HomeMy WebLinkAboutCT 03-01-01; LA COSTA RESORT & SPA MSTR PLAN; STORM WATER MGMT PLAN; 2005-07-19HUNSAKER
^ASSOCIATES
SAN DIECO,
PLANNiNG
ENGiNEERING
SURVEYING
IRVINE
LOS ANGELES
RIVERSIDE
SAN DIEGO
N C.
STORM WATER
MANAGEMENT PLAN
for
LA COSTA RESORT &
SPA PHASE II
City of Carlsbad, California
Prepared for:
KSL Development Corporation
2100 Costa Del Mar Road
Carlsbad, CA 92009
w.o. 2503-1
July 19, 2005
DAVE HAMMAR
LEX WILLIMAN
ALISA VIALPANDO
OAN SMITM
RAY MARTIN
10179 Huennekens St.
San Diego, CA 92121
(858) 558-4500 PH
(858)558-1414 FX
www.HunsakerSD.com
lnfo@HunsakerSD.com
Hunsaker & Associates
San Diego, Inc.
Vice President
1,
DE:kc H:\REPORTS\2503\01\SWMP03.doc
W-O. 2503-1 7/19/2005 2:49 PM
La Costa Resort & Spa Phase II
Storm Water Management Plan
TABLE OF CONTENTS
CHAPTER 1 - Executive Summary
1.1 Introduction
1.2 Sumnnary of Pre-Developed Conditions
1.3 Summary of Proposed Development
1.4 Results and Recommendations
1.5 Conclusion
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
3.7 Metals
3.8 Bacteria & Viruses
3.9 Pesticides
CHAPTER 4 - Conditions of Concern
4.1 Receiving Watershed Descriptions
4.2 Pollutants of Concern in Receiving Watersheds
CHAPTER 5 - Flow-Based BMPs
5.1 Design Criteria
5.2 Grass-Lined Swales
5.3 Pollutant Removal Efficiency Table
5.4 Maintenance Requirements
5.5 Annual Operations and Maintenance Plan & Costs
ICT: HSREPORTS12503«)1\SWMP02.doC
wo. 2352-107 5/18/2005 9:55 AM
La Costa Resort & Spa Phase II
Storm Water Management Plan
CHAPTER 6 - Source Control BMPs
6.1 Landscaping
6.2 Urban Housekeeping
6.3 Automobile Use
6.4 Site Design BMPs
CHAPTER 7 - Treatment Control BMP Design (Grassy Swale)
7.1 BMP Location
7.2 Determination of Treatment Flows
7.3 Grassy Swale Sizing
CHAPTER 8 - References
List of Tables and Figures
Chapter 1 - Watershed Map
Chapter 2 - Storm Water Requirements Applicability Checklist
Chapter 2 - Site Design and Source Control Storm Water BMP Selection Matrix
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 (Flow-Based BMPs)
Chapter 7 - BMP Location Map
Chapter 7 - Design Runoff Determination Summary Table
Chapter 7 - Swale Design Spreadsheet
Attachments
BMP Location Map
DE:(le H:\REPORTS\2503\01\SWMP02.cloc
W.O. 2503.1 S/18f2005 9:55 AM
La Costa Resort & Spa Phase II
Storm Water Management Plan
CHAPTER 1 - EXECUTIVE SUMMARY
1.1 - Introduction
The La Costa Resort & Spa Phase II site is located north ofthe intersection of El
Camino Real and Costa Del Mar Road in the City of Carlsbad, California (see
Vicinity Map on this page). The 3.2-acre site is located within the greater La Costa
Resort and Spa development.
CITY OF OCEANSlOE
CITY OF ENCINITAS
VICINITY MAP
NOT TO SCALE
IJECT
JION
All runofl'from the project site will drain south to the existing 36-inch RCP storm
drain within El Camino Real, ultimately draining to San Marcos Creek. Runoff from
San Marcos Creek eventually discharges into Batiquitos Lagoon.
Per the City of Carlsbad SUSMP, the La Costa Resort & Spa Phase II project is
classified as a Priority Project and subject to the City's Permanent Storm Water BMP
Requirements.
This Storm 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 consistentwith criteria setforth 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 a grass lined swale. See BMP Location Map in this chapter.
DE:<te H:\REPORTS\2S03\01\SWMP02.(loc
W.0.2503-1 5/18/2005 0:55 AM
La Costa Resort & Spa Phase II
Storm Water Management Plan
Furthermore, this report determines anticipated project pollutants, pollutants of
concern in the receiving watershed, peak flow mitigation, recommended source
control BMPs, and methodology used forthe design of flow-based BMPs.
1.2 - Summarv of Pre-Developed Conditions
Currently a mass graded lot, the project is located within the existing La Costa
Resort and Spa development, which is being constructed in multiple phases. Site
runoff currently flows overland to the receiving curb and gutter located to the west of
the proposed site.
A 24-inch storm drain, located to the west of the site (adjacent to El Camino Real)
discharges runoff from the Phase 1 portion ofthe La Costa Resort and Spa
development to a large, natural open space. Flow is then conveyed south via this
grassed natural area to the receiving 36-inch RCP located within the proximity of the
intersection of El Camino Real and Costa Del Mar Road.
Per the "Drainage Study for La Costa Resort and Spa Phases I & II" dated May,
2005 by Hunsaker & Associates, peak flow data from the adjacent Phase 1 ofthe La
Costa Resort development attributes 63.4 cfs from a developed area of 21.8 acres to
this existing 30-inch storm drain.
Priorto exiting the existing 30-inch storm drain, runoff from Phase I ofthe La Costa
Resort and Spa development is treated via a CDS unit. However, runoff from the
proposed La Costa Resort and Spa Phase II site is not treated within this existing
unit
The Regional Water Quality Control Board has identified San Marcos Creek as part
of the Carlsbad Hydrologic Unit, San Marcos Hydrologic Area, and the Batiquitos
Hydrologic Subarea (basin number 904.51).
1.3 - Summarv of Proposed Development
Development ofthe 3.2-acre area will consist of 38 multi-family residences, foot
paths, communal open space, onsite parking and underground utilities with a single
entrance from the adjacent Estrella Del Mar Road.
Peak flow generated by the proposed La Costa Resort & Spa Phase II development
will be conveyed to two (2) points of discharge. The western portion of the
development will drain via curb and gutter, entering the proposed extension to the
existing 30-inch storm drain located to the west of the project site. The eastern
portion ofthe developed site will drain to the receiving curb and gutter within Costa
Del Mar Road. It should be noted that all low flows, inclusive ofthe 85'" percentile
treatment flow, is contained within the area drain system for the La Costa Resort &
Spa Phase II site and is conveyed to the western storm drain system.
DE:lte H:\REPOKTS\2503\01\SWMP02.doc
w.o. 2503-1 5/18/2005 10:31 AM
La Costa Resort & Spa Phase II
Storm Water Management Plan
85 percentile runoff from the proposed La Costa Resort & Spa Phase II and the
existing Phase 1 portion ofthe La Costa Resort and Spa via a grass lined BMP prior
to discharge to the existing storm drain system within El Camino Real.
Based on County of San Diego criteria, runoff coefficient of 0.82 was assumed for
the proposed multi-family residential development.
1.4 - Results and Recommendations
Table 1 below summarizes rational method 85"^ percentile calculations for the
proposed water quality treatment swale for the La Costa Resort & Spa Phase II and
the attributing La Costa Resort and Spa Phase I development.
Table 1 - Developed Conditions 85*^ Percentile Calculations
BMP
Drainage
Area
(acres)
Rainfall
Intensity
(inches/hour)
Runoff
Coefficient
85'" Pct.
Design Flow
(cfs)
Grassy Swale 23.3* 0.2 0.82 3.8
*Note: Inclusive of the adjoining La Costa Resort and Spa Phase I
Rational Method calculations predicted an 85"^ percentile runoff flow of roughly 3.8
cfs for the area discharging to the existing vegetated open space area adjacent to El
Camino Real. Calculations show that this existing natural open space has sufficient
treatment capacity in order to treat this developed flow (refer to Chapter 7).
It should be noted that this natural swale area is a temporary BMP treatment area.
Future phases ofthe La Costa Resort and Spa propose to construct a parking lot
where this current natural area exists, continuing the storm drain system within this
future development and connecting directly to the existing 36-inch storm drain within
El Camino Real. This future development will incorporate a proposed flow based
treatment unit (CDS or similar approved, flow based treatment unit) priorto entering
the existing 36-inch storm drain.
The existing CDS treatment unit currently servicing flow from Phase 1 ofthe La
Costa Resort and Spa development will remain, providing additional treatment.
1.5 - Conclusion
The combination of proposed construction and permanent BMP's will reduce, to the
maximum extent practicable, the expected project pollutants and will not adversely
impact the beneficial uses of the receiving waters.
