2026-08-19 Item 12D BMP Design Manual Update — Encinitas City Council, August 19, 2026 (part 3 of 3)

H.10 IntroductionStep 1: Identify CCSYAs
A CCSYA is an active or potential source of bed sediment to downstream channel reaches. When a Priority Development Project (PDP) is constructed, it has the potential to negatively impact characteristics of sediment supply and delivery which can lead to degradation of receiving waters. In order to prevent these impacts, PDP applicants must examine the tributary areas identified in their storm water management plans and identify sources of critical coarse sediment within the following areas:
• Onsite CCSYAs: CCSYAs identified within the project’s property boundary as indicated in the SWQMP. Refer to Section 1.3 for defining a project. • Upstream CCSYAs: CCSYAs identified within the drainage area draining through the project’s property boundary as indicated in the SWQMP. Refer to Section 1.3 for defining a project.

Applicants must first identify potential critical coarse sediment yield areas (PCCSYAs) using one of the methods presented in Section H.1.1. Applicants may then elect to accept the mapping results and remove the “potential” designation, or may elect to further refine the results of the mapping through consideration of the refinement methods outlined in Section H.1.2. At the end of Step 1, applicants will have identified CCSYAs that must be avoided and bypassed by the project.

H.10.1 Identification Methods
Identification of potential critical coarse sediment yield areas for San Diego County has been prepared based on GLU analysis. Criteria for the GLU analysis were developed and documented in the "San Diego County Regional WMAA" (herein "Regional WMAA"). Regional-level mapping of potential critical coarse sediment yield areas was prepared using regional data sets and included in the Regional WMAA. The original Regional WMAA document can be found on the Project Clean Water website at the following address:
http://www.projectcleanwater.org/index.php?option=com_content&view=article&id=75&Itemid= 99 The regional-level mapping was distributed to WQIP preparers to incorporate into the WMAA attachment to the WQIP for all watersheds in San Diego County. The regional-level mapping is based on the following sources:

Dataset Source Year Description
2026-08-19 Item #12D Page 598 of 816
Appendix H: Guidance for Investigation Potential Critical Coarse Sediment Yield Areas H-79 2023
Elevation USGS 2013 1/3rd Arc Second (~10 meter cells) digital elevation model for San Diego County
Land Cover SanGIS 2013 Ecology-Vegetation layer for San Diego County downloaded from SanGIS
Geology
Kennedy,
M.P., and
Tan, S.S.
2002
Geologic Map of the Oceanside 30’x60’
Quadrangle, California, California Geological
Survey, Regional Geologic Map No. 2, 1:100,000
scale.

Kennedy,
M.P., and
Tan, S.S.
2008
Geologic Map of the San Diego 30’x60’
Quadrangle, California, California Geological
Survey, Regional Geologic Map No. 3, 1:100,000
scale.

Todd, V.R. 2004
Preliminary Geologic Map of the El Cajon 30’x60’
Quadrangle, Southern California, United States
Geological Survey, Southern California Areal
Mapping Project, Open File Report 2004-1361,
1:100,000 scale.

Jennings et al. 2010
“Geologic Map of California,” California Geological
Survey, Map No. 2 – Geologic Map of California,
1:750,000 scale
The regional data set is a function of the inherent data resolution of the macro-level data sets and may not conform to all site conditions, or does not reflect changes to particular areas that have occurred since the underlying data was developed. This means slopes, geology, or land cover at the project site can be mischaracterized in the regional data set. This appendix presents criteria for the GLU analysis, excerpted from the Regional WMAA, to be used when detailed project-level investigation of GLUs onsite is needed.
2026-08-19 Item #12D Page 599 of 816

C I T Y O F E N C I N I T A S B M P D E S I G N M A N U A L I-1 2023
Appendix
I
Appendix I Appendix Significant
Site Design Significant Site
Design BMP (SSD-BMP) Sizing
Methods and Calculations
I.1 Significant Site Design BMPs (SSD-BMPs)
I.2 Step 1: Determine DCV
I.3 Step 2: Dispersion Areas
I.4 Step 3: Tree Wells
2026-08-19 Item #12D Page 600 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-2 2023
I.1 Significant Site Design BMPs (SSD-BMPs)
Significant site design BMPs (SSD-BMPs) are site design BMPs designed to fully retain the Design Capture Volume (DCV) for the Drainage Management Area (DMA) (Section 5.2.3). Tree Wells (Fact Sheet SD-A), Impervious Area Dispersion (Fact Sheet SD-B), Permeable Pavement (Fact Sheet SDD), or any other SSD-BMP acceptable to the County may be used. This Appendix provides sizing methods for impervious area dispersion (“dispersion areas”) and tree wells used as SSD-BMPs. An automated worksheet is available to prepare the calculations described in this Appendix. Dispersion areas and tree wells may be sized for pollutant control only or for pollutant control plus hydromodification control.

Permeable pavement may be used as an SSD-BMP for pollutant control only. Sizing methods for permeable pavement as an SSD-BMP for pollutant control only are provided in Section 5.2.3 and are not included in this Appendix or the automated worksheet. Hydromodification management performance standards can be satisfied using permeable pavement only if the permeable pavement is constructed to structural BMP specifications in accordance with the requirements of Appendix B and Fact Sheet INF-3.

I.2 Step 1: Determine DCV
The first step in performing design calculations for SSD-BMPs is to calculate the DCV. The DCV represents the volume of storm water runoff that must be retained and/or biofiltered in order to satisfy pollutant control requirements. This step is very similar to the first step in performing storm water pollutant control calculations described in Appendix B for the design of structural BMPs, except that the tree well volume reduction described in Appendix B Section B.1.4, when applicable, will be addressed in Step 3 of the SSD-BMP calculations instead of Step 1.

The DCVs for SSD-BMPs can be calculated through use of the SSD-BMP Automated Worksheet I1: Step 1. Calculation of Design Capture Volume depicted on the following page or can be calculated manually by following procedures presented in Appendix B, Sections B.1.1 through B.1.3 as well as the rain barrel reduction procedure presented in Appendix B, Section B.1.4 when applicable. =

12 −

Where:

DCV: Design Capture Volume (ft3).

D: Rainfall Depth (inches), refer to Appendix B Section B.1.1.

A: Tributary Area (ft2), refer to Appendix B Section B.1.2.

C: Runoff Factor (unitless), refer to Appendix B Section B.1.3.

R: Site Design Volume Reductions from Rain Barrels (ft3). Refer to Appendix B Section B.1.4 regarding rain barrels (note that when tree wells are used as SSD-BMPs, the volume reduction from the use of tree wells will be addressed in Step 3). 2026-08-19 Item #12D Page 601 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-3 2023
If the project includes dispersion areas, proceed to Step 2: Dispersion Areas. If no dispersion areas are proposed, skip Step 2 and proceed to Step 3: Tree Wells.

SSD-BMP Automated Worksheet I-1: Step 1. Calculation of Design Capture Volume 2026-08-19 Item #12D Page 602 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-4 2023
2026-08-19 Item #12D Page 603 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-5 2023
I.3 Step 2: Dispersion Areas
Dispersion areas are dedicated pervious areas, typically vegetated, with in-situ soil infiltration capacity for partial or full infiltration (Figure I.3-1). Impervious area dispersion refers to the practice of effectively disconnecting impervious areas from directly draining to the storm drain system by routing runoff from the impervious area onto an adjacent pervious dispersion area. The pervious dispersion area surface may consist of natural in-situ soils, amended soils, or permeable pavement. This appendix discusses natural in-situ soils and amended soils. For permeable pavement dispersion areas, refer to Section 5.2.3.

Figure I.3-1 Dispersion Area Schematic
When a dispersion area is proposed to be used as an SSD-BMP, the calculated DCV (Line 37 of the SSD-BMP Automated Worksheet I-1 depicted on the previous pages, “Remaining Design Capture Volume Tributary to Tree Well(s)”) must be zero. This is achieved when the ratio of dispersed impervious surface area to total engineered pervious surface and/or natural hydrologic soil group A or B soil dispersion area meets the requirements outlined in Fact Sheet SD-B (2:1 or 1:1 depending on the dispersion area surface and whether hydromodification control applies) and there are no other surfaces within the DMA that contribute to the project DCV, such as surfaces not directed to the dispersion area, semi-pervious surface used as dispersion area, or natural (non-amended) hydrologic soil group C or D soils used as dispersion area.

Semi-pervious surfaces and/or natural (non-amended) hydrologic soil group C or D soils that receive runoff from impervious surfaces may be used as a regular site design BMP to reduce DCV but may not be used as an SSD-BMP because they do not reduce DCV to zero. When soils are amended in accordance with Fact Sheet SD-F, this is considered “engineered pervious surface” regardless of the subgrade. Any natural hydrologic soil group or fill soil may be amended in accordance with Fact Sheet SD-F and then be considered engineered pervious surface. 2026-08-19 Item #12D Page 604 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-6 2023
If the dispersion area is used for pollutant control plus hydromodification control, the dispersion area must include amended soil. As a minimum, the top 11 inches of the pervious area must use amended soils in accordance with Fact Sheet SD-F.

Table I.3-1 summarizes certain design criteria for the use of dispersion areas as SSD-BMPs and illustrates the difference between the criteria for pollutant control only and for pollutant control plus hydromodification control. Refer to Fact Sheet SD-B for additional requirements applicable to all types of dispersion areas.

Table I.3-1 Criteria for use of Dispersion Areas as SSD-BMPs for Pollutant Control Only vs. Pollutant Control Plus Hydromodification Control SSD-BMP Criteria for Pollutant Control Only
Criteria for Pollutant Control Plus
Hydromodification Control
Dispersion
Area (SDB)
• Ratio of impervious area to
engineered pervious surface and/or
natural hydrologic soil group A soil
area is 2:1 or less; OR ratio of
impervious area to natural hydrologic
soil group B soil area is 1:1 or less
• Sheet flow travel length across
dispersion area is 10 feet or more*
• Slope is less than 5%
• Ratio of impervious area to
engineered pervious surface area is
1:1 or less
• Sheet flow travel length across
dispersion area is 10 feet or more*
• Slope is less than 5%
• The top 11 inches of soil is amended
in accordance with Fact Sheet SD-F
*Exemption to this minimum travel length criterion may be allowed when the contributing flow path length of the impervious area /pervious area travel length ≤ 2 The dispersion area sheet flow travel length, slope, and amended soil when applicable must be shown on the project plans. When the SSD-BMP Automated Worksheet is used, these characteristics may be documented in SSD-BMP Automated Worksheet I-2: Step 2. Dispersion Area Validation depicted on the following page in addition to the plans.

Dispersion areas meeting the SSD-BMP criteria do not need an additional downstream BMP.

Dispersion areas not meeting the SSD-BMP criteria can be used as regular site design BMPs to reduce the DCV draining to a tree well just as they can be used to reduce the DCV draining to a structural BMP pursuant to Appendix B. If the project includes tree wells, proceed to Step 3: Tree Wells. 2026-08-19 Item #12D Page 605 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-7 2023
SSD-BMP Automated Worksheet I-2: Step 2. Dispersion Area Validation 2026-08-19 Item #12D Page 606 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-8 2023
I.4 Step 3: Tree Wells
A tree well as a storm water management feature consists of a tree with a minimum amount of soil media to allow for storage, infiltration, and evapotranspiration of runoff (Figure I.4-1).

Figure I.4-1 Tree Well Schematic
Tree wells as SSD-BMPs must provide tree credit volume equal to or greater than the DCV for pollutant control only; or for pollutant control plus hydromodification control provide tree credit volume equal to or greater than the required retention volume (RRV), where RRV accounts for a multiplier applied to the DCV value. Tree credit volume for a single tree is based on the mature canopy diameter of the tree. More than one tree may be used in a single DMA in order to provide the total required volume. The tree well must also include tree well soil based on the mature tree canopy diameter in accordance with Fact Sheet SD-A.

Table I.4-1 summarizes certain design criteria for the use of tree wells as SSD-BMPs and illustrates the difference between the criteria for pollutant control only and for pollutant control plus 2026-08-19 Item #12D Page 607 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-9 2023
hydromodification control. Refer to Fact Sheet SD-A for additional requirements applicable to all types of tree wells.

Table I.4-1 Criteria for use of Tree Wells as SSD-BMPs
for Pollutant Control Only vs. Pollutant Control Plus Hydromodification Control SSD-BMP Criteria for Pollutant Control Only
Criteria for Pollutant Control Plus
Hydromodification Control
Tree Well (SD-A) • The total tree credit volume is
greater than DCV
• Provide tree well soil based on
the mature tree canopy
diameter in accordance with
Fact Sheet SD-A
• The total tree credit volume is
greater than RRV, where RRV
accounts for a multiplier
applied to the DCV value
• Provide tree well soil based on
the mature tree canopy
diameter in accordance with
Fact Sheet SD-A
Tree well design can be prepared through the use of SSD-BMP Automated Worksheet I-3: Step 3.

Tree Well Sizing depicted on the following page or can be calculated manually by following procedures below in Sections I.4.1 through I.4.4.
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Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-10 2023
SSD-BMP Automated Worksheet I-3: Step 3. Tree Well Sizing 2026-08-19 Item #12D Page 609 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-11 2023
2026-08-19 Item #12D Page 610 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-12 2023
I.4.1 Step 3.1: Determine DCV or RRV as applicable
To design a tree well as an SSD-BMP, first determine whether the tree well is to be sized for pollutant control only or pollutant control plus hydromodification control. Tree wells sized for pollutant control only must provide tree credit volume for the total DCV from the DMA (previously determined in Step 1) tributary to the tree well. Tree wells sized for pollutant control plus hydromodification control must be provide tree credit volume for the RRV tributary to the tree well, where RRV is the total DCV from the DMA increased by a DCV multiplier provided in Fact Sheet SD-A. Table I.4-1 presents the DCV multipliers from Fact Sheet SD-A.

Table I.4-1 DCV Multiplier Table from Fact Sheet SD-A
Minimum
Tree Well
Soil Depth
(inches)
Hydrologic Soil Group
A B C
D
(Default)
30” 1.60 2.20 2.50 2.90
DCV
Multiplier
36” 1.80 2.47 2.83 3.17
42” 2.00 2.73 3.17 3.43
48” 2.20 3.00 3.50 3.70
The DCV multiplier to determine RRV is based on the underlying hydrologic soil group at the location of the tree well and the minimum tree well soil depth. Determining the tree well soil depth requires coordination with the selection of the tree species (Step 3.2). Therefore, determination of the DCV multiplier and RRV may be an iterative process with Step 3.2, selection of tree species and tree well soil depth. The minimum tree well soil depth is 30 inches. If the actual proposed tree well soil depth is not shown in the table of DCV multipliers, select the next lower depth from the table for the purpose of determining the DCV multiplier. For example, if the proposed tree well soil depth is 60 inches, select 48 inches from the table for the purpose of determining the DCV multiplier.

Multiply the DCV by the DCV multiplier to obtain the RRV.

(qre
) = (qre) N-trLjtLo.
2026-08-19 Item #12D Page 611 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-13 2023
I.4.2 Step 3.2: Select a tree species and tree well soil depth
Select a tree species that will provide sufficient tree credit volume to meet the DCV or RRV as applicable. Fact Sheet SD-A provides a tree palette table and the tree credit volume per tree, which is based on the mature canopy diameter of the tree. Selection of the tree species should be coordinated with the project landscape architect. Multiple trees may be used in a single DMA to collectively provide sufficient tree credit volume, provided that drainage from the DMA is distributed equally to the trees.

If the DMA drainage is not distributed equally to the proposed trees, split the DMA into smaller DMAs and size the proposed tree wells individually based on the DCV or RRV tributary to each tree.

Coordinate with the project landscape architect to determine the tree well soil depth. Ensure that the proposed tree well soil depth is appropriate to the size and type of tree(s) proposed.

I.4.3 Step 3.3: Determine the minimum soil volume required in the tree well
The minimum soil volume required in the tree well is based on the mature canopy diameter of the proposed tree. A tree well for storm water control requires a minimum of 2 cubic feet of soil per square foot of mature tree canopy projection area in accordance with the SD-A Tree Wells Fact Sheet.

The minimum tree well soil volume can be calculated by the following equation:

NLMLO-O 2.oo uott X,Lt ,t-Oo (qre
) = 2 ë í

2 ì

Where D = mature canopy diameter (feet)
I.4.4 Step 3.4: Determine tree well soil installation area and show on plans
Based on the required tree well soil volume and proposed tree well soil depth, the minimum area required for the tree well soil can be determined.

NLMLO-O 2.oo uott X,Lt .oU (qr

) =
NLMLO-O 2.oo uott X,Lt ,t-Oo (qre)

2.oo uott X,Lt ojrℎ (qr)
Show the proposed tree well soil area on the project plans. Ensure that the area reserved for tree well soil meets the following requirements:
• The tree well soil must be placed within 1.5 times the mature tree canopy radius. 2026-08-19 Item #12D Page 612 of 816
Appendix I: Significant Site Design BMP (SSD-BMP) Sizing Methods and Calculations I-14 2023
When multiple trees are used, the trees must be spaced so that the minimum tree well soil volume for each tree does not overlap.
2026-08-19 Item #12D Page 613 of 816

C I T Y O F E N C I N I T A S B M P D E S I G N M A N U A L J-1 2023
Appendix
J
Appendix J Forms and Checklists
2026-08-19 Item #12D Page 614 of 816
Appendix J: Forms and Checklists
J-2 2023
The following Forms/Checklists/Worksheets were developed for use by the project applicant to document the stormwater management design:
• J-1: Applicability of Permanent, Post-Construction Stormwater BMP Requirements • J-2: Project Type Determination Checklist (Standard Project or PDP) • J-3A: Site Information Checklist for Standard Projects • J-3B: Site Information Checklist for PDPs
• J-4: Source Control BMP Checklist for All Development Projects • J-5: Site Design BMP Checklist for All Development Projects • J-6: Summary of PDP Structural BMPs
• J-7: Harvest and Use Feasibility Screening Checklist
• J-8: Categorization of Infiltration Feasibility Condition • J-9: Factor of Safety and Design Infiltration Rate
• J-10: Determination of Downstream Systems Requirements for Preservation of Coarse Sediment Supply
• Environmentally Sensitive Areas Map
2026-08-19 Item #12D Page 615 of 816
Appendix J: Forms and Checklists
J-3 2023
Applicability of Permanent, Post-Construction
Stormwater BMP Requirements
(Stormwater Intake Form for all Development Permit Applications) Form J-1
Project Identification
Project Name:

Permit Application Number: Date:

Determination of Requirements
The purpose of this form is to identify permanent, post-construction requirements that apply to the project. This form serves as a short summary of applicable requirements, in some cases referencing separate forms that will serve as the backup for the determination of requirements.

Answer each step below, starting with Step 1 and progressing through each step until reaching "Stop". Refer to the manual sections and/or separate forms referenced in each step below.

Step Answer Progression
Step 1: Is the project a "development project"? See Section

1.3 of the manual for guidance.
Yes Go to Step 2.
No Stop.

Permanent BMP requirements do not apply.

No SWQMP will be required. Provide
discussion below.

Discussion / justification if the project is not a "development project" (e.g., the project includes only interior remodels within an existing building):

Step 2: Is the project a Standard Project, PDP, or exception to PDP definitions?
To answer this item, see Section 1.4 of the manual in its entirety for guidance, AND complete Form J-2, Project Type Determination.
Standard
Project
Stop.

Standard Project requirements apply,
including Standard Project SWQMP.
PDP PDP requirements apply, including PDP
SWQMP.

Go to Step 3.
Exception to
PDP
definitions
Stop.

Standard Project requirements apply. Provide
discussion and list any additional
requirements below. Prepare Standard
Project SWQMP.

Discussion / justification, and additional requirements for exceptions to PDP definitions, if applicable:
2026-08-19 Item #12D Page 616 of 816
Appendix J: Forms and Checklists
J-4 2023
Form J-1 Page 2 of 2
Step Answer Progression
Step 3. Is the project subject to earlier PDP
requirements due to a prior lawful approval?
See Section 1.10 of the manual for guidance.
Yes Consult the City Engineer to
determine requirements.

Provide discussion and identify
requirements below.

Go to Step 4.
No BMP Design Manual PDP
requirements apply.

Go to Step 4.

Discussion / justification of prior lawful approval, and identify requirements (not required if prior lawful approval does not apply):

Step 4. Do hydromodification control
requirements apply?
See Section 1.6 of the manual for guidance.
Yes PDP structural BMPs required for
pollutant control (Chapter 5) and
hydromodification control
(Chapter 6).

Go to Step 5.
No Stop.

PDP structural BMPs required for
pollutant control (Chapter 5) only.

Provide brief discussion of
exemption to hydromodification
control below.

Discussion / justification if hydromodification control requirements do not apply:

Step 5. Does protection of critical coarse
sediment yield areas apply?
See Section 6.2 of the manual for guidance.
Yes Management measures required
for protection of critical coarse
sediment yield areas (Chapter 6.2).

Stop.
No Management measures not
required for protection of critical
coarse sediment yield areas.

Provide brief discussion below.

Stop.
2026-08-19 Item #12D Page 617 of 816
Appendix J: Forms and Checklists
J-5 2023
Discussion / justification if protection of critical coarse sediment yield areas does not apply:
2026-08-19 Item #12D Page 618 of 816
Appendix J: Forms and Checklists
J-6 2023
Project Type Determination Checklist Form J-2
Project Information
Project Name:

Permit Application Number:

Project Type Determination: Standard Project or PDP
The project is (select one): ϒ New Development ϒ Redevelopment The total proposed newly created or replaced impervious area is: ________ ft2 (________) acres Is the project in any of the following categories, (a) through (f)? Yes
ϒ
No
ϒ
(a) New development projects that create 10,000 square feet or more of impervious surfaces (collectively over the entire project site). This includes commercial, industrial, residential, mixed-use, and public development projects on public or private land.

Yes
ϒ
No
ϒ
(b) Redevelopment projects that create and/or replace 5,000 square feet or more of impervious surface (collectively over the entire project site on an existing site of 10,000 square feet or more of impervious surfaces). This includes commercial, industrial, residential, mixed-use, and public development projects on public or private land.

Yes
ϒ
No
ϒ
(c) New and redevelopment projects that create and/or replace 5,000 square feet or more of impervious surface (collectively over the entire project site), and support one or more of the following uses:
(i) Restaurants. This category is defined as a facility that sells prepared foods and drinks for consumption, including stationary lunch counters and refreshment stands selling prepared foods and drinks for immediate consumption SIC code 5812).
(ii) Hillside development projects. This category includes development on any natural slope that is twenty-five percent or greater. (iii) Parking lots. This category is defined as a land area or facility for the temporary parking or storage of motor vehicles used personally, for business, or for commerce.
(iv) Streets, roads, highways, freeways, and driveways. This category is defined as any paved impervious surface used for the transportation of automobiles, trucks, motorcycles, and other vehicles.
2026-08-19 Item #12D Page 619 of 816
Appendix J: Forms and Checklists
J-7 2023
Form J-2 Page 2 of 2
Yes
ϒ
No
ϒ
(d) New or redevelopment projects that create and/or replace 2,500 square feet or more of impervious surface (collectively over the entire project site), and discharging directly to an Environmentally Sensitive Area (ESA). “Discharging directly to” includes flow that is conveyed overland a distance of 200 feet or less from the project to the ESA, or conveyed in a pipe or open channel any distance as an isolated flow from the project to the ESA (i.e. not commingled with flows from adjacent lands).

Note: ESAs are areas that include but are not limited to all Clean Water Act Section 303(d) impaired water bodies; areas designated as Areas of Special Biological Significance by the State Water Board and SDRWQCB; State Water Quality Protected Areas; water bodies designated with the RARE beneficial use by the State Water Board and SDRWQCB; and any other equivalent environmentally sensitive areas which have been identified by the Copermittees. See manual Section

1.4.2 for additional guidance.

