HomeMy WebLinkAboutCT 02-05; LA COSTA OAKS SOUTH NEIGHBORHOOD 3.15; ADDENDUM TO STORM WATER MGMT PLAN; 2004-08-19ADDENDUM TO STORM WATER
MANAGEMENT PLAN
for
LA COSTA OAKS SOUTH
NEIGHBORHOODS 3.15
City of Carlsbad, California
RECEIVED
HAR 3 0 200^
ENGINEERING
•EPARTMENT
Prepared for:
Real Estate Collateral Management Company
c/o Morrow Development
1903 Wright Place, Suite 180
Carlsbad, CA 92008
W.O. 2352-39
August 19, 2003
Amended March 23, 2004
Eric Mosolgo, R.(^E.
Water Resources Department Manager
Hunsaker & Associates San Diego, Inc.
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cx c 2- 'Ob
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La Costa Oaks South (Neighborhood 3.15)
Addendum to 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 (Neighborhood 3.15)
Addendum to 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 Detemnination 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 - 85'^ Percentile Rainfall Isopluvial 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 (Neighborhood 3.15)
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 85'*' percentile runoff from
Neighborhood 3.15. The majority ofthe runoff from Neighborhood 3.15 drains to the
regional water quality basin located at the downstream end of Neighborhood 3.12
(see Watershed Map on the following page). A small portion ofthe northeast corner
of Neighborhood 3.15 drains to the public storm drain system in Avenida Junipero
Perthe "Hydrology Study for La Costa Oaks Neighborhoods 3.15", dated
January 6, 2003, the storm drain systems from Neighborhood 3.15 had the following
drainage parameters upon their discharge to the public storm drain system.
Neighborhood 3.15 - discharge to regional water qualitv basin
Drainage Area = 41.9 acres
85**^ Percentile Runoff Volume =1.3 acre-feet
Neighborhood 3.15 - discharge to Avenida Junipero (treated in Vortechs Unit)
Drainage Area = 5.4 acres (1.3 acres contributed from Neighborhood 3.14)
85"^ Percentile Design Flow = 0.6 cfs
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 85"^ percentile runoff volume from
Neighborhood 3.15 tributary to the regional water quality basin is equal to 1.3 acre-
feet, which is less than the 3.0 acre-feet of treatment storage provided in the water
quality basin downstream. The 85*"^ percentile design flow from Neighborhood 3.15
that is discharged into the public storm drain in Avenida Junipero is equal to 0.6 cfs,
which is less than the 1.6 cfs that the Vortechs treatment unit has been designed to
treat.
85"^ percentile design runoff calculations are provided in Chapter 8 and 9 of this
report. Since the downstream treatment facilities are a volume-based BMP and one
flow-based BMP, hydrograph method and the rational method were used to
determine the corresponding 85"^ percentile runoff volume and flow from
Neighborhood 3.15.
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LEGEND
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WATERSHED SUB-BOUNDARY
WATERSHED BOUNDARY
NODES (•J*
AREA M-o-ss -"^l
HYDROLOGY MAP
LA COSTA PA 3.15
CITY OF CARLSBAD, CALIFORNIA
SHEET
1
OF
1
Ri\0299\lHyd\OS99«3.l5HYD.d*gC 2085]Mar-23-2004iIOi55
La Costa Oaks South (Neighborhood 3.15)
Addendum to Storm Water Management Plan
1.1 - Introduction
The La Costa Oaks South development is located east of the existing alignment of
Rancho Santa Fe Road, north ofthe existing extension of La Costa Avenue, and
south ofthe 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 BMP
Requirements.
This Storni Water Management Plan (SWMP) has been prepared pursuant to
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 - Summarv 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 ofthe 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 ofthe Carlsbad Hydrologic Unit, San Marcos Hydrologic
Area, and the Batiquitos Hydrologic Subarea (basin number 4.51).
1.3 - Summarv of Proposed Development
Development of the La Costa Oaks South site will include the construction of single-
family 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 ofthe project in Neighborhood 3.12.
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BMP LOCATION MAP FOR
LA COSTA OAKS SOUTH
CITY OF CARLSBAD, CALIFORNIA
SHEET
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ill -iiarfPi:?*
ENCIN TA
^itiWATERSHEI^^^
5^ Si'
I HUNSAKER I ^ASSOCIATES
HYDROLOGY MAP FOR
LA COSTA OAKS SOUTH
r^iTV r»c/-"ADI CP An PAMcnnMiA
SHEEI
1
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1
La Costa Oaks South (Neighborhood 3.15)
Addendum to 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 ofthe 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. 85**^
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 Isopluvial Map at the end ofthis
chapter) and assuming 20 percent imperviousness in the contributing watershed,
HEC-HMS calculations predicted an 85'*^ 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 of 293 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
85*'' percentile runoff volume, the BMP meets SUSMP criteria.
Each of the proposed Vortechs units is an offline precast treatment unit. The 85*^
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 (Neighborhood 3.15)
Addendum to Storm Water Management Plan
CHAPTER 2 - STORM WATER CRITERIA
2.1 - Regional Water Qualitv 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 referto
specific storm water management techniques that are applied to manage
construction and post-construction 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 85*^ percentile rainfall) prior to its discharge to any
receiving watercourse supporting beneficial uses.
2.2 - Citv 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
VI.
APPENDIXA
STORM WATER REQUIREMENTS APPLICABILITY CHECKLIST
Complete Sections 1 and 2 of the following checklist to detemiine your project's
pennanent and construction storm water best management practices requirements.
This fonn 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 Stonn Water BMP Requirements," and "Standard Pennanent Stonn
Water BMP Requirements" in Section III, "Permanent Stomri Water BMP Selection
Procedure" in the Storm Water StantJards manual.
If all answers to Part A are "No," and any answers to Part B are "Yes," your project is
only subject to th6 "Standard Pennanent 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: Determine Priority Project Permanent Storm Water BMP Requirements.
Does the project meet the definition of one or more of the priority project
categories?* Yes No
1. Detached residential development of 10 or more units /
2. Attached residential development of 10 or more units l/
3. Commercial development greater than 100,000 square feet
4. Automotive repair shop
5. Restaurant • 6. Steep hillside development greater than 5,000 square feet
7. Project discharqinq to receivinq waters within Environmentally Sensitive Areas
8. Parking lots greater than or equal to 5,000 ft' or with at least 15 parking spaces, and
potentially exposed to urban runoff
9. Streets, roads, highways, and freeways which wouid create a new paved surface that is
5,000 square feet or qreater /
* Refer to the definitions section in the Stomj Water Standards for expanded definitions of the priority
project categories.
Umited 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 (Neighborhood 3.15)
Addendum to Storm Water Management Plan
CHAPTER 3 - IDENTIFICATION OF TYPICAL POLLUTANTS
3.1 - Anticipated Pollutants from Proiect Site
The following table details typical anticipated and potential pollutants generated by
various land use types. The La Costa Oaks South development will consist of
detached single-family residences. Thus, the Detached Residential Development
category has been highlighted to clearly illustrate which general pollutant categories
are anticipated from the project area.
