HomeMy WebLinkAboutCT 04-18; OCEAN MIST CONDOMINIUMS; STORM WATER MANAGEMENT PLAN FOR OCEAN MIST CONDOMINIUMS TENTATIVE MAP; 2004-10-08$ )
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2410 Stromberg Circle, Carlsbad, CA 92008
Tel: (760) 942-1106 Fax: (760) 730-3059
Email: brian@rdc2000.com
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STORM WATER MANAGEMENT PLAN
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OCEAN MIST CONDOMINIUMS TENTATIVE MAP
PREPARED FOR:
SANDRA BOVENZI
PROJECT SITE LOCATION
335 OAK AVENUE, CARLSBAD, CALIFORNIA
REPORT DATE:
OCTOBER 8, 2004
I
PREPARED BY:
Brian Donald, RCE 26175
License Expires 3/31/06
(ir aRLN
DONALD I No. 26175 c1vIL
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Storm Water Ividnagement Plan (SWMP)
Ocean Mist Condominiums Tentative Map
Contents
Section 1. Introduction .........................................................I
Section 1.01 Introduction ...................................................i
Section 2. Project ...................................................I
Section 2.01 Description ....................................................I
Section 2.02 Topography and Land Use ..............................1
Section 2.03 Hydraulic Unit Contributions ..............................2
Section 3. Water Quality Environment .................................2
Section 3.01 Beneficial Uses .............................................2
3.01.l Inland Surface Waters .......................................3
Section 3.02 303(d) Status ................................................4
Section 4. Characterization of Project Runoff 4
Section 4.01 Existing and Post Construction Drainage 4
Section 4.02 Post-Development Expected Discharges ...............5
Section 4.03 Soil Runoff Characteristics .................................5
Section 5. Mitigation Measures to Protect Water Quality 5
Section 5.01 Construction BMP's ..........................................5
Section 5.02 Post-Construction BMP's .................................6
5.02.1 Site Design BMP's ..........................................6
5.02.2 Source Control BMP's .................................6
5.02.3 Treatment Control BMP's .................................6
5.02.3 (i) Bio-Filters ..........................................6
5.02.3 (i) (a) Appropriate Applications and Siting Constraints6
Section 6. Operation and Maintenance Program ...............7
Section 6.01 Bio-Filters ...................................................7
6.01.1 Inspection Frequency .................................7
6.01.2 Aesthetic and Functional Maintenance ...............7
6.01.2 (i) Aesthetic Maintenance ........................8
6.01.2 (ii) Functional Maintenance ........................8
6.01.3 Maintenance Frequency .................................8
Section 7. Mechanisms to Assure Maintenance ...............8
Section 7.01 Stormwater Ordinance Requirement ...............8
Section 7.02 Public Nuisance Abatement ........................8
Section 7.03 Notice to Purchasers .................................9
Section 7.04 Subdivision Public Report .................................9
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
Section 7.05 Funding ...................................................9
Section 8. Summary Conclusions .................................9
Section 9. Certification ...................................................10
Attachment A Vicinity Map ..................... . ............................. A-I
Attachment B Site Drainage Plan ..........................................B-I
Attachment C Hydrology and Drainage Design Calculations C-I
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
Section 1
Introduction
Section 1.01 Introduction
A Storm Water Management Plan (SWMP) for this project is required by the County of San
Diego Watershed Protection, Storm Water Management, and Discharge Control Ordinance
(Section 67.817). The, purpose of this SWMP is to address the water quality impacts from the
proposed development of the Ocean Mist Condominium Project. Best Management Practices
(BMP's) will be utilized to provide a long-term solution to water quality. This SWMP is also
intended to ensure the effectiveness of the BMP's through proper maintenance that is based on
long-term fiscal planning. The SWMP is subject to future revisions as needed or required by
either the Project Engineer or the City of Carlsbad to ensure that the goal of permanent minimal
impacts to storm water discharge by project development is met.
Section 2
Project
Section 2.01 Description
The proposed project is the development of a 0.77 acre site located on Oak Avenue in the City
of Carlsbad, California into a five unit Airspace Condominium Project. The site is approximately
% mile east of the Pacific Ocean and I mile north of Agua Hedionda Lagoon.