Yes
ϒ
No
ϒ
(e) New development projects, or redevelopment project that create and/or replace 5,000 square feet or more of impervious surface, that support one or more of the following uses:
(i) Automotive repair shops. This category is defined as a facility that is categorized in any one of the following SIC codes: 5013, 5014, 5541, 7532-7534, or 7536- 7539.
(ii) Retail gasoline outlets. This category includes retail gasoline outlets that meet the following criteria: (a) 5,000 square feet or more or (b) a projected Average Daily Traffic of 100 or more vehicles per day.

Yes
ϒ
No
ϒ
(f) New or redevelopment projects that result in the disturbance of one or more acres of land and are expected to generate pollutants post construction.

Note: See manual Section 1.4.2 for additional guidance.

Does the project meet the definition of one or more of the PDP categories (a) through (f) listed above?
ϒ No – the project is not a PDP (Standard Project).

ϒ Yes – the project is a PDP.

The following is for redevelopment PDPs only:

The area of existing (pre-project) impervious area at the project site is: ________ ft2 (A) The total proposed newly created or replaced impervious area is: ________ ft2 (B) Percent impervious surface created or replaced (B/A)*100: _______% The percent impervious surface created or replaced is (select one based on the above calculation):

ϒ less than or equal to fifty percent (50%) – only new impervious areas are considered PDP OR
ϒ greater than fifty percent (50%) – the entire project site is a PDP 2026-08-19 Item #12D Page 620 of 816
Appendix J: Forms and Checklists
J-8 2023
2026-08-19 Item #12D Page 621 of 816
Appendix J: Forms and Checklists
J-9 2023
Site Information Checklist
For Standard Projects
Form J-3A (Standard
Projects)
Project Summary Information
Project Name
Project Address
Assessor's Parcel Number(s)
Permit Application Number
Project Watershed (Hydrologic Unit) Select One:
Santa Margarita 902
San Luis Rey 903
Carlsbad 904
San Dieguito 905
Penasquitos 906
San Diego 907
Pueblo San Diego 908
Sweetwater 909
Otay 910
Tijuana 911
Parcel Area
(total area of Assessor's Parcel(s) associated
with the project)
________ Acres (____________ Square Feet)
Area to be disturbed by the project
(Project Area) ________ Acres (____________ Square Feet) Project Proposed Impervious Area
(subset of Project Area) ________ Acres (____________ Square Feet) Project Proposed Pervious Area
(subset of Project Area) ________ Acres (____________ Square Feet) Note: Proposed Impervious Area + Proposed Pervious Area = Area to be Disturbed by the Project.

This may be less than the Parcel Area.
2026-08-19 Item #12D Page 622 of 816
Appendix J: Forms and Checklists
J-10 2023
Form J-3A Page 2 of 4
Description of Existing Site Condition and Drainage Patterns Current Status of the Site (select all that apply)
Existing development
Previously graded but not built out
Agricultural or other non-impervious use
Vacant, undeveloped/natural
Description / Additional Information
Existing Land Cover Includes (select all that apply)
Vegetative Cover
Non-Vegetated Pervious Areas
Impervious Areas
Description / Additional Information
Underlying Soil belongs to Hydrologic Soil Group (select all that apply):
NRCS Type A
NRCS Type B
NRCS Type C
NRCS Type D
Existing Natural Hydrologic Features (select all that apply) Watercourses
Seeps
Springs
Wetlands
None
Description / Additional Information
2026-08-19 Item #12D Page 623 of 816
Appendix J: Forms and Checklists
J-11 2023
Description of Existing Site Drainage [How is storm water runoff conveyed from the site? At a minimum, this description should answer (1) whether existing drainage conveyance is natural or urban; (2) describe existing constructed storm water conveyance systems, if applicable; and (3) is runoff from offsite conveyed through the site? If so, describe.] 2026-08-19 Item #12D Page 624 of 816
Appendix J: Forms and Checklists
J-12 2023
Form J-3A Page 3 of 4
Description of Proposed Site Development and Drainage Patterns Project Description / Proposed Land Use and/or Activities List proposed impervious features of the project (e.g., buildings, roadways, parking lots, courtyards, athletic courts, other impervious features)
List proposed pervious features of the project (e.g., landscape areas) Does the project include grading and changes to site topography? Yes
No
Description / Additional Information
Does the project include changes to site drainage (e.g., installation of new storm water conveyance systems)?
Yes
No
Description / Additional Information
2026-08-19 Item #12D Page 625 of 816
Appendix J: Forms and Checklists
J-13 2023
Form J-3A Page 4 of 4
Identify whether any of the following features, activities, and/or pollutant source areas will be present (select all that apply)
Onsite storm drain inlets
Interior floor drains and elevator shaft sump pumps
Interior parking garages
Need for future indoor & structural pest control
Landscape/outdoor pesticide use
Pools, spas, ponds, decorative fountains, and other water features Food service
Refuse areas
Industrial processes
Outdoor storage of equipment or materials
Vehicle and equipment cleaning
Vehicle/equipment repair and maintenance
Fuel dispensing areas
Loading docks
Fire sprinkler test water
Miscellaneous drain or wash water
Plazas, sidewalks, and parking lots
2026-08-19 Item #12D Page 626 of 816
Appendix J: Forms and Checklists
J-14 2023
Site Information Checklist
For PDPs
Form J-3B (PDPs)
Project Summary Information
Project Name
Project Address
Assessor's Parcel Number(s)
Permit Application Number
Project Watershed (Hydrologic Unit) Select One:
Santa Margarita 902
San Luis Rey 903
Carlsbad 904
San Dieguito 905
Penasquitos 906
San Diego 907
Pueblo San Diego 908
Sweetwater 909
Otay 910
Tijuana 911
Parcel Area
(total area of Assessor's Parcel(s) associated
with the project)
________ Acres (____________ Square Feet)
Area to be disturbed by the project
(Project Area) ________ Acres (____________ Square Feet) Project Proposed Impervious Area
(subset of Project Area) ________ Acres (____________ Square Feet) Project Proposed Pervious Area
(subset of Project Area) ________ Acres (____________ Square Feet) Note: Proposed Impervious Area + Proposed Pervious Area = Area to be Disturbed by the Project.

This may be less than the Parcel Area.
2026-08-19 Item #12D Page 627 of 816
Appendix J: Forms and Checklists
J-15 2023
Form J-3B Page 2 of 9
Description of Existing Site Condition and Drainage Patterns Current Status of the Site (select all that apply):
Existing development
Previously graded but not built out
Agricultural or other non-impervious use
Vacant, undeveloped/natural
Description / Additional Information:

Existing Land Cover Includes (select all that apply):
Vegetative Cover
Non-Vegetated Pervious Areas
Impervious Areas
Description / Additional Information:

Underlying Soil belongs to Hydrologic Soil Group (select all that apply):
NRCS Type A
NRCS Type B
NRCS Type C
NRCS Type D
Approximate Depth to Groundwater:
Groundwater Depth < 5 feet
5 feet < Groundwater Depth < 10 feet
10 feet < Groundwater Depth < 20 feet
Groundwater Depth > 20 feet
2026-08-19 Item #12D Page 628 of 816
Appendix J: Forms and Checklists
J-16 2023
Existing Natural Hydrologic Features (select all that apply):
Watercourses
Seeps
Springs
Wetlands
None
Description / Additional Information:
2026-08-19 Item #12D Page 629 of 816
Appendix J: Forms and Checklists
J-17 2023
Form J-3B Page 3 of 9
Description of Existing Site Topography and Drainage [How is storm water runoff conveyed from the site? At a minimum, this description should answer (1) whether existing drainage conveyance is natural or urban; (2) describe existing constructed storm water conveyance systems, if applicable; and (3) is runoff from offsite conveyed through the site? If so, describe]:
2026-08-19 Item #12D Page 630 of 816
Appendix J: Forms and Checklists
J-18 2023
Form J-3B Page 4 of 9
Description of Proposed Site Development and Drainage Patterns Project Description / Proposed Land Use and/or Activities:

List/describe proposed impervious features of the project (e.g., buildings, roadways, parking lots, courtyards, athletic courts, other impervious features):

List/describe proposed pervious features of the project (e.g., landscape areas):

Does the project include grading and changes to site topography? Yes
No
Description / Additional Information:
2026-08-19 Item #12D Page 631 of 816
Appendix J: Forms and Checklists
J-19 2023
Does the project include changes to site drainage (e.g., installation of new storm water conveyance systems)?
Yes
No
Description / Additional Information:
2026-08-19 Item #12D Page 632 of 816
Appendix J: Forms and Checklists
J-20 2023
Form J-3B Page 5 of 9
Identify whether any of the following features, activities, and/or pollutant source areas will be present (select all that apply):
Onsite storm drain inlets
Interior floor drains and elevator shaft sump pumps
Interior parking garages
Need for future indoor & structural pest control
Landscape/outdoor pesticide use
Pools, spas, ponds, decorative fountains, and other water features Food service
Refuse areas
Industrial processes
Outdoor storage of equipment or materials
Vehicle and equipment cleaning
Vehicle/equipment repair and maintenance
Fuel dispensing areas
Loading docks
Fire sprinkler test water
Miscellaneous drain or wash water
Plazas, sidewalks, and parking lots
2026-08-19 Item #12D Page 633 of 816
Appendix J: Forms and Checklists
J-21 2023
Form J-3B Page 6 of 9
Identification of Receiving Water Pollutants of Concern Describe path of storm water from the project site to the Pacific Ocean (or bay, lagoon, lake or reservoir, as applicable):

List any 303(d) impaired water bodies within the path of storm water from the project site to the Pacific Ocean (or bay, lagoon, lake or reservoir, as applicable), identify the pollutant(s)/stressor(s) causing impairment, and identify any TMDLs for the impaired water bodies:
303(d) Impaired Water Body Pollutant(s)/Stressor(s) TMDLs Identification of Project Site Pollutants*
*Identification of project site pollutants is only required if flow-thru treatment BMPs are implemented onsite in lieu of retention or biofiltration BMPs (note the project must also participate in an alternative compliance program unless prior lawful approval to meet earlier PDP requirements is demonstrated)
Identify pollutants anticipated from the project site based on all proposed use(s) of the site (see manual Appendix B.6):

Pollutant
Not Applicable to
the Project Site
Anticipated from the
Project Site
Also a Receiving
Water Pollutant of
Concern
Sediment
Nutrients
Heavy Metals
Organic Compounds
Trash & Debris
Oxygen Demanding
Substances
Oil & Grease
Bacteria & Viruses
2026-08-19 Item #12D Page 634 of 816
Appendix J: Forms and Checklists
J-22 2023
Pesticides
2026-08-19 Item #12D Page 635 of 816
Appendix J: Forms and Checklists
J-23 2023
Form J-3B Page 7 of 9
Hydromodification Management Requirements
Do hydromodification management requirements apply (see Section 1.6 of the manual)? Yes, hydromodification management flow control structural BMPs required. No, the project will discharge runoff directly to existing underground storm drains discharging directly to water storage reservoirs, lakes, enclosed embayments, or the Pacific Ocean. No, the project will discharge runoff directly to conveyance channels whose bed and bank are concrete-lined all the way from the point of discharge to water storage reservoirs, lakes, enclosed embayments, or the Pacific Ocean.
No, the project will discharge runoff directly to an area identified as appropriate for an exemption by the WMAA for the watershed in which the project resides.

Description / Additional Information (to be provided if a 'No' answer has been selected above):

Critical Coarse Sediment Yield Areas*
*This Section only required if hydromodification management requirements apply 2026-08-19 Item #12D Page 636 of 816
Appendix J: Forms and Checklists
J-24 2023
Based on the maps provided within the WMAA, do potential critical coarse sediment yield areas exist within the project drainage boundaries?
Yes
No, no critical coarse sediment yield areas to be protected based on WMAA maps If yes, have any of the optional analyses presented in Section 6.2 of the manual been performed? 6.2.1 Verification of GLUs Onsite
6.2.2 Downstream Systems Sensitivity to Coarse Sediment 6.2.3 Optional Additional Analysis of Potential Critical Coarse Sediment Yield Areas Onsite No optional analyses performed, the project will avoid critical coarse sediment yield areas identified based on WMAA maps
If optional analyses were performed, what is the final result? No critical coarse sediment yield areas to be protected based on verification of GLUs onsite. Critical coarse sediment yield areas exist but additional analysis has determined that protection is not required. Documentation attached in Attachment 8 of the SWQMP. Critical coarse sediment yield areas exist and require protection. The project will implement management measures described in Sections 6.2.4 and 6.2.5 as applicable, and the areas are identified on the SWQMP Exhibit.

Discussion / Additional Information:
2026-08-19 Item #12D Page 637 of 816
Appendix J: Forms and Checklists
J-25 2023
Form J-3B Page 8 of 9
Flow Control for Post-Project Runoff*
*This Section only required if hydromodification management requirements apply List and describe point(s) of compliance (POCs) for flow control for hydromodification management (see Section 6.3.1). For each POC, provide a POC identification name or number correlating to the project's HMP Exhibit and a receiving channel identification name or number correlating to the project's HMP Exhibit.

Has a geomorphic assessment been performed for the receiving channel(s)? No, the low flow threshold is 0.1Q2 (default low flow threshold) Yes, the result is the low flow threshold is 0.1Q2
Yes, the result is the low flow threshold is 0.3Q2
Yes, the result is the low flow threshold is 0.5Q2
If a geomorphic assessment has been performed, provide title, date, and preparer:

Discussion / Additional Information: (optional)
2026-08-19 Item #12D Page 638 of 816
Appendix J: Forms and Checklists
J-26 2023
Form J-3B Page 9 of 9
Other Site Requirements and Constraints
When applicable, list other site requirements or constraints that will influence storm water management design, such as zoning requirements including setbacks and open space, or local codes governing minimum street width, sidewalk construction, allowable pavement types, and drainage requirements.

Optional Additional Information or Continuation of Previous Sections As Needed 2026-08-19 Item #12D Page 639 of 816
Appendix J: Forms and Checklists
J-27 2023
This space provided for additional information or continuation of information from previous sections as needed.
2026-08-19 Item #12D Page 640 of 816
Appendix J: Forms and Checklists
J-28 2023
Source Control BMP Checklist
for All Development Projects
(Standard Projects and PDPs)
Form J-4
Project Identification
Project Name
Permit Application Number
Source Control BMPs
All development projects must implement source control BMPs SC-1 through SC-6 where applicable and feasible. See Chapter 4 and Appendix E of the manual for information to implement source control BMPs shown in this checklist.

Answer each category below pursuant to the following.
• "Yes" means the project will implement the source control BMP as described in Chapter 4 and/or Appendix E of the manual. Discussion / justification is not required. • "No" means the BMP is applicable to the project but it is not feasible to implement.

Discussion / justification must be provided.
• "N/A" means the BMP is not applicable at the project site because the project does not include the feature that is addressed by the BMP (e.g., the project has no outdoor materials storage areas). Discussion / justification may be provided.

Source Control Requirement Applied?
SC-1 Prevention of Illicit Discharges into the MS4 Yes No N/A Discussion / justification if SC-1 not implemented:

SC-2 Storm Drain Stenciling or Signage Yes No N/A
Discussion / justification if SC-2 not implemented:

SC-3 Protect Outdoor Materials Storage Areas from Rainfall, RunOn, Runoff, and Wind Dispersal Yes No N/A
Discussion / justification if SC-3 not implemented:

SC-4 Protect Materials Stored in Outdoor Work Areas from Rainfall, Run-On, Runoff, and Wind Dispersal
Yes No N/A
2026-08-19 Item #12D Page 641 of 816
Appendix J: Forms and Checklists
J-29 2023
Discussion / justification if SC-4 not implemented:

Form J-4 Page 2 of 2
Source Control Requirement Applied?
SC-5 Protect Trash Storage Areas from Rainfall, Run-On, Runoff, and Wind Dispersal
Yes No N/A
Discussion / justification if SC-5 not implemented:

SC-6 Additional BMPs Based on Potential Sources of Runoff Pollutants (must answer for each source listed below)
Onsite storm drain inlets
Interior floor drains and elevator shaft sump pumps
Interior parking garages
Need for future indoor & structural pest control
Landscape/outdoor pesticide use
Pools, spas, ponds, decorative fountains, and other water features
Food service
Refuse areas
Industrial processes
Outdoor storage of equipment or materials
Vehicle and equipment cleaning
Vehicle/equipment repair and maintenance
Fuel dispensing areas
Loading docks
Fire sprinkler test water
Miscellaneous drain or wash water
Plazas, sidewalks, and parking lots
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
2026-08-19 Item #12D Page 642 of 816
Appendix J: Forms and Checklists
J-30 2023
Discussion / justification if SC-6 not implemented. Clearly identify which sources of runoff pollutants are discussed. Justification must be provided for all "No" answers shown above. 2026-08-19 Item #12D Page 643 of 816
Appendix J: Forms and Checklists
J-31 2023
Site Design BMP Checklist
for All Development Projects
(Standard Projects and PDPs)
Form J-5
Project Identification
Project Name
Permit Application Number
Site Design BMPs
All development projects must implement site design BMPs SD-1 through SD-8 where applicable and feasible. See Chapter 4 and Appendix E of the manual for information to implement site design BMPs shown in this checklist.

Answer each category below pursuant to the following.
• "Yes" means the project will implement the site design BMP as described in Chapter 4 and/or Appendix E of the manual. Discussion / justification is not required. • "No" means the BMP is applicable to the project but it is not feasible to implement.

Discussion / justification must be provided.
• "N/A" means the BMP is not applicable at the project site because the project does not include the feature that is addressed by the BMP (e.g., the project site has no existing natural areas to conserve). Discussion / justification may be provided.

Site Design Requirement Applied?
SD-1 Maintain Natural Drainage Pathways and Hydrologic
Features
Yes No N/A
Discussion / justification if SD-1 not implemented:

SD-2 Conserve Natural Areas, Soils, and Vegetation Yes No N/A Discussion / justification if SD-2 not implemented:

SD-3 Minimize Impervious Area Yes No N/A
Discussion / justification if SD-3 not implemented:

SD-4 Minimize Soil Compaction Yes No N/A
2026-08-19 Item #12D Page 644 of 816
Appendix J: Forms and Checklists
J-32 2023
Discussion / justification if SD-4 not implemented:
2026-08-19 Item #12D Page 645 of 816
Appendix J: Forms and Checklists
J-33 2023
Form J-5 Page 2 of 2
Site Design Requirement Applied?
SD-5 Impervious Area Dispersion Yes No N/A
Discussion / justification if SD-5 not implemented:

SD-6 Runoff Collection Yes No N/A
Discussion / justification if SD-6 not implemented:

SD-7 Landscaping with Native or Drought Tolerant Species Yes No N/A Discussion / justification if SD-7 not implemented:

SD-8 Harvesting and Using Precipitation Yes No N/A
Discussion / justification if SD-8 not implemented:
2026-08-19 Item #12D Page 646 of 816
Appendix J: Forms and Checklists
J-34 2023
Summary of PDP Structural BMPs Form J-6 (PDPs)
Project Identification
Project Name
Permit Application Number
PDP Structural BMPs
All PDPs must implement structural BMPs for storm water pollutant control (see Chapter 5 of the manual). Selection of PDP structural BMPs for storm water pollutant control must be based on the selection process described in Chapter 5. PDPs subject to hydromodification management requirements must also implement structural BMPs for flow control for hydromodification management (see Chapter 6 of the manual). Both storm water pollutant control and flow control for hydromodification management can be achieved within the same structural BMP(s).

PDP structural BMPs must be verified by the local jurisdiction at the completion of construction. This may include requiring the project owner or project owner's representative to certify construction of the structural BMPs (see Section 1.12 of the manual). PDP structural BMPs must be maintained into perpetuity, and the local jurisdiction must confirm the maintenance (see Section 7 of the manual).

Use this form to provide narrative description of the general strategy for structural BMP implementation at the project site in the box below. Then complete the PDP structural BMP summary information sheet (page 3 of this form) for each structural BMP within the project (copy the BMP summary information page as many times as needed to provide summary information for each individual structural BMP).

Describe the general strategy for structural BMP implementation at the site. This information must describe how the steps for selecting and designing storm water pollutant control BMPs presented in Section 5.1 of the manual were followed, and the results (type of BMPs selected). For projects requiring hydromodification flow control BMPs, indicate whether pollutant control and flow control BMPs are integrated or separate.
(Continue on page 2 as necessary.)
2026-08-19 Item #12D Page 647 of 816
Appendix J: Forms and Checklists
J-35 2023
2026-08-19 Item #12D Page 648 of 816
Appendix J: Forms and Checklists
J-36 2023
Form J-6 Page 2 of 3
(Page reserved for continuation of description of general strategy for structural BMP implementation at the site)
(Continued from page 1)
2026-08-19 Item #12D Page 649 of 816
Appendix J: Forms and Checklists
J-37 2023
2026-08-19 Item #12D Page 650 of 816
Appendix J: Forms and Checklists
J-38 2023
Form J-6 Page 3 of X (Copy as many as needed)
Structural BMP Summary Information
(Copy this page as needed to provide information for each individual proposed structural BMP)
Structural BMP ID No.

Construction Plan Sheet No.

Type of structural BMP:
Retention by harvest and use (HU-1)
Retention by infiltration basin (INF-1)
Retention by bioretention (INF-2)
Retention by permeable pavement (INF-3)
Partial retention by biofiltration with partial retention (PR-1) Biofiltration (BF-1)
Flow-thru treatment control with prior lawful approval to meet earlier PDP requirements (provide BMP type/description in discussion section below)
Flow-thru treatment control included as pre-treatment/forebay for an onsite retention or biofiltration BMP (provide BMP type/description and indicate which onsite retention or biofiltration BMP it serves in discussion section below) Flow-thru treatment control with alternative compliance (provide BMP type/description in discussion section below)
Detention pond or vault for hydromodification management Other (describe in discussion section below)
Purpose:
Pollutant control only
Hydromodification control only
Combined pollutant control and hydromodification control Pre-treatment/forebay for another structural BMP
Other (describe in discussion section below)
Who will certify construction of this BMP?
Provide name and contact information for the
party responsible to sign BMP verification forms
if required by the City Engineer (See Section

1.12 of the manual)
Who will be the final owner of this BMP?
Who will maintain this BMP into perpetuity?
2026-08-19 Item #12D Page 651 of 816
Appendix J: Forms and Checklists
J-39 2023
What is the funding mechanism for
maintenance?
Discussion (as needed):

Harvest and Use Feasibility Checklist Form J-7

1. Is there a demand for harvested water (check all that apply) at the project site that is reliably present during the wet season?
Toilet and urinal flushing
Landscape irrigation
Other:______________

2. If there is a demand; estimate the anticipated average wet season demand over a period of 36 hours. Guidance for planning level demand calculations for toilet/urinal flushing and landscape irrigation is provided in Section B.3.2.
[Provide a summary of calculations here]

3. Calculate the DCV using worksheet B-2.1.

DCV = __________ (cubic feet)
3a. Is the 36 hour demand greater
than or equal to the DCV?
ϒ Yes / ϒ No
3b. Is the 36 hour demand greater than

0.25DCV but less than the full DCV?
ϒ Yes / ϒ No
3c. Is the 36 hour demand
less than 0.25DCV?
ϒ Yes
Harvest and use appears to be
feasible. Conduct more detailed
evaluation and sizing calculations
to confirm that DCV can be used
at an adequate rate to meet
drawdown criteria.

Harvest and use may be feasible.

Conduct more detailed evaluation and
sizing calculations to determine
feasibility. Harvest and use may only be
able to be used for a portion of the site,
or (optionally) the storage may need to be
upsized to meet long term capture targets
while draining in longer than 36 hours.

Harvest and use is
considered to be infeasible.
2026-08-19 Item #12D Page 652 of 816
Appendix J: Forms and Checklists
J-40 2023
Is harvest and use feasible based on further evaluation? ϒ Yes, refer to Appendix E to select and size harvest and use BMPs.