General Pollutant Categories
Priority
Project
Categories Sediments Nutrients Heavy IVIetals Organic Compounds Trash & Debris Oxygen Demanding Substances Oil & Grease Bacteria & Viruses Pesticides Detached
Residential
Development
i X' BBB
X •
Attached
Residential
Development
X X X p(i) p(2) P X
Commerciai
Development
>100,000 ft^
pd) pd) p(2) X p(5) X p(3) p(5)
Automotive
Repair
Shops
X X(4)(5) X X
Restaurants X X X X
Hillside
Deveiopment
>5,000 ft^
X X X X X X
Parking Lots p(1) p(1) X X pd) X p(1)
Streets,
Highways &
Freeways
x p(1) X X(4) X p(5) X
Retail Gas
Outlets X X(4) X X
X = anticipated
P = potential
(1) A potential pollutant if landscaping exists on-site.
(2) A potential pollutant if the project includes uncovered parking areas.
(3) A potential pollutant if land use involves food or animal waste products.
(4) Including petroleum hydrocarbons.
(5) Including solvents.
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La Costa Oaks South (Neighborhood 3.15)
Addendum to 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 dweiling 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 - Oxvgen-Demanding Substances
Biodegradable organic material as weli 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 - Oii & 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 ofthe water body, as well as the water
quality.
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La Costa Oaks South (Neighborhood 3.15)
Addendum to 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 majority of 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 ofthe 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 watenways (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 ofthe San Marcos hydrologic area.
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p^'' ENCINITAS ^mSi'j^
•;4S7H3REEK^^
\feTERSH£^^
HYDROLOGY MAP FOR
LA COSTA OAKS SOUTH
La Costa Oaks South (Neighborhood 3.15)
Addendum to Storm Water Management Plan
4.3 - Peak Flow Attenuation (Regional Detention Facilitv)
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 faciiity 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 ofthe 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
1/2/01
BASIN
NUMBER HYDROLOGIC BASIN BASIN
NUMBER HYDROLOGIC BASIN
1.00
1.10
1.11
1.12
1.13
1.14
1.20
IJI
1.22
1.24
1.25
1.26
1.27
1.28
1.30
IJI
1.32
1.40
1.50
1.S1
1.52
1.53
2.0O
2.10
2.11
2.12
2.13
2.20
2.21
2.22
2.23
2.30
2J1
2.32
2.33
2.34
2.35
2J6
2.40
2.41
2.42
2.43
2.44
2.50
2.51
2.52
2.60
2.61
2.62
2.63
2.70
2.71
2.72
2.73
SAN JUAN HYDROLOGIC
Laguna
San Joaquin Hills
Laguna Beadi
Allso
Oana Point
MbsionVfeJo
Oso
Upfser Trabuco
Middle Ttabuco
Gobemadora
UpperSanJuan
Middle San Juan
Lower San Juan
San elementa
Prima Deshecha
Segunda DestMcha
San Mateo Canyon
SanOnofte
San Onofre Valley
Las Pulgas
Stuart
UNrr
HA
HSA
HSA
HSA
HSA
HA
HSA
HSA
HSA
HSA
HSA
HSA
HSA
HSA
HA
HSA
HSA
HA
HA
HSA
HSA
HSA
SANTA MARGARrTA HYDROLOGIC UNn*
Ysidora HA
LowerYsidora HSA
Chappo HSA
Upper Ysidora HSA
DaLuz HA
DeLuzCreelc HSA
Gaviian HSA
Vallecitos hiSA
Murrieta HA
Wlldoinar HSA
Murrioa HSA
French HSA
Lower Domenlgoni HSA
Domenigonl IHSA
Diamond HSA
Auld HA
Bachelar Mountain HSA
Gertrudls IHSA
Lower Tucalota HSA
TUcalota HSA
Pechanga HA
Pauba HSA
Wolf HSA
• Wilson HA
Lancaster valley HSA
Lewis HSA
Reed Valley HSA
CaveRocks HA
Lower Coahuila HSA
Upper Coahuila HSA
Anza HSA
2.74
2.80
2^1
2.82
2.az
2.84
2.90
2.91
^92
2.93
2.94
3.00
3.10
3.11
3.12
3.13
3.14
3.15
3.18
3.20
3.21
3.22
3.23
3.30
3.31
3.32
4.00
4.10
4.20
4.21
4.22
4.30
4.31
4.32
4.40 rrsr
\ 4.51 Hisr
- 4.53
4.60
4.61
4.62
4.63
5.00
5.10
5.11
5.12
5.20
5.21
5.22
5.23
5.24
Bumt HSA
Aguanga HA
Vali HSA
Devils Hole HSA
Redec HSA
Tula Creek HSA
Oakgrove HA -
LovwfCulp HSA
PrevittCanyon HSA
Dodge • HSA
Chihuahua HSA
SAN LUIS REY HYDROLOGIC UNH"
Lower San Luis HA
Misskm HSA
Bonsall HSA ,'•
Moosa HSA.
Vall^ Center HSA
Woods HSA
Rincon HSA
Monserate
Pala . HSA
Pauma ,• HSA
La Jolla Amago • HSA
VtbmerVall^ HA
Wamer HSA
Combs HSA
CARLSBAO HYDROLOGIC UNIT
Loma Alta
Buena Vlsta Creek
Q Salto
Vlsta
Agua Hedionda
Los Monos
Buena
Endnas
San
HA
HA
HSA
HSA
HA
HSA
HSA
HA
Marcos
Badoultos
Richland
TMn Oaks
Escondldo Creek
San Elijo
Escondido
LakaWohifbrd
TW
HSA
HSA
HA
HSA
HSA HSA
3v/
SAN DIEGUrrO HYDROLOGIC UNIT
Solana Beach HA
Rancho Santa Fe HSA
La Jolla HSA
Hodges HA
Dei Dios HSA
Green HSA
Feildta HSA
Bear HSA
T-M
Hylrobgfo" ^^^^"^ 2002 Section 303(d) Update
Descriptor Waterbody Segment / Area ^
21 Loma Alta HA
(904.10) Pacific Ocean Shoreline at Loma Alta Creek Mouth
22 Loma Alta HA Loma Alta Slouqh
(904.10)
23 Buena Vista Creek
HA (904.20) Pacific Ocean Shoreline
at Buena Vista Creek
24 El Salto HSA
(904.21)
Carisbad City Beach at Carisbad
Village Drive
Carisbad State Beach at Pine
Avenue
Buena Vista Lagoon
25 Los Monos HSA
(904.31) ^9ua Hedionda Lagoon
26 Los Monos HSA
(904.31)
San Marcos HA
.(904.50)
28 Escondido Creek
HA (904.60)
29 San Elijo HSA
(904.61)
30 San Dieguito HU
(905.00)
^1 Del Dios HSA
(905.21)
32 Del Dios HSA
(905.21)
33 Felicita HSA
(905.23)
34 Felicita HSA
(905.23)
35 Highland HSA
(905.31)
Sutheriand HSA
(905.53)
lower portion
Agua Hedionda Creek
Pacific Ocean Shoreline at Moonlight State Beach
Pacific Ocean Shoreline at San Elijo Lagoon
at Solana Beach
San Elijo Lagoon
Pacific Ocean Shoreline
Green Valley Creek
Hodges Reservoir
at San Dieguito Lagoon Mouth
Ton-ey Pines State Beach at Del
Mar (Anderson Canyon)
Entire Reservoir
Felicita Creek
Kit Carson Creek
Cloverdale Creek
Sutheriand Reservoir Entire Reservoir
Pollutant /
Stressor
Bacterial
Indicators^
Bacterial
Indicators^
Eutrophic
-Bacterial
Indicators^
Extent of Year
Impairment ° LiRfprt
1 mile
8 acres
0.65 miles
Bacterial
Indicators^ ^^^^^^^
Sedimentation /
Siltation 350 acres
Nutrients
Bacterial
Indicators^
150 acres
5 acres
Sedimentation /
Siltation