The project site is at present approximately 80% vacant. There is a small two-story garage type
building with a living quarter over the top of it located at the northwest corner of the site. There
are two small sheds located near the middle of the easterly property line. Both structures will be
demolished to when the site is developed.
The Ocean Mist Condominium project proposes the construction of single 7,200 square foot
footprint building to contain 5 Condominium Airspace Units on two floors over underground
parking. A concrete driveway off of Oak Avenue leads to basement level parking. Three guest
parking spaces are proposed onsite adjacent to Oak Avenue. The construction of the basement
level parking portion of the structure will generate approximately 2,000 cubic yards of excavated
earth to be exported off site. The grades around the edges of the proposed building will be
raised slightly to provide positive drainage flow to Oak Avenue.
Section 2.02 Topography and Land Use
The site is located at the high point of the block between Lincoln Street and Washington Avenue
on the south side of Oak Avenue. The site is generally flat and consists of mostly very pervious
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
sandy soils. Any storm runoff not absorbed directly onsite is shed by sheet flow to the adjacent
easterly and westerly properties, and to Oak Avenue. There are existing small apartment
buildings to the east and west of the project site. There is a small commercial building adjacent
to the project site on the west at Oak Avenue.
Section 2.03 Hydrologic Unit Contributions
The project site is located in the Agua Hedionda Lagoon Hydrologic Area within the Carlsbad
Hyrologic Unit (904.31). Stormwater runoff from the developed project site will flow via surface
flow and storm drain pipes to a large recently constructed public storm drain pipe in the railroad
right-of-way at the east end of Oak Avenue. That public storm drain pipe delivers runoff from
the project site, and a very large tributary area surrounding the project site in a southerly
direction from Oak Avenue to Aqua Hedionda Lagoon and the Pacific Ocean.
Section 3
Water Quality Environment
Section 3.01 Beneficial Uses
The Beneficial Uses for the Hydrologic Unit are included in Table 3.1. This table has been
extracted from the Carlsbad Watershed Management Plan. The Beneficial Uses are defined as
follows:
MUN - Municipal and Domestic Supply: Includes uses of water for community,
military, or individual water supply systems including, but not limited to, drinking water
supply.
AGR - Agricultural Supply: Includes uses of water for farming, horticulture, or
ranching including but not limited to, irrigation, stock watering, or support of vegetation
for range grazing.
IND - Industrial Services Supply: Includes uses of water for industrial activities that
do not depend primarily on water quality including, but not limited to, mining, cooling
water supply, hydraulic conveyance, gravel washing, fire protection, or oil well re-
pressurization.
COMM - Commercial and Sport Fishing: Includes the uses of water for commercial or
recreational collection of fish, shellfish, or other organisms including, but not limited to,
uses involving organisms intended for human consumption or bait purposes.
EST - Estuarine Habitat: Includes uses of water that support estuarine ecosystems,
including but not limited to preservation or enhancement of marine habitats, vegetation,
fish, shellfish, or wildlife.
MAR - Marine Habitat: Includes uses of water that support marine ecosystems,
including but not limited to preservation or enhancement of marine habitats, vegetation,
fish, shellfish, or wildlife.
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
MIGR - Migration of Aquatic Organisms: Includes uses of water that support habitats
necessary for migration, acclimatization between fresh and salt water, or other
temporary activities by aquatic organisms, such as anadramous fish.
RARE - Rare, Threatened or Endangered Species: Includes uses of water
necessary, at least in part, for the survival and successful maintenance of plant or
animal species established under State or Federal Law as rare, threatened or
endangered.
RECI - Contact Recreation: Includes uses of water for recreational activities involving
body contact with water, where ingestion of water is reasonably possible. These uses
include, but are not limited to, swimming, wading, water-skiing, skin and SCUBA diving,
surfing, white water activities, fishing, or use of natural hot springs.
REC2 - Non-Contact Recreation: Includes the uses of water for recreational activities
involving proximity to water, but not normally involving body contact with water, where
ingestion of water is reasonably possible. These uses include, but are not limited to,
picnicking, sunbathing, hiking, camping, boating, tide pool and marine life study, hunting,
sightseeing, or aesthetic enjoyment in conjunction with the above activities.
SHELL - Shellfish Harvesting: Includes the uses of water that support habitats
suitable for the collection of filter-feeding shellfish (e.g., clams, oysters and mussels) for
human consumption, commercial, or sport purposes.