ϒ No, select alternate BMPs.
2026-08-19 Item #12D Page 653 of 816
Appendix J: Forms and Checklists
J-41 2023
Categorization of Infiltration Feasibility Condition Form J-8 Part 1 - Full Infiltration Feasibility Screening Criteria Would infiltration of the full design volume be feasible from a physical perspective without any undesirable consequences that cannot be reasonably mitigated?
Criteria Screening Question Yes No
1 Is the estimated reliable infiltration rate below proposed facility locations greater than 0.5 inches per hour? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D.

Provide basis:

Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability.
2 Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2.

Provide basis:

Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability.
2026-08-19 Item #12D Page 654 of 816
Appendix J: Forms and Checklists
J-42 2023
Form J-8 Page 2 of 4
Criteria Screening Question Yes No
3 Can infiltration greater than 0.5 inches per hour be allowed without increasing risk of groundwater contamination (shallow water table, stormwater pollutants or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3.

Provide basis:

Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability.
4 Can infiltration greater than 0.5 inches per hour be allowed without causing potential water balance issues such as change of seasonality of ephemeral streams or increased discharge of contaminated groundwater to surface waters? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3.

Provide basis:

Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability.

Part 1
Result
*
If all answers to rows 1 - 4 are “Yes” a full infiltration design is potentially feasible. The feasibility screening category is Full Infiltration
If any answer from row 1-4 is “No”, infiltration may be possible to some extent but would not generally be feasible or desirable to achieve a “full infiltration” design.

Proceed to Part 2
2026-08-19 Item #12D Page 655 of 816
Appendix J: Forms and Checklists
J-43 2023
Form J-8 Page 3 of 4
Part 2 – Partial Infiltration vs. No Infiltration Feasibility Screening Criteria Would infiltration of water in any appreciable amount be physically feasible without any negative consequences that cannot be reasonably mitigated?
Criteria Screening Question Yes No
5 Do soil and geologic conditions allow for infiltration in any appreciable rate or volume? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2 and Appendix D.

Provide basis:

Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability and why it was not feasible to mitigate low infiltration rates. 6 Can Infiltration in any appreciable quantity be allowed without increasing risk of geotechnical hazards (slope stability, groundwater mounding, utilities, or other factors) that cannot be mitigated to an acceptable level? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.2.

Provide basis:

Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability and why it was not feasible to mitigate low infiltration rates. 2026-08-19 Item #12D Page 656 of 816
Appendix J: Forms and Checklists
J-44 2023
Form J-8 Page 4 of 4
Criteria Screening Question Yes No
7 Can Infiltration in any appreciable quantity be allowed without posing significant risk for groundwater related concerns (shallow water table, stormwater pollutants or other factors)? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3.

Provide basis:

Summarize findings of studies; provide reference to studies, calculations, maps, data sources, etc. Provide narrative discussion of study/data source applicability and why it was not feasible to mitigate low infiltration rates. 8 Can infiltration be allowed without violating downstream water rights? The response to this Screening Question shall be based on a comprehensive evaluation of the factors presented in Appendix C.3.

Provide basis:

Part 2
Result*
If all answers from row 1-4 are yes then partial infiltration design is potentially feasible. The feasibility screening category is Partial Infiltration.

If any answer from row 5-8 is no, then infiltration of any volume is considered to be infeasible within the drainage area. The feasibility screening category is No Infiltration. *To be completed using gathered site information and best professional judgment considering the definition of MEP in the MS4 Permit. Additional testing and/or studies may be required by Agency/Jurisdictions to substantiate findings 2026-08-19 Item #12D Page 657 of 816
Appendix J: Forms and Checklists
J-45 2023
Factor of Safety and Design Infiltration Rate
Worksheet Form J-9
Factor Category Factor Description
Assigned
Weight (w)
Factor
Value (v)
Product (p)
p = w x v
A Suitability
Assessment
Soil assessment methods 0.25
Predominant soil texture 0.25
Site soil variability 0.25
Depth to groundwater / impervious
layer

0.25 Suitability Assessment Safety Factor, SA = Σp
B Design
Level of pretreatment/ expected
sediment loads 0.5
Redundancy/resiliency 0.25
Compaction during construction 0.25
Design Safety Factor, SB = Σp
Combined Safety Factor, Stotal= SA x SB
Observed Infiltration Rate, inch/hr, Kobserved
(corrected for test-specific bias)
Design Infiltration Rate, in/hr, Kdesign = Kobserved / Stotal Supporting Data
Briefly describe infiltration test and provide reference to test forms:
2026-08-19 Item #12D Page 658 of 816
Appendix J: Forms and Checklists
J-46 2023
Downstream Systems Requirements for
Preservation of Coarse Sediment Supply
Form J-10
When it has been determined that potential critical coarse sediment yield areas exist within the project site, the next step is to determine whether downstream systems would be sensitive to reduction of coarse sediment yield from the project site. Use this form to document the evaluation of downstream systems requirements for preservation of coarse sediment supply.

Project Name:

Project Tracking Number / Permit Application Number:
1 Will the project discharge runoff to a hardened
MS4 system (pipe or lined channel) or an unlined channel? Hardened MS4 system Go to 2
Un-lined channel Go to 4
2 Will the hardened MS4 system convey sediment
(e.g., a concrete-lined channel with steep slope
and cleansing velocity) or sink sediment (e.g.,
flat slopes, constrictions, treatment BMPs, or
ponds with restricted outlets within the system
will trap sediment and not allow conveyance of
coarse sediment from the project site to an unlined system). Convey Go to 3
Sink Go to 7
3 What kind of receiving water will the hardened
MS4 system convey the sediment to?
Un-lined channel Go to 4
Lake
Reservoir
Bay
Go to 7
Lagoon
Ocean
Go to 6
4 Is the un-lined channel impacted by deposition
of sediment? This condition must be
documented by the local agency.
Yes Go to 7
No Go to 5
2026-08-19 Item #12D Page 659 of 816
Appendix J: Forms and Checklists
J-47 2023
Form J-10 Page 2 of 2
5 End – Preserve coarse sediment supply to protect un-lined channels from accelerated erosion due to reduction of coarse sediment yield from the project site unless further investigation determines the sediment is not critical to the receiving stream. Sediment that is critical to receiving streams is the sediment that is a significant source of bed material to the receiving stream (bed sediment supply) (see Section 6.2.3 and Appendix H.2 of the manual). 6 End – Provide management measures for preservation of coarse sediment supply (protect beach sand supply).
7 End – Downstream system does not warrant preservation of coarse sediment supply, no measures for protection of critical coarse sediment yield areas onsite are necessary. Use the space below to describe the basis for this finding for the project. 2026-08-19 Item #12D Page 660 of 816

C I T Y O F E N C I N I T A S B M P D E S I G N M A N U A L 2023
Environmentally Sensitive Areas Map
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C I T Y O F E N C I N I T A S B M P D E S I G N M A N U A L 2023
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C I T Y O F E N C I N I T A S B M P D E S I G N M A N U A L K-1 2023
Appendix
K
Appendix K Guidance on Green
Infrastructure
Table of Contents:

K.1 Guidance on Green Infrastructure
K.2 Green Streets
K.2.1 Green Streets Performance Standard
K.2.2 Green Streets Guidelines
K.3 Green Parking Lots
K.3.1 Green Parking Lots Guidelines
Design Criteria, Design Standard Drawings, and Specifications for Green Streets and Green Parking Lots can be found on the County’s Watershed Protection Program website under Green Infrastructure Resources within the Development Resources tab:
https://www.sandiegocounty.gov/stormwater
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K-2 2023
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Appendix K: Guidance on Green Infrastructure
K-3 2023
K.1 Guidance on Green Infrastructure
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Appendix K: Guidance on Green Infrastructure
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COUNTY OF SAN DIEGO

GUIDANCE ON

GREEN INFRASTRUCTURE
Green Infrastructure is an approach to stormwater and flood management that protects, restores, and mimics the natural water cycle using vegetation, mulch, soils, and natural processes while creating healthier environments. At the County scale, green infrastructure refers to the network of natural features that provides habitat, flood protection, cleaner air, and cleaner water. At the scale of a neighborhood or site, green infrastructure refers to stormwater and flood management systems that mimic nature by soaking up and storing water. Roadways and parking lots present many opportunities for coordinated Green Infrastructure use. A Green Street or Parking Lot use a natural system approach to reduce stormwater flow, improve water quality, reduce urban heating, enhance pedestrian safety, reduce carbon footprints, and beautify neighborhoods. Green Streets and Parking Lots are components of Green Infrastructure, integrating strategies into roads and right-of-ways. Green Streets Guidelines are an outreach tool and are also intended to serve as a companion to the rest of the Green Streets publications. They include an introduction, strategies, procedures and design examples for implementing Green Streets projects. The strategies include tree wells, dispersion areas, biofiltration, and permeable pavement. Green Streets Design Criteria lay out general definitions, general policy, and landscape design criteria for Green Infrastructure strategies in the right-of-way. This can be found on the County’s Development Resources website. Green Streets Supplement to County Design Standard Drawings includes construction details which may be referenced in improvement plans similar to current County Design standard drawings. This can be found on the County’s Development Resources website within the Green Streets Standard Drawings. Green Streets Maintenance Schedules include a list with maintenance tasks, frequency, and time of year for initial, routine, and as- needed maintenance of each Green Infrastructure strategy. This can be found on the County’s Development Resources website. 2026-08-19 Item #12D Page 668 of 816
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K-7 2023
Green Streets Specifications include detailed construction material and installation requirements for Green Infrastructure strategies including aggregates, geosynthetics, underdrains, permeable pavement, bioretention soil media, mulch, overflow risers, check dams, and tree grates. This can be found on the County’s Development Resources website. Green Parking Lots Guidelines are an outreach tool and are also intended to serve as a companion to the rest of the Green Parking Lots publications. They include an introduction, strategies, procedures and design examples for implementing Green Parking Lots projects. The strategies include tree wells, dispersion areas, biofiltration, and permeable pavement. Green Parking Lots Design Criteria lay out general definitions, general policy, and landscape design criteria for Green Infrastructure strategies in parking lots. This can be found on the County’s Development Resources website. Green Parking Lots Supplement to County Design Standard Drawings includes construction details which may be referenced in improvement plans similar to current County Design standard drawings. This can be found on the County’s Development Resources website within the Green Streets Standard Drawings. Green Parking Lots Maintenance Schedules does not have parking lot specific maintenance and references the Green Streets Maintenance Schedules. Green Parking Lots Specifications does not have unique parking lot specifications and references the Green Streets Specifications.
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Appendix K: Guidance on Green Infrastructure
K-8 2023
K.2 Green Streets
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K-9 2023
K.2.1 Green Streets Performance Standard
This section builds on text from Section 1.4.3 providing more detailed guidance on compliance with the performance standard for Green Street PDP Exempt projects (herein referred to as Green Street projects).

Green Street projects must provide stormwater treatment for the volume of runoff associated with the project’s net increase in impervious area. Compliance with this standard may be demonstrated at the project-scale, meaning there is no obligation to treat runoff from each discrete segment of new impervious area. Green Street projects are encouraged to achieve compliance through treatment of runoff from any combination of land uses including existing/proposed surfaces, onsite/offsite surfaces, pervious/impervious surfaces. As summarized below, Green Street compliance can be demonstrated through determination of the following 1) Required Treatment Volume, 2) Provided Treatment Volume, and 3) Comparison of Required and Provided Treatment. 1) REQUIRED TREATMENT VOLUME
Project proponent must calculate a single water quality runoff volume associated with the net increase in impervious area across the entire project site. This calculation should exclude runoff volumes associated with existing/replaced impervious areas within the project footprint, as treatment is not mandated for these areas. Supporting exhibits delineating new impervious areas, existing/replaced impervious areas, and removed impervious areas must be provided as needed to support this determination.
2) PROVIDED TREATMENT VOLUME
Project proponent must calculate the total volume of stormwater runoff treated through site design elements and/or structural BMPs proposed by the project. Completion of this step requires consideration of all surfaces draining to proposed treatment elements (existing/proposed, onsite/offsite, pervious/impervious areas draining to BMPs).

Project proponent must provide treatment through use of “Conventional” treatment elements where feasible but may also be permitted to use “Alternative” treatment elements upon demonstration of infeasibility.

Conventional Treatment Elements: Elements that utilize conventional retention and/or biofiltration designs that are consistent with the City BMPDM7. Use of these elements may achieve Green Street compliance and are eligible to generate alternative compliance credits if implemented sufficiently. [Examples: tree wells, dispersion areas, biofiltration basins (lined or unlined), 7 Minimum retention requirements waived for Green Streets. 2026-08-19 Item #12D Page 671 of 816
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K-10 2023
bioretention basins, infiltration basins (vegetated or non-vegetated), pervious pavements without impermeable liners.]
Alternative Treatment Elements: Elements that provide filtration for anticipated pollutants at medium to high efficacy and provide significant pore storage capacity. [Examples: vegetated swales, non-vegetated filtration BMPs (sand filters, biofiltration soil media, pervious pavements with impermeable liners and underdrains), detention basins, wet ponds, proprietary filtration devices with significant pore storage capacity.]
Treatment Elements lacking significant pore storage such as filter fabrics, debris racks, filter baskets, CDS units, hydrodynamic separators or similar devices may not be classified as either of the two categories above.
3) COMPARISON OF REQUIRED AND PROVIDED TREATMENT
Project proponent must demonstrate that the provided treatment volume is greater than or equal to the required treatment volume. This may be demonstrated at the project-scale, meaning there is no obligation to demonstrate treatment for each discrete segment of new impervious area. The pages that follow present a standard calculation template for demonstrating Green Street compliance as well as several calculation examples.
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Appendix K: Guidance on Green Infrastructure
K-11 2023
Table K.2-1 : Green Street Performance Standard Calculations Item Value Description
Required
Treatme
nt
Volume
1 Land Use of Net
Impervious Area Transportation Per project drawings.
2 Total Net
Impervious Area 8
ft2 Per project drawings.
3 85th Percentile
Rainfall Depth in. Determine per BMPDM Appendix B.1.
4 Runoff Coefficient 0.90 Value of 0.90 applies to new impervious areas. 5 Required
Treatment Volume ft3
(Line 2 x Line 3 x Line 4) / 12
Provided
Treatme
nt
Volume
6 Land Use of
Treated Area9 Per project drawings.
7 Land Use Factor10 Determine per Note 5 below.
8 Conventional
Treatment
Volume11
ft3 Determine per Note 6 below.
9 Alternative
Treatment Volume
Determine per supplemental applicant
calculations.
10 Final Treatment
Volume ft3 Line 7 x (Line 8 + Line 9)
Result
11 Is Project Green
Street Compliant?
Compliant if Line 10 ≥ Line 5. Otherwise,
non-compliant.
12 Optional Credit (Line 7 x Line 8) – Line 5
8 The Net Increase in Impervious Area should not reflect any work occurring within existing impervious areas. 9 Classify drainage area into following land use types (may use more than one) agriculture, commercial, education, industrial, multi-family residential, orchard, rural residential, single family residential, transportation, open space. 10 If Land Uses from Lines 1 and 6 match, use a value of 1.0. Otherwise, refer to Regional Water Quality Equivalency Guidance for determination of appropriate Land Use Factor. 11 Conventional Treatment Volume may be determined by subtracting the project’s total “Deficit of Effectively Treated Stormwater” from the project’s total Design Capture Volume. These values can be found in Version 2.0 of the City of Encinitas Automated Control Worksheet on Line 48 of the BMP Performance Tab and Line 26 of the DCV Tab respectively.
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Appendix K: Guidance on Green Infrastructure
K-12 2023
Example 1: Green Street Compliance using Conventional Treatment Elements A green street project will create 20,000 SF of new impervious surface through the addition of a center turn lane on an existing road that currently has a vegetated center divide. The project is divided into two Drainage Management Areas
(DMAs) as shown below. DMA 1
consists of impervious roadway
surfaces that drain westerly to a
proposed biofiltration basin. DMA 2
consists of impervious roadway
surfaces that sheet flow in an easterly
direction and leave the site without
treatment. The project applicant
demonstrates compliance with the
Green Street Performance Standard as
presented below.

Item Value
Required
Treatment
Volume
1 Land Use of New Impervious Area Transportation
2 Total New Impervious Area 20,000 ft2
3 85th Percentile Rainfall Depth 0.70 in.
4 Runoff Coefficient 0.90
5 Required Treatment Volume (See Excerpt 1 for calculations) 1,050 ft3 Provided
Treatment
Volume
6 Land Use of Treated Area Transportation
7 Land Use Factor 1.00
8 Conventional Treatment Volume (See Excerpt 2 for calculations) 3,150 ft3 9 Alternative Treatment Volume 0 ft3
10 Final Treatment Volume 3,150 ft3
Result
11 Is Project Green Street Compliant? Compliant
12 Optional Credit 2,100 ft3
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K-13 2023
Example 2: Green Street Compliance using Alternative Treatment Elements If the project described in the previous Example 1 implemented a sand filter instead of biofiltration, the project would demonstrate compliance with the Green Street Performance Standard as presented below.

Item Value
Required
Treatment
Volume
1 Land Use of New Impervious Area Transportation
2 Total New Impervious Area 20,000 ft2
3 85th Percentile Rainfall Depth 0.70 in.
4 Runoff Coefficient 0.90
5 Required Treatment Volume (See Excerpt 1 for calculations) 1,050 ft3 Provided
Treatment
Volume
6 Land Use of Treated Area Transportation
7 Land Use Factor 1.00
8 Conventional Treatment Volume 0 ft3
9 Alternative Treatment Volume (Applicant Calculations) 3,150 ft3 10 Final Treatment Volume 3,150 ft3
Result
11 Is Project Green Street Compliant? Compliant
12 Optional Credit (Alternative treatment not eligible) 0 ft3 2026-08-19 Item #12D Page 675 of 816
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K-14 2023
Example 3: Green Street Compliance using Conventional Treatment Elements for Offsite Run-on If the project described in Example 1 provided stormwater treatment for offsite run-on from an adjacent commercial area, the project would demonstrate compliance with the Green Street Performance Standard as presented below.

Item Value
Required
Treatment
Volume
1 Land Use of New Impervious Area Transportation
2 Total New Impervious Area 20,000 ft2
3 85th Percentile Rainfall Depth 0.70 in.
4 Runoff Coefficient 0.90
5 Required Treatment Volume (See Excerpt 1 for calculations) 1,050 ft3 Provided
Treatment
Volume
6 Land Use of Treated Area Transportation
& Commercial
7 Land Use Factor (See Excerpt 3 for calculations) 0.82 8 Conventional Treatment Volume (See Excerpt 2 for calculations) 3,150 ft3 9 Alternative Treatment Volume 0 ft3
10 Final Treatment Volume 2,583 ft3
Result
11 Is Project Green Street Compliant? Compliant
12 Optional Credit 1,533 ft3
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Appendix K: Guidance on Green Infrastructure
K-15 2023
Excerpt 1 - Required Treatment Volume for New Impervious Surface of 20,000 SF City of Encinitas Automated Stormwater Pollutant Control Worksheet B.1 (Version 2.0)

Category # Description i Units
1 Drainage Basin ID or Name Perf Std unitless
2 85th Percentile 24-hr Storm Depth 0.70 inches
3 Impervious Surfaces Not Directed to Dispersion Area (C=0.90) 20,000 sq-ft 4 Semi-Pervious Surfaces Not Serving as Dispersion Area (C=0.30) sq-ft 5 Engineered Pervious Surfaces Not Serving as Dispersion Area (C=0.10) sq-ft 6 Natural Type A Soil Not Serving as Dispersion Area (C=0.10) sq-ft 7 Natural Type B Soil Not Serving as Dispersion Area (C=0.14) sq-ft 8 Natural Type C Soil Not Serving as Dispersion Area (C=0.23) sq-ft 9 Natural Type D Soil Not Serving as Dispersion Area (C=0.30) sq-ft 10 Does Tributary Incorporate Dispersion, Tree Wells, and/or Rain Barrels? No yes/no 11 Impervious Surfaces Directed to Dispersion Area per SD-B (Ci=0.90) sq-ft 12 Semi-Pervious Surfaces Serving as Dispersion Area per SD-B (Ci=0.30) sq-ft 13 Engineered Pervious Surfaces Serving as Dispersion Area per SD-B (Ci=0.10) sq-ft 14 Natural Type A Soil Serving as Dispersion Area per SD-B (Ci=0.10) sq-ft 15 Natural Type B Soil Serving as Dispersion Area per SD-B (Ci=0.14) sq-ft 16 Natural Type C Soil Serving as Dispersion Area per SD-B (Ci=0.23) sq-ft 17 Natural Type D Soil Serving as Dispersion Area per SD-B (Ci=0.30) sq-ft 18 Number of Tree Wells Proposed per SD-A #
19 Average Mature Tree Canopy Diameter ft
20 Number of Rain Barrels Proposed per SD-E #
21 Average Rain Barrel Size gal
22 Total Tributary Area 20,000 sq-ft
23 Initial Runoff Factor for Standard Drainage Areas 0.90 unitless 24 Initial Runoff Factor for Dispersed & Dispersion Areas 0.00 unitless 25 Initial Weighted Runoff Factor 0.90 unitless
26 Initial Design Capture Volume 1,050 cubic-feet
27 Total Impervious Area Dispersed to Pervious Surface 0 sq-ft 28 Total Pervious Dispersion Area 0 sq-ft
29 Ratio of Dispersed Impervious Area to Pervious Dispersion Area n/a ratio 30 Adjustment Factor for Dispersed & Dispersion Areas 1.00 ratio 31 Runoff Factor After Dispersion Techniques 0.90 unitless 32 Design Capture Volume After Dispersion Techniques 1,050 cubic-feet 33 Total Tree Well Volume Reduction 0 cubic-feet
34 Total Rain Barrel Volume Reduction 0 cubic-feet
35 Final Adjusted Runoff Factor 0.90 unitless
36 Final Effective Tributary Area 18,000 sq-ft
37 Initial Design Capture Volume Retained by Site Design Elements 0 cubic-feet 38 Final Design Capture Volume Tributary to BMP 1,050 cubic-feet Dispersion
Area, Tree
Well & Rain
Barrel Inputs
(Optional)
Standard
Drainage
Basin Inputs
Results
Tree & Barrel
Adjustments
Initial Runoff
Factor
Calculation
Dispersion
Area
Adjustments
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Appendix K: Guidance on Green Infrastructure
K-16 2023
Excerpt 2- Summary of Stormwater Pollutant Control Calculations (Part 1 of 2) City of Encinitas Automated Stormwater Pollutant Control Worksheet B.1 (Version 2.0)