DE:de H:\REPORTS\2503V01\SVVMP02.doc
w o. 2503-1 5/18/2005 0:55 AM
HUNSAKER & ASSOCIATES
1 AH D I te^ , N c
BMP LOCATION EXHIBIT FOR
LA COSTA RESORT & SPA
PHASE 2
CITY OF CARLSBAD, CALIFORNIA
SHEET
1
OF
1
Ri\a615MHyd\SI5SH03-BHP.ctog[ ZOB5»tay-lB-a005ilOilO
La Costa Resort & Spa Phase II
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 refer to
specific stonTi 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 ofthe urban development ofthe 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 Resort & Spa Phase II 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.
DE:<le H:\REPORTS\2503\01\SWMP02.(loc
W.O. 2503-1 5/18/2005 0:55 AM
Storm Water Standards
4/03/03
VL RESOURQES & REFERENCES ^ ^ =^"Jf^ - ^ _ -
APPENDIX A
STORM WATER REQUIREMENTS APPLICABILITY CHECKLIST
Complete Sections 1 and 2 of the following checklist to determine your project's
permanent and construction storm water best management practices requirements.
This form must be completed and submitted with your permit application.
Section 1. Permanent Storm Water BMP Requirements:
If any answers to Part A are answered "Yes," your project is subject to the "Priority
Project Permanent Storm Water BMP Requirements," and "Standard Permanent Stomi
Water BMP Requirements" in Section ill, "Permanent Storm Water BMP Selection
Procedure" in the Storm H/aterSteA7dards manual.
If all answers to Part A are "No," and any answers to Part B are "Yes," your project is
only subject to the "Standard 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 ofthe priority project
categories?* Yes No
1. Detached residential development of 10 or more units '7'
2. Attached residential development of 10 or more units
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 discharging to receiving waters within Environmentally Sensitive Areas
8. Parking lots greater than or equal to 5,000 ff' or with at least 15 parking spaces, and
potentially exposed to urban runoff
9. Streets, roads, highways, and freeways which would create a new paved surface that is
5,000 square feet or greater
* Referto the definitions section in the Stortn Water Standards for expanded definitions ofthe priority
project categories.
Limited Exclusion: Trenching and resurfacing work associated with utility projects are not considered
priority projects. Parking lots, buildings and other stmctures 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
storm Water Standards
4/03/03
Does the project propose: Yes No
1. New impervious areas, such as rooftops, roads, parking lots, driveways, paths and
sidewalks?
2. New pervious landscape areas and irrigation systems?
3. Permanent stmctures within 100 feet of any natural water body?
4. Trash storage areas?
5. Liquid or solid material loading and unloading areas?
6. Vehicle or equipment fueling, washing, or maintenance areas?
7. Require a General NPDES Pennit for Stonn Water Discharges Associated with
Industrial Activities (Except constmction)?*
8. Commercial or industrial waste handling or storage, excluding typical office or
household waste?
9. Any grading or ground disturbance during constmction?
10. Any new stonm drains, or alteration to existing storm drains?
*To find out if your project is required to obtain an individual General NPDES Pennit for Stonn Water
Discharges Associated with Industrial Activities, visit the State Water Resources Control Board web site
at, www.swrcb.ca.gov/stonnwtr/industrial.html
Section 2. Construction Storm Water BMP Requirements:
If the answer to question 1 of Part C is answered "Yes," your project is subject to
Section IV, "Construction Storm Water BMP Performance Standards," and must prepare
a Storm Water Pollution Prevention Plan (SWPPP). If the answer to question 1 is "No,"
but the answer to any of the remaining questions is "Yes," your project is subject to
Section IV, "Construction Storm Water BMP Performance Standards," and must prepare
a Water Pollution Control Plan (WPCP). If every question in Part C is answered "No,"
your project is exempt from any construction stomn water BMP requirements. If any of
the answers to the questions in Part C are "Yes," complete the construction site
prioritization in Part D, below.
Part C: Determine Construction Phase Storm Water Requirements
Would the project meet any of these criteria during construction? Yes No
1. Is the project subject to California's statewide General NPDES Pennit for Stomn Water
Discharges Associated With Constmction Activities? /
2. Does the project propose grading or soil disturiaance?
3. Would stomri water or urban runoff have the potential to contact any portion of the
construction area, including washing and staging areas?
4. Would the project use any construction materials that could negatively affect water
quality if discharged from the site (such as, paints, solvents, concrete, and
stucco)?
/
31
Storm Water Standards
4/03/03
Part D: Determine Construction Site Priority
In accordance with the Municipal Permit, each construction site with construction storm
water BMP requirements must be designated with a priority: high, medium or low.
This prioritization must be completed with this form, noted on the plans, and included in
the SWPPP or WPCP. Indicate the project's priority in one of the check boxes using the
criteria below, and existing and surrounding conditions of the project, the type of
activities necessary to complete the construction and any other extenuating
circumstances that may pose a threat to water quality. The City reserves the right to
adjust the priority of the projects both before and during construction. [Note:
The construction priority does NOT change construction BMP requirements that apply
to projects; all construction BMP requirements must be identified on a case-by-case
basis. The construction priority does affect the frequency of inspections that will be
conducted by City staff. See Section IV.I for more details on construction BMP
requirements.]
or A) High Prionty
1) Projects where the site is 50 acres or more and grading will occur during the
rainy season
2) Projects 5 acres or more. 3) Projects 5 acres or more within or directiy
adjacent to or discharging directly to a coastal lagoon or other receiving water
within an environmentally sensitive area
Projects, active or inactive, adjacent or tributary to sensitive water bodies
• B) hAedium Priority
1) Capital Improvement Projects where grading occurs, however a Storm Water
Pollution Prevention Plan (SWPPP) is not required under the State Generai
Construction Permit (i.e., water and sewer replacement projects, intersection
and street re-aiignments, widening, comfort stations, etc.)
2) Permit projects in the public right-of-way where grading occurs, such as
installation of sidewalk, substantial retaining walls, curb and gutter for an
entire street frontage, etc., however SWPPPs are not required.
3) Permit projects on private property where grading permits are required,
however, Notice Of intents (NOIs) and SWPPPs are not required.
• C; Low Priority
1) Capital Projects where minimal to no grading occurs, such as signal light and
loop installations, street light instaliations, etc.
2) Permit projects in the pubiic right-of-way where minimal to no grading occurs,
such as pedestrian ramps, driveway additions, small retaining walls, etc.
3) Pennit projects on private property where grading permits are not required,
such as small retaining wails, single-family homes, small tenant
improvements, etc.
32
Table 2. Site Design and Souree Control Storm Water BMP Selection IVIatrix.
Priority
Project
Category
Site
Design
Sourcs
Corrtrol
BMP^
Requirements Applicable to Individual Priority Project
Categories' reways & Maintenance Bays ihicls Wash Areas isIng Areas •h Areas a> c a Ivate Roads jsldential Drl\ jest Parking jck Areas Maintenance Bays ihicls Wash Areas jtdoor Procea julpment Wat irkIng Areas 1
•a a leiing Areas llslde Landsct a. cccs Q Maintenance Bays > O u Ui Q. o
o:
u. X
-es .n d •d d £ • — •-^
Detached
Residential
Development
R R R R R
Attached
Residential
Development
R R R
Commerciai
Development
>100,000 ft*
R R R ' R R R
Automotive
Repair Shop R R R R R R R
Restaurants R R R R
Hillside
Development
>5,000
R R R R
Parking Lots R R
streets,
Highways &
Freeways
R R R
R = Required; select BMPs as required from the applicable steps in Section Vl.2.a & b, or equivalent as Identified
in Appendix A.
(1) Refer to Section V1.2.a.
(2) Refer to Section VI.2.b.
(3) Priority project categories must apply specific storm wafer BMP requirements, where applicable. Projects are
subject to the requirements of all priority project categories that apply.
(4) Applies if the paved area totals >5,000 square feet or with >15 parking spaces and is potentially exposed to
urban runoff.
Page 18 of 51 FINAL MODEL SUSMP
Jointly Developed "by
San Diego Co-Permittees 2/14/02, Approved by SDRWQCB 6/12/02
La Costa Resort & Spa Phase II
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 Resort & Spa Phase II development will
consist of attached multi-family residences. The existing La Costa Resort and Spa
Phase I development consists of attached multi-family and commercial development.
Thus, the Attached Residential Development & Commercial Development categories
have been highlighted to cleariy illustrate which general pollutant categories are
anticipated from the project area.
General PoUutant Categories
Priority
Project
Categories
m c 0
E
'•B
(O
c
0) 2: «
M •o c
«I
Jr O O O
00
!S ^
I- Q
c « a> >.
X
O
.E O •D C
E .Q
O 3 Q (0
ra
o w re
O
oS
CQ >
w tt
X3
O
w tt Q.
