •
I.--
Existing Beneficial Use 1 Waterbodles are listed multiple times if they cross hydrologic area or sub area boundErles.
0 Potential Beneficial Use 2 Beneficial use designations apply to all tributaries to the Indicated waterbody. If not listed separately.
+ Excepted From MUN (See Text) -
Table 2-2
BENEFICIAL USES . 2-27 . September 8. 1094
- -Qll -v, ----. - - - - - -
Table 3-2. WATER QUALITY OBJECTIVES
Concentrations not to be exceeded more than 10% of the time during any one one year period.
Inland Surface Waters. Hydrologic I Unit Basin TDS Cl SO 4 %Na N&P Fe Number
Constitluent (mglL or as
Mn MBAS B ODO Color F Units
=
SAN LUIS REV HYDROLOGIC UNIT 903.00
Lower
IR
San Luis HA 3.10 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 1.0
Monserat HA 3.20 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 1.0
Warner Valley . HA 3.30 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 1.0
(CARLSBAD HYDROLOGIC UN~JT 904.00
Loma Ma HA 4.10 - - - - - - - - none 1 20 20 1.0
Buena Vista Creek HA 4.20 500 250 250 60 a 0.3 0.05 0.5 10.75 none 1 20 20 1.0
Ague Hedionda HA 4.30 500 250 250 60 - a 0.3 0.05 0.5 10.75 none 1 20 20 1.0
Encinas HA 4.40 - - - - - - - - none 20 20 1.0
Ea~nMarcos H - 4.50 500 250 250 1 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0
Escondido Creek HA 4.60 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0
SAN DIEGUITO HYDROLOGIC UNIT 905.00
Solana Beach . I-lA 5.10 500 250 250 1 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0
Hodges HA 5.20 500 250
1 250
250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0
San Pasqual HA 5.30 500 250 60 a 03 0.05 0.5 0.75 none 20 20 1.0
Santa Maria Valley HA 5.401 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0
Santa Ysabel HA . 5.501 500 250 250 60 I a - 0.3 10.051 0.5 10.751 none 1 20 1 20 1.0
PENASQUITOS HYDROLOGIC UNIT . 906.00'
Miramar Reservoir HA . 6.101 500 12501 250 1 60 1 a :0.3. 0.05 0.5 0.75 none 1 20 20 1 1.0
Poway HA
I-IA - &A-4-1 1. A.
6.20 500 250 250 1 60 1 a L 0.3 0.05 1 0.5 0.75 none 20 20 1 1.0
HSA - Hydrologic Sub Area (Lower case letters indicate endnotee following the table.)
Table 3-2
WATER QUALITY OBJECTIVES Page 3-23 September 8. 1994
La Costa Oaks South (Neighborhoods 3.08 7 3.15)
Storm Water Management Plan
Chapter 5— VOLUME-BASED BMPs
5.1 - Design Criteria
Volume-based BMPs shall be designed to mitigate the volume of runoff produced
from a 24-hour 85th percentile storm event, as determined from the local historical
rainfall record. The 85th percentile rainfall for the La Costa Oaks site is 0.68 inches
(see figure in Chapter 7).
Such facilities are usually designed to store the first flush runoff event below the
principle spillway elevation (riser, weir, etc.) while providing a means for low flow
dewatering. Outlet structures will be designed to convey runoff from the 100-year
frequency storm to the basin.
5.2 - Extended Detention Basin
j The La Costa Oaks South site contains one volume* based BMP - the bottom portion
of the regional detention facility that operates as an extended duration storm water
quality basin. This basin will collect the first flush runoff volume and retain it in the
basin for a period of 24-48 hours.
85th percentile, runoff volume, contained below the overflow elevation of the basin
riser, will be slowly discharged from the treatment control basin via low flow orifices in
the basin riser. After passing through the riser, an outlet pipe will déwater the basin
and discharge runoff to the natural drainage course downstream.
Runoff in excess of the first flush runoff volume will bypass the basin, via a large
diameter riser opening (top elevation = 293 feet).
5.3 - Pollutant Removal
As shown in the table (from the City of Carlsbad SUSMP) on the following page,
extended detention basins provide the following treatment efficiencies:
Sediment -
Nutrients -
Heavy Metals -
Trash & Debris -.
Oxygen-Demanding Substances -
Oil& Grease -
High removal efficiency
Medium removal efficiency
Medium removal efficiency
High removal efficiency
Medium removal efficiency
Medium removal efficiency
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Storm Water Standards
4/03/03
Table 4. Structural Treatment Control BMP Selection Matrix.
Pollutant of Concern Treatment Control BMP Categories
Blotilters Detention Infiltration Wet Ponds or Drainage Filtration Hydrodynamic Basins Basins() Wetlands Inserts Separator Systems(2) Sediment M H H H I H M Nutilents L M M M L M L Heavy Metals M M M H L H L Organic Compounds U U U U I M L Trash & Debits L H U U M H M Oxygen Demanding L M M M L M L Substances
Bacteria U U H U L M L OR & Grease M M U U L H I Pesticides U U U U L U L IncludIng trenches and porous pavemenL
Also known as hydrodynamic devices and baffle boxes.
Low removal efficiency
- Medium removal efficiency
H: High removal efficiency
U: Unknown removal efficiency
Sources: Guidance Specifying' Management Measures for Sources of Nonpoint Pollution in Coastal Waters (1993). NatIonal Storm water Best Management Practices Database (2001), and Guide for BMP Selection in Urban Developed Areas (2001).
La Costa Oaks South (Neighborhoods 3.08--r%3.15)
Storm Water Management Plan
5.4 -Maintenance Requirements
Proper maintenance is required to insure optimum performance of the basins.
General BMP inspections should check .for structural integrity of the riser, debris and
litter removal to prevent blockage of outlet orifices, etc. Fencing should be provided
at the top of the basins to serve as protection to the public from the safety hazards
inherent with standing water in the basin.
Maintenance of the extended detention basin will be the responsibility of the
Homeowners Association until the time at which the City of Carlsbad assumes
maintenance responsibilities. For proper maintenance to be performed, the storm
water treatment facility must be accessible to both maintenance personnel and their
equipment and materials.
Factors that affect the operational performance of a volume-based extended
detention ponds include mowing, control of pond vegetation, removal of accumulated
bottom sediments, removal of debris from all inflow and outflow structures,
unclogging of orifice perforations, etc. Periodic inspections should be performed
following each significant storm. These basins should be inspected at least twice a
year to evaluate facility operation.
Periodic inspections of both Water Quality Basins should be performed at regular
intervals throughout the year. Additional inspections will be required after major
rainfall events (defined per this Maintenance Plan as 24-hour rainfall events in
excess of 1 inch).
During the periodic and post-major event rainfall inspections, the inspector must•
identify any repairs and maintenance activities deemed necessary, including the
removal of trash, debris, and sediment from the upper chamber of the basin area.
All riser orifices should be unclogged during the periodic and post-rainfall inspections.
A Registered Civil Engineer will conduct an annual inspection of each basin. This
inspection will include a thorough inspection of the basin area, outlet structure and
internal gabion structure. The engineer will identify any required repairs as well as
corrective maintenance activity required to maintain the hydraulic performance of the
basins. Annual maintenance activities will include the removal of the heavy
vegetation that will inevitably grow in the basin. Roughly ½ half of the vegetation
should be removed from the basin at each annual maintenance session, including all
woody or aquatic vegetation and other obstructions to flow. All sediment, trash, and
debris should be removed from the upper and lower chambers of the basin at the
annual maintenance session.