Category # Description ii Units
1 Drainage Basin ID or Name DMA 1 unitless
2 85th Percentile 24-hr Storm Depth 0.70 inches
3 Impervious Surfaces Not Directed to Dispersion Area (C=0.90) 60,000 sq-ft 4 Semi-Pervious Surfaces Not Serving as Dispersion Area (C=0.30) sq-ft 5 Engineered Pervious Surfaces Not Serving as Dispersion Area (C=0.10) sq-ft 6 Natural Type A Soil Not Serving as Dispersion Area (C=0.10) sq-ft 7 Natural Type B Soil Not Serving as Dispersion Area (C=0.14) sq-ft 8 Natural Type C Soil Not Serving as Dispersion Area (C=0.23) sq-ft 9 Natural Type D Soil Not Serving as Dispersion Area (C=0.30) sq-ft 10 Does Tributary Incorporate Dispersion, Tree Wells, and/or Rain Barrels? No yes/no 11 Impervious Surfaces Directed to Dispersion Area per SD-B (Ci=0.90) sq-ft 12 Semi-Pervious Surfaces Serving as Dispersion Area per SD-B (Ci=0.30) sq-ft 13 Engineered Pervious Surfaces Serving as Dispersion Area per SD-B (Ci=0.10) sq-ft 14 Natural Type A Soil Serving as Dispersion Area per SD-B (Ci=0.10) sq-ft 15 Natural Type B Soil Serving as Dispersion Area per SD-B (Ci=0.14) sq-ft 16 Natural Type C Soil Serving as Dispersion Area per SD-B (Ci=0.23) sq-ft 17 Natural Type D Soil Serving as Dispersion Area per SD-B (Ci=0.30) sq-ft 18 Number of Tree Wells Proposed per SD-A #
19 Average Mature Tree Canopy Diameter ft
20 Number of Rain Barrels Proposed per SD-E #
21 Average Rain Barrel Size gal
22 Total Tributary Area 60,000 sq-ft
23 Initial Runoff Factor for Standard Drainage Areas 0.90 unitless 24 Initial Runoff Factor for Dispersed & Dispersion Areas 0.00 unitless 25 Initial Weighted Runoff Factor 0.90 unitless
26 Initial Design Capture Volume 3,150 cubic-feet
27 Total Impervious Area Dispersed to Pervious Surface 0 sq-ft 28 Total Pervious Dispersion Area 0 sq-ft
29 Ratio of Dispersed Impervious Area to Pervious Dispersion Area n/a ratio 30 Adjustment Factor for Dispersed & Dispersion Areas 1.00 ratio 31 Runoff Factor After Dispersion Techniques 0.90 unitless 32 Design Capture Volume After Dispersion Techniques 3,150 cubic-feet 33 Total Tree Well Volume Reduction 0 cubic-feet
34 Total Rain Barrel Volume Reduction 0 cubic-feet
35 Final Adjusted Runoff Factor 0.90 unitless
36 Final Effective Tributary Area 54,000 sq-ft
37 Initial Design Capture Volume Retained by Site Design Elements 0 cubic-feet 38 Final Design Capture Volume Tributary to BMP 3,150 cubic-feet Dispersion
Area, Tree
Well & Rain
Barrel Inputs
(Optional)
Standard
Drainage
Basin Inputs
Results
Tree & Barrel
Adjustments
Initial Runoff
Factor
Calculation
Dispersion
Area
Adjustments
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Appendix K: Guidance on Green Infrastructure
K-17 2023
Excerpt 2- Summary of Stormwater Pollutant Control Calculations (Part 2 of 2) City of Encinitas Automated Stormwater Pollutant Control Worksheet B.3 (Version 2.0) Category # Description ii Units
1 Drainage Basin ID or Name DMA 1 sq-ft
2 Design Infiltration Rate Recommended 0.000 in/hr
3 Design Capture Volume Tributary to BMP 3,150 cubic-feet 4 Is BMP Vegetated or Unvegetated? Vegetated unitless
5 Is BMP Impermeably Lined or Unlined? Lined unitless
6 Does BMP Have an Underdrain? Underdrain unitless
7 Does BMP Utilize Standard or Specialized Media? Standard unitless 8 Provided Surface Area 1,620 sq-ft
9 Provided Surface Ponding Depth 6 inches
10 Provided Soil Media Thickness 21 inches
11 Provided Gravel Thickness (Total Thickness) 14 inches 12 Underdrain Offset 3 inches
13 Diameter of Underdrain or Hydromod Orifice (Select Smallest) 8.00 inches 14 Specialized Soil Media Filtration Rate in/hr
15 Specialized Soil Media Pore Space for Retention unitless 16 Specialized Soil Media Pore Space for Biofiltration unitless 17 Specialized Gravel Media Pore Space unitless
18 Volume Infiltrated Over 6 Hour Storm 0 cubic-feet
19 Ponding Pore Space Available for Retention 0.00 unitless 20 Soil Media Pore Space Available for Retention 0.05 unitless 21 Gravel Pore Space Available for Retention (Above Underdrain) 0.00 unitless 22 Gravel Pore Space Available for Retention (Below Underdrain) 0.40 unitless 23 Effective Retention Depth 2.25 inches
24 Fraction of DCV Retained (Independent of Drawdown Time) 0.10 ratio 25 Calculated Retention Storage Drawdown Time 120 hours 26 Efficacy of Retention Processes 0.12 ratio
27 Volume Retained by BMP (Considering Drawdown Time) 381 cubic-feet 28 Design Capture Volume Remaining for Biofiltration 2,769 cubic-feet 29 Max Hydromod Flow Rate through Underdrain 2.8291 cfs 30 Max Soil Filtration Rate Allowed by Underdrain Orifice 75.44 in/hr 31 Soil Media Filtration Rate per Specifications 5.00 in/hr 32 Soil Media Filtration Rate to be used for Sizing 5.00 in/hr 33 Depth Biofiltered Over 6 Hour Storm 30.00 inches
34 Ponding Pore Space Available for Biofiltration 1.00 unitless 35 Soil Media Pore Space Available for Biofiltration 0.20 unitless 36 Gravel Pore Space Available for Biofiltration (Above Underdrain) 0.40 unitless 37 Effective Depth of Biofiltration Storage 14.60 inches 38 Drawdown Time for Surface Ponding 1 hours
39 Drawdown Time for Effective Biofiltration Depth 3 hours 40 Total Depth Biofiltered 44.60 inches
41 Option 1 - Biofilter 1.50 DCV: Target Volume 4,154 cubic-feet 42 Option 1 - Provided Biofiltration Volume 4,154 cubic-feet 43 Option 2 - Store 0.75 DCV: Target Volume 2,077 cubic-feet 44 Option 2 - Provided Storage Volume 1,971 cubic-feet
45 Portion of Biofiltration Performance Standard Satisfied 1.00 ratio 46 Do Site Design Elements and BMPs Satisfy Annual Retention Requirements? Yes yes/no 47 Overall Portion of Performance Standard Satisfied (BMP Efficacy Factor) 1.00 ratio 48 Deficit of Effectively Treated Stormwater 0 cubic-feet Retention
Calculations
BMP Inputs
Biofiltration
Calculations
Result
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Appendix K: Guidance on Green Infrastructure
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Excerpt 3 – Determination of Land Use Factor for Example 2 Water Quality Equivalency Automated Land Use Factor Worksheets (Version 1.0) 2026-08-19 Item #12D Page 680 of 816
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K.2.2 Green Streets Guidelines
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K-21 February 2023
Green Streets
Guidelines
A Guide to Green Street Implementation in the
County of San Diego
January 2019
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K-23 February 2023
WHAT IS A GREEN STREET? Pavement on roadways can contribute to excess stormwater runoff and increased levels of pollutants in the County’s waterways. Green infrastructure reduces stormwater runoff and improves water quality. The Green Streets program incorporates a wide variety of Green Infrastructure design elements including, but not limited to: tree wells, dispersion areas and biofiltration, and permeable pavement. The use of Green Streets offers the capability of transforming a significant stormwater and pollutant source into an innovative treatment system.

Additionally, the State of California is in the midst of a severe drought, with water years of 2012-14 recording the driest three consecutive years in the state’s history, as well as setting new records for statewide average temperatures. On April 1st, 2015 Governor Brown signed executive order B-29-15 setting the first mandatory statewide water restrictions. This order prohibits ornamental turf on public street medians, and requires a reduction in potable water use for irrigation. The Green Streets program promotes water conservation through the use of low water use and drought tolerant plants (xeriscape) and improving groundwater supplies through infiltration. Green infrastructure, unlike traditional “gray” infrastructure approaches to stormwater management, provides multiple benefits to communities. Planting more trees and landscaping in public spaces cleans the air, cools the land, provides more habitat for wildlife, adds green maintenance jobs, increases property values and promotes a better, healthier quality of life for County residents and visitors. Under the Municipal Separate Storm Sewer System (MS4) Permit for San Diego Region (Permit [Order No. R9-2013-0001]), the County may make Priority Development Project (PDP) Exemptions for projects redeveloping or retrofitting existing paved roads, streets, and alleys as “EPA Green Streets.” This is accomplished by meeting the criteria set forth in section 1.4.3 of the County of San Diego’s BMP Design Manual and based in part on the EPA publication “Green Streets: Municipal Handbook, Managing Wet Weather with Green Infrastructure.” This guide is to be used along with the County of San Diego’s BMP Design Manual for meeting stormwater requirements within the County’s public right-of-way. These Green Streets measures, when implemented, will ensure the County remains a green community for many years to come. 2026-08-19 Item #12D Page 686 of 816
K-24 February 2023
TABLE OF CONTENTSCHAPTER 1 – INTRODUCTION TO GREEN STREETS........................................................................................K-25

1.1 INTRODUCTION

1.2 THE NATURAL AND DEVELOPED ENVIRONMENT

1.3 GREENING THE STREETS

1.4 THE COUNTY ENVIRONMENT

1.5 COUNTY RIGHT OF WAY
CHAPTER 2 – GREEN STREETS STRATEGIES………………………………………...…………………………..K-30

2.1 INTRODUCTION

2.2 TREE WELLS

2.3 DISPERSION AREAS AND BIOFILTRATION

2.4 PLANTING & IRRIGATION OF DISPERSION AREAS, BIOFILTRATION, TREE WELLS,

AND OTHER AREAS

2.5 TYPES OF PERMEABLE PAVEMENT
CHAPTER 3 – PROCEDURES & DESIGN EXAMPLES………………………………………………………………K-55

3.1 INTRODUCTION

3.2 DESIGN PROCEDURE

3.3 MEDIANS

3.4 INTERSECTIONS

3.5 TRAVELED WAY, BIKE LANE, AND SHOULDER PERMEABLE PAVEMENT

3.6 PARKWAY

3.7 PUTTING IT ALL TOGETHER
CHAPTER 4 – IMPLEMENTING GREEN STREETS PROJECTS……………………………………………………..K-69

4.1 DESIGN AND CONSTRUCTION

4.2 MAINTENANCE

4.3 FUNDING
REFERENCES………………………………………………………………………………………………………K-71
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K-25 2023

1.1 INTRODUCTIONThese guidelines have been prepared to assist in the design and construction of projects that retrofit or redevelop existing paved streets and roads. These Guidelines and Standards have been developed in accordance with the United States Environmental Protection Agency Green Streets Guidance “Green Streets: Municipal Handbook, Managing Wet Weather with Green Infrastructure.” These Guidelines may also be used to assist in the design and construction of new or retrofit paved sidewalks, bicycle lanes, or trails.

The functional goals of these guidelines are to:
• Provide source control of stormwater; • Limit stormwater transport and pollutant conveyance to the collection system; • Restore predevelopment hydrology to the extent possible by slowing the runoff down and allowing for infiltration; and
• Provide environmentally enhanced roads.

A review of existing County policies has been performed and included in the accompanying Green Streets Standards document that includes an addendum to the Public Road Standards, as well as Green Streets Standard Drawings and Specifications. Green Streets configurations and locations presented in this guideline are schematic/conceptual in nature. The configurations (or locations) could be modified as long as the design and construction details are in conformance with the Green Streets technical documents (i.e. – Green Streets Supplement to Public Road Standards, Standard Drawings, Specifications, Plant List, and Maintenance Schedule).

CHAPTER 1 Introduction to Green Streets
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K-26 2023

1.2 THE

NATURAL AND

DEVELOPED

ENVIRONMENT

NATURAL
AREAS
In areas such as meadows, thickets, woodlands, and parks, rain can soak into the ground and be used by plants. Trees and shrubs intercept rainfall and it slowly trickles down to the ground where it is absorbed by mulch and humic soil. Shaded areas are cooler, moister and provide wildlife habitat. Very little rainwater runs off the ground. Natural Area Diagram (Source: DDOT, 2014)
URBAN
AREAS
In urban areas, building rooftops, streets, alleys, sidewalks, and other paved surfaces are smooth and mostly impervious. Very little rain has a chance to soak into the ground. These paved urban areas are hotter and offer very little wildlife habitat. Most of the rain that falls in the urban areas quickly runs off impervious surfaces picking up pollutants and carrying them into storm drains. These flows quickly combine to create flash floods that degrade downstream waterways.

Urban Area Diagram
(Source: DDOT, 2014)
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K-27 2023

1.3 GREENING
THE

STREETS
Green Streets, which includes Green Infrastructure (GI), incorporates elements found in natural areas into the County road right of way. GI is the living network that connects impervious areas to landscape areas, natural areas, and waterways. GI captures rainfall; cools buildings and pavement; and creates natural pathways for wildlife. GI includes Low Impact Development (LID) techniques, which mimic nature to capture and treat stormwater as close to the source as possible. When implemented, GI creates living green streets that capture, store, and infiltrate stormwater to treat it as a resource and improve the County environment.

Green Streets Stormwater Diagram
(Source: DDOT, 2014)

STORMWATER

CAPTURE
Runoff from impervious surfacing
STORE
Store and retain captured runoff

INFILTRATE/EVAPOTRANSPIRE
Water is infiltrated into the ground,
evapotranspired by plants or drained
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K-28 2023

1.4 THE
COUNTY

ENVIRONMENT
The County of San Diego is a unique environment made up of natural, rural, and urban areas. When rain falls in the County and becomes stormwater runoff, it flows through eleven major watersheds. Stormwater carries the pollutants, trash, and warmer temperatures it collects from roads, buildings, and other impervious surfaces and delivers them into our rivers, streams, bays, lagoons, and ocean. Urbanization and other land use changes in the County can modify the natural watershed hydrologic processes and stormwater runoff characteristics resulting in increased stormwater runoff and erosion.

Watershed Divide
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K-29 2023

1.5 COUNTY
RIGHT
-OF-WAY
Land within the road right-of-way (ROW) presents a significant opportunity to reduce runoff and improve the urban environment through Green Streets. This manual introduces techniques to install green infrastructure in the median, street, bike lane, shoulder, parkway, and slope and drainage easements. This guide and the “Green Streets Standards,” which includes supplements to the Public Road Standards, Green Streets Standard Drawings, and specifications, should be used the maximum extent practicable for all public and private project design in the County ROW.

ROAD RIGHT-OF-WAY DIAGRAM
(Source: DDOT, 2014)
Early in the green street planning and design process careful consideration should be given to the location of existing and proposed utilities and appurtenances (utility poles, vaults, and pedestals), fire hydrants, traffic signals, signage, mail boxes, bus stops, and their interaction with the proposed green street measures. 2026-08-19 Item #12D Page 692 of 816
K-30 2023

2.1 INTRODUCTIONGreen Streets, including Green Infrastructure (GI), and Low Impact Development (LID) solutions are intended to be sustainable, attractive, and cost effective. The range of opportunities includes tree wells, landscape areas, dispersion areas, biofiltration, permeable pavement, and removal of impervious pavement. These strategies use natural processes to reduce the volume of runoff, peak flow, and pollutants. This chapter will focus on five (5) areas appropriate for use in the road right-of-way. TREE WELLS Trees are a powerful green streets tool due to their ability to intercept water on leaves, slowly deliver it to the mulch and soil, absorb it through root systems, and transpire it as water vapor directly back to the atmosphere. DISPERSION AREAS
Dispersion areas disconnect impervious areas from directly running to the storm drain system. Dispersion areas use the natural functions of plants, mulch, and soils to remove pollutants and slow stormwater runoff. The strategy uses storage, sediment capture, and biological processes to clean the water. These mimic processes that occur in nature before water reaches waterways. BIOFILTRATION Biofiltration facilities are vegetated surface water systems that filter water through vegetation, and soil or biofiltration soil media prior to discharge to the storm drain system. They also utilize shallow depressions to provide storage and evapotranspiration. PERMEABLE

PAVEMENT
Permeable paving systems provide a hard surface, while allowing water to flow through to the underlying soils instead of directly to the drainage system. The areas where this strategy may be used include: sidewalks, pathways, medians, and parking lanes. REMOVE IMPERVIOUS

PAVEMENT
Roadway improvement projects have the opportunity to remove portions of impervious pavement within the right of way and replace it with permeable material. CHAPTER 2 Green Streets Strategies
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2.2 TREE
WELLS
WHY
ARE
TREES IMPORTANT?
Trees make a streetscape feel welcoming, help manage stormwater, and reduce the urban heat island effect by providing shade. An urban heat island remains significantly warmer than the surrounding rural areas due to less vegetation. Trees promote air quality, natural habitat, the human environment, and well-being. Trees in a congested road right-of-way are confined to small planting areas where they struggle to reach a mature size or live a long life. Through the use of Structural Soil, Structural Cell, or Suspended Sidewalk techniques, soil volumes and space for tree roots to grow uninhibited can be greatly increased. These techniques also allow for more water and air to reach the tree roots. (Source: DDOT, 2014)
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K-32 2023
(Source: DDOT, 2014)
Note: Trees may also be located behind the sidewalk/pathway.

SOIL
VOLUME
SIZING
• Adequate planting soil space provides
the nutrients, water, air, and root space that trees need to have a long, healthy life. • The planting soil volume required
depends on the fully-grown tree size (generally two cubic feet of soil per one square foot of the tree’s mature drip line area). • Planting soil amendments for trees
should be three-feet deep; the length and width must ensure the appropriate volume for the tree species and site.

OTHER

CONSIDERATIONS
• Provide as much open space as
possible for the tree to allow the tree to grow and access water. • Providing structural soils, suspended
sidewalks, or structural slabs to edges of paved areas prevents planting soil compaction and encourages tree roots to extend further and into adjacent green areas. • Evaluate temporary and permanent
irrigation needs
• Evaluate utility locations and required
clearance.

DESIGN ISSUES• Maintenance Access: allow for
maintenance access from road
• Pedestrian Considerations: allow for
18-inch minimum setback from curb and minimum 48-inch sidewalk width. Comply with ADA requirements. • Suspended sidewalks and structural
slabs/cells: may require evaluation by geotechnical and structural engineers • Clear Recovery Zone: Consider clear
recovery zone requirements and minimum setback requirements. • Tree Size: Evaluate tree size versus
the right of way width.
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TREE
WELLS
–
WHAT’S
UNDERNEATH?
(Source: DDOT, 2014)
Note: Other options include suspended sidewalks and structural cells as shown on page K-30.

PUTTING IT

TOGETHER
• Permeable Paver: Permeable pavers
allow water to infiltrate into the planting soil to be used by the trees. • Mulch: A soil topping that may be
organic or inorganic material which covers the planting soil to retain water and trap pollutants. • Planting Soil: Uncompacted and
amended soil mix allows root growth when used in open areas, with structural cells, or suspended sidewalks. • Structural Soil: Supports pavement
and allows root growth.
• Sand: Acts as a drainage layer for
excess stormwater (when needed).
• Uncompacted Subgrade: Existing soil
where stormwater may infiltrate.

WATER

TREES WITH

STORMWATER
In addition to large planting soil volumes, trees need sufficient water, air, and nutrients to be successful in the road rightof-way environment. Tree space design includes integrating opportunities for directing stormwater into the soil. See the County of San Diego’s Water Conservation in Landscaping Ordinance for irrigation requirements. 2026-08-19 Item #12D Page 696 of 816
K-34 2023
Runoff follows the existing curb line and enters the facility through curb cuts. Excess runoff flows through the system or into drain inlets.

Runoff follows the existing curb line and enters the facility through curb cuts. Excess runoff flows through the system or into drain inlets.

2.3 TYPES OF

DISPERSION

AREAS AND

BIOFILTRATION
WHAT
ARE

DISPERSION

AREAS AND
BIOFILTRATION?
Dispersion Areas and Biofiltration are landscape systems that filter pollutants and sediment from runoff.

The layers of plant material, mulch, biofiltration soil media (a mix of planting soil, sand, and compost), and stone capture metals, nutrients, and bacteria that would otherwise flow into the surrounding creeks and rivers. The rainwater is held in the planting bed until it infiltrates into the ground or evaporates. The entire system can fit into small spaces, making it adaptable to tree spaces along the road, planter boxes, curb extensions, medians, roundabouts, and open areas.

PLANTER
BOXES
Runoff enters the facility through curb cuts. Excess runoff exits through the same curb cuts or into drains located in the planting area.

CURB

EXTENSION
Runoff enters the facility following the existing curb line. Excess runoff flows through the system and returns to the curb and gutter downstream.

MEDIANS

BULB-OUT AT INTERSECTION
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K-35 2023
(Source: County of San Diego, 2014)

VEGETATED
FILTER
STRIP
Runoff enters the facility directly via sheet flow. Excess runoff flows through the system to a drain inlet downslope.

SWALES
Runoff enters the facility directly or through curb cuts. Excess runoff flows through the system to a drainage outlet.

TRAFFIC

CIRCLE/ROUNDABOUT
Runoff follows the existing curb line and enters the facility through curb cuts. Excess runoff flows through the system or into drains located in the planting area.

OPEN
AREAS
Runoff drains into the planting area from the surrounding area. The size and shape can fit the available space.
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PLANTER
BOX

ADJACENT TO

ROADWAY

WHERE TO
USE?
• Street with no adjacent on-street
parking.
• Where Tree wells are needed. • Street where bike lane is adjacent to curb.

LIMITATIONS• Not for on-street parking. DESIGN ISSUESMaintenance Access: Allow for adequate maintenance access from road. Pedestrian Considerations: Allow for minimum allowable sidewalk width. Consider trip hazards and fall protection. Comply with ADA requirements.

SEE
PAGE
S
K-43-K-47 FOR

DETAILS
(Source: DDOT, 2014)
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K-37 2023

PLANTER

BOX WITH
STEP
OUT
ZONE

WHERE TO
USE?
• Wide sidewalk area with
adjacent on-street parking.
• High-volume pedestrian areas. • Areas with other streetscape features (lights, bike racks, bus
stops, etc.).

LIMITATIONS• Do not disturb existing, mature
trees and root systems.
• Provide low fence or curb for
pedestrian safety.

DESIGN ISSUESPlanting Design: Same as for planter box adjacent to roadway. Maintenance Access: Allow for adequate maintenance access from road. Pedestrian Considerations: Areas in the streetscape can have dropped or have sloped sides. Short fences or curbs prevent pedestrians from stepping into a recessed area. Planter boxes with side slopes can use a small step-out area in place of a fence or curb. When the planter box is next to street parking areas, a step-out zone must be provided to allow access from the vehicle to the sidewalk. Crossing areas must be provided between street parking and the sidewalk. Comply with ADA requirements. (Source: DDOT, 2014)
SEE
PAGE
S
K-43-K-47 FOR

DETAILS
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K-38 2023
CURB

EXTENSION

WHERE TO
USE?
• Areas with low on-street parking
demand.
• In wide roadways. • For traffic calming. • In “no parking areas” on street (excluding loading zones and curb cuts).
• Next to mature trees. LIMITATIONS• Sufficient street parking or off-street parking must be available to residents.
• Do not disturb existing, mature trees
and root systems.
• Ensure sight lines and turning radii
are preserved.

DESIGN ISSUES
Maintenance Access: Allow for adequate
maintenance access from road. Pedestrian Considerations: Consider trip hazards and fall protection. Short fences or curbs prevent pedestrians from stepping into a recessed area. A 3:1 transition from the sidewalk to planter bottom is an alternative. Comply with ADA requirements.

Parking: Consider trip hazards and adequate spacing in order to park. Flood Control: Locate so that stormwater can drain away from the roadway and be directed through the curb inlet. Bike Lanes: Consider bike lane traffic.

SEE
PAGE
S
K-43-K-47 FOR

DETAILS
(Source: DDOT, 2014)
2026-08-19 Item #12D Page 701 of 816
K-39 2023
SWALE

ADJACENT TO

ROADWAY

WHERE TO
USE?
• On street with no curb. • In wide ROW area with or
without sidewalk.
• Areas with less pedestrian
use.

LIMITATIONS• Not suitable for narrow
sidewalk areas.