Detached
Residential
Development
X
Automotive
Repair
Shops
x X(4)(5) x x
Restaurants x x x x
Hillside
Development
>5,000 ft^
X x X x X X
Parking Lots p(i) pO) X x pd) x pd)
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.
DE:(le H:\REPORTS\2503\01\SWMP02.doc
w.o. 2503-1 5/180005 9:55 AM
La Costa Resort & Spa Phase II
Storm Water Management Plan
3.2 - Sediment
Soils or other surface materials eroded and then transported or deposited by the
action of wind, water, ice, or gravity. Sediments can increase turbidity, clog fish gills,
reduce spawning habitat, smother bottom dwelling organisms, and suppress aquatic
vegetative grov\/th.
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 mnoff 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 well as chemicals that react with dissolved
oxygen in water to form other compounds. Compounds such as ammonia and
hydrogen sulfide are examples of oxygen-demanding compounds. The oxygen
demand of a substance can lead to depletion of dissolved oxygen in a water body
and possibly the development of septic conditions.
3.6 - Oil & Grease
Characterized as high high-molecular weight organic compounds. Primary sources
of oil and grease are petroleum hydrocarbon products, motor products from leaking
vehicles, oils, waxes, and high-molecular weight fatty acids. Elevated oil and grease
content can decrease the aesthetic value of the water body, as well as the water
quality.
DE:de H:\REPORTS\2503V)1\SWMP02.<)OC
W.0.2503.1 5/18/2005 9:55 AM
La Costa Resort & Spa Phase 11
Storm Water Management Plan
3.7 - Metals
Metals are raw material components in non-metal products such as fuels, adhesives,
paints and other coatings. Primary sources of metal pollution in storm water are
typically commercially available metals and metal products. Metals of concern
include cadmium, chromium, copper, lead, mercury and zinc. Lead and chromium
have been used as corrosion inhibitors in primer coatings and cooler tower systems.
At low concentrations naturally occurring in soil, metals are not toxic. However, at
higher concentrations, certain metals can be toxic to aquatic life. Humans can be
impacted from contaminated groundwater resources, and bioaccumulation of metals
in fish and shellfish. Environmental concerns, regarding the potential for release of
metals to the environment, have already led to restricted metal usage in certain
applications.
3.8 - Bacteria & Viruses
Bacteria and viruses are ubiquitous micro-organisms that thrive under certain
environmental conditions. Their proliferation is typically caused by the transport of
animal or human fecal wastes from the watershed. Water, containing excessive
bacteria and viruses can alter the aquatic habitat and create a harmful environment
for humans and aquatic life. Also, the decomposition of excess organic waste
causes increased growth of undesirable organisms in the water.
3.9 - Pesticides
Pesticides (including herbicides) are chemical compounds commonly used to control
nuisance growth or prevalence of organisms. Excessive application of a pesticide
may result in runoff containing toxic levels of its active component.
DE:iie H:\REPORTS\2503\0HSWMP02.<loc
W.0.2503-1 5/18/2005 9:55 AM
La Costa Resort & Spa Phase 11
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 pre-developed La Costa
Resort & Spa Phase II site drains to San Marcos Creek which eventually discharges
to the Batiquitos Lagoon within the San Marcos Creek watershed.
Development ofthe site will not cause any diversion to or from the existing
watershed to the storm drain system.
The Regional Water Quality Control Board has identified San Marcos Creek as part
ofthe Carisbad Hydrologic Unit, San Marcos Creek Watershed, and the Batiquitos
Hydrologic Subarea (basin number 904.51).
4.2 - Pollutants of Concern in Receiving Watersheds
San Marcos Creek and Batiquitos Lagoon are not listed on the EPA's 303(d) List of
endangered waterways (included in this Chapter). Per the "Water Quality Plan for
the San Diego Basin", the beneficial uses for the Batiquitos Lagoon and San Marcos
Creek includes agricultural supply, contact water recreation, non-contact recreation,
warm freshwater habitat, and wildlife habitat.
Table 3-2 from the "Water Quality Plan for the San Diego Basin" (included at the end
of this Chapter) lists water quality objectives for a variety of potential pollutants
required to sustain the beneficial uses of the San Marcos hydrologic area.
De:(le H:\REPORTS\2503\01\SVVMP02.(loc
W.O. 2503-1 5/18/2005 0:55 AM
CARLSBAD
WATERSHED MAP FOR
LA COSTA RESORT
& SPA PHASE 2
criY OF CAHLSBAD, CALIFORNIA
a at
CO
cc
LU
< u
O
<
cc
D
W
O
LJJ
</)
<
O
LL
LU
z
UJ
CQ
I
(0
H
CO 0. § z
a: < Q: UJ
o o
5 < a: 5
m — o -I
UJ CO
cc UJ O cvl
< o
u.
Ul z Ul m
cr: UJ c
Q. o 5
u. D: CO X
o § a:
D. DC o o
z Q
< o K
S 3 Z
{= (D
a> .3 o Z
S •£
X
12
(0
0)
o
CO
c
(0
eo
CO c 'o c UJ
ID
a
•a c o >. c n O
03
2
(0 a. a> ea
IS •a • c
m £
(0
.o 3 CO o
(0 s
(0 u "5 _o
9
5 i
•a o
•e
CO
(0 CJ TD C
41
a.
"3
E •a
a
10
10
•e
JB
JO
CO
o >.
CL a. eo to c _o v. (0
c
D>
°I0 ID ' XJ
m
IS tt c
CQ
li= CD « C C tt o m
Ol
c TS
Ul
03
c
<D
•H
CL
I
tt tt CO
E 2 u. •a tt
Q. tt
UJ
• O +
Ul Ul CO 3
a tu B Z a UJ I- OQ
Table 2-3. BENEFICIAL USES OF COASTAL WATERS
BENEFICIAL USE
Coastal Waters Hydrologic
Unit Basin
1
N
N
A
R
E
R
E
C
.0
B
1
E
S
W
1
R
A
M
A
A
Q
M
1
S
P
W
A
s
H
Hydrologic
Unit Basin D V C C M 0 T L R R U G W R E Number V
1 2 M L D E A R N M L
L
Pacific Ocaan • • • • • • • • • • • • •
Dana Point Harbor • • • • • • • • • • •
Del Mar Boat Basin • • • • • • • • • • •
Mission Bay • • • • • • • • • • •
Oceanside i-iarbor • • • • • • • • • • •
San Diego Bay ^ • • • • • • • • • •
Coastal Lagoons
" Tijuana River Estuary • • • • • • • • • • •
Mouth of San Diego River 7.11 • • • • • • • • • •
2
Los Penasquitos Lagoon 6.10 • • • • • • • • • •
San Dieguito Lagoon 5.11 • • • • • • • • •
Batiquitos. Lagoon 4.51 • • • • • • • • •
San Elijo Lagoon . 5.61 • • • • • • • • •
Aqua Hedionda Lagoon 4.31 • •• • • • • • • •
•
1 Includes the tidal prisms of the Otay and Sweetwater Rivers.
2 Fishlnfl from shore or boat permitted, but other water contact recreational (REC-1) uses are prohibited.
Existing Beneficial Use March 12, 1997
Table 2-3
BENEFICIAL USES 2-47
Table 3-2. WATER QUALITY OBJECTIVES
Concentrations not to ba exceeded more than 10% of the time during any one one year period.
Const tiuent (mg/L or as notad)
Inland Surface Waters Hydrologic
Unit Basin
Number
TDS Cl SO 4 %Na N&P Fe Mn MBAS B ODOR Turb
NTU
Color
Units F
SAN LUIS REY HYDROLOGIC UNIT 903.00
Lower San Luis HA 3.10 500 250 250 60 a 0.3 0.06 0.5 0.75 none 20 20 1.0
Monserat HA 3.20 500 250 250 60 a 0.3 0.05 0.5 0,75 nona 20 20 1.0
Warner Valley HA 3.30 500 250 250 60 a 0.3 0.05 0.5 0.75 nona 20 20 1.0
CARLSBAD HYDROLOGIC UNIT 904.00
Loma Alta HA 4.10 ---------nona 20 20 1.0
Buena Vista Creek HA 4.20 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0
Agua Hedionda HA 4.30 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0
Encinas HA 4.40 ---------none 20 20 1.0
San Marcos HA 4.50 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0
Escondido Creek HA 4.60 500 250 250 60 a 0.3 0.05 0.5 0,75 none 20 20 1.0
SAN DIEGUITO HYDROLOGIC UNIT 906.00
Solana Beach HA 5.10 500 250 250 60 a 0.3 0.06 0.5 0.75 nona 20 20 1.0
Hodges HA 5.20 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0
San Pasqual HA 5.30 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0
Santa Maria Valley HA 5,40 500 250 250 60 a 0.3 0.05 0.5 0.75 nona 20 20 1.0
Santa Ysabel HA 5.50 500 250 250 60 a 0.3 0.05 0.5 0.75 nona 20 20 1.0
PENASQUITOS HYDROLOGIC UNIT 906.00
Miramar Reservoir HA 6.10 500 250 250 60 a 0.3 0.05 0.6 0.75 none 20 20 1.0
Poway HA 6.20 500 250 250 60 a 0.3 0.05 0.5 0.75 none 20 20 1.0
HA - Hydrologic Araa
HSA - Hydrolosic Sub Arsa (Lower caae letters indicate endnotes following the table.)