Sediment removed during periodic, post-major rainfall event, and annual
maintenance can be placed in a sanitary landfill or used for composting activities. If
no basin maintenance takes places for a period of longer than 1 year, then trapped
pollutants may be deemed hazardous and special requirements may apply to
disposal activities. In such a case, removals would require testing prior to disposal in
a sanitary landfill.
EM:EM h:\sw quaIity.2352\39swmp-oaks-south.doc
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La Costa Oaks South (Neighborhoods 3.08-3.15)
Storm Water Management Plan
Chapter 6— FLOW-BASED BMPs
6.1 - Design Criteria
Flow-based BMPs shall be designed to mitigate the maximum flowrate of runoff
produced from a rainfall intensity of 0.2 inch per hour. Such basins utilize either
mechanical devices (such as vaults that produce vortex effects) or non-mechanical
devices (based on weir hydraulics and specially designed filters) to promote settling
and removal of pollutants from the runoff.
Per the request of the City of Carlsbad, 85th percentile flow calculations were
performed using the Rational Method. The basic Rational Method runoff procedure is
as follows:
Design flow (Q) = C l*A
Runoff Coefficient (C) -. In accordance with the County of San Diego standards, the
weighted runoff coefficient for all the areas draining to the treatment .unit was
determined using the areas analyzed in the final engineering hydrology report. The
runoff coefficient is based on the following characteristics of the watershed:
- Land Use - Single Family Residential in Developed Areas
Soil Type - Hydrologic soil group D was assumed for all areas. Group D soils
have very slow infiltration rates when thoroughly wetted. Consisting chiefly of
clay soils with a high swelling potential, soils with a high permanent water
table, soils with clay pan or clay layer at or near the surface, and shallow soils
over nearly impervious materials, Group D soils have a very slow rate of water ,
transmission.
Rainfall Intensity (I) -Regional Water Quality Control Board regulations and NPDES
criteria have established that flow-based BMPs shall be designed to mitigate a rainfall
intensity of 0.2 inch per hour.
Watershed Area (A) - Corresponds to total area draining to treatment unit.
6.2 - Vortechs Treatment Units
The Vortechs- Storm Water Treatment System is designed to efficiently remove grit,
contaminated sediments, metals, hydrocarbons and floating contaminants from
surface runoff. Combining swirl-concentrator and flow-control technologies to
eliminate turbulence within the system, the Vortechs System ensures-the effective
capture of sediment and oils and prevents resuspension of trapped pollutants for
flows up to 25 cfs.
EM:EM h:\sw quaIIty2352\39swmp-oaks-south.doc
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La Costa Oaks South (Neighborhoods 3.Oa—,3.15)
Storm Water Management Plan
6.4 - Maintenance Requirements
Flow-based storm water treatment devices should be inspected periodically to assure
their condition to treat anticipated runoff. Maintenance of the proposed Vortechnics
units includes inspection and maintenance I to .4 times per year.
Maintenance of the Vortechs units involves the use of a "vactor truck", which clears
the grit chamber of the treatment unit by vacuuming all the grit, oil and grease, and
water from the sump. Typically a 3-man crew is required to perform the maintenance
of the treatment unit. Properly maintained Vortechs Systems will only require
evacuation of the grit chamber portion of the system. In some cases, it may be
necessary to pump out all chambers. In the event of cleaning other chambers, it is
imperative that the grit chamber be drained first.
Proper inspection includes a visual observation to ascertain whether the unit is
functioning properly and measuring the amount of deposition in the unit. Floatables
should be removed and sumps cleaned when the sump storage exceeds 85 percent
of capacity specifically, or when the sediment depth has accumulated within 6 inches
of the dry-weather water level. The rate at which the system collects pollutants will
depend more heavily on site activities than the size of the unit.
EM:EM h:sw quaIity\235239swmp-oaks-south.doc
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La Costa Oaks South (Neighborhoods 3.08,-:!3115)
Storm Water Management Plan
Chapter 7— SOURCE CONTROL BMPs
7.1 - Landscaping
Manufactured slopes shall be landscaped with suitable ground cover or installed with
an erosion control system. Homeowners should be educated as to the proper routine
maintenance to landscaped areas including trimming, pruning, weeding, mowing,
replacement or substitution of vegetation in ornamental and required landscapes.
Per the RWQCB Order, the following landscaping activities are deemed unlawful and
are thus prohibited:
- Discharges of sediment
- Discharges of pet waste
- Discharges of vegetative clippings
- Discharges of other landscaping or construction-related wastes.
7.2 -Urban Housekeeping
Fertilizer applied by homeowners, in addition to organic matter such as leaves and
lawn clippings, all result in nutrients in storm water. runoff. Consumer use of
excessive herbicide or pesticide contributes toxic chemicals to runoff. Homeowners
should be educated as to the proper application of fertilizers and herbicides to lawns
and gardens.
The average household contains a wide variety of toxins such as oil/grease,
antifreeze, paint, household cleaners and solvents. Homeowners should be
educated as to the proper use, storage, and disposal of these potential storm water
runoff contaminants.
Per the RWQCB Order, the following housekeeping activities are deemed unlawful
and are thus prohibited:
Discharges of wash water from the cleaning or hosing of impervious surfaces
including parking lots, streets, sidewalks, driveways, patios, plazas, and
outdoor eating and drinking areas (landscape irrigation and lawn watering, as
well as non-commercial washing of vehicles in residential zones, is exempt
from this restriction)
Discharges of pool or fountain water containing chloride, biocides, or other
chemicals -
Discharges or runoff from material storage areas containing chemicals, fuels,
- grease, oil, or other hazardous materials
Discharges of food-related wastes (grease, food processing, trash bin wash
water, etc.).
EM:EM h:sw quaIity%235239swmp-oaks-south.doc
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La Costa Oaks South (Neighborhoods 3.08.-3.15)
Storm Water Management Plan
7.3 - Automobile Use
Urban pollutants resulting from automobile use include oil, grease, antifreeze,
hydraulic fluids, copper from brakes, and various fuels. Homeowners should be
educated as to the proper use, storage, and, disposal of these potential storm water
contaminants. .
Per the RWQCB Order, the following automobile use activities are deemed unlawful
and are thus prohibited:
- Discharges of wash water from the hosing or cleaning of gas stations, auto
repair garages, or other types of automotive service facilities.
- Discharges resulting from the cleaning, repair, or maintenance of any type of
equipment, machinery, or facility including motor vehicles, cement-related
equipment, port-a-potty servicing, etc.
- Discharges of wash water from mobile operations such as mobile automobile
washing, steam cleaning, power washing, and carpet cleaning.
The Homeowners Association should make all homeowners aware of the
aforementioned RWQCB regulations through a homeowners' education program. A
monitoring program should also be implemented to insure compliance.
EM:EM h:\sw quaflty\2352\39\swmp-oaks-9outh.doc
mo. 2352-39 7/25/03 6:42 AM
La Costa Oaks South 3.08 and 3.09 - Storm Water Quality Facility Sizing
RUNOFF HYDROGRAPH (SBUH METHOD -6-Hour Storm Event)
Given: Area = 61.7 acres
Pt = 0.68 Inches (Total rainfall for an 85th percentile - 24 hour storm event)
dt = 10.0 mm.