DESIGN ISSUESSlope and Check Dams: Swales are placed where street runoff is flowing and optimally before catch basins that convey water from the street to the drainage system. Swales may be built on moderate slopes with the use of check dams. Rock armoring or turf reinforcement mat may be required in steep areas with erosive velocities between check dams. Maintenance Access: Allow for adequate maintenance access from road. Pedestrian Considerations: Limit pedestrian access to swale. Transition swale at intersections for pedestrian facilities. Comply with ADA requirements. Driveway Crossings: Driveway crossings may limit swale lengths.

SEE
PAGES K-43-K-47 FOR

DETAILS
(Source: DDOT, 2014)
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WHERE TO
USE?

VEGETATED
FILTER
STRIP
• Where runoff can sheet flow into filter strip area.
• Moderate slopes (less than 5%) adjacent to impervious area of treatment (sidewalk or road). • Rural areas.

LIMITATIONS• Not recommended on steep slopes. • Prone to rill formation. • Areas with on-street parking. DESIGN ISSUESMaintenance: Vegetated cover must be maintained to ensure that filter strips do not export sediment due to erosion of exposed ground. Slope: Maximum slopes in the direction of flow will be based upon drainage area size, soil type, vegetation cover, and slope length to prevent rill formation. Slopes less than 5% are preferred. Maintenance Access: Allow for adequate maintenance access from road. Pedestrian Considerations: Limit pedestrian access across filter strip to prevent formation of dirt pathways. Comply with ADA requirements. 2026-08-19 Item #12D Page 703 of 816
K-41 2023
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VEGETATED

TERRACED
FILTER
STRIP

WHERE TO
USE?
• Where runoff can sheet flow into
filter strip area.
• Steep slopes (greater than 5%)
adjacent to impervious area of treatment (sidewalk or road). • Rural areas.

LIMITATIONS• Prone to rill formation. • Areas with on-street parking. • Walls over 3 feet tall require structural design.

DESIGN ISSUESMaintenance: Vegetated cover must be maintained to ensure that filter strips do not export sediment due to erosion of exposed ground. Slope: Maximum slopes in the direction of flow will be based upon drainage area size, soil type, vegetation cover, and slope length to prevent rill formation. Slopes less than 5% are preferred. Maintenance Access: Allow for adequate maintenance access from road and bottom of slope. Pedestrian Considerations: Limit pedestrian access across filter strip to prevent formation of dirt pathways. Comply with ADA requirements. 2026-08-19 Item #12D Page 705 of 816
K-43 2023

BULB-OUT AT INTERSECTION

WHERE TO
USE?
• Areas with low on-street
parking demand.
• In wide roadways. • For traffic calming. • In “no parking areas” on street (excluding loading
zones and curb cuts).

LIMITATIONS• Sufficient street parking or offstreet parking must be available to residents.
• Ensure sight lines and turning
radii are preserved.

DESIGN ISSUESMaintenance access: Allow for adequate maintenance access from road. Pedestrian considerations: Short fences or curbs prevent pedestrians from stepping into a recessed area. Walkways and ramps may need to be designed through bulb-outs to provide pedestrian access at intersections. Comply with ADA requirements. Design: Requires County Traffic Engineering Section approval. 2026-08-19 Item #12D Page 706 of 816
K-44 2023
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ROUNDABOUT

WHERE TO
USE?
• Areas with low on-street
parking demand.
• In wide roadways. • For traffic calming.

LIMITATIONS• Sufficient street parking or offstreet parking must be available to residents.
• Ensure sight lines and turning
radii are preserved.

DESIGN ISSUESMaintenance Access: Allow for adequate maintenance access from road. Pedestrian Considerations: Short fences or curbs prevent pedestrians from stepping into a recessed area. Comply with ADA requirements. Design: Requires County Traffic Engineering Section approval. 2026-08-19 Item #12D Page 708 of 816
K-46 2023
2026-08-19 Item #12D Page 709 of 816
K-47 2023

DISPERSION

AREAS AND

BIOFILTRATION
–
WHAT’S
UNDERNEATH?
SOIL

TYPE AND INFILTRATION
RATE
Dispersion areas and biofiltration can be located in many areas. However, site constraints will help to determine what goes underneath the dispersion area or biofiltration. Common considerations include soil type, relative soil compaction, required utility setbacks, slope setbacks, and structural setbacks. Depending on the factors at the site, what’s underneath the dispersion area or biofiltration is determined by the level of infiltration: high, medium, low, or none.

A qualified engineer practicing geotechnical services shall review the proposed stormwater infiltration to provide a professional opinion regarding the potential adverse geotechnical conditions that the implementation of these practices may create. Geotechnical conditions such as slope stability, expansive soils, compressible soils, seepage, groundwater, and loss of foundation or pavement subgrade strength should be considered. The U.S. Department of Agriculture Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service, conducted a soil survey of the San Diego area in the early 1970s. The NRCS has classified San Diego area soils with respect to: (1) their ability to accept and absorb water, (2) their tendency to produce runoff, and (3) their erodibility. The soil survey classified soil runoff potential into four hydrologic soil groups labeled A through D.

Group A and B soils exhibit the greatest infiltration rates (unless soils are compacted during construction) and are generally best suited to stormwater percolation. The San Diego area, however, has a relatively high concentration of group C and D soils, which exhibit lower percolation rates that generally limit the use of infiltration-based stormwater management systems. Instead, dispersion areas and biofiltration facilities are often equipped with underdrains. Such a design provides for filtration of the water quality design event through a biofiltration soil media as well as incidental infiltration of low flows.

Retaining a geotechnical engineer and conducting exploratory excavations at the site are highly recommended. Consideration should be given to the effects of urbanization on the natural hydrologic soil group. If heavy equipment can be expected to compact the soil during construction, or if grading will mix the surface and subsurface soils, appropriate changes should be made in the soil group selected.

The NRCS hydrologic soil groups are defined as:
• Group A soils have a high rate of
percolation and a low runoff potential. The rate of water transmission is high; thus, runoff potential is low. Group A soils are generally referred to as sandy soils. • Group B soils have moderate percolation rates when thoroughly wet. These are chiefly soils that are moderately deep to deep, moderately well-drained to well-drained, and moderately coarse textured. Rate of water transmission is moderate. • Group C soils have a slow percolation rate when thoroughly wet. They are chiefly soils that have a layer impeding the downward movement of water, or they are moderately fine to fine-textured soils that have a slow infiltration rate. The rate of water transmission is slow. • Group D soils have very slow percolation rates when thoroughly wet. They are clays that have a high shrinkswell potential, soils that have a high permanent water table, soils that have a claypan or clay layer at or near the surface, or soils that are shallow over nearly impervious material. The rate of water transmission for group D soils is very slow. 2026-08-19 Item #12D Page 710 of 816
K-48 2023

HIGH INFILTRATION

PUTTING IT

TOGETHER
• Ponding Depth: Stores runoff
within the planting area prior to treatment.
• Mulch: A soil topping that may be
organic or inorganic material which covers the planting soil to retain water and trap pollutants. • Biofiltration Soil Media: A specific
blend of soil, compost, and sand to retain and drain water and support plant growth. • Geotextile: Prevents existing soil
from migrating into the biofiltration soil media.
• Uncompacted Subsoil: Existing soil
where stormwater infiltrates.

COMMON

DESIGN ISSUES
Utilities: In the County, utility lines are common and necessary components of infrastructure within the right-of-way. Utility lines should be avoided where necessary and allowed to coexist where possible.

HIGH INFILTRATION
Notes: 1. Geotextile per Geotechnical Engineer’s Recommendations (street side and sidewalk side). 2026-08-19 Item #12D Page 711 of 816
K-49 2023

MEDIUM INFILTRATION

PUTTING IT

TOGETHER
• Ponding Depth: Stores runoff
within the planting area prior to treatment.
• Mulch: A soil topping that may be
organic or inorganic material which covers the planting soil to retain water and trap pollutants. • Biofiltration Soil Media: A specific
blend of soil, compost, and sand to retain and drain water and support plant growth. • Choker Layer: Sand and gravel to
prevent biofiltration soil media from migrating into the reservoir. • Reservoir Layer: Stone to hold
excess water until it infiltrates.
• Geotextile: Prevents existing soil
from migrating into the biofiltration soil media and stone reservoir layer. • Uncompacted Subgrade: Existing
soil where stormwater infiltrates.

COMMON

MEDIUM INFILTRATION
Notes: 1. Geotextile per Geotechnical Engineer’s Recommendations (street side and sidewalk side). 2. Choker layer may be required depending the type of reservoir layer. 2026-08-19 Item #12D Page 712 of 816
K-50 2023

LOW INFILTRATION

PUTTING IT

TOGETHER
• Ponding Depth: Stores runoff
within the planting area prior to treatment.
• Overflow Riser: Pipe to capture
high water flow.
• Mulch: A soil topping that may be
organic or inorganic material which covers the planting soil to retain water and trap pollutants. • Biofiltration Soil Media: A specific
blend of soil, compost, and sand to retain and drain water and support plant growth. • Choker Layer: Sand and gravel to
prevent biofiltration soil media from migrating into the reservoir. • Reservoir Layer: Stone to hold
excess water until it infiltrates.
• Underdrain: An underdrain is
required.
• Geotextile: Prevents existing soil
from migrating into the biofiltration soil media and stone reservoir layer. • Uncompacted Subgrade: Existing
soil where stormwater infiltrates.

COMMON

DESIGN ISSUES
Utilities: In the County, utility lines are common and necessary components of infrastructure within the right-ofway. Utility lines should be avoided where necessary and allowed to coexist where possible.

LOW INFILTRATION
Notes: 1. Geotextile per Geotechnical Engineer’s Recommendations (street side and sidewalk side). 2. Choker layer may be required depending the type of reservoir layer. 2026-08-19 Item #12D Page 713 of 816
K-51 2023

NO INFILTRATION

PUTTING IT

TOGETHER
• Ponding Depth: Stores runoff
within the planting area prior to treatment.
• Overflow Riser: Pipe to capture
high water flow.
• Mulch: A soil topping that may be
organic or inorganic material which covers the planting soil to retain water and trap pollutants. • Biofiltration Soil Media: A specific
blend of soil, compost, and sand to retain and drain water and support plant growth. • Choker Layer: Sand and gravel
to prevent biofiltration soil media from migrating into the reservoir. • Reservoir Layer: Stone to hold
excess water until it enters the underdrain.
• Underdrain: An underdrain is
required.
• Impermeable Liner: Prevents
infiltration and prevents existing soil from migrating into the biofiltration soil media and stone reservoir layer.

COMMON

NO INFILTRATION
Notes: 1. Choker layer may be required depending the type of reservoir layer. 2026-08-19 Item #12D Page 714 of 816
K-52 2023

2.4 PLANTING
& IRRIGATION OF

DISPERSION
AREAS,

BIOFILTRATION, TREE

WELLS, AND
OTHER
AREAS

PLANTING
DESIGN
Tree wells, dispersion areas, and biofiltration add a landscape amenity to the street-scape.

Trees, shrubs, grasses and perennials are used to create a diverse landscape suitable for the site conditions and neighborhood. Plants should be chosen based on the level of care expected at the facility. Planting design must be done to ensure sight lines are preserved for pedestrians, cyclists, and vehicles on the street. Existing trees are an important component of the green street. Mature trees capture stormwater, provide shade, and cool pavement. Existing trees should be protected when implementing green streets and not disturbed during construction. Refer to the County of San Diego’s Water Efficient Landscape Design Manual and Low Impact Development Handbook for suitable plant species to use in dispersion areas and biofiltration.

Also refer to the community right of way development standards for suitable plants within specific communities.

IRRIGATION
DESIGN
Irrigation design should comply with the County of San Diego’s Water Efficient Landscape Design Manual. PLANTING

ZONES (HYDROZONES)
Grouping plants into hydrozones is an approach to irrigation and planting design where plants with similar water needs are grouped together. Ideally, each zone of the irrigation system will supply plants with the same water needs with the appropriate amount of water. WATER

CONSERVATION
State executive order B-29-15 requires mandatory statewide water restrictions. This order prohibits ornamental turf on public street medians, and requires a reduction in potable water use for irrigation. Low water use, drought tolerant, native plants should be used for Green Streets applications. The use of reclaimed water is recommended to reduce the amount of potable water used for irrigation. 2026-08-19 Item #12D Page 715 of 816
K-53 2023

2.5 TYPES OF

PERMEABLE

PAVEMENT

WHAT IS

PERMEABLE

PAVEMENT
Permeable pavement is an engineered top layer and base layer that allows water to move through it. The goal is to take rainwater as it falls and quickly move it to the lower layers of the system. Stormwater is stored in an underlying stone layer until it infiltrates into the soil below, aiding in groundwater recharge, or releases slowly to the storm drain system. Pollutants are filtered through the pavement and base layers. The terms ‘Permeable Concrete Pavers’, ‘Pervious Concrete’, ‘Porous Asphalt’, and ‘Porous Rubber’ are industry standard names, but all surfaces are ‘permeable’ and provide sufficient openings at the surface to allow stormwater to infiltrate.

PERMEABLE

CONCRETE
PAVERS
Unlike traditional pavers, there are gaps between each paver to allow water to flow between the pavers and into the base layer.

PERVIOUS

CONCRETE
Sands and “fines” are reduced in the concrete mix to allow water to flow through the pavement into a stone bed and eventually the ground.
2026-08-19 Item #12D Page 716 of 816
K-54 2023

TYPES OF

PERMEABLE

PAVEMENT (CONTINUED)
POROUS

ASPHALT
Porous asphalt is very similar to traditional asphalt except that the sands or “fines” are reduced in the mix so water can move through the pavement.

POROUS
RUBBER
Made from recycled rubber and small stones, porous rubber works like pervious concrete, but can be installed over tree roots.

DECOMPOSED

GRANITE (DG)

PATHWAY
Decomposed granite can be used for pathways. It can be installed and compacted to meet ADA handicapped accessibility specifications and criteria. Although highly compacted, the surface has some infiltration capacity.

BOARDWALK
Made from wood or composite, boardwalks may be used for pathways. Rain easily passes through the spaces between the boards to the earth below. 2026-08-19 Item #12D Page 717 of 816
K-55 2023

PERMEABLE

PAVEMENT
–
WHAT’S
UNDERNEATH?
As with dispersion areas and biofiltration, there are multiple options for the subsurface components for permeable pavement including:
• Reservoir layer only with no underdrain • Reservoir layer with underdrain (shown) • Reservoir layer with underdrain and impermeable liner

PUTTING IT

TOGETHER
• Permeable Surface:

Permeable concrete pavers, pervious concrete, porous asphalt, porous rubber, DG, or boardwalk. • Bedding Layer: Used for
pavers so they can be laid flat.
• Choker Layer: A layer of
small rock to prevent fine material from migrating into the reservoir layer. • Reservoir Layer: Stone to
hold excess water until it infiltrates.
• Underdrain: Conveys excess
water into drainage system when the reservoir fills.
• Filter Layer/Geotextile: A
layer of stone or permeable geotextile to separate the reservoir layer from the soil below and prevent migration of fines into the reservoir layer. • Impermeable Liner: Prevents
infiltration into subgrade or adjacent roadway structural section. • Uncompacted Subgrade:

Existing soil into which stormwater infiltrates.
(Source: DDOT, 2014)
2026-08-19 Item #12D Page 718 of 816
K-56 2023

PERMEABLE

PAVEMENT

SUBSURFACE
DESIGN

OPTIONS
Reservoir layer only with no underdrain
Reservoir layer with underdrain

WHERE TO
USE?
• Pedestrian areas • Pathways • Parking lanes LIMITATIONS• Use is limited to areas curbseparated from the traveled way. • Use in areas with little to no
sediment production.

DESIGN ISSUESSoil Infiltration and Drainage: Soil infiltration tests must be completed to determine if an underdrain system is required. Structural Section: A qualified and licensed professional should complete a pavement structural analysis. Edge Restraints: Provide a concrete transition strip between any permeable and impermeable surface and around the perimeter of paver installations. Pedestrian Considerations: Provide signage to indicate prohibited activities that cause premature clogging. Maintenance Access: Provide adequate access for sweeping and/or vacuuming of surface. 2026-08-19 Item #12D Page 719 of 816
K-57 2023
Soo

PERMEABLE

PAVEMENT

SUBSURFACE
DESIGN

OPTIONS
(CONTINUED)
Reservoir layer with upturned underdrain
Reservoir layer with underdrain and impermeable liner
2026-08-19 Item #12D Page 720 of 816
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2026-08-19 Item #12D Page 721 of 816
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CHAPTER 3 Procedures and Design
Examples

3.1 INTRODUCTION
Implementing Green Infrastructure (GI) and Low Impact Development (LID) within the road right-ofway requires a number of considerations to create an amenity that is attractive while treating stormwater from the surrounding streets and sidewalks. Implementation of Green Streets features can be approached from evaluating the opportunities within each zone of the right-of-way: median, traveled lane, bike lane, shoulder, parkway, sidewalk/pathway, slopes and drainage easements. Each zone presents different opportunities, benefits, risks and technical design factors for GI and LID implementation to enhance stormwater quality within the right-of-way. Conducting a comprehensive inventory and assessment of site conditions is the crucial initial step for implementing GI and LID. The County LID Handbook inventory check list can be used to assist with identifying and evaluating a potential site for LID and to produce a list of opportunities and constraints. The LID concept from the EPA of “slow it down, spread it out, and soak it in” should be at the forefront in the planning stages of project evaluating the implementation of Green Streets design practices to control runoff and enhance water quality. 2026-08-19 Item #12D Page 722 of 816
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The following site design principles should be evaluated and implemented to “slow it down, spread it out, and soak it in”:
• Minimize the impervious footprint of the site by constructing streets and sidewalks to the minimum required widths.
• Minimize soil compaction in landscaped areas. Landscape with native or droughttolerant species. • Disconnect impervious surfaces by dispersing runoff from impervious surfaces to pervious areas. To be considered ‘disconnected’ impervious areas should be designed to drain to a pervious area at least one-half their size. • Design and construct tree wells, dispersion areas, biofiltration, and permeable pavements to effectively receive and infiltrate or retain runoff from impervious areas before it discharges to the storm drain or exits the right of way.

When green street design principles are employed over street design techniques that utilize conventional stormwater quality treatment techniques they have the potential to significantly reduce impervious areas and provide potential project cost savings.

Conventional Design Approach Green Street Design Approach - Impervious median and parking lane - Permeable median and parking lane - Biofiltration and stormwater vault in parkway - Tree wells and biofiltration in parkway GREEN STREET APPROACHDirect stormwater runoff from impervious roadway elements to: • Tree wells, dispersion areas, and biofiltration in the median
or parkway.
• Permeable pavement
surfaces located in the
median or parking lane.

Construct sidewalks and trails with permeable pavement or direct runoff to adjacent landscaped area.

CONSTRAINTSIn no way shall green streets LID features be designed to block sight distance for motorists from adjacent streets and driveways, create obstacles for pedestrians, impede the visibility and maintenance of traffic control devices and signs, and reduce or eliminate clear recovery area and minimum horizontal clearances from fixed objects. (Source: DDOT, 2014)
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3.2 DESIGN

PROCEDURE
QUALIFICATIONUnder the Municipal Separate Storm Sewer System (MS4) Permit for San Diego Region (Permit [Order No. R9-2013-0001]), the County may make Priority Development Project (PDP) Exemptions for projects redeveloping or retrofitting existing paved roads, streets, and alleys as “EPA Green Streets.” This is accomplished under an adopted Green Streets program by the County of San Diego and based in part on the EPA publication “Green Streets: Municipal Handbook, Managing Wet Weather with Green Infrastructure.”OPPORTUNITIES AND

CONSTRAINTS
• Conduct a comprehensive inventory and assessment of site conditions. • Evaluate each zone of the right-of-way for Green Street implementation opportunties:
median, traveled lane, shoulder, parkway, sidewalk/pathway, slopes and drainage easements. • Evaluate constraints including, but not limited to: right-of-way width, utilities, roadway geometry and slope, site distance, proximity to storm drain, maintenance access, pedestrian and vehicle safety, bike and parking lanes, etc.

DESIGN

CAPTURE

VOLUME/FLOW
RATE
• For volume based features () use the 24-hour, 85th percentile volume. For flow based features (swales) utilize the 24-hour, 85th percentile rainfall intensity (use CASQA method within Caltrans Basin Sizer).

TREATMENT
TRAIN
• Utilize a treatment train approach that connects and combines features to maximize water quality treatment within the Green Street. An example Green Street treatment train approach is provided in Section 3.6.

3.3 MEDIANSThe median presents an opportunity to implement green streets principles by use of Tree wells, biofiltration, or permeable pavements. The graphics below illustrate various green streets design concepts that can be utilized within the median.

Roadway before Green Streets Roadway with depressed median and bulb out planter at intersection
Conventional raised median curb,
impermeable surfacing and trees
Green street depressed median with
curb cuts and planter/swale
DESIGN

ELEMENTS
• Raised median:
- Plant low water use/drought tolerant trees and landscaping. - Install permeable pavement. • Depressed median: Utilize
roadway cross slope to direct stormwater runoff from impervious roadway elements to:- Tree wells - Planter boxes - Vegetated swale DESIGN

CONSIDERATIONS
• Vehicle safety • Median width and length • Roadway longitudinal and cross slope
• Structural integrity of adjacent
traveled way (design to prevent
subsurface infiltration or ponding under traveled way)
• Underdrain and overflow devices • Proximity of storm drain • Maintenance access • ‘Mid-block’ pedestrian crossing potential
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3.4 INTERSECTIONS

ROUNDABOUTS
The design elements and design considerations for roundabouts are similar to medians.

Aerial view of rural intersection
before roundabout
Aerial view of constructed roundabout
with permeable pavement and
biofiltration with connection to storm drain
Closeup view of same roundabout Street view of same roundabout DESIGN

ELEMENTS
• Raised section:
- Plant low water use/drought tolerant trees and landscaping. - Install permeable pavement. • Depressed section: Utilize
roadway cross slope to direct stormwater runoff from impervious roadway elements to:- Tree wells - Planter boxes - Vegetated swale DESIGN

CONSIDERATIONS
• Roadway geometrics • Structural integrity of adjacent traveled way to prevent
subsurface infiltration or ponding under traveled way
• Underdrain and overflow
devices
• Proximity of storm drain
• Maintenance access
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BULB-OUT AT INTERSECTION
The design elements and design considerations for bulb-outs are similar to curb extensions.

Bulb-outs provide traffic calming at intersections, increase pedestrian visibility, and decrease cross-walk lengths. Bulb-outs at intersections prevent motorists from parking too close to a cross-walk or from blocking a curb ramp. Motor vehicles parked too close to corners present a safety concern, since they block sight lines, obscure visibility of pedestrians and other vehicles, and make turning difficult for emergency vehicles and trucks. Bulb-outs are only appropriate where there is an on-street parking lane or shoulder and must not extend into bike lanes or travel lanes. The turning requirements of larger vehicles such as fire trucks and school buses require consideration in design.

Bulb-out planter box at intersection Bulb-out at intersection DESIGN

ELEMENTS
• Raised section:
- Plant low water use/drought tolerant Tree wells and landscaping - Install permeable pavement. • Depressed section: Utilize
roadway cross slope to direct stormwater runoff from impervious roadway elements to:- Tree wells - Planter boxes - Vegetated swale DESIGN

CONSIDERATIONS
• Appropriate only where there is
on-street parking or shoulder
• Roadway geometrics • Structural integrity of adjacent traveled way to prevent
subsurface infiltration or ponding under traveled way
• Underdrain and overflow
devices
• Proximity of storm drain
• Maintenance access
• Turning requirements for large
vehicles
• Bike lanes
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3.5 TRAVELED WAY, BIKE

LANE, AND SHOULDER

PERMEABLE

PAVEMENT
The use of permeable pavements within the traveled way and bike lanes of County maintained roads is not currently permitted. However, their use may be considered for low volume driving lanes in parking lots, private streets, alleys, and fire access roads. The use of permeable pavement in the shoulder/parking lane should be evaluated based upon the following design considerations listed to the left.