Tabla 3-2
WATER QUALITY OBJECTIVES Page 3-23 Septambar 8, 1994
2002 CWA SECTION 303(d) LIST OF WATER QUALITY LIMITED SEGMENT '"'""'''""'^^^^^
SAN DIEGO REGIONAL WATER QUALITY CONTROL BOARD
i-niQKiL'lilBtSKflillp^ffli^Sm
9 R Agua Hedionda Creek
E Agua Hedionda Lagoon
R Aliso Creek
E Aliso Creek (moutli)
E Buena Vista Lagoon
90431000
90431000
90113000
90113000
90421000
Total Dissolved Solids
Urban Runoff/Storm Sewers
Unknown Nonpoint Source
Unknown point source
Bacteria Indicators
Sedimentation/Siltation
Bacteria Indicators
Nonpoint/Point Source
Nonpoint/Point Source
Urban Runoil/Storm Sewers
Unknown point source
Nonpoint/Point Source
Phosphorus
ImpairmenI locaied at lower 4 miles.
Urban Runofi/Storm Sewers
Unknown Nonpoint Source
Unknown point source
Toxicity
Urban Runofi/Storm Sewers
Unknown Nonpoint Source
Unknown point source
Bacteria Indicators
Bacteria Indicators
Nonpoint/Point Source
Low
Low
Low
Medium
Low
Low
Medium
Low
Low
Nonpoint/Point Source
Nutrients
Eslimaied size of impairment is ISO acres locaied in upper poriion of lagoon.
Nonpoint/Point Source
Sedimentation/Siltation Medium
7 Miles
6.8 Acres
6.8 Acres
19 Miles
19 Miles
19 Miles
0.29 Acres
202 Acres
202 Acres
202 Acres
Nonpoint/Point Source
Page 1 of 16
2002 CWA SECTION 303(d) LIST OF WATER QUALITY LIMITED SEGMENT
SAN DIEGO REGIONAL WATER QUALITY CONTROL BOARD
Approved li.v USEPA:
.fuly 2003
R Sandia Creek
9 R Santa Margarita River (Upper)
Industrial Point Sources
Agriculture-storm runoff
Urban Runofi/Storm Sewers
Surface Mining
Flow Regulation/Modirication
Natural Sources
Golfcourse activities
Unknown Nonpoint Source
Unknown point source
Total Dissolved Solids Low
Urban Runoff/Storm Sewers
Flow Regulation/Modiflcation
Natural Sources
Unknown Nonpoint Source
Unknown point source
Phosphorus Low
Urban Runoff/Storm Sewers
Unknown Nonpoint Source
Unknown point source
Phosphorus
Turbidity
Page 13 of 16
Urban Runofi/Storm Sewers
Unknown Nonpoint Source
Unknown point source
Construction/Land Development
Urban Runofi/Storm Sewers
Channelization
Flow Regulation/Modification
Unknown Nonpoint Source
Unknown point source
Low
Low
1.S Miles
18 Miles
mmmmmmm
0.92 Miles
0.92 Miles
La Costa Resort & Spa Phase II
Storm Water Management Plan
Chapter 5 - FLOW-BASED BMPs
5.1 - 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 BMP's 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 mnoff.
Per the request of the City of Carisbad, 85*^ percentile flow calculations were
performed using the Rational Method. The basic Rational Method runoff procedure
is as follows:
Design flow (Q) = C * I * A
Runoff Coefficient C - In accordance with the County of San Diego standards, the
weighted runoff coefficient for all the areas draining to the treatment unit was
detemnined using the areas analyzed in the final engineering hydrology report. The
runoff coefficient is based on the following characteristics ofthe watershe(j:
- Land Use - Multi-Family and Commercial.
- 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.
5.2 - Grassy Swales
Grass-lined swales, herein referred to as grassy swale, is an example of a flow-
based BMP. Designed to trap pollutants through filtration, grassy swales have the
following basic requirements:
• Serves areas with soil groups C or D (A or B with liners)
• Maximum maintained side slopes = 4:1
• Water application rate = peak flow rate from water quality design storm
DE:lie H:\REPORTStt503V)1\SWMP02.(lM
W.O. 2503-1 5/18/2005 9:55 AM
La Costa Resort & Spa Phase II
Storm Water Management Plan
Per the City of Portland, Oregon Stormwater Management Manual
(September 2000), the swale width and profile shall be designed to convey the water
quality design storm event as follows:
• Maximum design depth = 0.33 foot
• Maximum design velocity = 0.9 foot per second
• Hydraulic residence time > 9 minutes
• Minimum longitudinal slope = 1.5 percent
• Maximum longitudinal slope = 5 percent
• For longitudinal slopes > 5 percent, use check dams
• Use Manning "n" value of 0.25
• Minimum swale length = 100 feet
A minimum of 1 foot of freeboard above the standard storm design water surface
shall be provided for facilities not protected by high-flow diversion devices. Velocity
through the facility shall not exceed 3 feet per second during the high-flow events.
The swale shall incorporate a flow-spreading device at the inlet. The fiow spreader
shall provide a uniform flow distribution across the swale bottom. In swales with a
bottom width greater than 8 feet, a flow spreader shall be installed at least every 100
feet. To minimize flow channelization, the swale bottom shall be smooth, with
unifonn longitudinal slope, and with a minimum bottom width of 4 feet Check dams
may need to be installed to reduce flow channelization.
Woody or shrubby vegetation shall not be planted in the active treatment area ofthe
swale. Grasses shall be established as soon as possible after the swale is
completed. Grasses shall be seeded within 2 days. The initial rate of application
shall be 5 pounds of see mix per 1,000 square feet, or as approved by the City.
All 85'^ percentile runoff from the La Costa Resort & Spa Phase II and neighboring
La Costa Resort and Spa Phase I development will be treated via a single grassy
swale.
5.3 - Pollutant Removal Efficiencv Table
The table on the following page shows the generalized pollutant removal efficiencies
for grassy swales.
DE:de H:\REPORTS\2503«)1\SWMP02.i»c
w.o. 2503-1 5/16/2005 0:55 AM
Table 3. Treatment Control BMP Seleertion Matrix'^'.
Pollutant of
Concem Treatment Controi BMP Categories
Biofilters Detantion
Basins
Infiltration
Basins®
Wet Ponds
or Wetlands
Drainage
Inserts
Filtration Hydrodynamic
Separator
Systems'^'
Sediment M H H H L H M
Nutrients L M M M L • M L
Heavy Metals M M M H L H L
Orgartic
Compounds U U U U L M L
Trash & Debris L H U U M H M
Oxygen
Demainding
Substances
L M M M L M L
Bacteria U U H u L M L
Oil & Grease M U U L H L
Pesticides u •U U U L U L
update this table.
(2) Including trenches and porous pavement
(3) Also known as hydrodynamic devices and baffle boxes.
L Low remcwal efficiency
M: Medium removal efficiency
H: High removal efficiency
U: Unknown removal efficiency
Sources: Guidance Specifying Managertient Measures for Sources af Nonpoint Pollution in Coastal Waters (1993),
National Stormwater Best Management Practices Datatiase (2001), and Guide for BMP Selection in Urban
Developed Areas (2001).
a. Site Design BIVIPs
Priority projects shall be designed so as to minimize, to the maximum extent
practicable, the introduction of pollutants and conditions of concern that may result in
significant impacts, generated from site runoff to the storm water conveyance system.
Priority Projects shall also control post-development peak stomn water runoff discharge
rates and velocities to maintain or reduce pre-development downstream erosion and to
protect stream habitat Although not mandatory, priority projects can address these
objectives through the creation of a hydrologically functional project design that
attempts to mimic the natural hydrologic regime. Mimicking a site's natural hydrologic
regime can be pursued by:
« Reducing imperviousness, conserving natural resources and areas, maintaining
and using natural drainaga courses in the stonm water conveyance system, and
minimizing clearing and grading.
• Providing runoff storage measures dispersed uniformly throughout a site's
landscape with the use of a variety of detention, retention, and mnoff practices.
• Implementing on-lot hydrologically functional landscape (design and management
practices.