Tc = 18.2 mm. (Developed site conditions)
%IMP= 7%
PERVIOUS Parcel IMPERVIOUS Parcel
Area = 57.6 acres Area = 4.1 acres
CN = 68 CN = 98 (assuming dry antecedent moisture condition)
S = 4.71 S = 0.20
0.2S = 0.94 0.2S = 0.04
Compute: Developed Conditions Runoff hydrograph
Column (3) = Rainfall Distribution for San Diego County
Column (4) = Col. (3) x Pt = 85th percentIle -6 Hour Hyetograph at this location.
Column (5) = Accumulated Sum of Col. (4)
Column (6) = [If P <= 0.2S] = 0; use PERVIOUS Area"S value, [if P > 0.2S] = (Col.(5) - 0.2S)2/(CoI.(5) + 0.8S); use PERVIOUS AreS value.
Column (7) = Col.(6) of present time step - Col.(6) of previous time step
Column (8) = Same method as for Col.(6), except use the IMPERVIOUS Area "S"value.
Column (9) = Col.(8) of the present time step - C01.(8) of the previous time step.
Column (10) = ((PERVIOUS area /Total area) x Col.(7)) + ((IMPERVIOUS area /Total area) x Col.(9))
Column (11) = (60.5 x Col.(10) x Total Area)/10 (dt = 10 minutes); Routing Constant, w = dt I (2Tc + dt) =0.2153
Column (12) = Col.(12) of previous time step + (w x [Col.(11) of previous time step + Col.(11) of present time step - (2 x CoI.(12) of previous time step)])
Pervious Area Impervious Area
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
Time Time Rainfall Incre- Accumu- Accumu- Incre- Accumu- Incre- Total Instant design
Increment distri- mental lated lated mental lated mental Runoff hydro- hydro-
butlon Rainfall Rainfall Runoff Runoff Runoff Runoff graph graph
mm. %ofPt in. in. in. in. In. In. in. cfs cfs
1
2
10
20
0.0166
0.0166
0.0113
0.0113
0.0113
0.0226
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.0000
0.00
0.00
0.00
0.00
3 30 0.0166 0.0113 0.0339 0.0000 0.0000 0.0000 0.0000 0.0000 0.00 0.00
4 40 0.0200 0.0136 0.0475 0.0000 . 0.0000 0.0002 0.0002 0.0000 0.01 0.00
5 50 0.0200 0.0136 0.0811 0.0000 0.0000 0.0018 0.0016 0.0001 0.04 0.01
6 60 0.0200 0.0136 0.0747 0.0000 0:0000 0.0048 0.0030 0.0002 0.07 0.03
7 70 0.0226 0.0154 0.0900 0.0000 0.0000 0.0096 0.0047 0.0003 0.12 0.06
8 80 0.0226 0.0154 0.1054 0.0000 0.0000 0.0155 0.0060 0.0004 0.15 0.09
9 90 0.0226 0.0154 0.1208 0.0000 0.0000 0.0225 0.0070 0.0005 0.17 0.12
10 100 0.0334 0.0227 0.1435 0.0000 0.0000 0.0344 0.0119 0.0008 0.29 0.17
11 110 0.0334 0.0227 0.1662 0.0000 0.0000 0.0477 0.0134 0.0009 0.33 0.23
12 120 0.0334 0.0227 0.1889 0.0000 0.0000 0.0623 0.0146 0.0010 0.36 0.28
13 130 0.0778 0.0529 0.2418 0.0000 0.0000 0.0997 0.0374 0.0025 0.93 0.44
14 140 0.0778 0.0529 0.2947 0.0000 0.0000 0.1407 0.0410 0.0027 1.02 0.67
15 150 0.0778 0.0529 0.3476 0.0000 0.0000 0.1842 0.0435 0.0029 1.08 0.83 <<cpeak
16 160 0.0334 0.0227 0.3703 0.0000 0.0000 0.2034 0.0192 0.0013 0.48 0.81
17 170 0.0334 0.0227 0.3930 0.0000 0.0000 0.2230 0.0195 0.0013 0.48 0.67
34-9.RWQBSBUH.CO$VORTECftxls 1 of 2 7/28/2003
La Costa Oaks South 3.08 and 3.09 - Storm Water Quality Facility Sizing
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
Time Time Rainfall Incre- Accumu- Accumu- Incre- Accumu- Incre- Total Instant design
Increment distri- mental lated lated mental lated mental Runoff hydro- hydro-
bution Rainfall Rainfall Runoff Runoff Runoff Runoff graph graph
18
mm.
180
%ofPt in.
0.0227
in.
0.4157
in. in. in. In. in. cfs cfs
19 190
0.0334
0.0316 0.0215 0.4372
0.0000
.0.0000
0.0000
0.0000
0.2427
0.2617
0.0198
0.0189
0.0013
0.0013
0.49
0.47
0.59
0.54
20 200 0.0316 0.0215 0.4587 0.0000 0.0000 0.2808 0.0191 0.0013 0.47 0.51
21 210 0.0316 0.0215 0.4802 0.0000 0.0000 0.3000 0.0193 0.0013 0.48 0.50
22 220 0.0234 0.0159 0.4961 0.0000 0.0000 0.3144 0.0143 0.0010 0.36 0.46
23 230 0.0234 0.0159 0.5120 0.0000 0.0000 0.3288 0.0144 0.0010 0.36 0.42
24 240 0.0233 0.0158 0.5278 0.0000 0.0000 0.3432 0.0144 0.0010 0.36 0.39
25 250 0.0213 0.0145 0.5423 0.0000 0.0000 0.3565 0.0132 0.0009 . 0.33 0.37
26 260 0.0213 0.0145 . 0.5568 0.0000 0.0000 0.3698 0.0133 0.0009 0.33 0.35
27 270 0.0213 0.0145 0.5713 0.0000 0.0000 0.3831 0.0133 0.0009 0.33 0.34
28 280 0.0175 0.0119 0.5832 0.0000 0.0000 0.3941 0.0110 0.0007 0.27 0.33
29 290 0.0175 0.0119 0.5951 0.0000. 0.0000 0.4051 0.0110 0.0007 0.27 0.30
30 300 0.0175 0.0119 0.6070 0.0000 0.0000 0.4162 0.0111 0.0007 0.27 0.29
31 310 0.0183 0.0124 0.6194 0.0000 0.0000 0.4278 0.0116 0.0008 0.29 0.29
32 320 0.0183 0.0124 0.8319 0.0000 0.0000 0.4394 0.0116 0.0008 0.29 0.29.