Conventional street with bike lane
and shoulder
Green street with permeable
pavement in parking lane
DESIGN

ELEMENTS
• Traveled Way and Bike Lane:
- Design lane widths to minimum allowable.
• Shoulder/Parking Lane:
- Utilize permeable pavement with edge restraint at interface with traveled way DESIGN

CONSIDERATIONS
• Permeable pavement not
acceptable in traveled way,
bike lane, and parkway
• Structural section design to
handle vehicle loading
• Shoulder utilization (with or
without parking, temporary use
during lane closures)
• Roadway geometrics • Hydrologic design
requirements (stone reservoir
depth and underdrain requirements)
• Design to maintain structural
integrity of adjacent traveled way with edge restraints and prevention of infiltration beneath traveled way section • Interrupt permeable pavement
at intersections
• Surrounding land use and
sediment sources
• Long term maintenance
• Pedestrian safety• Maintenance access
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CURB

EXTENSIONS
Curb extensions reduce overall street dimensions and provide traffic calming. Among other benefits, curb extensions provide added space for biofiltration. Curb extensions shall never encroach upon the traveled way or bike lanes. When existing tree roots are damaging adjacent curb, gutter, or pavement curb extensions provide an excellent opportunity to preserve the tree and provide green infrastructure. Careful survey of street parking impacts should be considered when locating curb extensions.

Curb extension with planter box
Curb extenstion with planter box
DESIGN

ELEMENTS
• Low water use/drought tolerant
trees and landscaping
• Permeable pavement • Planter boxes
DESIGN

CONSIDERATIONS
• Roadway geometrics • Structural integrity of adjacent traveled way to prevent
subsurface infiltration or ponding under traveled way
• Underdrain and overflow
devices
• Sight distance at intersection • Proximity of storm drain • Utility conflicts
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PARKWAY
DESIGN

ELEMENTS
• Landscape area:
- Tree wells - Planter boxes - Curb extensions - Bulb outs at intersections - Swales • Sidewalk or trail:
- Drain to adjacent landscaping - Drain to green street LID practice - Permeable pavement • Other areas:
- Filter Strip - Dispersion Area

3.6 PARKWAYThe parkway including the tree space, planting strip, sidewalk, pathway, and other areas has numerous opportunities for Green Street implementation. TREE WELLS
Existing Road Conceptual desgin with Tree wells, and
permeable sidewalk
Existing Road Reconstructed Road with Trees and
planter boxes
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PLANTER
BOXES
Before and After Concept Road retrofit with planter boxes and trees Planter Box with step out zone Planter box with step out zone

PARKWAY
DESIGN
CONSIDERATIONS• Roadway classification and
parkway width
• Location (urban or rural setting) • Tree type and spacing requirements
• Sidewalk or trail width
requirements
• Streetside parking requirements • Roadway and parkway horizontal and vertical geometrics (curves and longitudinal slope) • Pedestrian mobility and safety • Maintenance access • Interface with driveways • Utilities and appurtenant structure locations
• Hydrologic design requirements • Proximity of storm drain systems • Structural integrity of adjacent traveled way (utilize edge
restraints and prevent infiltration beneath roadway section) • Low water use/drought tolerant
Trees and landscaping
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SWALES
Swale adjacent to road Rock swale adjacent to road
Rock swale adjacent to road Swale adjacent to road
DESIGN

ELEMENTS
• Low water use/drought tolerant
landscaping
• Rock • Curb cuts and outlet design • Energy dissipation • Check dams DESIGN

CONSIDERATIONS
• Roadway geometrics • Structural integrity of adjacent traveled way to prevent
subsurface infiltration or ponding under traveled way
• Underdrain and overflow
devices
• Proximity of storm drain
• Pedestrian mobility aspects • Maintenance access
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SIDEWALKS AND

PATHWAYS
Permeable pavement sidewalk with
biofiltration planter in curb extension DG pathway with rock swale Pervious concrete sidewalk Porous asphalt pathway
DESIGN

ELEMENTS
a. Drain to adjacent landscaping or
adjacent LID facility
b. Permeable pavement DESIGN

CONSIDERATIONS
• Sidewalk width and ADA
requirements
• Public safety • Pedestrian mobility aspects • Maintenance access 2026-08-19 Item #12D Page 737 of 816
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OTHER

PARKWAY
AREAS
Swale outside of sidewalk and road Curb cuts with filter strip Dispersion Area Rock swale
DESIGN

ELEMENTS
• Low water use/drought tolerant
landscaping
• Swales • Dispersion areas • Vegetated filter strips
DESIGN

CONSIDERATIONS
• Available space • Vehicle and public safety • Structural integrity of adjacent traveled way to prevent
subsurface infiltration or ponding under traveled way
• Underdrain and overflow
devices
• Proximity of storm drain
• Maintenance access
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3.7 PUTTING IT
ALL

TOGETHER
This graphic shows a treatment train concept as an example of how several different techniques may be combined for Green Street implementation. 2026-08-19 Item #12D Page 739 of 816
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4.1 DESIGN AND

CONSTRUCTION
The goal of the County of San Diego (the County) Low Impact Development (LID) Program is to protect stormwater quality by preserving and simulating natural hydrologic functions through the use of stormwater planning and management techniques on a project site. Both public and private projects constructing in the ROW are required to retain stormwater to the maximum extent practicable. Designers must examine all uses of public space and place stormwater management where space and use allows. DPW is installing green infrastructure as part of regulated construction projects and retrofit projects to reduce stormwater runoff in more areas of the County. Green Street projects utilize green infrastructure techniques and may be constructed independently to improve watershed health, or as a part of other infrastructure improvement projects. These Green Street Guidelines are a planning tool intended to assist project engineers with identifying and selecting suitable Best Management Practices (BMPs) for their respective Green Infrastructure projects. Technical standards, including drawings, specifications, maintenance schedule, and plant list, can be found in the Green Street Standards document.

CHAPTER 4 Implementing Green Streets
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4.2 MAINTENANCE
Implementing green infrastructure and Low Impact Development (LID) practices requires maintenance to keep them attractive and functioning. Maintenance levels of care should be considered during the design phase and plants selected from the Green Streets Plant List according to the following levels: • Low level of care: Annual maintenance; no irrigation • Medium level of care: Quarterly maintenance; some water available • High level of care: Monthly maintenance; site is potentially irrigated San Diego County DPW is typically responsible for maintaining publicly-installed green infrastructure and LID facilities within their right-of-way. The final determination of maintenance responsibility is determined during project review. Private installations must have a maintenance covenant from the owner. Residents can help with maintenance by removing trash and weeds. Refer to the Green Streets Maintenance Schedule for frequency and detail of maintenance.

Type of Maintenance Dispersion Areas
and Biofiltration
Permeable
Pavement
Tree Space
Inspect after storms • •Remove trash/sediment/leaves • • •Clean inlets/outlets •Adjust mulch and/or stone •Water for establishment • •Weed/remove invasive species • •Prune (as needed) • •Replace mulch (3” depth) • •Street sweeper/vacuum (as needed) •

4.3 FUNDING
Funding mechanisms for Green Streets maintenance may include: • Community Service Districts • Home Owner’s Associations or other private sources 2026-08-19 Item #12D Page 741 of 816
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REFERENCES
Central Coast Low Impact Development Initiative, 2015:
http://www.centralcoastlidi.org/resources.php
City of Los Angeles – Green Streets and Green Alleys Design Guidelines Standards, 2009:
nacto.org/docs/usdg/green_streets_and_green_alleys_la.pdf County of San Diego – Low Impact Development Handbook, 2014:
sandiegocounty.gov/content/sdc/dpw/watersheds/susmp/lid County of San Diego – Standard Urban Stormwater Mitigation Plan Requirements for Development Applications, 2012: sandiegocounty.gov/dpw/watersheds/susmp/susmp
DDOT – Greening DC Streets, 2014:
ddot.dc.gov/GreenInfrastructure
Low Impact Development Center, Inc. - Low Impact Development Manual for Southern California, 2010:
https://www.casqa.org/resources/lid/socal-lid-manual
Montgomery County, MD - Environmental Site Design Implementation in Montgomery County, Maryland: Image Library,2011:
http://www.montgomeryplanning.org/environment/documents/esd_implementation_graph ics_201108.pdf
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Green Parking Lots
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K.2.3 Green Parking Lots Guidelines
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Green Parking
Lots Guidelines
A Guide to Green Parking Lots
Implementation in the County of San Diego
January 2019
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WHAT IS A
GREEN

PARKING
LOT
?
Pavement on parking lots can contribute to excess stormwater runoff and increased levels of pollutants in the County’s waterways. Green infrastructure reduces stormwater runoff and improves water quality. Green Parking Lots incorporate a wide variety of Green Infrastructure design elements including, but not limited to: trees, dispersion areas and biofiltration, and permeable pavement. The use of Green Parking Lots offers the capability of transforming a significant stormwater and pollutant source into an innovative treatment system. On April 1st, 2015 Governor Brown signed executive order B-29-15 setting the first mandatory statewide water restrictions. This order prohibits ornamental turf on public street medians, and requires a reduction in potable water use for irrigation. Green Parking Lots promote water conservation through the use of low water use and drought tolerant plants (xeriscape) and improving groundwater supplies through infiltration. Green infrastructure, unlike traditional “gray” infrastructure approaches to stormwater management, provides multiple benefits to communities. Planting more trees and landscaping in public spaces cleans the air, cools the land, provides more habitat for wildlife, adds green maintenance jobs, increases property values and promotes a better, healthier quality of life for County residents and visitors. This guide is to be used along with the County’s Green Parking Lots Standards. These Green Parking Lots measures, when implemented, will ensure the County remains a green community for many years to come. 2026-08-19 Item #12D Page 749 of 816
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TABLE OF

CONTENTS
CHAPTER 1 – INTRODUCTION TO
GREEN

PARKING
LOTS…………………………………………………K-80

1.6 INTRODUCTION

1.7 THE

NATURAL AND

DEVELOPED

ENVIRONMENT

1.8 GREENING

PARKING
LOTS

1.9 THE
COUNTY

ENVIRONMENT

1.10 PARKING
LOTS

CHAPTER
2 –
GREEN

PARKING
LOTS
STRATEGIES……………………………………………………….K-85

2.1 INTRODUCTION

2.2 TREES

2.3 TYPES OF

DISPERSION

AREAS AND

BIOFILTRATION

2.4 PLANTING
& IRRIGATION OF

DISPERSION

AREAS, BIOFILTRATION, TREES AND
OTHER
AREAS

2.5 TYPES OF

PERMEABLE

PAVEMENT

CHAPTER
3 –

PROCEDURES
&
DESIGN
EXAMPLES……………………………………………………….K-105

3.1 INTRODUCTION

3.2 SITE
DESIGN

PRINCIPLES

3.3 DESIGN

PROCEDURE

3.4 PUTTING IT
ALL

TOGETHER

CHAPTER
4 – IMPLEMENTING
GREEN

PARKING
LOTS…………………………………………………….K-117

4.1 DESIGN AND

CONSTRUCTION

4.2 MAINTENANCE
REFERENCES………………………………………………………………………………………………..K-115
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1.1 INTRODUCTION
These guidelines have been prepared to assist in the design and construction of parking lots projects for new or redeveloped parking lots. These Guidelines may also be used to assist in the design and construction of new or retrofit paved sidewalks, bicycle lanes, or trails.

A review of existing County policies has been performed and included in the accompanying Green Parking Lots Standards document that includes an addendum to the 2016 County of San Diego BMP Design Manual. The Green Parking Lots Standards publications include an addendum to the 2016 County of San Diego BMP Design Manual. The intent is to utilize the current standard drawings with suggested modifications where appropriate. Green Parking Lot configurations and locations presented in this guideline are schematic/conceptual in nature. The configurations (or locations) could be modified as long as the design and construction details are in conformance with the Green Parking Lots technical documents (i.e. – Green Parking Lots Supplement to the BMP Design Manual, Standard Drawings, Specifications, and Maintenance Schedule).

CHAPTER 1 Introduction to Parking Lots
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1.2 THE

NATURAL AND

DEVELOPED

ENVIRONMENT

NATURAL
AREAS
In areas such as meadows, thickets, woodlands, and parks, rain can soak into the ground and be used by plants. Trees and shrubs intercept rainfall and it slowly trickles down to the ground where it is absorbed by mulch and humus soil. Shaded areas are cooler, moister and provide wildlife habitat. Very little rainwater runs off the ground. Natural Area Diagram (Source: DDOT, 2014)
URBAN
AREAS
In urban areas, building rooftops, streets, alleys, sidewalks, and other paved surfaces are smooth and mostly impervious. Very little rain has a chance to soak into the ground. These paved urban areas are hotter and offer very little wildlife habitat. Most of the rain that falls in the urban areas quickly runs off impervious surfaces picking up pollutants and carrying them into storm drains. These flows quickly combine to create flash floods that degrade downstream waterways.

Urban Area Diagram
Urban Area Diagram
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1.3 GREENING

PARKING
LOTS
A Green Parking Lot includes Green Infrastructure (GI), incorporating elements found in natural areas into a parking lot area. GI is the living network that connects impervious areas to landscape areas, natural areas, and waterways. GI captures rainfall; cools buildings and pavement; and creates natural pathways for wildlife. GI includes Low Impact Development (LID) techniques, which mimic nature to capture and treat stormwater as close to the source as possible. When implemented, GI creates living green parking lots that capture, store, and infiltrate stormwater to treat it as a resource and improve the County environment.

Stormwater Diagram
(Source: DDOT, 2014)

STORMWATER

CAPTURE
Runoff from impervious surfacing
STORE
Store and retain captured runoff

INFILTRATE/EVAPOTRANSPIRE
Water is infiltrated into the ground,
evapotranspired by plants or drained
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1.4 THE
COUNTY

Watershed Divide
(Source: DDOT, 2014)
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(Source: County of San Diego Parking Design Manual)

PARKING
LOTS
Land within parking lots present a significant opportunity to reduce runoff and improve the urban environment through Green Infrastructure. This manual introduces techniques to install green infrastructure in areas within and around parking lots. This guide includes supplements to the BMP Design Manual, Standard Drawings, and specifications, and should be used to the maximum extent practicable for all public and private project design of parking lots.

CONCEPTUAL PARKING LOT DIAGRAM
(Source: County of San Diego, Parking Design Manual)
Early in the planning and design process careful consideration should be given to the location of existing and proposed utilities and appurtenances in the parking lot and their interaction with the proposed green parking lot measures. 2026-08-19 Item #12D Page 756 of 816
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2.1 INTRODUCTION
Green Parking Lots, including Green Infrastructure (GI), and Low Impact Development (LID) solutions are intended to be sustainable, attractive, and cost effective. The range of opportunities includes trees, landscape areas, dispersion areas, biofiltration, and permeable pavement. These strategies use natural processes to reduce the volume of runoff, peak flow, and pollutants. This chapter will focus on four (4) areas appropriate for use in the road right-of-way. TREESTrees are a powerful tool due to their ability to intercept water on leaves, slowly deliver it to the mulch and soil, absorb it through root systems, and transpire it as water vapor directly back to the atmosphere. DISPERSION AREAS
Dispersion areas disconnect impervious areas from directly running to the storm drain system. Dispersion areas use the natural functions of plants, mulch, and soils to remove pollutants and slow stormwater runoff.

The strategy uses storage, sediment capture, and biological processes to clean the water. These mimic processes that occur in nature before water reaches waterways.

BIOFILTRATION
Biofiltration facilities are vegetated surface water systems that filter water through vegetation, and soil or biofiltration soil media prior to discharge to the storm drain system. They also utilize shallow depressions to provide storage and evapotranspiration. PERMEABLE

CHAPTER
2 Green Parking Lots Strategies
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2.2 TREES
WHY
ARE
TREES IMPORTANT?
Trees make a parking lot feel welcoming, help manage stormwater, and reduce the urban heat island effect by providing shade. An urban heat island remains significantly warmer than the surrounding rural areas due to less vegetation. Trees promote air quality, natural habitat, the human environment, and well-being. Trees in parking lots are sometimes confined to small planting areas where they struggle to reach a mature size or live a long life. Through the use of Structural Soil, Structural Cell, or Suspended Sidewalk techniques, soil volumes and space for tree roots to grow uninhibited can be greatly increased. These techniques also allow for more water and air to reach the tree roots. 2026-08-19 Item #12D Page 759 of 816
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(Source: DDOT, 2014)
SOIL
VOLUME
SIZING
• Adequate soil space provides the
nutrients, water, air, and root space that trees need to have a long, healthy life. • The soil volume required depends on
the fully-grown tree size (generally two cubic feet of soil per one square foot of the tree’s mature drip line area). • Soil for trees should be three-feet
deep; the length and width must ensure the appropriate volume for the tree species and site.

OTHER

CONSIDERATIONS
• Provide as much open space as
possible for the tree to allow the tree to grow and access water. • Providing structural soils, suspended
sidewalks, or structural slabs to edges of paved areas encourages tree roots to extend further and into adjacent green areas. • Evaluate temporary and permanent
irrigation needs
• Evaluate utility locations and required
clearance.

DESIGN ISSUES• Maintenance Access: allow for
maintenance access
• Pedestrian Considerations: allow for
18-inch minimum setback from curb. Comply with ADA requirements. • Suspended sidewalks and structural
slabs/cells: may require evaluation by geotechnical and structural engineers • Tree Size: Evaluate tree size versus
the required parking lot dimensions.
• Tree Location: Refer to Parking
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TREES
–
WHAT’S
UNDERNEATH?
(Source: DDOT, 2014)
Note: Other options include suspended sidewalks and structural cells as shown on page 7.

PUTTING IT

TOGETHER
• Permeable Paver: Permeable
pavers allow water to infiltrate into the soil to be used by the trees. • Mulch: Shredded hardwood layer
to retain water and trap pollutants.
• Planting Soil: Uncompacted soil
mix allows root growth when used in open areas, with structural cells, or suspended sidewalks. • Structural Soil: Supports pavement
and allows root growth.
• Sand: Acts as a drainage layer for
excess stormwater (when needed).
• Uncompacted Subgrade: Existing
soil where stormwater may infiltrate.

WATER

TREES WITH

STORMWATER
In addition to large soil volumes, trees need sufficient water, air, and nutrients to be successful in the road right-ofway environment. Tree space design includes integrating opportunities for directing stormwater into the soil. See Water Efficient Landscape Design Manual for irrigation requirements. 2026-08-19 Item #12D Page 761 of 816
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2.3 TYPES OF

DISPERSION

AREAS AND

BIOFILTRATION
WHAT
ARE

DISPERSION

AREAS AND
BIOFILTRATION?
Dispersion Areas and Biofiltration are landscape systems that filter pollutants and sediment from runoff. The layers of plant material, mulch, planting media (a mix of soil, sand, and compost), and stone capture metals, nutrients, and bacteria that would otherwise flow into the surrounding creeks and rivers. The rainwater is held in the planting bed until it infiltrates into the ground or evaporates. The entire system can fit into small spaces, making it adaptable to tree spaces, planter boxes, and islands.

PLANTER
BOXES
Runoff follows the existing curb line and enters the facility through curb cuts. Excess runoff exits through the same curb cuts or into drains located in the planting area.

PARKING ISLANDS
Runoff follows the existing curb line and enters the
facility directly. Excess runoff flows through the system or into drain inlets.

SWALES
Runoff enters the facility directly or through curb cuts. Excess runoff flows through the system to a drainage outlet.

FILTER

STRIP/DISPERSION
AREA
Runoff enters the facility directly via sheet flow. Excess runoff flows through the system to a drain inlet downslope.
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PLANTER
BOX

WHERE TO
USE?
• Parking lot areas adjacent to
sidewalk/walkway/plaza area.
• Where trees and landscaping
are needed.

LIMITATIONS• Limited pedestrian access
across planter.

DESIGN ISSUESMaintenance Access: Allow for adequate maintenance access from parking lot. Pedestrian Considerations: Allow for minimum allowable sidewalk width. Consider trip hazards and fall protection. Comply with ADA requirements.

S
P
F
D
SEE
PAGES K-91-K-95
FOR

DETAILS
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K-101 2023

PARKING ISLANDS

WHERE TO
USE?
• Parking lots with islands. • For parking lot traffic calming. • Next to mature trees. LIMITATIONS• Do not disturb existing, mature trees and root systems.
• Ensure sight lines and turning
radii are preserved.

DESIGN ISSUES
Maintenance Access: Allow for adequate maintenance access from road. Pedestrian Considerations: Consider trip hazards and fall protection. Short fences or curbs prevent pedestrians from stepping into a recessed area. A 3:1 transition from the sidewalk to planter bottom is an alternative. Comply with ADA requirements. Parking: Consider trip hazards and adequate spacing in order to park.

SEE
PAGES K-91-K-95
FOR

DETAILS
(Source: DDOT, 2014)
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SWALE

ADJACENT TO

PARKING

WHERE TO
USE?
• In parking lots with zero
height curb or curb cuts.
• In parking lot areas with less
pedestrian use.

LIMITATIONS• Not suitable for narrow
island areas.

DESIGN ISSUESSlope and Check Dams: Swales are placed where runoff is flowing and optimally before catch basins that convey water from the parking lot to the drainage system. Swales may be built on moderate slopes with the use of check dams. Rock armoring or turf reinforcement mat may be required in steep areas with erosive velocities between check dams. Maintenance Access: Allow for adequate maintenance access from parking lot. Pedestrian Considerations: Limit pedestrian access to swale. Transition swale at intersections for pedestrian facilities. Comply with ADA requirements.

SEE
PAGES K-91-K-95
FOR

DETAILS
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K-104 2023

VEGETATED
FILTER

STRIP/DISPERSION
AREA

WHERE TO
USE?
• Where runoff can sheet flow into
filter strip area.
• Moderate slopes (less than 5%)
adjacent to impervious area of
treatment (parking lot).
• Rural areas.

LIMITATIONS• Not recommended on steep
slopes.
• Prone to rill formation.

DESIGN ISSUESMaintenance: Vegetated cover must be maintained to ensure that filter strips do not export sediment due to erosion of exposed ground. Slope: Maximum slopes in the direction of flow will be based upon drainage area size, soil type, vegetation cover, and slope length to prevent rill formation. Slopes less than 5% are preferred. Maintenance Access: Allow for adequate maintenance access from parking area. Pedestrian Considerations: Limit pedestrian access across filter strip to prevent formation of dirt pathways. Comply with ADA requirements. 2026-08-19 Item #12D Page 767 of 816
K-105 2023

DISPERSION

AREAS AND

BIOFILTRATION
–
WHAT’S
UNDERNEATH?
SOIL

The soil survey classified soil runoff potential into four hydrologic soil groups labeled A through D. Group A and B soils exhibit the greatest infiltration rates (unless soils are compacted during construction) and are generally best suited to stormwater percolation. The San Diego area, however, has a relatively high concentration of group C and D soils, which exhibit lower percolation rates that generally limit the use of infiltration-based stormwater management systems. Instead, dispersion areas and biofiltration facilities are often equipped with underdrains. Such a design provides for filtration of the water quality design event through a biofiltration soil media as well as incidental infiltration of low flows.Retaining a geotechnical engineer and conducting exploratory excavations at the site are highly recommended.

Consideration should be given to the effects of urbanization on the natural hydrologic soil group. If heavy equipment can be expected to compact the soil during construction, or if grading will mix the surface and subsurface soils, appropriate changes should be made in the soil group selected.