These design principles offer an innovative approach to urban storm water
management, one that does not rely on the conventional end-ofiDipe or in-the-pipe
Page 19 of 51 RNAL MODEL SUSMP
Jointly Developed by
San Diego Co-Pennittces 2/14/02, Approved by SDRWQCB 6/12/02
La Costa Resort & Spa Phase 11
Storm Water Management Plan
5.4 - Maintenance Requirements
Maintenance for grassy swales is minimal and aimed at keeping grass cover dense
and vigorous. A pest management plan should be developed for vegetated areas
specifying how problem insects and weeds will be controlled with minimal use of
insecticides and herbicides. Lawn-mowing should be performed routinely
throughout the growing season. Grass height should be maintained at two inches
above the design water depth. Swales should be inspected at least twice annually
to check for erosion and damage to vegetation, debris and litter. Excess sediment
should be removed periodically as determined through inspection.
5.5 - Operations and Maintenance Plan & Costs
Maintenance for grassy swales will consist of:
o Trash and Debris Removal
o Grass height maintenance (Mowing)
o Sediment Removal
All costs of maintaining the water quality basin will be the responsibility of the La
Costa Resort & Spa Phase II Homeowners Association and also the La Costa
Resort and Spa.
The following outlines approximate Annual Maintenance costs for the proposed
grassy swales:
- Cut Vegetation to average height of 6" = $540
- Ensure adequate vegetation = $550
- Inspect for debris and sediment = $1,050 General Maintenance
- Inspection = $750
Subtotal = $2890
10% Contingency = $289
Approximate Total Annual Maintenance Costs
of Swale = $3200
DE:de H:\REPORTS\2503V)1\SWMPa2.(loc
WJ). 2503-1 5/18/2005 9:55 AM
Grassy Swale
Description: Grassy swales are long narrow grassy depressions used to collect
and convey stonnwater runoff, allowing pollutants to settle and filter out as the
water infiltrates into the ground or flows through the faciUty. In addition to
providing poUution reduction, flow rates and volumes can also be managed for
smaU projects (<15,000 square feet of impervious surface) with grassy swales.
Swales should be integrated into the overaU site design and can be used to help
fiimU a site's required landscaping area requirement An approved conveyance
and disposal method per Section 1.4 wiU be required at the end of the swale.
Design Considerations: When designing grassy swales, slopes and depth should
be kept as mUd as possible to avoid safety risks and prevent erosion within the
facUity.
Construction Considerations: Grassy swale areas should be clearly marked
before site work begins to avoid soU disturbance during construction. No
vehicular traffic, except that specificaUy used to construct the facUity, should be
aUowed within 10 feet of swale areas.
Design Requirements:
Soil Suitability: Grassy swales are appropriate for aU soU types. TopsoU shaU be
used within the top 12 inches of the facUity, or the soU shaU be amended per
Appendbc F to support plant growth.
Dimensions and Slopes: FaciUty storage depth may vary firom 6 to 12 inches.
Maximum side slopes are 4 horizontal to 1 vertical. Minimum flat bottom width
is 2 feet for private swales, and 4 feet for pubUc swales. Maximum longitudinal
slope is 5%, whUe minimum slope is 0.5%. Maximum surrounding ground
slopes shaU be 10%.
Stormwater Management Manual
Adopted July 1,1999; revised September 1,2004
Page 2-70
Grassy Swale
Setbacks: Required setback from centerUne of swale to property lines is 5 feet,
and 10 feet from buUding foundations unless Uned with impermeable fabric.
Sizing: Grassy swales sized wifh the simplified approach shaU be designed to
receive less than 15,000 square-fe§t of impervious area nmoff. For fhese projects,
a simplified approach sizing factor of 0.1 may be used to receive credit for
poUution reduction and flow control. A high-flow by-pass mechanism wiU not
be required in fhese cases, but a high-flow overflow must be provided at the
downstream end of the swale to an approved disposal point, per Section 1.4. In
cases when poUution reduction is the only stormwater management goal, or
there is more than 15,000 square feet of impervious area to manage, the
prestimptive approach must be used size the swale for poUution reduction, and
additional facilities wiU be required to meet flow control requirements, where
appUcable.
Presumptive Approach Sizing Criteria:
Exhibit 2-15 shows swale side slopes of 4:1 and lengthwise slopes of IV2 percent,
3 percent and 5 percent These charts are based on the Qty standards shown
below and may be used to easUy determine swale length, given the peak flow
rate and the desired swale bottom width.
Stormwater Management Manual Page 2-71
Adopted July 1,1999; revised September 1,2004
Grassy Swale
0)
s
C
0)
« n
(0
180
170
160
150
140
130
120
110
100
90
Exhibit 2-15 (Sheetl)
Swale Length at 1.5% Longitudinal Siope
Bottom Width = 6'
Bottom Width = 4' ^.^Bottom Width = 8'
Swaie Data
Side slopes are 4:1
Minimum length is
100'
1
Side slopes are 4:1
Minimum length is
100'
1
Side slopes are 4:1
Minimum length is
100'
1
0.2 0.4 0.6
Flow Rate, Q, cfs
0.8
Stormwater Management Manual
Adopted July 1,1999; revised September 1,2004
Page 2-72
Grassy Swale
Exhibit 2-15 (Sheet 2)
270
250
230
210
190
170
150 H
130
90
...
1 T —
i
1
Wth = 6' • " "
...
sinaie uac
Sideslope!
Minimum le
1
s are 4:1
figth is 100"
„ „ . Bottom \A Bottom Width = 4'
T —
i
1
Wth = 6' • " "
-
om Width = 8'
-
1
0.2 0.4 0.6 0.8 1
Flow Rate, Q, cfs
1.2 1.4 1.6
340
290
«
^- 240
cn c a
_l «
% tn
190 --
140 -
90
Exhibit 2-15 (Sheet 3)
1
1
1-
1
Bottom Width =
1
Swale Data
Side slopes are 4:1
Minimum length is 100'
Bottom Width = 4' Swale Data
Side slopes are 4:1
Minimum length is 100' Bottom Width = 8"
-
, X ,
0-2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
Flow Rate, Q, cfs
Stormwater Management Manual
Adopted July 1,1999; revised September 1,2004
Page 2-73
Grassy Swale
1) The swale width and profile shaU be designed to convey runoff from the
poUution reduction design storm intensity (see Section 1.5.2) at
• Maximum design depth of 0.33 feet
• Maximum design velocity of 0.9 feet per second.
• Minimum hydrauUc residence time (time for Qdesign to pass through
the swale) of 9 minutes.
• Minimum longitudinal slope of 0.5 percent, maximtun slope of 5
percent For slopes greater than 5 percent, check dams shaU be used
(one 6-inch high dam every 10 feet).
• Designed using a Manning "n" value of 0.25.
• 4:1 (or flatter) side slopes in the treatment area.
• Minimum length of 100 feet
A minimum of 1 foot of freeboard above the water surface shaU be
provided for facUities not protected by high-flow storm diversion devices.
Swales without high-flow diversion devices shaU be sized to safely convey
the 25-year storm event, analyzed using the Rational Method (peak 25-
year, 5 minute intensity = 3.32 inches per hour).
Velocity through the faciHty shaU not exceed 3 feet per second (fps) during
fhe high-flow events (i.e., when flows greater than those restdting from
the poUution reduction design intensity are not passed around the
fadUty).
2) The swale shaU incorporate a flow-spreading device at the inlet The flow
spreader shaU provide a uniform flow distribution across the swale
bottom. In swales with a bottom width greater than 6 feet a flow
spreader shaU be instaUed at least every 50 feet.
3) To minimize flow channelization, the swale bottom shaU be smooth, with
uniform longitudinal slope, and with a minimum bottom width of 2 feet
for private facilities and 4 feet for pubUc facUities. Maximiun bottom
width shaU be 8 feet
4) Grasses or sod shaU be estabUshed as soon as possible after fhe swale is
completed, and before water is aUowed to enter the fadUty.
5) Unless vegetation is established, biodegradable erosion contiol matting
appropriate for low-velodty flows (approximately 1 foot per second) shaU
be instaUed in the flow area of fhe swale before allowing water to flow
through the swale.
Stormwater Management Manual Page 2-74
Adopted Jvdy 1,1999; revised September 1, 2004
Grassy Swale
6) Access routes to the swale for maintenance purposes must be shown on the
plans. PubUc swales wiU need to provide a minimum 8-foot wide access
route, not to exceed 10 percent in slope.
Stormwater Report Requirements For Presumptive Approach: See Exhibit 2-2.
Landscaping: Plantings shaU be designed at the foUowing quantities per 200
square feet of facUity area. FacUity area is equivalent to the area of the swale
calculated from Form SIM. (Note: FaciUties smaUer than 200 square feet shaU
have a minimum of one tiee per faciHty.):
1 Evergreen or Deciduous tiee:
Evergreen tiees: Minimum height 6 feet
Dedduous tiees: Minimum caHper: 1 Vz inches at 6 inches above
base.