33 330 0.0183 0.0124 0.6443 0.0000 0.0000 0.4510 0.0118 0.0008 0.29 0.29
34 340 0.0175 0.0119 0.6562 0.0000 0.0000 0.4622 0.0112 0.0007 0.28 0.29
35 350 0.0175 0.0119 0.6681 0.0000 0.0000 0.4733 0.0112 0.0007 0.28 0.28
36 360 0.0175 0.0119 0.6800 0.0000 0.0000 . 0.4845 0.0112 0.0007 0.28 0.28
37 370 0.0000 0.0000 0.6800 0.0000 0.0000 0.4845 0.0000 0.0000 0.00 0.22
38 380 0.0000 0.0000 0.6800 0.0000 0.0000 0.4845 0.0000 . 0.0000 0.00 0.12
39 390 0.0000 0.0000 0.6800 0.0000 0.0000 0.4845 0.0000 0.0000 0.00 0.07
40 . 400 0.0000 0.0000 0.6800 0.0000 0.0000 0.4845 0.0000 0.0000 0.00 0.04
41 410 0.0000 0.0000 0.6800 0.0000 0.0000 0.4845 0.0000 0.0000 0.00 0.02
42 420 0.0000 0.0000 0.8800 0.0000 0.0000 0.4845 0.0000 0.0000 0.00 0.01
43 430 0.0000 0.0000 0.8800 0.0000 0.0000 0.4845 0.0000 0.0000 0.00 0.01
44 440 0.0000 0.0000 0.6800 0.0000 0.0000 0.4845 0.0000 0.0000 0.00 , 0.00
45 450 0.0000 0.0000 0.6800 0.0000 0.0000 0.4845 0.0000 0.0000 0.00 0.00
46 . 460 0.0000 0.0000 0.6800 0.0000 0.0000 0.4845 0.0000 0.0000 0.00 0.00
47 470 0.0000 0.0000 0.6800 0.0000 P0.0000 0.4845 0.0000 0.0000 0.00 0.00
48 . 480 0.0000 0.0000 0.6800 0.0000 0.0000 0.4845 0.0000. 0.0000 0.00 0.00
Time = 8.0 hours
* (Found by summing this column and multiplying by 600. 600 Is the conversion
required to convert SUM(Q) In cfs to total volume In cubic feet as follows:
V=SUM(Q)xdt
(cu.ft.) = (cu.ft/s) x (10 mm.) x (60 s/mm.)
Total Volume of Runoff = 7220 Cu. ft*
.0.17 ac-ft
Peak Hour Rainfall Intensity = . 0.227 in/hr
Total Flowrate of Runoff = 0.83 cfs
3-8-9.RW0B-SBUH.CDS-V0RTECIix1s 2 of 2 712812003
Rational Method Results at: La Costa Oaks South 3.08 & 3.09
Time of Concentration, Tc = .18.2 minutes
or T = [1. 8(1.1 C)*(D)aO.5]Is O.333
= :::::::: minutes, for L= ft, s= %
% Impervious
C
Development Area (ac)
--
EEA -
S..'
EE
rn
Sum of Areasl 45.3 1 Al 1 0.0 0.0 1 0.0 1 0.0 1 0.0 1 0.0 1 0.0 = 61.7 ac.
6.7% Impervious % lmeervioEsl 0 1 25 1 95 1 1 1 1 1
Weighted Average C = 0.46
is
La Costa Oaks South (Neighborhoods 3.08..-7 3.15)
Storm Water Management Plan
Chapter 8— SITE BMP DESIGN
EXTENDED DETENTION BASIN
8.1 - BMP Location
The water quality / regional detention facility is located at the downstream (south) end
of Neighborhood 3.12 (see BMP Location Map on the following page). Runoff from
Neighborhoods 3.08, 3.10, 3.11, 3.12, 3.13, 3.14 and 3.15 drains to this location.
Additionally, runoff from a large offsite area will also drain to the basin area. The
combined watershed area draining the basin was determined to be 401 acres.
8.2 -Determination of Treatment Volume
Per the "Addendum to Preliminary Hydrology Study for Villages of La. Costa - The
Ridge and The Oaks (dated October 23, 2001)," HEC-HMS output shows the
drainage area to the. regional detention /water quality basin is 401 acres. The
corresponding time of concentration (from a. previous Rational Method analysis
contained within the "Preliminary Hydrology Study for Villages of La Costa - The
Ridge and The Oaks" is 22.3 minutes.
Using the 85th percentile rainfall of 0.68 inches (see Ispoluvial Map at the end of this
chapter) and assuming 20 percent imperviousness in the contributing watershed,
HEC-HMS calculations predicted an 85th percentile runoff volume of roughly 3.0 acre-
feet.
8.3 - Water Quality Basin Design
The water quality I detention basin exhibit included in this chapter shows that the
riser makes this basin double as a detention and water quality basin. The riser will
extend from the basin bottom elevation of 285 feet to a top elevation of 293 feet.
Detention basin stage-storage calculations (included in this chapter) show that no
storage effects were considered below the riser top elevation of 293 feet. In other
words, peak flow attenuation was attained in the basin storage area above the Water
Quality Basin (above elevation 293 feet)
The stage-storage data shows that the water quality basin area has a peak storage
volume of 2.97 acre-feet at the riser top elevation of 293 feet. The total basin storage
volume for detention (above elevation 293 feet) is 7.65 acre-feet.
Stage-discharge data for the riser dewatenng (included in this chapter) shows that
the peak outflow from the water quality basin area is 9 cfs at elevation 293 feet. At
lower elevations in the Water Quality Basin, the corresponding outflow is less (for
instance, the discharge rate at elevation 288 feet is 2.4 cfs).
EM:EM h:\swquality\2352\39\swmp-oaks-south.doc
w.o. 2352-39 7/25103 8:06 AM
HUNSAKER & ASSOCIATES PROJECT: L.C. QAgS DES. BY: _rRa/ SAN DIEGO, INC. CHECKED BY: _______ DATE.ffol :I.1IFT':::1::..i.:F. ::r::i:::i:::j: I : ........ 1 .... ..... ..... ..... ..... ..... .1 .... ...._i....1........ .... ....... .......................1 ..•..I..................................t. ..I.. ...................4....... .................
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'VILLAGES OF LA COSTA - THE OAKS
HYDRAULIC ANALYSIS OF RISER SLOTS AT NODE 106
Orifice Equation (for h > M):
Q = Ca(2gh)° (Equation 4-10, KIngs Handbook)
Q = Ca(64.32h)°6; C 0.6 from Table 4-4 KIngs Handbook
Q = 4.812 a(h)°, where a = area of orifice opening, h = head (ft) above centerline of opening.
Weir Formula (for h <M)
Q = CLH'5 (Equation 5-10, Kings Handbook)
C = 3.2 from Fig. 5-3
For Riser where:
d = 36 In. • a 7.07 sq. ft., I = 9.42 ft. @ elevation 293.0 ft. (top of riser), 285.0 ft. (floor of basin)
and slots where:
I = 0.5 In. • M = 6.0 In., at 18.80 In. on center,
Then area = 0.021 sq. ft., and # of slots per row = 6.0
ELEV. ROW I ROW 2 ROW 3 ROW 4 ROW 5 ROW 6 ROW 7 TOTAL
(feet) H (it) Q (cis) H (it) Q (cia) H (it) Q (cis) H (ft) Q (cis) H (it) 0 (cis) H (it) 0 (cis) H (ft) Q (cis) Q (cia)
285.0 0.0 0.0 - - - - - - - - - - - - 0.0
285.500.50 0.57 - - - - - - - - - - - 0.6
286.00 1.00 0.60 0.00 0.0 - - - - . - - - - - 0.6
286.50 1.50 0.67 0.50 0.57 - - - - - - - - - 1.2
287.00 2.00 0.80 1.00 0.60 0.00 0.0 - - - - - - - 1.4
287.50 2.50 0.90 1.50 0.67 0.50 0.57 - 2.1
288.00 3.00 1.00 2.00 0.80 1.00 0.60 0.00 0.0 - - - - - 2.4
288.50 3.50 1.09 2.50 0.90 1.50 0.67 0.50 . 0.57 - - - - - - 3.2
289.00 4.00 1.17 3.00 1.00 2.00 0.80 1.00 0.60 0.00 0.0 - - - - 3.6
289.50 4.50 1.24 3.50 1.09 2.50 0.90 1.50 0.67 0.50 0.57 - - - - 4.5
290.00 5.00 1.31 4.00 1.17. 3.00 1.00 2.00 0.80 1.00 0.60 0.00 0.0 - - 4.9
290.50 5.50 1.38 4.50 1.24 3.50 1.09 2.50 0.90 1.50 0.67 0.50 0.57 - - 5.9
291.00 6.00 1.45 5.00 1.31 4.00 1.17 3.00 1.00 2.00 0.80 1.00 0.60 0.00 0.0 6.3
291.50 6.50 1.51 5.50 1.38 4.50 1.24 3.50 1.09 2.50 0.90 1.50 0.67 0.50 0.57 7.4
292.00 7.00 1.57 6.00 1.45 5.00 1.31 4.00 1.17 3.00 1.00 2.00 0.80 1.00 0.60 7.9
292.50 7.50 1.62 6.50 1.51 5.50 1.38 4.50 1.24 3.50 1.09 2.50 0.90 1.50 0.67 8.4
293.001 8.00 1 1.68 1 7.00 1 1.57 1 6.001.4 5 5.00 1.31 4.00 1.17. 3.00. 1.00 2.00 0.80 9.0
811412001
-IQ f) •
i.v
La Costa Oaks South (Neighborhoods 3.08 -3.15)
Storm Water Management Plan -.