Diazinon lower 2 miies"
Total Dissolved
Solids
Bacterial
Indicators^
bacterial
Indicators^
Bacterial
Indicators^
0.4 miles
0.8 miles
150 acres
Eutrophic 330 acres
Sedimentation /
Siltation 150 acres
-Bacterial 0-8 miles
Indicators^
Sulfate
Color
Nitrogen
Phosphorus
Total Dissolved
Solids
Total Dissolved
Solids
Total Dissolved
Solids
Phosphorus
1 mile
Entire
Reservoir
Total Dissolved
Solids
1 mile
1 mile
Color Entire
Reservoir
1998
1998
"1998"
1998
1998
1998
1998
2002
lower 8 miles 2002
1998
1998
1998
1998
2002
"2002"
lower 2 miles 2002
2002
"2002"
2002
last updated 7/22/2003
S:\WQSV3C3dlist\SD Staff Report-2002ea02 draft 303d llst\
http:;w.w«*.cagov/n«,cb9/progran,s003dli,.n-ab:a 4 - Combined 1998 and 2002 UpdS^aWe 4
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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
SAN LUIS REY HYDROLOGIC UNIT
Hydrologic
Unit Basin
Number TDS Cl
Constitluent
SO
_L
%Na N&P Fe
903.00
Mn
(mg/L or as noted)
MBAS B ODOR Turb
NTU
Color
Units
Lower San Luis HA
Monserat HA
3.10
3.20
500
500
250
250
250
250
60
60
0.3
0.3
0.05
0.05
0.5
0.5
0.75
0.75
none
none
20
20
20
20
1.0
1.0
Warner Valley HA
bARLSBAD HYDROLOGIC UNrp
3.30 500 250 250 60 0.3 0.05 0.5 0.75 none 20 20
904.00
HA - Hydrologic Area
HSA - Hydrologic Sub Area (Lower case letters Indicate endnotes
Table 3-2
WATER QUALITY OBJECTIVES
following the table.)
Page 3-23
1.0
Septembers, 199^
La Costa Oaks South (Neighborhood 3.15)
Addendum to Storm Water Management Plan
CHAPTER 5 - VOLUME-BASED BMPS
5.1 - Desiqn Criteria
Volume-based BMPs shall be designed to mitigate the volume of runoff produced
from a 24-hour 85**^ percentile storm event, as determined from the local historical
rainfall record. The SS**^ percentile rainfall for the La Costa Oalcs 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
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.
85"^ 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 dewater the
basin and discharge runoff to the natural drainage course downstream.
Runoff in excess ofthe 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 - High removal efficiency
Nutrients - Medium removal efficiency
Heavy Metals - Medium removal efficiency
Trash & Debris - High removal efficiency
Oxygen-Demanding Substances - Medium removal efficiency
Oil & Grease - Medium removal efficiency
5.4 - Maintenance Reauirements
Proper maintenance is required to insure optimum performance ofthe 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.
EM:de h:\swquality\2352\39\3.15.doc
w.o. 2352-39 3/23/04 9:55 AM
Storm Water Standards
4/03/03
Tabie 4. Structural Treatment Control BMP Selectfon Matrix.
Pollutant of Concem Treatment Control BMP Categories
Biofilters Detention
Basins
Infiltration
Basins(i)
Wet Ponds or
Wetlands
Drainage
Inserts
Ritration Hydrodynamic
Separator Systems^
Sediment M H H H L H M
Nutrients L lA M M L M L
Heaw Metals M M M H L H L
Orqanic Compounds U U U U . L M L Trash & Debris L H U U M H M Oxygen Demanding
Substances L M M M L M L
Bacteria U U H U L M L
Oil & Grease M M U U L H L
Pesticides U U U U L U L
(2) Mso known as hydrodynamic devices and baffle boxes.
L: Low removal efficiency
M: Medium removal efflciency
H: High removal efficiency
U: Unknown removal efficiency
Sources: Guidance Spedfying Management Measutes for Sources of Nonpoint Pollution in Coastal Wateis (1993), National
Stormwater Best Management Pradices Database (2001), and 6u/cfe for BMP Selection In Urban Developed Areas (2001).
La Costa Oaks South (Neighborhood 3.15)
Addendum to Storm Water Management Plan
Maintenance ofthe extended detention basin will be the responsibility ofthe
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 perfomiance 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 ofthe 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 ofthe heavy
vegetation that will inevitably grow in the basin. Roughly 14 half ofthe 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 priorto disposal in
a sanitary landfill.
EM:de h:\sw quality\2352\39\3.15.doc
W.O. 2352-39 3/23/04 9:55 AM
La Costa Oaks South (Neighborhood 3.15)
Addendum to 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, 85* percentile flow calculations were
performed using the Rational Method. The basic Rational Method runoff procedure
is as follows:
Designflow(Q) = C*l*A
Runoff Coefficient I - 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 ofthe 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:de h:\swquality\2352\39\3.15.doc
w.o. 2352-39 3/23/04 9:55 AM
La Costa Oaks South (Neighborhood 3.15)
Addendum to Storm Water Management Pian
Other features ofthe Vortechs Systems include the following:
Large capacity system provides an 80 percent net annual Total
Suspended Solids (TSS) removal rate
Unit is installed below grade
- Low pump-out volume and one-point access reduce maintenance costs
- Design prevents oils and other floatables from escaping the system during
cleanout
Enhanced removal efficiencies of nutrients and heavy metals with offline
configuration
The tangential inlet to the system creates a swirling motion that directs settleable
solids into a pile towards the center ofthe grit chamber. Sediment is caught in the
swirling flow path and settles back onto the pile after the stomn event is over.
Floatable entrapment is achieved by sizing the low flow control to create a rise in the
water level of thie vault that is sufficient to just submerge the inlet pipe with the 85"^
percentile flow.
6.3 - Pollutant Removal Efficiencv Table
PoUutant of Concern BMP Categories
Hydrodynamic
Separation
Devices*^'
;:'/-.,i.VortechsJ^K-.*^
; : StopriwateF^^
• Treatment Systehrr: •
Sediment M-H
Nutrients L-M
Heavy Metals L-M
Organic Compounds L-M ' •^v-^i.vKt-"l:-My«a§'*>.v.i'
Trash & Debris M-H ' "'"'•'•if .Iri'Jfc$s.'-'i\".