Grass: Seed or sod is required to completely cover the grassy swale
bottom and side slopes. (Shrubs are optional)
For the swale flow path, approved native grass mixes are preferable and may be
substituted for standard swale seed mix. Seed shaU be appHed at the rates
specified by the suppUer. The appHcant shaU have plants established at the time
of faciHty completion (at least 3 months after seeding). No runoff shaU be
aUowed to flow in the swale until grass is established. Trees and shrubs may be
aUowed in the flow path within swales if the swale exceeds the minimum length
and widths specified.
Native wUdflowers, grasses, and ground covers used for BES-maintained
faciUties shaU be designed not to reqiiire mowing. Where mowing carmot be
avoided, faciHties shaU be designed to require mowing no more than once or
twice annuaUy. Ttirf and lawn areas are not aUowed for BES-maintained
facUities; any exceptions wUl require BES approval.
Environmental zones shaU meet requirements estabUshed by Titie 33 for grass in
E-zones.
*Link to Grassy Swale Recommended Seed Mixes
Checklist of minimal information to be shown on the permit drawings:
(Additional information may be required on fhe drawings during permit review,
depencHng on individual site conditions.)
Stormwater Management Manual Page 2-75
Adopted July 1,1999; revised September 1, 2004
Grassy Swale
1) FadUty dimensions and setbacks from property Hnes and structures
2) Profile view of fadUty, induding typical cross-sectioris with dimensions
3) Growing medixtm specification
4) FUter fabric specification (if appHcable)
5) AU stormwater piping associated with the f adHty, induding pipe materials,
sizes, slopes, and invert elevations at every bend or connection
6) Landscaping plan
Inspection requirements and schedtde: The foUowing table shaU be used to
determine which stormwater faciHty components require Qty inspection, and
when the inspection shaU be requested:
Facility Component Inspection Requirement
Swale gracHng CaU for inspection
Piping CaU for inspection
FUter fabric (if appHcable)
Growing medium
Plantings/ seeding/ sod CaU for inspection
Operations and Maintenance requirements: See Chapter 3.0.
* Link to grassy swale O&M form
Additional photos and drawings:
Link to grassy swale photos
Link to grassy swale drawings
Stormwater Management Manual Page 2-76
Adopted July 1,1999; revised September 1,2004
La Costa Resort & Spa Phase II
Storm Water Management Plan
CHAPTER 6 - SOURCE CONTROL BMPS
6.1 - Landscaping
Manufactured slopes shall be landscaped with suitable ground cover or installed with
an erosion control system. Homeowners will 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.
Perthe RWQCB Order, thefollowing 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.
6.2 - 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
will 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 will be educated
as to the proper use, storage, and disposal ofthese 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.).
DE:<te H:\REPORrSa503«l1\SWMP02.doc
w.0.2503-1 5/18/2005 9:55 AM
La Costa Resort & Spa Phase II
Storm Water Management Plan
6.3 - Automobile Use
Urban pollutants resulting from automobile use include oil, grease, antifreeze,
hydraulic fluids, copper from brakes, and various fuels. Homeowners will be
educated as to the proper use, storage, and disposal of these potential storm water
contaminants.
Per the RWQCB Order, the following automobile use activities are deemed unlawful
and are thus prohibited:
- Discharges of wash water from the hosing or cleaning of gas stations,
auto repair garages, or other types of automotive service facilities.
Discharges resulting from the cleaning, repair, or maintenance of any type
of equipment, machinery, or facility including motor vehicles, cement-
related equipment, port-a-potty servicing, etc.
Discharges of wash water from mobile operations such as mobile
automobile washing, steam cleaning, power washing, and carpet
cleaning.
The Homeowners Association will make all homeowners aware of the
aforementioned RWQCB regulations through a homeowners' education program.
Sample information has been provided at the end of this chapter.
6.4 - Site Design BMPs
Priority projects, such as the La Costa Resort & Spa Phase II development, shall be
designed to minimize, to the maximum extent practicable the introduction of
pollutants and conditions of concern that may result in significant impact, generated
from site runoff to the storm water conveyance system. Site design components can
significantly reduce the impact of a project on the environment The following design
techniques have been proposed to accomplish this goal.
- Implementing on-lot hydrologically functional landscape design and
management practices; Additional detail regarding landscaping design is
discussed in section 6.1.
- Minimizing project's impervious footprint. Methods of accomplishing this goal
include constructing streets, sidewalks, and parking lots to the minimum
widths necessary without compromising public safety. Another example for
minimizing impervious area includes incorporating landscaped areas in the
drainage system to encourage infiltration and reduce the amount of directly
connected impervious areas.
- Minimizing directly connected Impervious Areas. Where landscaping is
proposed, drain rooftops into adjacent landscaping prior to discharging to the
storm water conveyance system.
DE:de H:\REPORTS\2503\01\SWMP02.doc
W.O. 2503.1 5/18/2005 0:55 AM
A clean environment is
important to ail of us!
Did you know that storm drains are
NOT connected to sanitary sewer
systems and treatment plants? The
primary purpose of storm drains is to
carry rainwater away from developed
areas to prevent flooding. Untreated
storm water and the pollutants it
carries, flow directly into creeks,
lagoons and the ocean.
In recent years, sources of water
pollution like industrial waters from
factories have been greatly reduced.
However now, the majority of water
pollution occurs from things like cars
leaking oil, fertilizers from farms, lawns
and gardens, failing septic tanks, pet
waste and residential car washing into
the storm drains and into the ocean
and watenways.
All these sources add up to a pollution
problem! But each of us can do small
things to help clean up our water and
that adds up to a pollution solution!
Motor oil photo is used
courtesy of the Water
Quality Consortium, a
cooperative venture
between the Washington
State Department of
Ecology, King County and
the cities of Bellevue,
Seattle and Tacoma.
Only Rain in the Storm DrainI
City of Carlsbad
Storm Water Protection
Program
City of Carlsbad
1635 Faraday Avenue
Carlsbad CA 92008
Storm Water HOTIine:
760-602-2799
i
RECYC LE
USED on.
Funded by a grant
from the California
Integrated Waste
Management Board
Motor Oil
'.f.pn\y Rain in the Storm DrainI
City of Carlsbad
Storm Water Protection
Program
Storm Water HOTIine:
760-602-2799
^ Printed on recycled paper
• A
(-
gill • Ms •1
1 ws
T
What's the problem with
motor oil?
Oil does not dissolve in water. It
lasts a long time and sticks to
everything from beach sand to bird
feathers. Oil and other petroleum
products are toxic to people, wildlife
and plants.
One pint of oil can make a slick
larger than a football field. Oil that
leaks from our cars onto roads and
driveways is washed into storm
drains, and then usually flows
directly to a creek or lagoon and
finally to the ocean.
Used motor oil is the largest single
source of oil pollution in our ocean,
creeks and lagoons. Americans spill
180 million gallons of used oil each
year into our waters. _
This is 16 times the
amount spilled by the
Exxon Valdez in
Alaska.
: •
mv.
How can YOU help keep our environment clean?
Having a clean environment
is of primary importance for
our health and economy.
Clean waten/vays provide
commercial opportunities,
recreation, fish habitat and
add beauty to our
landscape. YOU can help
keep our ocean, creeks and
lagoons clean by applying
the following tips:
• Stop drips. Check for oil
leaks regulariy and fix them
promptly. Keep your car tuned to
reduce oil use.
• Use ground cloths or drip pans
beneath your vehicle if you have leaks
or are doing engine work.
• Clean up spills immediately.
Collect all used oil in containers with
tight fitting lids. Do not mix different
engine fluids.
' When you change your oil,
dispose of it properly. Never dispose
of oil or other engine fluids down the
storm drain, on the ground or into a
ditch.
• Recycle used motor oil. There
are several locations in Carisbad that
accept used motor oil. For hours and
locations, call 760434-2980.
• Buy recycled ("refined") motor oil
to use in your car.
What you should know
before using Concrete
and Mortar ...
In the City of CaHsbad, storm drains flow
directly into local creeks, lagoons and the
ocean without treatment. Storm water
pollution is a serious problem for our
natural environment and for people who
live near streams or wetlands. Storm
water pollution comes from a variety of
sources including oil, fuel, and fluids,
from vehicles and heavy equipments,
pesticide runoff from landscaping, and
from materials such as concrete and
mortar from construction activities. The
City of Carlsbad is committed to
improving water quality and reducing the
amount of pollutants that enter our
precious waterways.
A Clean Environment is
Important to AW of Us!
''^'•Protec^^o''
City of Carlsbad
1635 Faraday Avenue
Carlsbad, CA 92008
Storm Water HOTIine: 760-602-2799
stormwater@ci.carlsbad.ca.us
March 2003
nly Rain in the Storm Drain!