AQUA - Aquaculture: Includes the uses of water for aquaculture or mariculture
operations including, but not limited to, propagation, cultivation, maintenance, or
harvesting of aquatic plants and animals for human consumption or bait purposes.
WARM - Warm Freshwater Habitat: Includes uses of water that support warm water
ecosystems including, but not limited to, preservation or enhancement of aquatic
habitats, vegetation, fish or wildlife, including invertebrates.
WILD - Wildlife Habitat: Includes uses of water that support terrestrial ecosystems
including, but not limited to, preservation and enhancement of terrestrial habitats,
vegetation, wildlife (e.g., mammals, birds, reptiles, amphibians, invertebrates), or wildlife
water and food sources.
3.01.1 Inland Surface Waters
Inland Surface Waters have the following beneficial uses as shown on Table 3.1.
Table 3.1 - Beneficial Uses for Inland Surface Waters
Hydrologic
Unit z 0 0 Agua Lu N 0 D o -J uJ
Hedionda 4 ! 0 0 'Ii
Lagoon
904.31 - - - • • •
Existing Beneficial Use
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
3.02 303(d) Status
According to the California 2002 303(d) list published by the San Diego Regional Water Quality
Control Board, Agua Hedionda Lagoon is subject to Bacterial Indicators and Siltation!
Sedimentation stressors. These indicators require the governing jurisdiction to establish an
action plan, called as Total Maximum Daily Loads (TMDL), to improve water quality. The TMDL
priority for Aqua Hedionda Lagoon is "LOW
Section 4
Characterization of Project Runoff
Section 4.01 Existing and Post Construction Drainage
The proposed project will not significantly alter drainage patterns on the site or the surrounding
area. Storm Water Discharge Points will not divert runoff from existing conditions.
There will be a significant increase in the amount of impervious surface area on the project site
from the proposed development on a percentage basis relative to the project site area. The
project site is relatively small so the increase in runoff to the much larger Hydrologic Unit, to
Agua Hedionda Lagoon and the Pacific Ocean, and to the local storm drain system is relatively
small in terms of storm water runoff volume. Approximately 14% of the project site is covered
with existing buildings in the existing pre-development state. That would increase to 61% of the
0.39 acre site with the proposed development. This would result in an increase in the runoff
coefficient from C = 0.38 to C = 0.67, and an increase in peak 100 year storm runoff from 0.59
cfs to 1.02 cfs, a net increase of 0.43 cfs. A detailed description of the pre- and post-
development drainage patterns and flow calculations are contained in the "Hydrology and
Drainage Design Calculations" prepared for this project and attached to this SWMP as Appendix
C.
The majority of storm water runoff from this site from driveway, parking, and roof areas will be
directed to surface flow over a grassy swale and landscaped area located at the southerly rear
yard and along the westerly boundary of the proposed development. Bio-Filtration of
stormwater runoff will occur prior to collection of stormwter runoff in an on-site storm drain inlet
and connection to the existing public storm drain located in Oak Avenue. A smaller portion of
storm runoff from roof and sidewalk areas will be directed to small landscape planters and then
collected in a series of landscape drains and delivered to the public storm drain. All of the site
runoff will be filtered by flow over vegetated surfaces prior to entering the public storm drain. A
Site Drainage Plan is attached to this SWMP as Appendix B.
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
Section 4.02 Post-Development Expected Discharges
The proposed development is not expected to generate significant amounts of storm water
pollutants. The following constituents are commonly found at similar developments and could
affect water quality:
Sediment Discharge due to construction activities.
Nutrients from fertilizers.
Hydrocarbons from paved areas.
Pesticides from landscaping and home use.
Section 4.03 Soil Runoff Characteristics
The project site consists of Soil Group B with a minimum runoff coefficient of C = 0.25 for
saturated conditions and 0% impervious surfaces based on the Soil Type Map contained in
Appendix A of the County of San Diego Hydrology Manual.
Section 5.
Mitigation Measures to Protect Water Quality
In order to protect water quality from stormwater runoff from the proposed project, Best
Management Practices (BMP's) will be implemented during construction and on a permanent
basis after construction is complete.