Oxygen Demanding Substances L
Bacteria L - .•• t--:^ii-v
Oil & Grease L-H
Pesticides L L
(1) The County will periodically assess the performance characteristics ofthese BMPs to
update this table.
(2) Proprietary Structural BMPs. Not all serve the same function.
L (Low): Low removal efficiency (roughly 0-25%)
M (Medium): Medium removal efficiency (roughly 25-75%)
H (High): High removal efficiency (roughly 75-100%)
U: Unknown removal efficiency, appiicant must provide evidence supporting use
Sources: Guidance Specifying Management Measures for Sources of Nonpoint Poiiution in
Coastal Waters (1993), Nationai Stonvwater Best Management Practices Database (2001),
and Guide for BMP Selection in Urban Developed Areas (2001).
EM:de h:\sw quality\2352\39\3.15.doc
W.O. 2352-39 3/23/04 9:55 AM
La Costa Oaks South (Neighborhood 3.15)
Addendum to 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 ofthe proposed
Vortechnics units includes inspection and maintenance 1 to 4 times per year.
Maintenance of the Vortechs units involves the use of a "vactor truck", which clears
the grit chamber ofthe treatment unit by vacuuming all the grit, oil and grease, and
water from the sump. Typically a 3-man crew is required to perfonn the
maintenance of the treatment unit. Properly maintained Vortechs Systems will only
require evacuation ofthe grit chamber portion ofthe 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:de h:\swquality\2352\39\3.15.doc
W.O. 2352-39 3/23/04 9:55 AM
La Costa Oaks South (Neighborhood 3.15)
Addendum to Storm Water Management Plan
CHAPTER 7 - SOURCE CONTROL BMPS
7.1 - Landscapinq
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:de h:\sw quality\2352\39\3.15.doc
W.O. 2352-39 3/23/04 9:55 AM
La Costa Oaks South (Neighborhood 3.15)
Addendum to 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 ofthese potential stonn 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:de h:\swquality\2352\39\3.15.doc
W.O. 2352-39 3/23/04 9:55 AM
La Costa Oaks South (Neighborhood 3.15)
Addendum to 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 85'^ percentile rainfall of 0.68 inches (see Isopluvial Map at the end ofthis
chapter) and assuming 20 percent imperviousness in the contributing watershed,
HEC-HMS calculations predicted an 85"^ percentile runoff volume of roughly 3.0
acre-feet.
8.3 - Water Qualitv Basin Design
The water quality / 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 dewatering (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:de h:\swquality\2352\39\3.15.doc
W.O. 2352-39 3/23/04 9:55 AM
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VILLAGES OF LA COSTA
STAGE- STORAGE DATA
DETENTION BASIN AT NODE 106
without a water quality component with a water quality component
13 JSl :AI?!5V1
285.0 0.00 0.00 0.00 285.0 0.00 0.00 0.00
286.0 0.23 0.12 0.12 286.0 •023 0.12 0.12
287.0 0.35 0.29 0.41 287.0 0.35 0.29 0.41
288.0 0.38 0.36 0.77 288.0 0.38 0.36 0.77
289.0 0.40 0.39 1.16 289.0 0.40 0.39 1.16'
290.0 0.43 0.42 1.58 290.0 0.43 0.42 1.58
291.0 0.45 0.44 2.02 291.0 0.45 0.44 2.02
292.0 0.48 0.47 2.48 292.0 0.48 0.47 2.48
293.0 0.50 0.49 2.97 293.0 0.50 0.49 2.97
294.0 0.53 0.51 3.49
295.0 0.55 0.54 4.03 293.0 0.50 0.00 0.00
296.0 0.69 0.62 4.65 293.5 0.51 025 0.25
297.0 0.82 0.75 5.40 294.0 0.53 0.51 0.51
298.0 0.94 0.88 6.28 295.0 0.55 0.54 1.05
299.0 1.02 0.98 7.26 296.0 0.69 0.62 1.67
300.0 1.10 1.06 8.32 297.0 0.82 0.75 2.42 .
301.0 1.16 1.13 9.44 298.0 0.94 0.88 3.30
302.0 1.21 1.T8 10.63 299.0 1.02 0.98 4.28
300.0 1.10 1.06 5.34
301.0 1.16 1.13 6.47
302.0 1.21 1.18 7.65
for stormwater quality
fbr detention
^K*f ^^^^
VILLAGES OF LA COSTA - THE OAKS
HYDRAULIC ANALYSIS OF RISER SLOTS AT NODE 106
Orifice Eguation (forh > M):
Q = Ca(2gh)° » (Equation 4-10. Kings Handbook)
Q= Ca(64.32h)° ''; C= 0.6 ftom Table 4-4, Kings Handbook
Q - 4.812 a(h)''''', where a = area of oriflce opening, h = head (ft) above centeriine of opening.
Weir Formula (for h < M):
Q= CLH^ " (Equation 5-10, Kings Handbook)
0= 3.2 from Rg. 5-3
7.07 sq. ft.. L = 9.42 ft @ elevation 293.0 ft. (top of riser). 285.0 ft. (floor of basin)
For Riser where:
d = 38 In., a =
and sipts where:
L = 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
H
i
••
ELEV. 1 ROWl 1 ROW 2 1 ROW 3 1 ROW 4 1 ROWS 1 ROW 6 1 ROW 7 J TOTAL
(feet) •asnoBsainRiaEiBiiMiiicnEi^ I Q(cfs)
265.0 0.0 0.0 0.0
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
293.00 8.00 1.68 7.00 1.57 6.00 1.45 5.00 1.31 4.00 1.17 3.00 1.00 2.00 0.80 9.0
slot 8/14/2001
ENCINITAS
85TH PERCENTILE PEAK FLOW AND VOLUME DETERMINATION
Modified Rational Method - Effective for Watersheds < 1.0 mi^
Hunsaker & Associates - San Diego
Note: Only Enter Values in Boxes - Spreadsheet Will Calculate Remaining Values
Project Name Villages of La Costa Oaks 3.15 |
Work Order 2352-42 1
Jurisdiction City of Carlsbad |
BMP Location [Master Treatment Basin
85th Percentile Rainfall = 0.68 1
(from County Isopluvial Map)
Developed Drainage Area = 41.9
Natural Drainage Area = 0.0
Total Drainage Area to BMP = 41.9
Dev. Area Percent Impervious = | 30 |
Overall Percent Impervious = 30
Dev. Area Runoff Coefficient = 0.55
Nat. Area Runoff Coefficient = 0.35
Runoff Coefficient = 0.55
Time of Concentration = 15.6 1
(from Drainage Study)
RATIONAL METHOD RESULTS
acres
acres
acres
Q = CIA where
V = CPA where
Q = 85th Percentile Peak Flow (cfs)
C = Runoff Coefficient
I = Rainfall Intensity (0.2 inch/hour per RWQCB mandate)
A = Drainage Area (acres)
Q = 85th Percentile Runoff Volume (acre-feet)
C = Runoff Coefficient
P = 85th Percentile Rainfall (inches)
A = Drainage Area (acres
Using the Total Drainage Area:
C =
1 =
0.55
0.2 inch/hour
P = 0.68 inches
A= 41.9 acres
Q =
V =
4.61 cfs
1.31 acre-feet
Using Developed Area Only:
0 =
1 =
P =
A =
Q =
V =
0.55
0.2 inch/hour
0.68 inches
41.9 acres
4.61 cfs
1.31 acre-feet
La Costa Oaks South (Neighborhood 3.15)
Addendum to Storm Water Management Plan
CHAPTER 9 - SITE BMP DESIGN
VORTECHS TREATMENT UNITS
9.1 - BMP Locations
The site design includes a Vortechs treatment unit (shown on BMP Location Map
located on the following page).