Pollution Prevention is up
to YOU!
Did you know that storm drains are NOT
connected to sanitary sewer systems or
treatment plants? The pnmary purpose of
storm drains is to carry rainwater away
from developed areas to prevent flooding.
Untreated pollutants
such as concrete and
mortar flow directly
into creeks, lagoons
and the ocean and
are toxic to fish,
wildlife, and the
aquatic environment
Disposing ofthese materials into storm
drains causes serious ecological
problems—and is PROHIBITED by law.
Do the Job Right!
This brochure was designed for do-it-
yourself remodelers, homeowners, masons
and bricklayers, contractors, and anyone
else who uses concrete or mortar to
complete a construction project Keep
storm water protection in mind whenever
you or people you hire work on your house
or property.
STORM WATER HOTLINE
760-602-2799
Best Management Practices
Best Management Practices
or BMPs are procedures and
practices that help to prevent
pollutants such as chemicals,
concrete, mortar, pesticides,
waste, paint, and other
hazardous materials from entering our storm
drains. All these sources add up to a
pollution problem. But each of us can do
our part to keep storm water clean. These
efforts add up to a pollution solution!
What YOU Can Po:
• Set up and operate small mixers on tarps
or heavy plastic drop cloths.
• Don't mix up more fresh concrete or
mortar than you will need for a project
• Protect applications of fresh concrete
and mortar from rainfall and runoff until
the material has dried.
• Always store both dry and wet materials
under cover, protected from rainfall and
runoff and away from storm drains or
waterways.
• Protect dry materials from wind. Secure
bags of concrete mix and mortar after
they are open. Don't allow dry products
to blow into driveways, sidewalks,
streets, gutters, or storm drains.
• Keep all construction debris away from
the street gutter and storm drains.
Never dispose of washout into the
street storm drains, landscape drains,
drainage ditches, or streams. Empty
mixing containers and wash out chutes
onto dirt areas that do not flow to
streets, drains or waterways, or allow
material to dry and dispose of properly.
Never wash excess material from
bricklaying, patio, driveway or sidewalk
construction Into a street or storm drain.
Sweep up and dispose of small amounts
of excess dry concrete, grout and
mortar in the trash.
Wash concrete or brick areas only
when the wash water can flow onto a
dirt area without further runoff or drain
onto a surface which has been bermed
so that the water and solids can be
pumped off or vacuumed up for proper
disposal.
Do not place fiil material, soil or
compost piles on the sidewalk or street.
If you or your contractor keep a
dumpster at your site, be sure it is
securely covered with a lid or tarp
when not in use.
During cleanup, check the street and
gutters for sediment refuse, or debris.
Look around the corner or down the
street and clean up any materials that
may have already traveled away from
your property.
A clean environment is
important to all of us!
K6T connected to sanitary sewer
%stems and treatment plants? The
Ipifimary purpose of storm drains is to
l^j-carry rainwater away from developed
'areas to prevent flooding. Untreated
' storm water and the pollutants it
. carries flow directly into creeks,
lagoons and the ocean.
In recent years, sources of water
• pollution like industrial waters from
•factories have been greatly reduced.
Hbwever, now the majority of water
' jjiollution occurs from things like cars
l^leaking oil, fertilizers from farms and
gardens, failing septic tanks, pet waste
|rid residential car washing into the
islorm drains and into the ocean and *.
lAwatenways.
^11 these sources add up to a pollution
Jfoblem! But each of us can do our
^art to help clean up our water and
pat adds up to a pollution solution!
Car washing!
courtesy of 1
Quality Cons
cooperative
between thei
State Depar
Ecology, Kir
the cities ofl
Seattle and
City of Car
1635 Farac
Carlsbad
Storm Wati
760-602-2:
car washing? How can YOU help keep the environment clean? w
ifhere's no problem with washing your
car. It's just how and where you do it.
Most soap contains phosphates and
other chemicals that harm fish and
water quality. The soap, together with
the dirt, metal and oil washed from
/our car, flows into nearby storm
idrains which run directly into lakes,
ftivers or marine waters.
•The phosphates from the soap can
sause excess algae to grow. Algae
look bad, smell bad, and harm water
'quality. As algae decay, the process
uses up oxygen in the water that fish
leed.
"Fish don't
^like to swim in
soap!"
. o
Having a clean environment
,is of primary importance for
our health and economy.
l^'Clean watenways provide
'\ commercial opportunities,
recreation, fish habitat and
'add beauty to our
landscape. YOU can help
' keep our ocean, creeks and
l^jagoons clean by applying
.'theifollowing tips:
If Use soap sparingly.
Use a hose nozzle with a trigger to
tJsave water.
lilFT,.,
J.' • Pour your bucket of soapy water
pf^' down the sink when you're done, not
fnthe street.
• Avoid using engine and wheel
rcleaners or degreasers.
• Take your car to a commercial car
• wash, especially if you plan to clean
¥ J
the engine or the bottom of your car.
Most car washes reuse wash water
several times before sending it to the
sewer system for treatment.
• Hire only mobile detail operators
that will capture wash water and
chemicals. It is unlawful for
commercial vehicle washing
operators to allow wash water to
enter the storm drain system.
A Clean Environment is
Important to All of Usi
In the City of Corlsbod, storm
drains flow directly into local
creeks, lagoons and the ocean
without treatment. Storm water
pollution is a serious problem for
our natural environment and for
people who live near streams or
wetlands.
Storm water pollution comes from
a variety of sources including oil,
fuel, and fluids, from vehicles and
heavy equipment, pesticide runoff
from landscaping, and from
materials such as concrete,
mortar and soil from construction
activities.
The City of Carlsbad is committed
to improving water quality and
reducing the amount of pollutants
that enter our precious
waterways.
'^^Protec^^'^
Storm Water Protection Program
stormwater@ci.carlsbad.ca.us
760-602-2799
City of Carlsbad
1635 Faraday Avenue
Carlsbad, CA 92008
^ ^Printed on recycled paper
Ifs All Just Water,
Isn't It?
Only Rain In the Storm Drain!
How Do I Get Rid of Chlorine? Pool Filters
Although we enjoy the fun and relaxing times
in them, the water used in swimming pools
and spas can cause problems for our creeks,
lagoons and the
ocean if not
disposed of
properly. When
you drain your
swimming pool,
fountain or spa
to the street, the high concentrations of
chlorine and other chemicals found in the
water flows directly to our storm drains.
Did you know that these storm drains are
NOT connected to sanitary sewer systems
and treatment plants? The primary purpose
of storm drains is to carry rainwater away
from developed areas to prevent flooding.
Improperly disposing of swimming pool and
spa water into storm drains may be harmful
to the environment.
Best Management Practices
Best Management Practices or BMPs are
procedures that help to prevent pollutants
like chlorine and sediment from entering our
storm drains. Each of us con do our port to
keep storm water clean. Using BMPs adds up
to a pollution solution!
Pool and spa water may be discharged to thc
storm drain if it has been properly
dechlorinated and doesn't contain other
chemicals. The good news is that chlorine
naturally dissipates over time. Monitor and
test for chlorine levels in the pool over a
period of 3 to 5 days. Drain the water
before algae starts to grow.
Consider hiring a professional pool service
company to clean your pool, fountain, or spa
and make sure they dispose of the water and
solids properly. For more information about
discharging wastewater to thc sanitary
sewer, please
contact thc
Encina
Wastewater
Authority at
(760)438-
3941.
Before you discharge your swimming pool
or spa water to the storm drain, the
water:
• Must not contain chlorine, hydrogen
peroxide, acid, or any other chemicals.
• Can not carry debris or vegetation.
• Should have an acceptable pH of 7-8.
• Con not contain algae or harmful bacteria
(no "green" present).
• Flow must be controlled so that it docs
not cause erosion problems.
Clean filters over a lawn or other landscaped
area where the discharge can be absorbed.
Collect materials on filter cloth and dispose into
the trash. Diatomaceous earth cannot be
discharged into the street or storm drain
systems. Dry it out as much as possible, bog it
in plastic and dispose into the trash.
Acid Washing
Acid cleaning wash water is NOT allowed into
the storm drains. Moke sure acid washing is
done in a proper and safe manner that is not
harmful to people or the environment. It may be
discharged into the sanitary sewer through a
legal sewer connection after the pH has been
adjusted to no lower than 5.5 and no higher
than 11.
Do the Job Right!
• Use the water for irrigation.Try draining
de-ch lor inot cd pool water gradually onto a
landscaped area. Water discharged to
landscape must not cross property lines and
must not produce runoff.
• Do not use copper-based algaecides.
Control algae with chlorine or other
alternatives to copper-based pool chemicals.
Copper is harmful to the aquatic
environment.