The NRCS hydrologic soil groups are defined as: • Group A soils have a high rate of percolation and a low runoff potential. The rate of water transmission is high; thus, runoff potential is low. Group A soils are generally referred to as sandy soils. • Group B soils have moderate percolation rates when thoroughly wet. These are chiefly soils that are moderately deep to deep, moderately well-drained to well-drained, and moderately coarse textured. Rate of water transmission is moderate. • Group C soils have a slow percolation rate when thoroughly wet. They are chiefly soils that have a layer impeding the downward movement of water, or they are moderately fine to fine-textured soils that have a slow infiltration rate. The rate of water transmission is slow. • Group D soils have very slow percolation rates when thoroughly wet. They are clays that have a high shrinkswell potential, soils that have a high permanent water table, soils that have a claypan or clay layer at or near the surface, or soils that are shallow over nearly impervious material. The rate of water transmission for group D soils is very slow. 2026-08-19 Item #12D Page 768 of 816
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HIGH INFILTRATION

PUTTING IT

COMMON

DESIGN ISSUES
Utilities: Utility lines should be avoided where necessary and allowed to coexist where possible.

HIGH INFILTRATION
Notes: 1. Geotextile per Geotechnical Engineer’s Recommendations. 2026-08-19 Item #12D Page 770 of 816
K-108 2023

MEDIUM INFILTRATION

PUTTING IT

TOGETHER
• Ponding Depth: Stores runoff
within the planting area prior to treatment.
• Mulch: Shredded hardwood layer
to retain water and trap pollutants.
• Biofiltration Soil Media: A specific
blend of soil, compost, and sand to retain and drain water and support plant growth. • Choker Layer: Sand and gravel to
prevent biofiltration soil media from migrating into the reservoir. • Reservoir Layer: Stone to hold
excess water until it infiltrates.
• Geotextile: Prevents existing soil
from migrating into the biofiltration soil media and stone reservoir layer. • Uncompacted Subgrade: Existing
soil where stormwater infiltrates.

COMMON

DESIGN ISSUES
Utilities: Utility lines should be avoided where necessary and allowed to coexist where possible.

MEDIUM INFILTRATION
Notes: 1. Geotextile per Geotechnical Engineer’s Recommendations. 2. Choker layer may be required depending the type of reservoir layer. 2026-08-19 Item #12D Page 771 of 816
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LOW INFILTRATION

PUTTING IT

TOGETHER
• Ponding Depth: Stores runoff
within the planting area prior to treatment.
• Overflow Riser: Pipe to capture
high water flow.
• Mulch: Shredded hardwood layer
to retain water and trap pollutants.
• Biofiltration Soil Media: A specific
blend of soil, compost, and sand to retain and drain water and support plant growth. • Choker Layer: Sand and gravel
to prevent biofiltration soil media from migrating into the reservoir. • Reservoir Layer: Stone to hold
excess water until it infiltrates.
• Underdrain: An underdrain is
required.
• Geotextile: Prevents existing soil
from migrating into the biofiltration soil media and stone reservoir layer. • Uncompacted Subgrade:

Existing soil where stormwater infiltrates.

COMMON

DESIGN ISSUES
Utilities: Utility lines should be avoided where necessary and allowed to coexist where possible.

LOW INFILTRATION
Notes: 1. Geotextile per Geotechnical Engineer’s Recommendations. 2. Choker layer may be required depending the type of reservoir layer. 2026-08-19 Item #12D Page 772 of 816
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NO INFILTRATION

PUTTING IT

TOGETHER
• Ponding Depth: Stores runoff
within the planting area prior to treatment.
• Overflow Riser: Pipe to capture
high water flow.
• Mulch: Shredded hardwood layer
to retain water and trap pollutants.
• Biofiltration Soil Media: A specific
blend of soil, compost, and sand to retain and drain water and support plant growth. • Choker Layer: Sand and gravel
to prevent biofiltration soil media from migrating into the reservoir. • Reservoir Layer: Stone to hold
excess water until it enters the underdrain.
• Underdrain: An underdrain is
required.
• Impermeable Liner: Prevents
infiltration and prevents existing soil from migrating into the biofiltration soil media and stone reservoir layer.

COMMON

DESIGN ISSUES
Utilities: Utility lines should be avoided where necessary and allowed to coexist where possible.

NO INFILTRATION
Notes: 1. Choker layer may be required depending the type of reservoir layer. 2026-08-19 Item #12D Page 773 of 816
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2.4 PLANTING
& IRRIGATION OF

DISPERSION
AREAS,

BIOFILTRATION, TREES, AND
OTHER
AREAS

PLANTING
DESIGN
Trees, dispersion areas, and biofiltration add a landscape amenity to the parking lot.

Trees, shrubs, grasses and perennials are used to create a diverse landscape suitable for the site conditions and neighborhood. Plants should be chosen based on the level of care expected at the facility. Planting design must be done to ensure sight lines are preserved for pedestrians, cyclists, and vehicles in the parking lot. Trees are an important component of a Green Parking Lot. Mature trees capture stormwater, provide shade, and cool pavement. Existing trees should be protected when possible in parking lot retrofit projects. Refer to the County of San Diego’s Water Efficient Landscape Design Manual and Low Impact Development Handbook for suitable plant species to use in dispersion areas and biofiltration. Also refer to the community right of way development standards for suitable plants within specific communities. IRRIGATION DESIGN
Irrigation design should comply with the County of San Diego’s Water Efficient Landscape Design Manual. PLANTING

CONSERVATION
State executive order B-29-15 requires mandatory statewide water restrictions. This order prohibits ornamental turf on public street medians, and requires a reduction in potable water use for irrigation. Low water use, drought tolerant, native plants should be used for Green Parking Lot applications. The use of reclaimed water is recommended to reduce the amount of potable water used for irrigation.2026-08-19 Item #12D Page 774 of 816 K-114 February 2023

2.5 TYPES OF

PERMEABLE

PAVEMENT

WHAT IS

PERMEABLE

CONCRETE
PAVERS
Unlike traditional pavers, there are gaps between each paver to allow water to flow between the pavers and into the base layer.

PERVIOUS

CONCRETE
Sands and “fines” are reduced in the concrete mix to allow water to flow through the pavement into a stone bed and eventually the ground.
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TYPES OF

PERMEABLE

PAVEMENT (CONTINUED)
POROUS

ASPHALT
Porous asphalt is very similar to traditional asphalt except that the sands or “fines” are reduced in the mix so water can move through the pavement.

POROUS
RUBBER
Made from recycled rubber and small stones, porous rubber works like pervious concrete, but can be installed over tree roots.

DECOMPOSED

GRANITE (DG)

BOARDWALK
Made from wood or composite, boardwalks may be used for pathways. Rain easily passes through the spaces between the boards to the soil below. 2026-08-19 Item #12D Page 776 of 816
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PERMEABLE

PUTTING IT

TOGETHER
• Permeable Surface:

Existing soil into which
stormwater infiltrates.
(Source: DDOT, 2014)
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K-117 February 2023

PERMEABLE

PAVEMENT

SUBSURFACE
DESIGN

OPTIONS
Reservoir layer only with no underdrain
Reservoir layer with underdrain

WHERE TO
USE?
• Pedestrian areas • Parking areas/stalls LIMITATIONS• Use in areas with little to no sediment production.

PERMEABLE

PAVEMENT

SUBSURFACE
DESIGN

OPTIONS (CONTINUED)
Reservoir layer with upturned underdrain
Reservoir layer with underdrain and impermeable liner
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CHAPTER 3 Procedures and Design
Examples

3.1 INTRODUCTION
Implementing Green Infrastructure (GI) and Low Impact Development (LID) within a parking lot requires a number of considerations to create an amenity that is attractive while treating stormwater from the surrounding streets and sidewalks. Implementation of Green Parking Lots features can be approached from evaluating the opportunities within each zone of the parking lot: traveled lane, parking stalls, islands, sidewalk/pathway, slopes and drainage easements. Each zone presents different opportunities, benefits, risks and technical design factors for GI and LID implementation to enhance stormwater quality. Conducting a comprehensive inventory and assessment of site conditions is the crucial initial step for implementing GI and LID. The County LID Handbook inventory check list can be used to assist with identifying and evaluating a potential site for LID and to produce a list of opportunities and constraints. The LID concept from the EPA of “slow it down, spread it out, and soak it in” should be at the forefront in the planning stages of project evaluating the implementation of Green Parking Lots design practices to control runoff and enhance water quality. 2026-08-19 Item #12D Page 780 of 816
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3.2 SITE
DESIGN

PRINCIPLES
The following site design principles should be evaluated and implemented to “slow it down, spread it out, and soak it in”:
• Minimize the impervious footprint of the site. • Minimize soil compaction in landscaped areas. Landscape with native or drought-tolerant species.
• Disconnect impervious surfaces by dispersing runoff from impervious surfaces to pervious areas. To be considered ‘disconnected’ impervious areas should be designed to drain to a pervious area at least one-half their size. • Design and construct trees, dispersion areas, biofiltration, and permeable pavements to effectively receive and infiltrate or retain runoff from impervious areas before it discharges to the storm drain or exits the right of way.

When Green Parking Lot design principles are employed over typical design techniques that utilize conventional stormwater quality treatment techniques they have the potential to significantly reduce impervious areas and provide potential project cost savings.

Conventional Design Approach Green Design Approach
- Conventional storm drain - Dispersion areas and biofiltration - Conventional pavement - Pervious pavement

GREEN PARKING LOT
SITE
DESIGN

APPROACH
Direct stormwater runoff from impervious parking lot elements to: • Trees, dispersion areas and biofiltration in islands or on
perimeter of parking lot.
• Permeable pavement
surfaces located in walkways
or parking stalls.
• Adjacent landscaped area
CONSTRAINTSIn no way shall green parking lots LID features be designed to block sight distance for motorists from adjacent streets and driveways, create obstacles for pedestrians, impede the visibility and maintenance of traffic control devices and signs, and reduce or eliminate clear recovery area and minimum horizontal clearances from fixed objects. 2026-08-19 Item #12D Page 781 of 816
K-121 February 2023
Continuous cross slope conveys the full aisle to an adjacent swale Crowned slope conveys half of each aisle to adjacent swale A curb inlet directs runoff into a
biofiltration planter
An overflow outlet conveys runoff
that exceeds the biofiltration area
capacity

GREEN PARKING LOTS
SITE
DESIGN

APPROACH
Grading and Drainage
Direct runoff to trees, biofiltration, swales, permeable pavement: • When designing large parking lots, break up and direct flows to multiple
LID features.
• Avoid compaction in biofiltration
areas during construction.

Inlets and Outlets
2 Direct runoff into, and out of
biofiltration areas. Proper placement
of inlets helps to spread runoff over the biofiltration planting areas, which slows the flow and reduces erosion. 3 Outlet, including overflow structures,
direct excess runoff to the storm drain system.
4 Avoid placing overflow structures
flush with soil to allow stormwater retention.
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A patterned steel grate inlet conveys flow under a pedestrian walkway Source: Central California Coast, Technical Assistance Memo, LID Parking Lots 2026-08-19 Item #12D Page 783 of 816 K-123 February 2023
Source: Central California Coast, Technical Assistance Memo, LID Parking Lots

GREEN PARKING LOTS
SITE
DESIGN

APPROACH
Parking Configuration
Parking configurations can be adapted to meet both parking and stormwater management needs by sizing biofiltration areas to fit compact and full sized parking stalls. Tree Considerations • Locate trees on side slope, above areas that pond
• Select trees that will tolerate
seasonally wet soils
• Do not specify trees with
invasive roots.
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3.3 DESIGN

PROCEDURE

GENERAL

REQUIREMENTS
• Green Parking Lots features will meet the requirements set forth in Section E.3.b.(3)(a)(iii) and (b) of the 2013 MS4 Permit.
• Many of the low impact development (LID) requirements for site design that were applicable only to Priority Development Projects under the 2007 MS4 Permit are applicable to all projects (Standard Projects and PDPs) under the MS4 Permit.

OPPORTUNITIES AND

CONSTRAINTS
• Conduct a comprehensive inventory and assessment of site conditions. • Evaluate each zone of the parking lot for implementation opportunities: traveled way, parking stalls, islands, sidewalk/pathway, slopes and drainage easements. • Evaluate constraints including, but not limited to: utilities, parking lot geometry and slope, site distance, proximity to storm drain, maintenance access, pedestrian and vehicle safety, etc.

DESIGN

CAPTURE

VOLUME/FLOW

RATE FOR

PRIORITY

DEVELOPMENT

PROJECTS
• The standard for storm water pollutant control (formerly treatment control) is retention of the 24-hour 85th percentile storm volume, defined as the event that has a precipitation total greater than or equal to 85 percent of all daily storm events larger than 0.01 inches over a given period of record in a specific area or location. • For situations where onsite retention of the 85th percentile storm volume is technically not feasible, biofiltration must be provided to satisfy specific “biofiltration standards”. These standards consist of a set of siting, selection, sizing, design and maintenance criteria that must be met for a BMP to be considered a “biofiltration BMP” – see Section 2.2.1 and Appendix F of the County BMP Design Manual.

TREATMENT
TRAIN
• Utilize a treatment train approach that connects and combines features to maximize water quality treatment within the Green Parking Lot. An example Green Parking Lot treatment train approach is provided in Section 3.6.

DOCUMENTATION• Document the design criteria, methodology, drainage areas/treatment areas, calculated volumes/flows, BMP selection, and maintenance requirements in the project Stormwater Management Plan and/or Drainage Report. 2026-08-19 Item #12D Page 785 of 816
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K-126 February 2023
Parking Islands The parking island presents an opportunity to implement GI principles by use of street trees, dispersion areas, biofiltration, or permeable pavements. The graphics below illustrate various design concepts that can be utilized within parking lot islands.

Conventional parking lot Green Parking Lot
Conventional parking lot Green Parking Lot Swale
DESIGN

ELEMENTS
• Raised Island:
- Plant low water use/drought tolerant street trees and landscaping. - Install permeable pavement. • Depressed Island: Utilize
roadway cross slope to direct stormwater runoff from impervious roadway elements to:- Trees - Planter Boxes - Vegetated Swale DESIGN

CONSIDERATIONS
• Vehicle safety • Island width and length • Parking lot longitudinal and cross slope
• Structural integrity of adjacent
traveled way (design to prevent
subsurface infiltration or ponding under traveled way)
• Underdrain and overflow devices • Proximity of storm drain • Maintenance access • Pedestrian crossing potential 2026-08-19 Item #12D Page 787 of 816
K-127 February 2023

PERMEABLE

PAVEMENT
The use of permeable pavements may be considered for walkways, low volume driving lanes in parking lots, driveways, and fire access roads.

Conventional parking lot with
Asphalt Concrete in stall
Green parking lot with permeable
pavement in parking stall
DESIGN

ELEMENTS
• Traveled Way:
- Design lane widths to minimum allowable.
• Shoulder/Parking Lane:
- Utilize permeable pavement with edge restraint at interface with traveled way DESIGN

CONSIDERATIONS
• Structural section design to
handle vehicle loading
• Parking space utilization (with or
without parking, temporary use
during lane closures)
• Parking lot geometrics • Hydrologic design requirements (stone reservoir depth and
underdrain requirements)
• Design to maintain structural
integrity of adjacent traveled way with edge restraints and prevention of infiltration beneath traveled way section • Interrupt permeable pavement at
intersections
• Surrounding land use and
sediment sources
• Long term maintenance
• Pedestrian safety• Maintenance access
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K-128 February 2023

PLANTER
BOXES
Planter Box with trees
Planter Box with trees
Biofiltration Planter Biofiltration with trees in Island DESIGN

CONSIDERATIONS
• Parking Lot layout • Location (urban or rural setting) • Parking Lot tree type and spacing requirements
• Sidewalk or path width
requirements
• Parking requirements • Parkway horizontal and vertical geometrics (curves and longitudinal slope)
• Pedestrian mobility and safety • Maintenance access • Interface with driveways • Utilities and appurtenant structure locations
• Hydrologic design requirements • Proximity of storm drain systems • Structural integrity of adjacent traveled way (utilize edge
restraints and prevent infiltration beneath roadway section) • Low water use/drought tolerant
street trees and landscaping
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K-129 February 2023
SWALES
Swale with trees
Swale with trees between parking
Bioswale adjacent to parking and
sidewalk
Swale in Island
DESIGN

ELEMENTS
• Low water use/drought tolerant
landscaping
• Rock • Curb cuts and outlet design • Energy dissipation • Check dams • DESIGN

CONSIDERATIONS
• Parking Lot geometrics • Structural integrity of adjacent traveled way to prevent
subsurface infiltration or ponding under traveled way
• Underdrain and overflow
devices
• Proximity of storm drain
• Pedestrian mobility aspects • Maintenance access
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SIDEWALKS/PATHWAYS/DRIVEWAYS
Permeable pavement sidewalk with
biofiltration DG pathway with rock swale
Pervious concrete sidewalk Permeable pavement driveway
DESIGN

ELEMENTS
- Drain to adjacent landscaping or
adjacent LID facility
- Permeable pavement SIDEWALK
DESIGN

CONSIDERATIONS
• Sidewalk width and ADA
requirements
• Public safety • Pedestrian mobility aspects • Maintenance access

DRIVEWAY

CONSIDERATIONS
• Permeable pavement may
require underdrain or overflow
storm drain system
• Not appropriate for use in areas
of high sediment loading (e.g. debris/soil from adjacent landscaping) 2026-08-19 Item #12D Page 791 of 816
K-131 February 2023

OUTSIDE OF

PARKING
AREAS
Swale outside of parking lot Curb cuts with filter strip/dispersion area DESIGN

ELEMENTS
• Low water use/drought tolerant
landscaping
• Swales • Vegetated filter strips
DESIGN

3.4 PUTTING IT ALL

TOGETHER
This graphic provides an example of how several different techniques may be combined for Green Parking Lot implementation. 2026-08-19 Item #12D Page 794 of 816
K-134 February 2023

4.1 DESIGN AND

CONSTRUCTION
The goal of the County of San Diego (the County) Low Impact Development (LID) Program is to protect stormwater quality by preserving and simulating natural hydrologic functions through the use of stormwater planning and management techniques on a project site. Both public and private projects constructing parking lots are required to retain stormwater to the maximum extent practicable. Designers must examine all uses of available space and place stormwater management where space and use allows. DPW is installing green infrastructure as part of regulated construction projects and retrofit projects to reduce stormwater runoff in more areas of the County. Green Parking Lots projects utilize green infrastructure techniques and may be constructed independently to improve watershed health, or as a part of other infrastructure improvement projects. These Green Parking Lots Guidelines are a planning tool intended to assist project engineers with identifying and selecting suitable Best Management Practices (BMPs) for their respective Green Infrastructure projects. Technical standards, including drawings, specifications, maintenance schedule, and plant list, can be found in the Green Parking Lots document. •

CHAPTER
4 Implementing Green Parking Lots
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4.2 MAINTENANCE
Implementing Green Infrastructure and Low Impact Development (LID) practices requires maintenance to keep them attractive and functioning. Maintenance levels of care should be considered during the design phase and plants selected from the County LID Manual or Water Efficient Landscape Design Manual according to the following levels:
• Low level of care: Annual maintenance; no irrigation
• Medium level of care: Quarterly maintenance; some water available • High level of care: Monthly maintenance; site is potentially irrigated San Diego County DPW is typically responsible for maintaining publiclyinstalled green infrastructure and LID facilities within their right-of-way. The final determination of maintenance responsibility is determined during project review. Private installations must have a maintenance covenant from the owner. Residents can help with maintenance by removing trash and weeds. Refer to the Green Parking Lots Maintenance Schedule for frequency and detail of maintenance.

Type of Maintenance Dispersion
Areas and
Biofiltration
Permeable
Pavement
Tree Space
Inspect after storms • •Remove trash/sediment/leaves • • •Clean inlets/outlets •Adjust mulch and/or stone •Water for establishment • •Weed/remove invasive species • •Prune (as needed) • •Replace mulch (3” depth) • •Street sweeper/vacuum (as needed) • 2026-08-19 Item #12D Page 797 of 816
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REFERENCES
Central California Coast Technical Assistance Memo, LID Parking Lots http://centralcoastlidi.org/uploads/LID%20Parking%20TAM_WEB_1.pdf County of San Diego – Best Management Practice Design Manual, 2016 http://www.sandiegocounty.gov/content/sdc/dpw/watersheds /DevelopmentandConstruction/BMP_Design_Manual.html
County of San Diego – Low Impact Development Handbook, 2014:
sandiegocounty.gov/content/sdc/dpw/watersheds/susmp/lid County of San Diego – Standard Urban Stormwater Mitigation Plan Requirements for Development Applications, 2012:
sandiegocounty.gov/dpw/watersheds/susmp/susmp
DDOT – Greening DC Streets, 2014:
ddot.dc.gov/GreenInfrastructure
City of Los Angeles – Green Streets and Green Alleys Design Guidelines Standards, 2009:
nacto.org/docs/usdg/green_streets_and_green_alleys_la.pdf Montgomery County, MD - Environmental Site Design Implementation in Montgomery County, Maryland: Image Library,2011:
http://www.montgomeryplanning.org/environment/documents /esd_implementation_graphics_201108.pdf
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C I T Y O F E N C I N I T A S B M P D E S I G N M A N U A L i February 2023
Glossary of Key Terms
50% Rule
Refers to an MS4 Permit standard for redevelopment PDPs (PDPs on previously developed sites) that defines whether the redevelopment PDP must meet storm water management requirements for the entire development or only for the newly created or replaced impervious surface. Refer to Section 1.7.

Aggregate
Hard, durable material of mineral origin typically consisting of gravel, crushed stone, crushed quarry or mine rock. Gradation varies depending on application within a BMP as bedding, filter course, or storage.

Aggregate Storage
Layer
Layer within a BMP that serves to provide a conduit for conveyance, detention storage, infiltration storage, saturated storage, or a combination thereof.

Alternative Compliance
Programs
A program that allows PDPs to participate in an offsite mitigation project in lieu of implementing the onsite structural BMP performance requirements required under the MS4 Permit. Refer to Section 1.8 for more information on alternative compliance programs.

Bed Sediment
The part of the sediment load in channel flow that moves along the bed by sliding or saltation, and part of the suspended sediment load, that principally constitutes the channel bed.

Bedding Aggregate used to establish a foundation for structures such as pipes, manholes, and pavement.

Biodegradation Decomposition of pollutants by biological means.

Biofiltration BMPs
Biofiltration BMPs are shallow basins filled with treatment media and drainage rock that treat storm water runoff by capturing and detaining inflows prior to controlled release through minimal incidental infiltration, evapotranspiration, or discharge via underdrain or surface outlet structure. Treatment is achieved through filtration, 2026-08-19 Item #12D Page 800 of 816

C I T Y O F E N C I N I T A S B M P D E S I G N M A N U A L Glossary of Key Terms
ii February 2023
sedimentation, sorption, biochemical processes and/or vegetative uptake. These BMPs must be sized to:[a] Treat 1.5 times the DCV not reliably retained onsite, OR[b] Treat the DCV not reliably retained onsite with a flow-thru design that has a total volume, including pore spaces and pre-filter detention volume, sized to hold at least 0.75 times the portion of the DCV not reliably retained onsite. (See Section 5.5.3 and Appendix B.5 for illustration and additional information).

Biofiltration Treatment Treatment from a BMP meeting the biofiltration standard.

Biofiltration with
Partial Retention BMPs
Biofiltration with partial retention BMPs are shallow basins filled with treatment media and drainage rock that manage storm water runoff through infiltration, evapotranspiration, and biofiltration. Partial retention is characterized by a subsurface stone infiltration storage zone in the bottom of the BMP below the elevation of the discharge from the underdrains. The discharge of biofiltered water from the underdrain occurs when the water level in the infiltration storage zone exceeds the elevation of the underdrain outlet. (See Section 5.5.2.1 for illustration and additional information).

Bioretention BMPs
Vegetated surface water systems that filter water through vegetation and soil, or engineered media prior to infiltrating into native soils.

Bioretention BMPs in this manual retain the entire DCV prior to overflow to the downstream conveyance system. (See Section 5.5.1.2 for illustration and additional information).

BMP
A procedure or device designed to minimize the quantity of runoff pollutants and / or volumes that flow to downstream receiving water bodies. Refer to Section 2.2.2.1.