At the southeast corner of the Oaks South site, a 5-acre watershed, which
includes area from Neighborhood 3.15 discharges to a side canyon near
Avenida Junipero. Prior to discharge to the natural canyon, 85'^ percentile
flow will be treated in an offline Vortechs Model 1000.
9.2 - Determination of Design Treatment Flows
The 85"^ 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.
The following table summarizes the parameters used for determination of design
flows to each ofthe Vortechs treatment units.
DESIGN RUNOFF DETERMINATION SUMMARY TABLE
Treatment Unit
Runoff
Coefficient
(C)
Rainfall
Intensity
(in/hr)
Drainage
Area
(acres)
85" Pet.
Design Flow
(cfs)
Avenida Junipero 0.55 0.2 5.4 0.6
EM:de h:\sw quality\2352\42\swmp02.doc
W.o. 2352-39 3/23/04 4:42 PM
La Costa Oaks South (Neighborhood 3.15)
Addendum to Storm Water Management Plan
9.3 - Vortechs Treatment Unit Selection
The proposed Vortechs unit is an offline precast treatment unit. The 85 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 the proposed Vortechs unit.
VORTECHS UNIT TREATMENT CAPACITY TABLE
Treatment Unit
85*" Pet.
Design Flow
(cfs)
Recommended
Vortechs
Model
Treatment Capacity
(cfs)
Avenida Junipero 0.5 1000 1.6
EM:de h:\sw quality\2352\42\swmp02.doc
w.o. 2352-39 3/23/04 4:42 PM
85TH PERCENTILE PEAK FLOW AND VOLUME DETERMINATION
Modified Rational Method - Effective for Watersheds < 1.0 mi^
Hunsaker & Associates - San Diego
Note: Only Enter Values In Boxes - Spreadsheet Will Calculate Remaining Values
Project Name Villages of La Costa Oaks 3.15 |
Work Order 2352-42 1
Jurisdiction City of Carlsbad 1
BMP Location |Vortech 1000 treatment Unit in Avenida Junipero
85th Percentile Rainfall = 0.68 1
(from County Isopluvial Map)
Developed Drainage Area = 5.4
Natural Drainage Area = 0.0
Total Drainage Area to BMP = 5.4
Dev. Area Percent Impervious = 30 1
Overall Percent Impervious = 30
Dev. Area Runoff Coefficient = 0.55
Nat. Area Runoff Coefficient = 0.35
Runoff CoefTicient = 0.55
Time of Concentration = 15.6 1
(from Drainage Study)
RATIONAL METHOD RESULTS
inches
acres
acres
acres
Q = CIA where
V = CPA where
C:
1 =
A =
C:
P:
A =
Using the Total Drainage Area:
C =
1 =
P =
A =
85th Percentile Peak Flow (cfs)
Runoff Coefficient
Rainfall Intensity (0.2 inch/hour per RWQCB mandate)
Drainage Area (acres)
85th Percentile Runoff Volume (acre-feet)
Runoff Coefficient
85th Percentile Rainfall (inches)
Drainage Area (acres
0.55
0.2 Inch/hour
0.68 inches
5.4 acres
Q:
V =
0.59 cfs
0.17 acre-feet
Using Developed Area Only:
C =
1 =
P =
A =
Q =
V =
0.55
0.2 inch/hour
0.68 inches
5.4 acres
0.59 Cfs
0.17 acre-feet
^ ' Q-it Chamben.
-nn> :
The swirling rijiotaon created by the ^~
|tangentia|^li|:|i!jgecte^s^lMb^
. S'aolids toward; the center qf this i>r"j'v.
JSR ^"^ 'chamber Sediment;is\iailpn|^^
"BX Cthe swirling ffow path and ^tties" '
-y-H^ back onto tl^e pile after ihe'atbrni'|?>
p.rchamte)y^F4^c^rit^,i>^OaChanJ^
T IPe center baffle traps flqatables in^
i^'^.^^.'^the oil chambei; even dunpgjleanf*^!,
*: ^^fSS^ Highly resistant to frcMs^giSMl
»|Snow Control ChS^^M,
i
i,?system asr flow rate increaaes/andr^^'i
S2) gradually dram tfje systenjfaV'^W
p^,Elevation VTew Dry-Weather - "^flow rate subsides »f»**#vJ^ ^1
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 contral
feature reduces turbulence and avoids resuspension
of pollutents.
3) Full Copocity Phase
When the highflow outlet approaches full discharge, stsnn
drains are fiowing at peak capacity The Vbrtechs System is
dea'gned to match your design storm flow and provide treat-
ment throughout the range of storm evente 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 tenk fills and the floating conteminant layer accu-
mulated from past storms rises. Swirling action increases
at this stege, while sediment pile remains steble.
4) Storm Subsidence Phase/Cleaning
Treated runofi' is decanted at a controlled rate, restoring the
water level to a low dryweather volume and revealing a conical
pile of sediment The low water level faciTitates inspection and
cleaning, and significantly reduces maintenance costs. The
system's central baffie prevente transfer of floatebles to the
outlet during cleaning or during the next ^rm.
. rUi.-^lt.ffmlfc. ..turt .< ' *n '\.J..........-..„c..^'t4...^,„feS«,i£feft^.^'^l*. ••
rtecl Stormwater Treatment System
Perforated Covers
3'tDS'
INV I
3tD*
/
6- to
Typical •
Plan -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.
Bevation View
Vcrtechs
Model
• Grit Chamber
•iameter./Area-
Peak
•esiqn
Flaw'
. cfs- .
Sediment
Storage"
Vda\.
A),Far nvJina Vtartocha Systems VMthaut a bypass, sons cntena la baaed an proMdng one squara fiiqt of gnt ^ <
i»?;;Warnl» sU^fewaiw^ / dat8il8,abpUt,>A]rtacl;^:;Si2^
Bl SediiTient^scarage volume aaaumaa a 3 fboc sump - I J-^-^""- ' 5^ - • - •
CimstructfanS^^
;: , i!atonB.vviII appear, ors^^rtwjhnica.cir^^ oaltVbrtMhriiii;(op.ilw w^^ of spa., 1
,K:.^8cial Nota: Oil atoi^ qa^ciqc vvhaii fe'is -iiaeded to' rrawtiS'^ja^ can faa '
^:?fiza<J to meet the- stpraga raquirairH^ iseleotadinnoitt'Varteehnics-tei* staff: inilil'optitt^ systarrr >
;.V~geannatry;to:nneeccoptainnwfer9qi%m.a»to .
iXMBtna SpedOcMxin-Chartarateeter lvfca$na Mrtadinfcai/atY30^ 37*3663. ''-sar.'Syfe'.\'¥&?