• During pool construction, contain ALL
materials and dispose of properly.
Materials such as cement, Gunite, mortar,
and sediment must not be discharged into
the storm drains.
A clean environment is important to all of us!
i(^ou l(now that storm drains are
pt connected to sanitary sewer
ijims and treatment plants?
Tie primary purpose of storm drains
I'to'carry rainwater away from
^Vigloped areas to prevent flooding.
Bteeated storm water and the
llutants it cames, flow directly into
Is
ks^ lagoons and the ocean.
tecent years, sources of water
Ijution like industrial waters from
factories have been greatly reduced,
owever now, the majority of water
llUtion occurs from things like cars
saking oil, fertilizers from famis and
ardens, failing septic tanks, pet
"ste and residential car washing into
Itorm drains and into the ocean
Mratenways.
^e sources add up to a pollution
blemi But each of us can do small
ngs to help clean up our water and
adds up to a pollution solution!
What's the problem with fertilizers
and pesticides?
Fertilizer isn't a problem—IF it's used
carefully. If you use too much
fertilizer or apply it at the wrong time,
it can easily wash off your lawn or
garden into stomi drains and then
flow untreated into lakes or streams.
Just like in your garden, fertilizer in
lagoons and streams makes plants
grow. In water bodies, extra fertilizer
can mean extra algae and aquatic
plant growth. Too much algae hanns
water quality and makes boating,
fishing and swimming unpleasant. As
algae decay, they use up oxygen in
the water that fish and other wildlife
need.
Fertilizer photo Is used courtesy
of the Water Quality Consortium,
a cooperative venture between
the Washington State Department
of Ecology, King County and the
cities of Bellevue, Seattle and
Tacoma.
Storm Water HOTIine: 760-602-2799
stormwater@ci .carlsbad.ca.us
City of Carlsbad
1635 Faraday Avenue
Carlsbad CA 92008
www.ci .carl s bad .ca.u s
^^PiMed on recyded paper
How can YOU help keep the environment clean?
ng a clean environment is of
Uary importance for our health and
'ti6my. Clean waten/vays provide
mercial opportunities, recreation,
habitat and add beauty to our
cape. YOU can help keep our
6ks, lagoons and ocean clean by
ng the foliowing tips:
^'t blow or rake leaves and other
^drd waste into the street or gutter.
^Recycle yard waste or start your own
f^c6mpost pile.
f!* t
i;Don't over irrigate. Use drip
•irrigation, soaker hoses or micro-
i spray system and water early in the
i,moming.
ou have a spray head sprinkler
Stem, consider adjusting your
itering method to a cycle and
p. Instead of watering for 15
§ minutes straight, break up the
session into 5 minute inten/als
allowing water to soak in before the
next application.
Keep imgation systems well-
maintained and water only when
needed to save money and prevent
over-watering.
Use fertilizers and pesticides
sparingly.
Have your soil tested to detemiine
the nutrients needed to maintain a
healthy lawn.
Consider using organic fertilizers—
they release nutrients more slowly.
Leave mulched grass clippings on
the lawn to act as a natural fertilizer.
• Use pesticides only when absolutely
necessary. Use the least loxic
product intended to target a specific
pest, such as insecticidal soaps,
boric acid, etc. Always read the label
and use only as directed.
• Use predatory insects to control
harmful pests when possible.
• Properiy dispose of unwanted
pesticides and fertilizers at
Household Hazardous Waste
collection facilities.
For more Information on
landscape irrigation, please
call 760-438-2722.
Gardeners can provide good infomiation
about dealing with specific pests and
plants. You may call the Master
Gardener Hotline at 858-694-2860 or
check out their website at
www.masterqardenerssandieqo.org.
The hotline is staffed Monday—Friday,
9 am—3 pm, by experienced gardeners
who are available to answer specific
questions. Information from Master
Gardeners is free to the public.
Master Gardeners
San Diego County has a
Master Gardener program
through the University of
California Cooperative
Extension. Master
1
,1
"A
La Costa Resort & Spa Phase II
Storm Water Management Plan
CHAPTER 7 - TREATMENT CONTROL BMP DESIGN
GRASSY SWALE
7.1 - BMP Locations
The proposed grassy swale is located within the existing natural open space to the
west ofthe proposed La Costa Resort & Spa Phase II development, bordering the
adjacent El Camino Real (see BMP Location Map on the following page).
7.2 - Determination of Desiqn 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 (C) = 0.82 for Commercial Development
- Rainfall Intensity (I) = 0.20 inches per hour
- Drainage area to treatment unit (A)
The following table summarizes the parameters used for determination of design
flows to the grassy swale.
DESIGN RUNOFF DETERMINATION SUMMARY TABLE
BMP Drainage Area
(acres)
Rainfall
Intensity
(inches/hour)
Runoff
Coefficient
85'" Pct.
Design Flow
(cfe)
Grassy Swale 23.3* 0.2 0.82 3.8
*Note: Inclusive of the adjoining La Costa Resort and Spa Phase I
7.3 - Grassy Swale Sizinq
The grassy swale has been designed with a 20 foot bottom width, a depth of 0.33 ft,
a channel slope of 4% and a side slope of 1:3. The required flow length to attain the
9 minute hydraulic residence time is 296.3 linear feet. Based on these parameters,
calculations (included at the end of this chapter) show the grassy swale is capable of
treating a peak flow of 3.8 cfs (refer to section 5.1 for treatment flow determination
and treatment flow determination spreadsheet at the end of this chapter).
DE:de H:\REPORTS\2503\01\SWMP02.doc
W.O. 2503-1 5/18/2005 9:55 AM
BMP LOCATION EXHIBIT FOR
LA COSTA RESORT & SPA
PHASE 2
CITY OF CARLSBAD, CALIFORNIA
SHEET
1
OF
1
Ri\061S\I.Hyd\615*H03-BI«>.dwgC 20853Hay-18-200S>10ilO
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
BMP Location
Project Name La Costa Resort & Spa Phase 2 j
Work Order 2503-1 1
Jurisdiction City of Carlsbad |
Open Space adjacent to El Camino Real
Developed Drainage Area = 23.3 acres
Natural Drainage Area = 0.0 acres
Total Drainage Area to BMP = 23.3 acres
Dev. Area Percent Impervious = 85 %
Overall Percent Impervious = 85 %
Dev. Area Runoff Coefficient = 0.82
Nat. Area Runoff Coefficient =
Runoff Coefficient = 0.82
Time of Concentration = 13.8 minutes
(from Drainage Study)
RATIONAL METHOD RESULTS
Q = CIA where Q = 85th Percentile Peak Flow (cfs)
C = Runoff Coefficient
I = Rainfall Intensity (0.2 inch/hour per RWQCB mandate)
A = Drainage Area (acres)
Using the Total Drainage Area:
C = 0.82
I = 0.2 inch/hour
A= 23.3 acres
Q = 3.82 cfs
Villas of La Costa
Grassy Swaie
Grassy Swale Sizing
(based on Manning's Equation)
Given:
Manning's n = 0.25
Bottom Width = 20.0 ft.
Side Slope, z = 3.0
Channel Slope = 0.04 ft/ft
if Depth = 0.33 ft
Hyd. Residence Time = 9.0 min
Results
then Q = 3.80 cfs
Flow Area = 6.927 ft^
Wetted Perimeter = 22.09 ft
Top Width = 21.98 ft
Velocity = 0.55 fps
Swale Length = 296.3 ft
La Costa Resort & Spa Phase II
Storm Water Management Plan
CHAPTER 8 - REFERENCES
"Standard Urban Storm Water Mitigation Plan - Storm Water Standards", City of
Carisbad, April 2003.
"Standards for Design and Construction of Public Works Improvements in the City of
Carisbad", City of Carisbad, California; April 1993.
"Master Drainage and Storm Water Quality Management Plan", City of Carisbad,
California; March 1994.
"Drainage Study for La Costa Resort and Spa - Phases I & If, Hunsaker &
Associates; May, 2005.
"Hydrology Manual", County of San Diego Department of Public Works - Flood
Control Division; Updated April 1993.
"San Diego County Hydrology Manual" County of San Diego Department of Public
Works - Flood Control Section; June 2003.
"Order No. 2001-01, NPDES No. CAS0108758 - Waste Discharge Requirements for
Discharges of Urban Runoff from the Municipal Separate Stomi Sewer Systems
(MS4s) Draining the Watersheds of the County of San Diego, the Incorporated Cities
of San Diego County, and San Diego Unified Port District", California Regional
Water Quality Control Board - San Diego Region; February 21, 2001.
"Water Quality Plan forthe San Diego Basin", California Regional Water Quality
Control Board - San Diego Region, September 8,1994.
DEide H:\REPORTS\2503\01\SWMP02.doc
W.O.2S03-1 5/18/2005 9:55 AM