Section 5.01 Construction Phase BMP's
A detailed description of the construction phase BMP's are available in the Cal-Trans
Construction Site Best Management Practices (BMP's) Manual. A summary of the construction
phase BMP's to be used for the proposed development is as follows:
SS-1 Scheduling
SC-I Silt Fence
SC-5 Fiber Rolls
SC-10 Storm Drain Inlet Protection
TC-1 Stabilized Construction Entrance
WM-I Material Delivery and Storage
WM-2 Material Use
WM-4 Spill Prevention and Control
A detailed Erosion and Sediment Control Plan will be prepared and approved by the City of
Carlsbad prior to the issuance of a Grading Permit for this project showing the detailed location,
placement and quantities of the Construction Phase BMP's listed above.
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
Section 5.02 Post-Construction BMP's
Pollutants of concern as noted in Section 4 will be addressed through three types of BMP's.
These types of BMP's are Site Design, Source Control, and Treatment Control.
Section 5.02.1 Site Design BMP's
The proposed development is designed so that all site generated storm runoff will surface flow
over landscaped vegetated and grassy surfaces prior to collection and delivery to the public
storm drain system.
Section 5.02.2 Source Control BMP's
Source Control BMP's will consist of measures to prevent polluted runoff. This program will
include an educational component directed at each homeowner. The homeowners will receive
a set of brochures developed by the County's Environmental Health Department. These will
include the following:
Storm Water Runoff Pollution Fact Sheet
Storm Water Runoff Pollution Prevention Tips for Homeowners
Storm Water Pollution Prevention Yard Work (Landscaping, Gardening, Pest Control)
Storm Water Pollution Prevention Pet Waste
Section 5.02.3 Treatment Control BMP's
The following Treatment Control BMP's will be implemented to address water quality:
Bio-Filters
Placement of the BMP's are noted on the Project Site Plan (Appendix B).
5.02.3 (i) Bio-Filters
Bio-Filtration swales are vegetated channels that receive directed flow and convey storm water.
Pollutants are removed by filtration through grass, sedimentation, adsorption to soil particles,
and infiltration through the soil. Swales are mainly effective at removing debris and solid
particles, although some dissolved constituents are removed by adsorption into the soil.
5.02.3 (i) (a) Appropriate Applications and Siting Constraints
Swales and strips should be considered wherever site conditions and climate allow vegetation
to be established and where flow velocities are not high enough to cause scour. Even where
strip cannot be site to accept directed sheet flow, vegetated areas provide treatment of rainfall
and reduce the overall impervious surfaces.
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
Factors Affecting Preliminary Design:
Swales have two design goals: 1) maximize treatment, 2) provide adequate hydraulic function
for flood routing, adequate drainage and scour prevention. Treatment is maximized by
designing the flow of storm runoff through the swale to be as shallow and long as site
constraints allow. No minimum .dimensions are required for treatment purposes, as this could
exclude swales from consideration at some sites. Swales should also be sized as a
conveyance system calculated according to County procedures for flood routing and scour.
To maximize treatment efficiency, strips should be designed to be as long (in the direction of
flow) and as flat as the site will allow. No minimum lengths or maximum slopes are required for -
treatment purposes. The area to be used for the strip should be free of gullies or rills that can
concentrate overland flow and cause erosion.
Section 6
Operation and Maintenance Program
The Operation and Maintenance requirements for each type of BMP is as follows:
Section 6.01 Bio-Filters
The operational and maintenance needs of a Swale are:
Vegetation management to maintain adequate hydraulic functioning.
Periodic inspection by the Homeowners Association to ensure the free flow of project site
runoff across Condominium Private Yard boundaries.
Section 6.01.1 Inspection Frequency
The facility will be inspected and inspection visits will be completely documented on an Annual
basis.
Section 6.01.2 Aesthetic and Functional Maintenance
Aesthetic Maintenance is important for individual homeowner's acceptance of the Bio-Filter
facility. Functional Maintenance is important for performance. Both forms of maintenance will
be combined into an overall Stormwater Manage System Maintenance program. The Ocean
Mist Homeowners Association will be responsible for providing a Landscape Maintenance
Contractor to provide the required maintenance. Individual homeowners will be required to
allow the Landscape Maintenance Contractor access to individual private yards for the purpose
of regular maintenance as described below.
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
Section 6.01.2 (i) Aesthetic Maintenance
The following activities will be included in the aesthetic maintenance program:
Grass Trimming. Lawn mowing and trimming of grass will be done on the swale, around
fences, and at the edge of patio concrete.