Vortechs System Inlet/Outlet Configxarations
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
)
f 1 Side Inlet
To
Pretreatment o^,.
SECTION 02721
STORMWATER TREATMENT SYSTEM
PART 1.00 GPNFRAl
1.01 DESCRIPTiniM
A. Worl< included:
The Contractor, and/or a manufacturer selected by the Contractor and approved
by the Engineer, shall fumish all labor, materials, equipment and incidentals
required and install ail precast concrete stomiwater treatment systems and
appurtenances in accordance with the Drawings and these specifications.
B. Related wori< described elsewhere:
1. Unit Masonry
2. Misceiianeous Metals
3. Waterproofing
1-02 QUALITY CONTROL INSPECTION
A. The quality of materials, the process of manufacture, and tiie finished sections
shall be subject to inspection by ttie Engineer. Such inspection may be made at
ttie place of manufacture, or on ttie wori< site after delivery, or at both places, and
ttie sections shall be subject to rejection at any time if material conditions fail to
meet any ofthe specification requirements, even tiiough sample sections may
have been accepted as satisfactory at tine place of manufacture. Sections
rejected after delivery to the site shall be mariced for identification and shall be
removed from tiie site at once. Ail sections which have been damaged beyond
repair during delivery will be rejected and, if already installed, shall be repaired to
ttie Engineer's acceptance level, if pennitted, or removed and replaced, entirely
at tiie Contractor's expense.
B. 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 e)q3osure of reinforcemenL
C. Imperfections may be repaired, subject to ttie acceptance of the Engineer, after
demonsttation by ttie 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 tiie
end of 7 days and 5,000 psi at tiie end of 28 days when tested in 3 inch diameter
by 6 inch long cylinders stored in tiie standard manner. Epoxy mortar may be
utilized for repairs.
1.03 SUBMITTALS
A. Shop Drawings
The Contractor shall be provided with dimensional drawings and, when specified,
utilize ttiese drawings as tiie basis for preparation of shop drawings showing
details for construction, reinfordng, 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 sttuctural analysis. Design calculations and shop drawings shall
be certified by a Professional Engineer retained by the system manufacturer or
conttactor and licensed In the state where ttie system is to be installed. Shop
drawings shall be prepared at a scale of not tess than 1/4" per foot Six (6) hard
copies of said shop drawings shall be submitted to tiie Engineer for review and
approval.
B. Affidavit on patent infringement
The Contiactor shall submit to the Engineer, prior to installation ofthe stonnwater
ti-eatment system, an affidavit regarding patent infringement rights stating ttiat
any suit or daim against tiie Owner due to alleged infringement rights shall be
defended by the Conti-actor who will bear ail ttie costs, expenses and attomey's
fees incun-ed tiiereof.
PART 2.00 PRODUCTS
2.01 MATERIALS AND DESIGN
A. Concrete for precast stomnwater tt"eatinent systems shall conform to ASTM
C 857 and C 858 and meet tiie following additional requirements:
1. The wall thickness shall not be less tiian 6 inches or as shown on the
dimensional drawings. In ail cases ttie wall tiiickness shall be no less tiian
the minimum thid<ness necessary to sustain i-IS20-44 loading requirements
as determined by a Licensed Professional Engineer.
2. Sections shall have tongue and groove or ship-lap joints with a butyl mastic
sealant confomiing to ASTM C 990.
3. Cement shall be Type 111 Portland cement confonning to ASTM C 150.
4. Pipe openings shall be sized to accept pipes of ttie specified size(s) and
materiai(s), and shall be sealed by ttie Contt^actor with a hydraulic cement
confomiing to ASTM C 595M
5. Intemal metal components shall be aluminum alloy 5052-H32 in accordance
witti ASTM B 209.
6. Brick or masonry used to build tiie manhole frame to grade shall conform to
ASTM C 32 or ASTM C 139 and ttie Masonry Section of these Specifications.
\\MD1\SYS\DATA\V0RTECHN\EMAIL\STDETA1L\V0RTSPEC.D0C SECTION 02721 Page 2
7.
8.
Casting for manhole frames and covers shall be in accordance with The
Miscellaneous Metals Section of tiiese Specifications.
All sections shall be cured by an approved metiiod. Sections shall not be
shipped until the concrete has attained a compressive stirength of 4,000 psi or
util 5 days after fabrication and/or repair, whichever is tiie longer.
9. A butimen sealant in confonnance witii ASTM C 990 shall be utilized in
affixing tiie aluminum swiri chamber to tiie concrete vault
2.02 PERFORMANCF
Each stonnwater treattnent system shall adhere to the following performance specifications
at the specified design flows, as listed below:
able 2.02
Vortechs
Model
Swirl
Chamber
Diameter
(ft)
Design
Treatment
Capacity
(cfs)
Sediment
Storage
(yd^)
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
11000 10 17.5 5.50
16000 12 25.0 7.00
Each stonnwater ti-eattnent system shall indude a circular aluminum "swiri chamber" (or "grit
chamber") witii a tangential inlet to induce a swiriing flow pattem that will accumulate and
store settieable solids in a manner and a location ttiat will prevent re-suspension of previously
captured particulates. Each swiri chamber diameter shall not be less ttian the diameter listed
in Table 2.02 (neglecting chamber wall tiiickness).
Each stonnwater treatinent system shall be of a hydraulic design ttiat indudes flow contirols
designed and certified by a pnsfessional engineer using accepted principles of fluid mechanics
that raise the water surface inside ttie tank to a pre-determined level In order to prevent the
re-entrainment of trapped floating contaminants.
Each stormwater tt-eatment system shall be capable of removing 80% of Uie net annual Total
Suspended Solids (TSS). Individual stonnwater treatinent systems shall have the Design
Treatment Capacity listed in Tabie 2.02, and shall not resuspend trapped sediments or re-
entt-ain floating contaminants at flow rates up to and induding the specified Design Treatment
Capacity.
Individual stonnwater treatment systems shall have usable sediment storage capacity of not
less than tiie con-esponding volume listed in Table 2.02. The systems shall be designed such
\\MDi\SYS\DATA\VORTECHN\EMAlL\STDETAIL\VORTSPEC.DOC SECTiON 02721 Pages
that the pump-out volume is less than Vz of tiie total system volume. The systems shall be
designed to not allow surcharge of ttie upstt-eam piping network during dry weather conditions.
A water-lock feature shall be incorporated into tiie design of the stonnwater treatment system
to prevent tiie intixDduction of ti-apped oil and floatable contaminants to tiie downsti-eam piping
during routine maintenance and to ensure that no oil escapes the system during Uie 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 stonnwater tt-eatment system manufacturer shall fumish documentetion which supports
all product perfonnance claims and featijres, storage capacities and maintenance
requirements.
Stormwater treatinent systems shall be completely housed witiiin one rectengular stiucture.