Chapter 9- SITE BMP DESIGN
VORTECHS TREATMENT UNITS
9.1 - BMP LocatiOns
The site design includes four Vortechs treatment units (shown on BMP Location
Maps located on the following pages.
Portions of Neighborhood 3.08 drain to the San Marcos Creek watershed via
an existing inlet to the old Rancho Santa Fe storm drain system. Prior to
discharge to the existing storm drain system, 85th percentile runoff will be
treated in an óffline Vortechs Mbdel 2000 (near Paseo Cónifera). In developed
conditions, the developed condition drainage area from the site area to the
San Marcos Creek watershed is roughly 24 acres.
- Runoff from Neighborhood 3.09 discharges to a storm drain system
constructed along with the new alignment of. Rancho Santa Fe Road. Prior to
discharge to the Rancho Santa Fe storm drain system, 85th percentile flow will be treated in an offline Vortechs Model 1000. In developed conditions, the
contributing drainage area to this treatment unit is roughly 14 acres.
At the southeast corner of the Oaks South site, a 5-acre watershed discharges
to a side canyon near Avenida Junipero. Prior to discharge to the natural
canyon, 85th percentile flow will be treated in an offline Vortechs Model 1000.
- Runoff from street. areas not reaching the Water Quality Basin will be treated
in an offline Vortechs Model in La Costa Avenue. The developed area from La
Costa Oaks South to this treatment unit is 2 acres.
9.2 - Determination of Design Treatment Flows
The 85th percentile design flow rates have been calculated using the Rational
Method. Required data for the Rational Method treatment flow determination include
the following: .
Runoff Coefficient I
Rainfall Intensity (I) = 0.20 inches per hour
Drainage area to treatment unit (A)
Runoff coefficients were derived based upon a weighted average of each area
tributary to the treatment unit and-the associated runoff coefficient.
EM:EM h:sw quaIity2352'.39swnip-oaks-south.doc
w.o. 2352-39 7/25/03 11:23 AM
La Costa Oaks South (Neighborhoods 3.08.- 3.15)
Storm Water Management Plan
The following table summarizes the parameters used for determination of design
flows to each of the Vortechs treatment units.
DESIGN RUNOFF DETERMINATION SUMMARY TABLE
Treatment Runoff Rainfall . Drainage 850 Pct.
Unit Coefficient Intensity Area Design Flow
(C) .(in/hr) (acres) (cfs)
Neigh. 3.08 0.49 0.2 23.9 2.3
Neigh. 3.09 0.49 .0.2 13.7 1.3
Avenida Junip 0.49 0.2 5.4 0.5
La Costa Ave 0.85 0.2 2.1* 0.4
W Developed area from La Costa Oaks South
9.3 - Vortechs Treatment Unit Selection
Each of the proposed. Vortechs units is an offline precast treatment unit. The 85th
percentile design flow, rate is forced into the treatment area by a diversion weir built in
the upstream junction. Flows in excess of the design flow rate pass over the weir and
proceed downstream.
The following table shows the treatment capacities of each of the (4) proposed
Vortechs units.
VORTECHS UNIT TREATMENT CAPACITY TABLE
Treatment
Unit
85th Pct.
Design Flow
(cfs)
Recommended
Vortechs
Model
Treatment Capacity
(cfs)
Neigh. 3.08 2.3 2000 2.8
Neigh. 3.09 1.3 1000 1.6
Avenida Junip 0.5 1000 1.6
La Costa Ave 0.4 1000 1.6
EM:EM h:\sw quality%2352\39swmp-oaks-south.doc
w.o. 2352-39 7/25/03 11:37 AM
I.
i
I
1) Initial Wet Weather Phase
During a two-month storm event the water level begins to
rise above the top of the inlet pipe. This influent control
feature reduces turbulence and avoids resuspension
of pollutants.
I .. 3) Full Capacity Phase I When the high-flow outlet approaches frill discharge. S=n
ä,s are flcMng at peek capadt The Vartechs System is
designed to math your design storm flaw and provide treat-
ment throughout the range of storm events without bypass-
ing. To accommodate very high flow rates, Vortechnics can
assist designers with configuring a peak-flow bypass.
2) Transition Phase
As the inflow rate increases above the controlled outflow
rate, the tank fills and the floating contaminant layer accu-
mulated from past storms rises. Swirling action increases
at this stage, while sediment pile remains stable.
4) Storm Subsidence Phase/Cleaning
Treated runoff is decanted at a controlled rate, restoring the
water level to a law dr?weather volume and revealing a conical
pile of sediment The low water level facilitates inspection and
cleaning, and significantly reduces maintenance costs. The
system's central baffle prevents transfer of floatables to the
outlet during cleaning or during the next storm.
I
1
- IjII
Stormwater Treatment
Perfcred COMB
I. 0 Plus 6' Typical rl
afse
ILI-
Plan -View
1 1' 3toff to IF
I Typa1
.t =
Elevation View
To begin the design of your
Vortechs System, refer to the
sizing chart below and com-
plete a Specifier's Worksheet to
provide details about your site
and design flows. Then simply
fax or mail the worksheet to
Vortechnics with your site plan,
and we'll produce detailed
Vortechs System scale draw-
ings free of charge.
Vortechs System Inlet/Outlet Configurations
Vortechs Systems can be configured to accommo-
date various. inlet and outlet pipe orientations.
The inlet pipe can enter the end or side of the
tank at right angles - outlet pipes can exit the end
or the side of system at most angles.
End Inlet Side Inlet
To
Polish
t Pretreatment OualI
SECTION 02721
STORM WATER TREATMENT SYSTEM
PART 1.00 GENERAL
1.01 DESCRIPTION
Work included:
The Contractor, and/or a manufacturer selected by the Contractor and approved
by the Engineer, shall furnish all labor, materials, equipment and Incidentals-
required and Install all precast concrete stormwater treatment systems and
appurtenances in accordance with the Drawings and these specifications.