Weed Control. Weeds will be removed through mechanical means. Herbicides will only
be allowed if included in the lawn fertilizer mix.
Fertilizing: Fertilizer will be used on a regular basis as required to maintain the grass in a
healthy and green state.
Section 6.01.2 (ii) Functional Maintenance
The Aesthetic Maintenance activities listed above will maintain the swale in a functional state.
In addition, periodic removal of leaves, debris and silt from the inlet structure at the downstream
end of the swale to reduce the potential for becoming clogged and inoperable during storm
events.
Section 6.01.3 Maintenance Frequency
Maintenance as described above will be performed on a weekly or bi-weekly basis depending
on seasonal growth of the grass within the swale. The Homeowners Association will be
responsible for determining the maintenance frequency required to maintain the aesthetics in a
manner satisfactory to the individual homeowners.
Section 7
Mechanisms to Assure Maintenance
This section is intended to provide information regarding the ability of the owner/developer to
ensure the construction and maintenance of post-construction BMP's.
Section 7.01 Stormwater Ordinance Requirement
The County of San Diego Watershed Protection, Stormwater Management, Discharge Control
Ordinance (S.0.) requires this ongoing maintenance. In the event that the mechanisms below
prove ineffective, or in addition to enforcing those mechanisms, civil action, criminal action or
administrative citation could also be pursued for violations of the ordinance.
Section 7.02 Public Nuisance Abatement
Under the S.O., failure to maintain a BMP would constitute a public nuisance, which may be
abated under the Uniform Public Nuisance Abatement Procedure. This provides an
enforcement mechanism additional to the above, and would allow costs of maintenance to be
billed to the Owner, a lien placed on the property, and the tax collection process to be used.
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
Section 7.03 Notice to Purchasers
Section 67.819(e) of the S.O. requires developers to provide clear written notification to persons
acquiring land upon which a BMP is located, or others assuming a BMP maintenance obligation,
of the maintenance duty.
Section 7.04 Subdivision Public Report
Tentative Map and Tentative Parcel Map approvals will be conditioned to require that, prior to
approval of a Final Map or Parcel Map, the Subdivider shall provide evidence to the Director of
Public Works, that the Subdivider has requested the California Department of Real Estate to
include in the public report to be issued for the sales of lots within the Subdivision, a notification
regarding the maintenance requirement. (The requirement for this condition would not be
applicable to subdivisions which are exempt from regulation under the Subdivided Lands Act, or
for which no public report will be issued.)
Section 7.05 Funding
None required.
Section 8
Summary Conclusions
This SWMP has been prepared in accordance with the Watershed Protection, Stormwater
Management, and Discharge Control Ordinance and the Stormwater Standards Manual. This
SWMP has evaluated and addressed the potential pollutants associated with this project and
their effects on water quality. A summary of the facts and findings associated with this project
and the measures addressed by this SWMP is as follows:
The beneficial uses for the receiving waters have been identified. None of these beneficial
uses will be impaired or diminish due to the construction and operation of the proposed
project.
The Ocean Mist Condominium project will not significantly alter drainage patterns on the
Site. The discharge points will not be changed.
Open areas will be landscaped to reduce or eliminate sediment discharge.
The vegetated swales proposed as part of the project will provide some mitigation of the
increased peak flows by detaining flows, reducing the velocities, and providing opportunities
for infiltration.
The proposed construction and post-construction BMP's address mitigation measures to
protect water quality and protection of water quality objectives and beneficial uses to the
maximum extent practicable.
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
Section 9
Certification
This Storm Water Management Plan has been prepared under the direction of the following
Registered Civil Engineer. The Registered Civil Engineer attests to the technical information
contained herein and the engineering data upon which recommendations, conclusions and
decisions are based.
Brian Donald, RCE 26175 Date
License Expires 3/31/06
BflINI
1DNALD t No 261Th
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Storm Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
Attachment A - Vicinity Map
Page A-I
Storm-Water Management Plan (SWMP)
Ocean Mist Condominiums Tentative Map
Attachment C - Hydrology and Drainage Design Calculations
Refer to Hydrology, and Drainage Design Calculations, Ocean Mist Condominiums, CT04-I 8,
224 Oak Avenue, Carlsbad, prepared by Resource Development Corporation dated September
1, 2004
Page C-I