2.03 MANUFACTURER
Each stonnwater ti-eatinent system shall be ofa type tiiat has been instelled and used
successfully for a minimum of 5 years. The manufacturer of said system shall have
been regulariy engaged in the engineering design and production of systems for the
physical tteatinent of stormwater runoff.
Each stormwater treatinent system shall be a Vortechs™ System as manufachjred 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. H
PART 3.00 EXECUTION .
3.01 INSTALLATION
A. Each Stonnwater Treatinent System shall be constiucted according to tiie sizes
shown on the Drawings and as specified herein. Instell at elevations and
locations shown on ttie Drawings or as otherwise directed by Uie Engineer.
B. 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
tiie precast base section of ttie ti-ap shall be checked for level at all four comers
after it is set If the slope from any comer to any ottier comer exceeds 0.5% ttie
base section shall be removed and tiie granular subbase material re-leveled.
C. Prior to setting subsequent sections place butimen sealant in conformance with ASTM
C990-91 along the constructton joint in tiie sedion that is already in place.
D. After setting ttie base and wall or riser sections instell the circular swiri chamber
wall by bolting ttie swiri chamber to tiie side walls at the three (3) tengent points
and at tiie 3-inch wide inlet teb using HILTI brand concrete anchors or equivalent
1/2-indi diameter by 2-3/4" minimum lengtii at heights of approximately three
inches (3") off tiie floor and at the mid-height of the completed trap (at locations
of pre-drilled holes in aluminum components). Seal the bottom edge oftiie swiri
\\MDI\SYS\DATA\VORTECHN\EMAlL\STDeTAIL\VORTSPEC.DOC SECTION 02721 Page 4
chamber to tiie tt-ap floor with tiie supplied aluminum angle flange. Adhere %"
thick by 1" wide neoprene sponge material to the flange witti half of it's widtii on
the horizontei leg of tiie flange and half of ifs width on the vertical leg. The
aluminum angle flange shall be affixed to tiie floor witii a minimum 3/8" diameter
by 2-3/4" drop in wedge anchor at the location of the predrilled holes. Affix the
swiri chamber to the flange witii hex head VA X 1-1/2" zinc coated self- tapping
screws at the location of tiie predrilled holes. Seal the vault sidewalls to the
outside of tiie swiri chamber from the floor to tiie same height as tiie inlet pipe
invert using butyl mastic or approved equal.
E. Prior to setting the precast roof section, butimen sealant equal to ASTM C990 shall be
placed along tiie top of the baffle wall, using more tiian one layer of mastic if
necessary, to a ttiickness at least one inch ("I") greater than ttie nominal gap between
ttie top of the baffle and tiie roof section.
The nominal gap shall be determined eitiier by field measurement or the shop
drawings. After placement of tiie roof section has compressed tiie butyl mastic sealant
in the gap, finish sealing tiie gap witti an approved non-shrink grout on botti sides of
the gap using tiie butyl mastic as a backing material to which to apply tiie grout Also
apply non-shrink grout to the joints at tiie side edges of tiie baffle wall.
F. After setting the precast roof section of tiie stonnwater tteatinent system, set
precast concrete manhole riser sections, to the height required to bring the cast
iron manhole covers to grade, so tiiat ttie sections are vertical and in true
alignment with a 1/4 inch maximum tolerance allowed. Backflll in a careful
manner, bringing tiie fill up in 6" lifts on all sides. If leaks appear, dean the inside
joints and caulk with lead wool to tiie satisfaction of the Engineer. Precast
sedions shall be set in a manner tiiat will result in a watertight joint In all
instances, installation of Stonnwater Treatinent Systems shall confonn to ASTM
specification C891 "Stendard Practice For Instellation of Underground Precast
Utility Stnjctures".
G. Plug holes in the concrete sedions made for handling or other purposes with a
nonshrink grout or by using grout in combination with concrete plugs.
H. Where holes must be cut in tiie precast sections to accommodate pipes, do all
cutting before setting the sedions in place to prevent any subsequent jarring
which may loosen the morter joints. The Contt-ador shali make all pipe
connections.
\\MD1\SYS\DATA\V0RTECHN\EMAIL\STDETAIL\V0RTSPEC.D0C SECTION 02721 Page 5
VORTECHS™ STORMWATER TREATMENT SYSTEM
DESIGN AND OPERATION
Basic Operation
The Vortechs System is sized on the basis of removing both sediment and floating pollutants
from stonnwater mnoff. 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 induding
this maximum rate and has been shown to produce positive removal efficiencies tiiroughout ttiis
range.
The Vortechs System wi|l provide a net annual removal efficiency in excess of 80% removal of
Totel Suspended Solids as they are typically encountered in runofl' from urban environments.
The Vortechs System will also effectively capture and contain floatables in stonnwater mnoff.
The tengential inlet creates a swiriing motion that direds settleable solids into a pile towards the
center of the grit chamber. Sediment is caught in the swiriing flow patii and settles back onto
the pile after the stonn event is over. Floatables enfrapment is achieved by sizing the low flow
control to create a rise in tiie water level in the tank tiiat is suffident to just submerge tiie inlet
pipe in tiie 2-month storm.
The Vortechs System is designed to create a backwater condition within the system in onjer to
maximize removal efficiencies. The amount of backwater varies and is detennined by tiie
Vortechnics steff. 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
consti-aints of the site and the site-specific flows. Each system is designed differently based on
tiiese charaderistics, and the intemal flow confrols are speciflcally designed to accommodate
the expeded flows.
The site engineer provides the Vortechs System rim and invert elevations, pipe sizes, design
flow rate, and design stonn recurrence inten/al. Anottier consideration is whether the system is
in an on-line or off-line (i.e. bypassed) configuration. If regulatory autiiorities allow freatment of
stonn flows less than the conveyance capadty 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 poilutent removal efficiency.
Sizing the Svstem
Each system is custom designed based on the design conditions provided. The weir, orifice,
sump depth, and height of tenk will vary depending on the site conditions and perfonnance
requirements. The rim and invert elevations will impact Uie overail height of the unit tiie sump
deptii, and tiie placement of the weir and orifice. Aiso affecting the placement of the weir and
VORTECHS™ STORMWATER TREATMENT SYSTEM
orifice is the pipe size, the orientetion of ttie intemal walls, and the potential for tailwater. The
flow rates determine the size of the weir, orifice, and tiie 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 tiiat tiie design flow rate is equal to or less tiien 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 tiie grit chamber area such that 24 gpm/sf of flow is realized
through ttie chamber.
Sumo: Typically a three-foot sump depth is provided in Vortechs Systems. This depth is most
common since it provides ample sediment storage and keeps ttie excavation depth to a
minimum. However, because each Vortechs System is custom designed, the individual sump
depths may vary to balance maintenance costs with capitel costs.
Oriflce: The function of ttie orifice is to raise the water level in ttie Vortechs System. This
increases the area of ttie flow in Uie pipe, which decreases tiie veiodty of the water flowing into
the system. A redudion in turbulence is realized at the inlet; tiiis aids in keeping the ti-apped
sediment and floatables conteined. In addition, tiie rise in water levei causes tiie floatebles to
rise above tiie 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 tiiat of a 2-month stonn event.