Related work described elsewhere:
Unit Masonry
Miscellaneous Metals
Waterproofing
1.02 QUALITY CONTROL INSPECTION
The quality of materials, the process of manufacture, and the finished sections
shall be subject to inspection by the Engineer. Such inspection may be made at
the place of manufacture, or on the work site after delivery, or at both places, and
the sections shall be subject to rejection at any time if material conditions fail to
meet any of the specification requirements, even though sample sections may
have been accepted as satisfactory at the place of manufacture. Sections
rejected after delivery to the site shall be marked for Identification and shall be
removed from the site at once. All sections which have been damaged beyond
repair during delivery-will be rejected and, if already installed, shall be repaired to.
the Engineer's acceptance level, If permitted, or removed and replaced, entirely
at the Contractor's expense.
All sections shall be inspected for general'appearance, dimensions, soundness,
etc. The surface shall be dense, dose textured and free of blisters, cracks,
roughness and exposure of reinforcement
Imperfections may be repaired, subject to the acceptance of the Engineer, after
demonstration by the manufacturer that strong and permanent repairs result.
Repairs shall be carefully inspected before final acceptance: Cement mortar
used for repairs shall have a minimum compressive strength of 4,000 psi at the
end of 7 days and 5,000 psi at the end of 28 days when tested in 3 inch diameter
by 6 Inch long cylinders stored in the standard manner. Epoxy mortar may be
utilized for repairs.
1.03 SUBMI17ALS
A. Shop Drawings
The Contractor shall be provided with dimensional drawings and, when specified,
utilize these drawings as the basis for preparation of shop drawings showing
details for construction, reinforcing, joints and any cast-in-place appurtenances.
Shop drawings shall be annotated to indicate all materials to be used and-all
applicable standards for materials, required tests of materials and design
assumptions for structural analysis. Design calculations and shop drawings shall
be certified by a Professional Engineer retained by the system manufacturer or
contractor and licensed in the state where the system Is to be installed. Shop
drawings shall be prepared at a scale of not less than 1/4" per foot. Six (6) hard
copies of said shop drawings shall be submitted to the Engineer for review and
approval.
B. Affidavit on patent Infringement
The Contractor shall submit to the Engineer, prior to installation of the stormwater
treatment system, an affidavit regarding patent infringement rights stating that
any suit àr claim against the Owner due to alleged infringement rights shall be
defended by the Contractor whowill bear all the costs, expenses and attorney's
- -, fees incurred thereof.
PART 2.00 PRODUCTS
2.01 MATERIALS AND DESIGN
A. Concrete for precast stormwater treatment systems shall conform to ASTM
C 857 and C 858 and meet the following additional requirements:
The wall thickness shall not be less than 6 inches or as shown on the
dimensional drawings. In all cases the wall thickness shall be no less than
the minimum thickness necessary to sustain HS20-44 loading requirements
as determined by a Licensed Professional Engineer.
Sections shall have tongue and groove or ship-lap joints with a butyl mastic
sealant conforming to ASTM C 990.
Cement shall be Type III Portland cement conforming to ASTM C 150.
Pipe openings shall be sized to accept pipes of the specified size(s) and•
material(s), and shall be sealed by the Contractor with a hydraulic cement
conforming to ASTM C 595M
5. Internal metal components shall be aluminum alloy 5052-H32 in accordance
with ASTM B 209.
6. Brick or masonry used to build the manhole frame to grade shall conform to
ASTM C 32 or ASTM C 139 and the Masonry Section of these Specifications.
\MDISYSDATAWORTECHNEWJL\STDETAlLWORTSPEC.DOC SECTION 02721 Page 2
S
2.02
Casting for manhole frames-and covers shall be in accordance with The
Miscellaneous Metals Section of these Specifications.
All sections shall be cured by an approved method. Sections shall not be
shipped until the concrete has attained a compressive strength of 4,000 psi or
util 5 days after fabrication and/or repair, whichever is the longer.
A butimen sealant in conformance with ASTM C 990 shall be utilized in
affixing the aluminum swirl chamber to the concrete vault
PERFORMANCE
Each stormwater treatment system shall adhere to the following performance specifications
at the specified design flows, as listed below:
Table 2.02
Vortechs
Model
Swirl
Chamber
Diameter
(ft)
Design
Treatment
Capacity
(cfs)
Sediment
Storage
(yd3)
1000 3.67 2.3 1.00
.2000 4 2.8 1.25
3000 5 4.5 1.75
4000 6 6.0 2.50
5000 7 8.5 3.25
7000 8 11.0 4.00
.9000 9 14.0 4.75
110.00 10 17.5 5.50
16000 - 12 25.0 7.00
Each stormwater treatment system shall include a ciróular aluminum "swirl chamber" (or "grit
chamber") with a tangential inlet to induce a swirling flow pattern that will accumulate and
store settleable solids in a manner and a location that will prevent re-suspension of previously
captured particulates. Each swirl chamber diameter shall not be less than the diameter listed
in Table 2.02 (neglecting chamber wall thickness).
Each stormwater treatment system shall be of a hydraulic design that includes flow controls
designed and certified by a professional engineer using accepted principles of fluid mechanics
that raise the water surface inside the tank to a pre-determined level in order to prevent the
re-entrainment of trapped floating contaminants.
Each stormwater treatment system shall be capable of removing 80% of the net annual Total
Suspended Solids (TSS). Individual stormwater treatment systems shall have the Design
Treatment Capacity listed in Table 2.02, and shall not resuspend trapped sediments or re-
entrain floating contaminants at flow rates up to and including the specified Design Treatment
Capacity.
Individual stormwater treatment systems shall have usable sediment storage capacity of not
less than the corresponding volume listed in Table 2.02. The systems shall be designed such
SECTION 02721 Page 3
that the pump-out volume is less than Y2 of the total system volume. The systems shall be
designed to not allow surcharge of the upstream piping network during dry weather conditions. , A water-lock feature shall be incorporated into the design of the stormwater treatment system
to prevent the introduction of trapped oil and floatable, contaminants to the downstream piping
during routine maintenance and to ensure that no oil escapes the system during the ensuing
rain event. Direct access shall be provided to the sediment and floatable contaminant storage "' chambers to facilitate maintenance. There shall be no appurtenances or restrictions within
these chambers.
The stormwater treatment system manufacturer shall furnish documentation which supports
all product performance claims and features, storage capacities and maintenance
requirements.
Stormwater treatment systems shall be completely housed within one rectangular structure.
2.03 MANUFACTURER
Each stormwater treatment system shall be of a type that has been Installed and used
successfully for a minimum of 5 years. The manufacturer of said system shall have
been regularly engaged in the engineering design and production of systems for the
physical treatment of stormwater rünoff
Each stormwater treatment system shall be a Vorteth TM s System as manufactured by Vortechnics, Inc., 41 Evergreen Drive, Portland, Maine 04103, phone: 207-878-3662,
fax: 207-878-8507; and as protected under U.S. Patent # 5,759,415.
PART 3.00 EXECUTION
3.01 INSTALLATION
Each Stormwater Treatment System shall be constructed according to the sizes
shown on the' Drawings and as specified herein. Install at elevations and
locations shown on the Drawings or as otherwise directed by the Engineer.
Place the precast base unit on a granular subbase of minimum thickness of six
inches. after compaction or of greater thickness and compaction if specified
elsewhere. The granular subbase shall be checked for level prior to setting and
the precast base section of the trap shall be checked for level at all four corners
after It is set. If the slope from any corner to any other,comer exceeds 0.5% the
base section shall be removed and the granular subbase material re-leveled.