BMP Sizing Calculator
An on-line tool that was developed under the 2007 MS4 Permit to facilitate the sizing factor method for designing flow control BMPs for hydromodification management. The BMP Sizing Calculator has been discontinued as of June 30, 2014.

Cistern A vessel for storing water. In this manual, a cistern is typically a rain barrel, tank, vault, or other artificial reservoir.
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C I T Y O F E N C I N I T A S B M P D E S I G N M A N U A L Glossary of Key Terms
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Coarse Sediment Yield
Area
A GLU with coarse-grained geologic material (material that is expected to produce greater than 50% sand when weathered). See the following terms modifying coarse sediment yield area: critical, potential critical.

Compact Biofiltration
BMP
A biofiltration BMP, either proprietary or non-proprietary in origin, that is designed to provide storm water pollutant control within a smaller footprint than a typical biofiltration BMP, usually through use of specialized media that is able to efficiently treat high storm water inflow rates.

Conditions of Approval
Requirements a jurisdiction may adopt for a project in connection with a discretionary action (e.g., issuance of a use permit). COAs may include features to be incorporated into the final plans for the project and may also specify uses, activities, and operational measures that must be observed over the life of the project.

Contemporary Design
Standards
This term refers to design standards that are reasonably consistent with the current state of practice and are based on desired outcomes that are reasonably consistent with the context of the MS4 Permit and Model BMP Design Manual. For example, a detention basin that is designed solely to mitigate peak flow rates would not be considered a contemporary water quality BMP design because it is not consistent with the goal of water quality improvement. Current state of the practice recognizes that a drawdown time of 24 to 72 hour is typically needed to promote settling. For practical purposes, design standards can be considered “contemporary” if they have been published within the last 10 years, preferably in California or Washington State, and are specifically intended for storm water quality management.

Continuous Simulation
Modeling
A method of hydrological analysis in which a set of rainfall data (typically hourly for 30 years or more) is used as input, and a continuous runoff hydrograph is calculated over the same time period.

Continuous simulation models typical track dynamic soil and storage conditions during and between storm events. The output is then analyzed statistically for the purposes of comparing runoff patterns under different conditions (for example, pre- and post-developmentproject). 2026-08-19 Item #12D Page 802 of 816

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Copermittees See Jurisdiction.

Critical Channel Flow
(Qc)
The channel flow that produces the critical shear stress that initiates bed movement or that erodes the toe of channel banks. When measuring Qc, it should be based on the weakest boundary material – either bed or bank.

Critical Coarse
Sediment Yield Areas
A GLU with coarse-grained geologic material and high relative sediment production, where the sediment produced is critical to the receiving stream (a source of bed material to the receiving stream). See also: potential critical coarse sediment yield area.

Critical Shear Stress The shear stress that initiates channel bed movement or that erodes the toe of channel banks. See also critical channel flow.

DCV
A volume of storm water runoff produced from the 85th percentile, 24-hour storm event. See Section 2.2.2.2.

De Minimis DMA
De minimis DMAs are very small areas that are not considered to be significant contributors of pollutants, and are considered not practicable to drain to a BMP. See Section 5.2.2.

Depth
The distance from the top, or surface, to the bottom of a BMP component.

Detention Temporarily holding back storm water runoff via a designed outlet (e.g., underdrain, orifice) to provide flow rate and duration control.

Detention Storage Storage that provides detention as the outflow mechanism.

Development Footprint The limits of all grading and ground disturbance, including landscaping, associated with a project.

Development Project
Construction, rehabilitation, redevelopment, or reconstruction of any public or private projects. Includes both new development and redevelopment. Also includes whole of the action as defined by CEQA. See Section 1.3.

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To qualify as a direct discharge, the discharge elevation from the project site outfall must be at or below either the normal operating water surface elevation or the reservoir spillway elevation, and properly designed energy dissipation must be provided. “Direct discharge” may be more specifically defined by each municipality.

Direct Infiltration
Infiltration via methods or devices, such as dry wells or infiltration trenches, designed to bypass the mantle of surface soils that is unsaturated and more organically active and transmit runoff directly to deeper subsurface soils.

DMAs See Section 3.3.3.

Drawdown Time
The time required for a storm water detention or infiltration facility to drain and return to the dry-weather condition. For detention facilities, drawdown time is a function of basin volume and outlet orifice size.

For infiltration facilities, drawdown time is a function of basin volume and infiltration rate.

Enclosed Embayments
(Enclosed Bays)
Enclosed bays are indentations along the coast that enclose an area of oceanic water within distinct headlands or harbor works. Enclosed bays include all bays where the narrowest distance between the headlands or outermost bay works is less than 75 percent of the greatest dimension of the enclosed portion of the bay. Enclosed bays do not include inland surface waters or ocean waters. In San Diego:

Mission Bay and San Diego Bay.

Environmentally
Sensitive Areas (ESAs)
Areas that include but are not limited to all Clean Water Act Section 303(d) impaired water bodies; areas designated as Areas of Special Biological Significance by the State Water Board and SDRWQCB; State Water Quality Protected Areas; water bodies designated with the RARE beneficial use by the State Water Board and SDRWQCB; and any other equivalent environmentally sensitive areas which have been identified by the Copermittees.

Filter Course
Aggregate used to prevent particle migration between two different materials when storm water runoff passes through.
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Filter Fabric
A permeable textile material, also termed a non-woven geotextile, that prevents particle migration between two different materials when storm water runoff passes through.

Filtration Controlled seepage of storm water runoff through media, vegetation, or aggregate to reduce pollutants via physical separation.

Flow Control Control of runoff rates and durations as required by the HMP.

Flow Control BMP
A structural BMP designed to provide control of post-project runoff flow rates and durations for the purpose of hydromodification management.

Flow-thru Treatment Treatment from a BMP meeting the flow-thru treatment control standard.

Flow-Thru Treatment
BMPs
Flow-thru treatment control BMPs are structural, engineered facilities that are designed to remove pollutants from storm water runoff using treatment processes that do not incorporate significant biological methods. Flow-thru BMPs include vegetated swales, media filters, sand filters, and dry extended detention basins. (See Section 5.5.4 for illustration and additional information).

Forebay
An initial storage area at the entrance to a structural BMP designed to trap and settle out solid pollutants such as sediment in a concentrated location, to provide pre-treatment within the structural BMP and facilitate removal of solid pollutants during maintenance operations.

Full Infiltration Infiltration of a storm water runoff volume equal to the DCV.

Geomorphic
Assessment
A quantification or measure of the changing properties of a stream channel.

Geomorphically
Significant Flows
Flows that have the potential to cause, or accelerate, stream channel erosion or other adverse impacts to beneficial stream uses. The range of geomorphically significant flows was determined as part of the development of the March 2011 Final HMP, and has not changed under the 2013 MS4 Permit. However, under the 2013 MS4 Permit, Q2 and Q10 must be based on the pre-development condition rather than the pre-project condition, meaning that no pre-project 2026-08-19 Item #12D Page 805 of 816

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impervious area may be considered in the computation of predevelopment Q2 and Q10.

GLUs
Classifications that provide an estimate of sediment yield based upon three factors: geology, hillslope, and land cover. GLUs are developed based on the methodology presented in the SCCWRP Technical Report 605 titled “Hydromodification Screening Tools: GIS-Based Catchment Analyses of Potential Changes in Runoff and Sediment Discharge” (SCCWRP, 2010).

Gross Pollutants
In storm water, generally litter (trash), organic debris (leaves, branches, seeds, twigs, grass clippings), and coarse sediments (inorganic breakdown products from soils, pavement, or building materials).

Harvest and Use BMP
Harvest and use (aka rainwater harvesting) BMPs capture and store storm water runoff for later use. These BMPs are engineered to store a specified volume of water and have no design surface discharge until this volume is exceeded. (See Section 5.5.1.1 for illustration and additional information).

HMP
A plan implemented by the Copermittees so that post-project runoff shall not exceed estimated pre-development rates and/or durations by more than 10%, where increased runoff would result in increased potential for erosion or other adverse impacts to beneficial uses. The March 2011 Final HMP and the updated MS4 Permit are the basis of the flow control requirements of this manual.

Hungry Water
Also known as "sediment-starved" water, "hungry" water refers to channel flow that is hungry for sediment from the channel bed or banks because it currently contains less bed material sediment than it is capable of conveying. The “hungry water” phenomenon occurs when the natural sediment load decreases and the erosive force of the runoff increases as a natural counterbalance, as described by Lane’s Equation.

Hydraulic Head
Energy represented as a difference in elevation, typically as the difference between the inlet and outlet water surface elevation for a BMP.
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Hydraulic Residence
Time
The length of time between inflow and outflow that runoff remains in a BMP.

Hydrologic Soil Group Classification of soils by the Natural Resources Conservation Service (NRCS) into A, B, C, and D groups according to infiltration capacity.

Hydromodification
The change in the natural watershed hydrologic processes and runoff characteristics (i.e., interception, infiltration, overland flow, interflow and groundwater flow) caused by urbanization or other land use changes that result in increased stream flows and sediment transport.

In addition, alteration of stream and river channels, installation of dams and water impoundments, and excessive stream-bank and shoreline erosion are also considered hydromodification, due to their disruption of natural watershed hydrologic processes.

Hydromodification
Management BMP
A structural BMP for the purpose of hydromodification management, either for protection of critical coarse sediment yield areas or for flow control. See also flow control BMP.

Impervious Surface Any material that prevents or substantially reduces infiltration of water into the soil.

Infeasible
As applied to BMPs, refers to condition in which a BMP approach is not practicable based on technical constraints specific to the site, including by not limited to physical constraints, risks of impacts to environmental resources, risks of harm to human health, or risk of loss or damage to property. Feasibility criteria are provided in this manual.

Infiltration
In the context of LID, infiltration is defined as the percolation of water into the ground. Infiltration is often expressed as a rate (inches per hour), which is determined through an infiltration test. In the context of non-storm water, infiltration is water other than wastewater that enters a sewer system (including sewer service connections and foundation drains) from the ground through such means as defective pipes, pipe joints, connections, or manholes. Infiltration does not include, and is distinguished from, inflow [40 CFR 35.2005(20)].

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specified volume of water and have no design surface discharge (underdrain or outlet structure) until this volume is exceeded. These types of BMPs may also support evapotranspiration processes, but are characterized by having their most dominant volume losses due to infiltration. (See Section 5.5.1.2 for illustration and additional information).

Jurisdiction
The term “jurisdiction” is used in this manual to refer to individual copermittees who have independent responsibility for implementing the requirements of the MS4 Permit.

LID
A storm water management and land development strategy that emphasizes conservation and the use of onsite natural features integrated with engineered, small-scale hydrologic controls to more closely reflect pre-development hydrologic functions. See Site Design.

Lower Flow Threshold
The lower limit of the range of flows to be controlled for hydromodification management. The lower flow threshold is the flow at which erosion of sediment from the stream bed or banks begins to occur. See also critical channel flow. For the San Diego region, the lower flow threshold shall be a fraction (0.1, 0.3, or 0.5) of the predevelopment 2-year flow rate based on continuous simulation modeling (0.1Q2, 0.3Q2, or 0.5Q2).

Media Storm water runoff pollutant treatment material, typically included as a permeable constructed bed or container (cartridge) within a BMP.

MEP
Refer to the definition in the MS4 Permit. [Appendix C, Definitions, Page C-6]
National Pollutant
Discharge Elimination
System
The national program for issuing, modifying, revoking and reissuing, terminating, monitoring and enforcing permits, and imposing and enforcing pretreatment requirements, under Sections 307, 318, 402, and 405 of the Clean Water Act.

New Development
Land disturbing activities; structural development, including construction or installation of a building or structure, the creation of impervious surfaces; and land subdivision.
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O&M
Requirements in the MS4 Permit to inspect structural BMPs and verify the implementation of operational practices and preventative and corrective maintenance in perpetuity.

Partial Infiltration Infiltration of a storm water runoff volume less than the DCV.

Partial Retention
Partial retention category is defined by structural measures that incorporate both infiltration (in the lower treatment zone) and biofiltration (in the upper treatment zone).

PDPs
As defined by the MS4 Permit provision E.3.b, land development projects that fall under the planning and building authority of the Copermittee for which the Copermittee must impose specific requirements in addition to those required of Standard Projects. Refer to Section 1.4 to determine if your project is a PDP.

PDPs with only
Pollutant Control
Requirements
PDPs that need to meet Source Control, Site Design and Pollutant Control Requirements (but are exempt from Hydromodification Management Requirements).

PDPs with Pollutant
Control and
Hydromodification
Management
Requirements
PDPs that need to meet Source Control, Site Design, Pollutant Control and Hydromodification Management Requirements.

Point of Compliance

1. For channel screening and determination of low flow threshold: the point at which collected storm water from a development is delivered from a constructed or modified drainage system into a natural or unlined channel. POC for channel screening may be located onsite or offsite, depending on where runoff from the project meets a natural or un-lined channel. 2. For flow control: the point at which predevelopment and post-development flow rates and durations will be compared. POC for flow control is typically onsite. A project may have a different POC for channel screening vs. POC for flow control if runoff from the project site is conveyed in hardened systems from the project site boundary to the natural or un-lined channel.

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Pollution Prevention
Pollution prevention is defined as practices and processes that reduce or eliminate the generation of pollutants, in contrast to source control BMPs, treatment control BMPs, or disposal.

Post-Project Hydrology
Flows, Volumes
The peak runoff flows and runoff volume anticipated after the project has been constructed taking into account all permeable and impermeable surfaces, soil and vegetation types and conditions after landscaping is complete, detention or retention basins or other water storage elements incorporated into the site design, and any other site features that would affect runoff volumes and peak flows.

Potential Critical
Coarse Sediment Yield
Area
A GLU with coarse-grained geologic material and high relative sediment production, as defined in the Regional WMAA. The Regional WMAA identified GLUs as potential critical coarse sediment yield areas based on slope, geology, and land cover. GLU analysis does not determine whether the sediment produced is critical to the receiving stream (a source of bed material to the receiving stream) therefore the areas are designated as potential.

Pre-Development
Runoff Conditions
Approximate flow rates and durations that exist or existed onsite before land development occurs. For new development projects, this equates to runoff conditions immediately before any new project disturbance or grading. For redevelopment projects, this equates to runoff conditions from the project footprint assuming infiltration characteristics of the underlying soil, and existing grade. Runoff coefficients of concrete or asphalt must not be used. A redevelopment PDP must use available information pertaining to existing underlying soil type and onsite existing grade to estimate pre-development runoff conditions.

Pre-Project Condition
The condition prior to any project work or the existing condition.

Note that pre-project condition and pre-development condition will not be the same for redevelopment projects.

Pretreatment
Removal of gross solids, including organic debris and coarse sediment, from runoff to minimize clogging and increase the effectiveness of BMPs.
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Project Area
All areas proposed by an applicant to be altered or developed, plus any additional areas that drain on to areas to be altered or developed. Also see Section 1.3.

Project Submittal
Documents submitted to a jurisdiction or Copermittee in connection with an application for development approval and demonstrating compliance with MS4 Permit requirements for the project. Specific requirements vary from municipality to municipality.

Proprietary BMP
BMP designed and marketed by private business for treatment of storm water. Check with City Engineer prior to proposing to use a proprietary BMP.

Receiving Waters See Waters of the United States.

Redevelopment
The creation and/or replacement of impervious surface on an already developed site. Examples include the expansion of a building footprint, road widening, and the addition to or replacement of a structure. Replacement of impervious surfaces includes any activity where impervious material(s) are removed, exposing underlying soil during construction. Redevelopment does not include routine maintenance activities, such as trenching and resurfacing associated with utility work; pavement grinding; resurfacing existing roadways, sidewalks, pedestrian ramps, or bike lanes on existing roads; and routine replacement of damaged pavement, such as pothole repair.

Retrofitting
Storm water management practice put into place after development has occurred in watersheds where the practices previously did not exist or are ineffective. Retrofitting of developed areas is intended to improve water quality, protect downstream channels, reduce flooding, or meet other specific objectives. Retrofitting developed areas may include, but is not limited to replacing roofs with green roofs, disconnecting downspouts or impervious surfaces to drain to pervious surfaces, replacing impervious surfaces with pervious surfaces, installing rain barrels, installing rain gardens, and trash area enclosures.

Regional Water Quality
Control Board
(SDRWQCB)
California RWQCBs are responsible for implementing pollution control provisions of the Clean Water Act and California Water Code within their jurisdiction. There are nine California RWQCBs. 2026-08-19 Item #12D Page 811 of 816

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Retention (Retention
BMPs)
A category of BMP that does not have any service outlets that discharge to surface water or to a conveyance system that drains to surface waters for the design event (i.e. 85th percentile 24-hour).

Mechanisms used for storm water retention include infiltration, evapotranspiration, and use of retained water for non-potable or potable purposes.

Saturated Storage
Storage that provides a permanent volume of water at the bottom of the BMP as an anaerobic zone to promote denitrification and/or thermal pollution control. Also known as internal water storage or a saturation zone.

Self-mitigating Areas
A natural, landscaped, or turf area that does not generate significant pollutants and drains directly offsite or to the public storm drain system without being treated by a structural BMP. See Section 5.2.1.

Self-retaining DMA via
Qualifying Site Design
BMPs
An area designed to retain runoff to fully eliminate storm water runoff from the 85th percentile 24 hours storm event; See Section 5.2.3.

SIC
A Federal government system for classifying industries by 4-digit code.

It is being supplanted by the North American Industrial Classification System but SIC codes are still referenced by the Regional Water Board in identifying development sites subject to regulation under the National Pollutant Discharge Elimination System permit. Information and an SIC search function are available at
https://www.osha.gov/pls/imis/sicsearch.html
Significant
Redevelopment
Redevelopment that meets the definition of a “PDP” in this manual.

See Section 1.4.

Site Design
A storm water management and land development strategy that emphasizes conservation of natural features and the use of onsite natural features integrated with engineered, small-scale hydrologic controls to more closely reflect pre-development hydrologic functions.

Sizing Factor Method
A method for designing flow control BMPs for hydromodification management using sizing factors developed from unit area continuous simulation models.
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Sorption Physical and/or chemical process where pollutants are taken out of runoff through attachment to another substance.

Source Control
Land use or site planning practices, or structures that aim to prevent runoff pollution by reducing the potential for contamination at the source of pollution. Source control BMPs minimizes the contact between pollutants and storm water runoff. Examples include roof structures over trash or material storage areas, and berms around fuel dispensing areas. Source control BMPs are described within this manual.

Standard Project Any development project that is not defined as a PDP by the MS4 Permit.

Storm Water
Conveyance System
A conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, manmade channels, or storm drains): (i) Owned or operated by a State, city, town, borough, county, parish, district, association, or other public body (created by or pursuant to State law) having jurisdiction over disposal of sewage, industrial wastes, storm water, or other wastes, including special districts under State law such as a sewer district, flood control district or drainage district, or similar entity, or an Indian tribe or an authorized Indian tribal organization, or designated and approved management agency under section 208 of the Clean Water Act that discharges to waters of the United States; (ii) Designated or used for collecting or conveying storm water; (iii) Which is not a combined sewer; (iv) Which is not part of the Publicly Owned Treatment Works as defined at 40 CFR 122.26.

Storm Water Pollutant
Control BMP
A category of storm water management requirements that includes treatment of storm water to remove pollutants by measures such as retention, biofiltration, and/or flow-thru treatment control, as specified in this manual. Also called a Pollutant Control BMP.

Structural BMP
Throughout the manual, the term "structural BMP" is a general term that encompasses the pollutant control BMPs and hydromodification BMPs required for PDPs under the MS4 Permit. A structural BMP may be a pollutant control BMP, a hydromodification management BMP, or an integrated pollutant control and hydromodification 2026-08-19 Item #12D Page 813 of 816

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management BMP. Structural BMPs as defined in the MS4 Permit are:
a subset of BMPs which detains, retains, filters, removes, or prevents the release of pollutants to surface waters from development projects in perpetuity, after construction of a project is completed.

Subgrade In-situ soil that lies underneath a BMP.

Tributary Area
The total surface area of land or hardscape that contributes runoff to the BMP; including any offsite or onsite areas that comingles with project runoff and drains to the BMP. Refer to Section 3.3.3 for additional guidance Also termed the drainage area or catchment area.

Unified BMP Design
Approach
This term refers to the standardized process for site and watershed investigation, BMP selection, BMP sizing, and BMP design that is outlined and described in this manual with associated appendices and templates. This approach is considered to be “unified” because it represents a pathway for compliance with MS4 Permit requirements that is anticipated to be reasonably consistent across the local jurisdictions in San Diego County. In contrast, applicants may choose to take an alternative approach where they demonstrate to the satisfaction of the Copermittee, in their submittal, compliance with applicable performance standards without necessarily following the process identified in this manual.

Upper Flow Threshold
The upper limit of the range of flows to be controlled for hydromodification management. For the San Diego region, the upper flow threshold shall be the pre-development 10-year flow rate (Q10) based on continuous simulation modeling.

Vactor
Refers to a sewer or storm drain cleaning truck equipped to remove materials from sewer or storm drain pipes or structures, including some storm water BMPs.

Vector
An animal or insect capable of transmitting the causative agent of human disease. An example of a vector in San Diego County that is of concern in storm water management is a mosquito.

Water Quality
Improvement Plan
Copermittees are required to develop a Water Quality Improvement Plan for each Watershed Management Area in the San Diego Region.

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Copermittees’ jurisdictional runoff management programs towards achieving the outcome of improved water quality in MS4 discharges and receiving waters. WQIPs requirements are defined in the MS4 Permit provision B.

Waters of the United
States
Surface bodies of water, including naturally occurring wetlands, streams (perennial, intermittent, and ephemeral (exhibiting bed, bank, and ordinary high water mark)), creeks, rivers, reservoirs, lakes, lagoons, estuaries, harbors, bays and the Pacific Ocean which directly or indirectly receive discharges from storm water conveyance systems.

The Copermittee shall determine the definition for wetlands and the limits thereof for the purposes of this definition, which shall be as protective as the Federal definition utilized by the United States Army Corps of Engineers and the United States Environmental Protection Agency. Constructed wetlands are not considered wetlands under this definition, unless the wetlands were constructed as mitigation for habitat loss. Other constructed BMPs are not considered receiving waters under this definition, unless the BMP was originally constructed within the boundaries of the receiving waters. Also see MS4 permit definition.

Watershed
Management Area
The ten areas defined by the SDRWQCB in Regional MS4 Permit provision B.1, Table B-1. Each Watershed Management Area is defined by one or more Hydrologic Unit, major surface water body, and responsible Copermittee.

Watershed
Management Area
Analysis
For each Watershed Management Area, the Copermittees have the option to perform a WMAA for the purpose of developing watershedspecific requirements for structural BMP implementation. Each WMAA includes: GIS layers developed to provide physical characteristics of the watershed management area, a list of potential offsite alternative compliance projects, and areas exempt from hydromodification management requirements.
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CITY OF ENCINITAS STORMWATER BMP DESIGN MANUAL
Manual Revisions Page R-1

SUMMARY OF PROPOSED REVISIONS
Below are the proposed revisions made to the 2023 BMP Design Manual Section Revision
Throughout References to “Basic Projects” have been removed xii Removed Structural BMP requirement reference for Standard Projects

1.4.3 Removed section 1.4.3.1 in full to remain consistent with industry standards.

1.5 Updated Table 1-4 to reflect the correct applicability specifications for all project types 2 Updated Table 2-2-1 to reflect the correct performance standards for all project types

3.3 Updated Table 3-3-1 to reflect the correct applicability for all project types

3.4 Updated Table 3-3-2 to reflect the correct applicability for all project types Appendix A.1
Updated Step 2 to reflect current applicability standards.

Removed Step 5
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Encinitas City CouncilAugust 19, 2026

Encinitas City Council
August 19, 2026