Weir Any event greater than tiie 2-month event causes tiie water level in the Vortechs System
to rise to the upper flow confrol, submerging tiie inlet The upper flow confrol is nonnally a
Cippoletti weir. A Cippoletti weir is a frapezoidal weir with 4 to 1 sloping sides. Like the orifice,
tiie weir also causes ttie water level in tiie system to rise, which promotes sediment and
floatable removal. As the water rises, tiie volume of water in the system increases, thus
stebillzing the detention time and allowing sediment to settle out. The swiri is mainteined by
allowing continuous flow through the system via tiie 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 maintein a velocity such tiiat re-entrainment of
floatebles and re-suspension of sediment is minimized. The baffle opening is at least 6 inches
to ensure against clogging. The largest opening of 15 inches is chosen to maximize tiie
distence between the floateble layer and ttie baffle opening. This keeps the floatables frapped
and maintains the oil storage volume. In most appiications, tiie flow under tiie 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 tiie diversion strudure that will be instelled upsfream of tiie spedfled Vortechs System. The
goal is to achieve a water surface elevation during tiie 100-year stonn that is at the same
elevation as the top of the Vortechs Cippoletti weir. The area of fiow over the bypass weir is
calculated based on the 100-year flow. From tiiis area, the height of flow is solved for a given
weir length. Since ttie area of flow remains constent ttie height of flow over ttie weir varies with
the bypass weir lengtii. See Tectinlcal Bulletin 3A tor more information.
VORTECHS™ STORMWATER TREATMENT SYSTEM
Flnw Control Calnnlatinns Vortechs Model 5000
System
Tiie Vortechs System W.Q.S. 1 is a Model 5000 with a 7.0-foot diameter grit chamber. In
this application, the runoff rate for a rainfall event with a retum frequency of 10 years is 6.13
cubic feet per second (cfs). The system design flow is 2751 gpm (6.13 cfs). The surface
area of the grit chamber is 38.5 square feet, ttierefore the peak operating rate is 2751
divided by 38.5 or 72 gpm/sf.
The low flow control is a trapezoidal orifice (Qoiafce). Since Uie intet is a 24-inch diameter
pipe, tiie orifice must raise the water level 24 inches, or 2.0 feet, in a 2-montii storni to
submerge the inlet pipe. According to Vortechnics Technical Bulletin #3, the 2-montii stonn
flow rate is approximately equal to ttie 10-year flow rate divided by 7. The orifice calculation
based on tiie full design flow is as follows:
Q^montfi =.Qtoy»ar+7 = 6.13 •*• 7 = 0.88 CfS
Qorsfce = C(A)(2g/?)" s: 0.56(0.14)(2.0 X 32.2 x 2.0) ""^ = 0.89 cfs 4
Where C = Orifice contraction coefficient = 0.56 (based on Vortechnics laboratory testing)
^ - Orifice flow area, ft^ (calculated by Vortechnics technical staff)
tl - Design head, ft (equal to the inlet pipe diameter)
A Cippoletti weir configuration is utilized as the high flow control (Qmk) which is
consen/atively designed for tiie system design flow (Quesign) ot 6.13 cfs. The weir
calculations are as follows:
Qvw*-=6.13 cfs
Qweir =C{L){H)'-^ = 3.37{0.50)(2.42)''' =6.34 cfs 4
Where C = Cippoletti Weir coefficient = 3.37 (based on Vortechnics laboratory testing)
H = Available head, ft (height of weir)
L- = Design weir crest lengtti, ft (calculated by Vortechnics technical stafl)
VORTECHS™ STORMWATER TREATMENT SYSTEM
MAINTENANCE
The Vortechs System requires minimal routine maintenance. However, it is important that ttie
system be inspeded at regular intervals and deaned when necessary to ensure optimum
performance. The rate at which tiie system colleds pollutents will depend more heavily on site
adivities than the size of tiie unit e.g., heavy winter sanding will cause ttie grit chamber to fill
more quickly but regular sweeping will slow accumulation.
Inspection
Inspection is Uie key to effective maintenance and it is easily perfonned. Vortechnics
recommends ongoing quarteriy inspections of tiie accumulated sediment Note ttiat is not
unusual for sediment accumulation tp be relatively light in ttie first year as initial sediment loads
in new stomi drainage systems may be diverted to catch basin sumps. Poilutent deposition and
transport may vary from year to year and quarterly inspedions will help insure ttiat systems are
deaned out at Uie appropriate time. Inspedions should be. perfonned more often in the winter
months in dimates where sanding operations may lead to rapid accumulations, or in equipment
washdown areas. It is very useful to keep a record of each inspedion. A simple fomi for doing
so is provided.
The Vortechs System only needs to be cleaned when Inspedion reveals ttiat it is neariy fuil;
specifically, when sediment deptti has accumulated to wittiin six inches of ttie dry-weattier
water level. This detennination can be made by teking 2 measurements witti a stedia rad or
similar measuring device: one measurement is the distence from ttie manhole opening to the
top of the sediment pile and ttie other is ttie distence from ttie manhole opening to ttie water
surface. If tiie difference between Uie two measurements is less ttian six indies ttie system
should be deaned out Note: to avoid underestimating tiie volume of sediment in ttie chamber,
the measuring device must be lowered to ttie top of tiie sediment pile carefully. Finer, silty
partides at ttie top of tiie pile typically offer less resistence to ttie end of the rod than larger
partides toward tiie bottom of ttie pile.
In Vortechs instellations where ttie risk of large petroleum spiiis is smail, liquid contaminants
may not accumulate as quickly as sediment However, an oil or gasoline spill should be
cleaned out Immediately. Oil or gas ttiat accumulates on a more routine basis should be
removed when an appreciable layer has been captured.
Cleanina
Cleanout of ttie Vortechs System with a vacuum .ttnck is generally tiie most effedive and
convenient method. Cleanout should not occur within 6 hours of a rain event to allow ttie entire
collecUon system to drain down. Properiy mainteined Vortechs Systems will only require
evacuation of ttie grit chamber portion of ttie system, in which case only tiie manhole cover
nearest to the system inlet need be opened to remove water and contaminants. However, all
chambers should be checked to ensure tiie integrity of ttie system. In instellations where a
"clamshell" is being utilized for solids removal, prior to removing tiie grit, absorbent pads or
piilows can be placed in tiie oil chamber to remove floating conteminants. Once Uiis is done,
sediment may Uien be easily removed witii tiie damshell.
I VORTECHS™ STORMWATER TREATMENT SYSTEM
IC
In some cases, it may be necessary to pump out all chambers. An important maintenance
feature built into Vortechs Systems is ttiat floatables remain frapped after a cleaning. A pocket
of water between ttie grit chamber and ttie outlet panel keeps ttie bottom of the baffle
submerged, so that all floatebles remain trapped when the system begins to fill up again.
Therefore, in ttie event of deaning ottier chambers it is imperative ttiat ttie grit chamber be
drained first. Manhole covers should be securely seated following cleaning activities, to ensure
ttiat surface runoff does not leak into ttie unit from above.