Prior to setting subsequent sections place butimen sealant in conformance with ASTM
C990-91 along the construction joint in the section that is already in place.
After setting the base and wall -or riser sections install, the circular swirl chamber
wall by bolting the swirl chamber to the side walls at the three (3) tangent points
and at the 34nch wide inlet tab using HILT] brand concrete anchors or equivalent
1/2-inch diameter by 2-3/4" minimum length at heights of approximately three
is inches (3") off the floor and at the mid-height of the completed trap (at locations
of pre-drilled holes in aluminum components). Seal the bottom edge of the swirl
\MDflSYSDATAWORTECHN\EMA1LSTDETA1LWORTSPEC.DOC
• SECTION 02721 Page 4
chamber to the trap floor with the supplied aluminum angle flange. Adhere 1,4
thick by 1" wide neoprene sponge material to the flange with half of it's width on
the horizontal leg of the flange and half of it's width on the vertical leg. The
aluminum angle flange shall be affixed to the floor with a minimum 3/8" diameter by 2-3/4" drop in wedge anchor at the location of the predrilled holes. Affix the
swirl chamber to the flange with hex head %" x 1-1/2' zinc coated self- tapping
screws at the location of the predrilled holes. Seal the vault sidewalls to the
outside of the swirl chamber from the floor to the same height as the inlet pipe
invert using butyl mastic or approved equal.
Prior to setting the precast roof section, butimen sealant equal to ASTM C990 shall be
placed along the top of the baffle wall, using more than one layer of mastic if
necessary, to a thickness at least one inch (1") greater than the nominal gap between
the top of the baffle and the roof section.
The nominal gap shall be determined either by field measurement or the shop
drawings. After placement of the roof section has compressed the .butyl mastic sealant
in the gap, finish sealing the gap with an approved non-shrink grout on both sides of
the gap using the butyl mastic as a backing material to which to apply the grout. Also
apply non-shrink grout to the joints at the side edges of the baffle wall.
After setting the precast roof section of the stormwater treatment system, set
precast concrete manhole riser sections, to the height required to bring the cast
Iron manhole covers to grade, so that the sections are vertical and in true
alignment with a 1/4 inch maximum tolerance allowed. Backfill In a careful
manner, bringing the fill up in 6" lifts on all sides. -If leaks appear, clean the Inside
joints and caulk with lead wool to the satisfaction of the Engineer. Precast
sections shall be set In a manner that will result in a watertight joint. In all
instances, installation of Stormwater Treatment Systems shall conform to ASTM
specification C891 TMStandard Practice For Installation of Underground Precast
Utility Structures".
Plug holes in the concrete sections made for handling or other purposes with a
- nonshrink grout or by using grout in combination with concrete plugs.
Where holes must be cut in the precast sections to accommodate pipes, do all
cutting before setting the sections In place to prevent any subsequent jarring
which may loosen the mortar joints. The Contractor shall make all pipe
connections.
'MDI\SYSDATAWORTECHEMA,L\STDETA1LWORTSPEC.D0C SECTION 02721 Page 5
VORTECHSTM STORMWATER TREATMENT SYSTEM
0 DESIGN AND OPERATION
Basic Operation
The Vortechs System is sized on the basis of removing both sediment and floating pollutants
from stormwater runoff. When the system is operating at its peak design capacity, the
maximum service rate will be approximately 100 gallons-per-minute per square foot of grit chamber area (gpm/sf). The Vortechs System has been tested for flows up to and including
this maximum rate and has been shown to produce positive removal efficiencies throughout this
range.
The Vortechs System will provide a net annual removal efficiency in excess of 80% removal of
Total Suspended Solids as they are typically encountered in runoff from urban environments.
The Vortechs System will also effectively capture and contain floatables In stormwater runoff.
The tangential Inlet creates a swirling motion that directs settleable solids into a pile towards the
center of the grit chamber. Sediment is caught in the swirling flow path and settles back onto
the pile after the storm event is over. Floatables entrapment is achieved by sizing the low flow
control to create a rise in the water level in the tank that is sufficient to just submerge the inlet
pipe in the 2-month storm.
The Vortechs System is designed to create a backwater. condition within the system In order to
maximize removal efficiencies. The amount of backwater varies and Is determined by the
Vortechnics staff. To prevent flooding, the final design of the system Incorporates all site
- conditions.
Design Process
During the Vortechs System design process consideration is given to both the physical
constraints of the site and the site-specific flows. Each system is designed differently based on
these characteristics, and the internal flow controls are specifically designed to accommodate
the expected flows.
The site engineer provides the Vortechs System rim and invert elevations, pipe sizes, design
flow rate, and design storm recurrence interval. Another consideration is whether the system is
in an on-line or off-line (i.e. bypassed) configuration. If regulatory authorities allow treatment of
storm flows, less than the conveyance capacity of the piping system, it may be possible to
provide a Vortechs System in an off-line configuration which will result in a cost savings without
a significant reduction in pollutant removal efficiency.
Sizing the System
Each system is custom designed based on the design conditions provided. The weir, orifice,
sump depth, and height of tank will vary depending on the site conditions and performance requirements. The rim and invert elevations will Impact the overall height of the unit the sump
depth, and the placement of the weir and orifice. Also affecting the placement of the weir and
VORTECHSTM STORMWATER TREATMENT SYSTEM
orifice is the pipe size, the orientation of the internal walls, and the potential for tailwater. The
- flow rates determine the size of the weir, orifice, and the baffle opening.
Size: The size of the system depends on whether or not the system is on-line or off-line. An
on-line system will be chosen such that the design flow rate is equal to' or less, then the
Vortechs rated design flow. For an off-line system, the 2-month flow rate is determined and the
model number is chosen based on the grit chamber area such that 24 gpmlsf of flow is realized
through the chamber.
Sump : Typically a three-foot sump depth is provided in Vortechs Systems. This depth is most
common since it provides ample sediment storage and keeps the excavation depth to a
S minimum. However, because each Vortechs System is custom designed, the individual sump
depths may vary to balance maintenance costs with capital costs.
Orifice: The function of the orifice is to raise the water level In the Vortechs. System. This
increases the area of the flow in the pipe, which decreases the velocity of the water flowing into
the system. A reduction in turbulence is realized at the inlet; this aids in keeping the trapped
sediment and floatables contained. in addition, the rise in water level causes the floatables to
rise above the inlet and away from the baffle opening, thus preventing the floatables from
becoming re-entrained and pulled under the baffle wall The orifice is designed to pass a flow
approximately equal to that of a 2-month storm event.
Weir. Any event greater than the 2-month event causes the water level In the Vortechs System
to rise to the upper flow control, submerging the inlet The upper flow control is normally a
Cippoletti weir. A Cippoletti weir is a trapezoidal weir with 4 to I sloping sides. Like the orifice,
the weir also causes .the water level In the system to rise, which promotes sediment and
floatable removal. As the water rises, the volume of water in the system increases, thus
stabilizing the detention time and allowing sediment to settle out The swirl is maintained by
allowing continuous flow through the system via the weir and orifice. The weir is sized to pass
the design flow rate minus the orifice flow at full head.
Baffle: The baffle opening is designed to maintain a velocity such that. re-entrainment of
-. floatables and re-suspension of sediment is minimized. The baffle opening is at least 6 inches
to ensure against dogging. The largest opening of 15 inches is chosen to maximize the
distance between the floatable layer and the baffle opening. This keeps the floatables trapped
-, and maintains the oil storage volume. In most applications, the flow under the baffle wall is
approximately 1.0 foot per second.
Bypass: For systems in an off-line configuration, a weir crest length and elevation is calculated
for the diversion structure that will be installed upstream of the specified Vortechs System. The
goal is' to achieve a water surface elevation during the 100-year storm that is at the same
elevation as the top of the Vortechs Cippoletti weir. The area of flow over the bypass weir is
calculated based on the 100-year flow. From this area, the height of flow Is solved for a given
weir length. Since the area of flow remains constant, the height of flow over the weir varies with
the bypass weir length. See Technical Bulletin 3A for more information.
TM VORTECHS STORMWATER TREATMENT SYSTEM
Flnw Contmi C21culitoons 0 Vortechs Model 5000
System
The Vortechs System W.Q.S. I is a Model 5000 with a 7.0-foot diameter grit chamber. In
this application, the runoff rate for a rainfall event with a return frequency of 10 years is 6.13
cubic feet per second (àfs). The system design flow is 2751 gpm (6.13th). The surface
area' of the grit chamber Is 38.5 square feet, therefore the peak operating rate is 2751
divided by 38.5 or 72 gpmlsf.
The low flow control is a trapezoidal orifice (Qomic.). Since the inlet is a 24-inch diameter
pipe, the orifice must raise the water level 24 inches, or 2.0 feet, in a 2-month storm to
submerge the inlet pipe. According to Vortechnics Technical Bulletin #3, the 2-month storm
flow rate is approximately equal to the 10-year flow rate divided by 7. The orifice calculation
based on the- full design flow is as follows:
Q2q7o,,m=.Qiow+7 ='6.13-'7=0.88cfs' Qcmc. = C(A)(29h)0 = 0.56(0.14)(2.0 x 32.2 x 2.0)°. =0.894
.
Where C = Orifice contraction coefficient = 0.56 (based on Vortechnics laboratory testing)
A = Orifice flow area, ft2 (calculated by Vortechnics technical staff).
h = Design head, ft (equal to the inlet pipe diameter)
A Cippoletti weir configuration, is utilized as the high flow control (Q) which is
conservatively designed for the system design flow (Qdesn) of 6.13 cfs. The weir
calculations.are as follows: .
Qr=6.13Cft .
= C(L)(H)'5 = 3.37(0.50)(2.42)15 = 6.34 cis
Where C = Cippoletti Weir coefficient = 3.37 (based on Vortechnics laboratory. testing)
H = Available head, ft (height of weir)
L = Design weir crest length, ft (calculated by Vortechnics technical staff).
VORTECHS STORMWATER TREATMENT SYSTEM
MAINTENANCE fo
The Vortechs System requires minimal routine maintenance. However, it is important that the
system be inspected at regular Intervals and cleaned when necessary to ensure optimum
performance. The rate at which the system collects pollutants will depend more heavily on site
activities than the size of the unit, e.g., heavy winter sanding will cause the grit chamber to fill
more quickly but regular sweeping will slow accumulation.
Inspection
Inspection is the key to effective maintenance and it is easily performed. Vortechnics
recommends ongoing quarterly inspections of the accumulated sediment. Note that is not
unusual for sediment accumulation to be relatively light In the first year as Initial sediment loads
In new storm drainage systems may be diverted to catch basin sumps. Pollutant deposition and
transport may vary from year to year and quarterly Inspections will help insure that systems are
cleaned out at the appropriate time. Inspections should be. performed more often in the winter
months in climates where sanding operations may lead to rapid accumulations, or in equipment
washdown areas. It Is very useful to keep a record of each inspection. A simple form for doing
so is provided.
The Vortechs System only needs to be cleaned when inspection reveals that it is nearly full;
specifically, when sediment depth has accumulated to within six Inches of the dry-weather
water level. This determination can be made by taking 2 measurements with a stadia rod or
similar measuring device: one measurement is the distance from the manhole opening to the
top of the sediment pile and the other is the distance from the manhole opening to the water
surface.. If the difference between the two measurements Is less than six inches the system
should be cleaned out. Note: to avoid underestimating the volume of sediment In the chamber,
the measuring device must be lowered to the top of the sediment pile carefully. Finer, silty
particles at the top of the pile typically offer less resistance to the end of the rod than larger
particles toward the bottom of the pile.
In Vortechs installations where the risk of large petroleum spills is small, liquid contaminants
may not accumulate as quickly as sediment. However, an oil or gasoline* spill should be
cleaned out Immediately. Oil or gas that accumulates on a more routine basis should be
removed when an appreciable layer has been captured.
Cleaning
Cleanout of the Vortechs System with a vacuum truck Is generally the most effective and
convenient method. Cleanout should not occur within 6 hours of a rain event to allow the entire
collection system to drain down. Properly maintained Vortechs Systems will only require
evacuation of the grit chamber portion of the system, in which case only the manhole cover
nearest to the system inlet need be opened to remove water and contaminants. However, all
chambers should be checked to ensure the integrity of the system. In installations where a
"clamshell" is being utilized for solids removal, prior to removing the grit, absorbent pads or
pillows can be placed in the oil chamber to remove floating contaminants. Once this is done,
sediment may then be easily removed with the clamshell..
VORTECHSN STORMWATER TREATMENT SYSTEM
In some cases, it may be necessary to pump out all chambers. An important maintenance
- - feature built into Vortechs Systems is that floatables remain trapped after a cleaning. A pocket
of water between the grit chamber and the outlet panel keeps the, bottom of the baffle S submerged, so that all floatables remain trapped when the system begins to fill up again.
Therefore, in the event of cleaning other chambers it is imperative that the grit chamber be
drained first. Manhole covers. should 'be securely seated following cleaning activities, to ensure
that surface runoff does not leak into the unit from above.
H ,'
2
La Costa Oaks South (Neighborhoods 3-08 7315)
-Storm Water Management Plan
Chapter 10- REFERENCES
"Standard Urban Storm Water Mitigation Plan - Storm Water Standards" City of
Carlsbad, April 2003.
"Standards for Design and Construction of Public Works Improvements in the City of
Carlsbad", City of Carlsbad, California; April 1993.
"Master Drainage and Storm Water Quality Management Plan" City of Carlsbad,
California; March 1994.
"Addendum to Preliminary Hydrology Study for Villages of La Costa - The Ridge and
The Oaks' Hunsaker & Associates San Diego, Inc.; Revised October 23, 2001.
"Hydrology Manual", County of San Diego Department of Public Works - Flood
Control Division; Updated April 1993.
"San Diego County Hydrology Manual - DRAFT", County of San Diego Department
of Public Works - Flood Control Section; September 2001.
"Order No. 2001-01, NPDES No. CAS0108758 - Waste Discharge Requirements for
Discharges of Urban Runoff from the Municipal Separate Storm Sewer Systems
(MS4s) Draining the Watersheds of the County of San Diego, the Incorporated Cities
of San Diego -County, and San Diego Unified Port District", California Regional Water
Quality Control Board - San Diego Region; February 21, 2001.
Water Quality Plan for the San Diego Basin", California Regional Water Quality
Control Board - San Diego Region, September 8, 1994.
"Vortechnics Storm Water Treatment System Manual", Vortechnics; Revised May
2000.
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