Item B- SP21-0003_Staff Report_Attach B-4- EIR Appx H- SWQMP — San Marcos City Council, June 27, 2023

Appendix H
Storm Water Quality Management Plan

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021

CITY OF SAN MARCOS

PRIORITY DEVELOPMENT PROJECT (PDP)

STORM WATER QUALITY MANAGEMENT PLAN (SWQMP)
FOR
Gran Vista
TBD
219-121-15-00 & 219-121-16-00
[SAN MARCOS, CA 92069]
ASSESSOR'S PARCEL NUMBER(S):
219-121-15-00 & 219-121-16-00
ENGINEER OF WORK:
___________________________________________________________________________________ [INSERT CIVIL ENGINEER'S NAME AND PE NUMBER HERE, PROVIDE WET SIGNATURE AND STAMP ABOVE LINE]
PREPARED FOR:

WPI-LAS POSAS/MISSION, LLC

ANDREW SUN
C/O WORLD PREMIER INVESTMENTS, INC.
[INSERT ADDRESS]
18300 VON KARMAN AVE., SUITE 880, IRVINE, CA 92612
949-943-8550 Ext. 850
PDP SWQMP PREPARED BY:

HUNSAKER& ASSOCIATES - SAN DIEGO, INC.
9707 WAPLES ST.

SAN DIEGO, CALIFORNIA 92121
(858) 558-4500
DATE OF SWQMP:

May 20, 2022
PLANS PREPARED BY:

Hunsaker & Associates San Diego, Inc.
9707 Waples Street, San Diego, CA 92121
(858) 558-4500
47945 May 20, 2022
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
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City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021

TABLE OF CONTENTS
Acronym Sheet
PDP SWQMP Preparer's Certification Page
PDP SWQMP Project Owner's Certification Page
Submittal Record
Project Vicinity Map
FORM I-1 Applicability of Storm Water BMP Requirements
FORM I-2 Project Type Determination Checklist (Standard Project or PDP) FORM I-3B Site Information Checklist for PDPs
FORM I-4 Source Control BMP Checklist for All Development Projects FORM I-5 Site Design BMP Checklist for All Development Projects FORM I-6 Summary of PDP Structural BMPs
Attachment 1: Backup for PDP Pollutant Control BMPs
Attachment 1a: DMA Exhibit
Attachment 1b: Tabular Summary of DMAs and Design Capture Volume Calculations Attachment 1c: Harvest and Use Feasibility Screening (when applicable) Attachment 1d: Categorization of Infiltration Feasibility Condition (when applicable) Attachment 1e: Pollutant Control BMP Design Worksheets / Calculations Attachment 2: Backup for PDP Hydromodification Control Measures Attachment 2a: Hydromodification Management Exhibit
Attachment 2b: Management of Critical Coarse Sediment Yield Areas Attachment 2c: Geomorphic Assessment of Receiving Channels Attachment 2d: Flow Control Facility Design
Attachment 3: Structural BMP Maintenance Plan
Attachment 3a: B Structural BMP Maintenance Thresholds and Actions Attachment 3b: Draft Maintenance Agreement (when applicable) Attachment 4: Copy of Plan Sheets Showing Permanent Storm Water BMPs City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021

ACRONYMS
APN Assessor's Parcel Number
BMP Best Management Practice
HMP Hydromodification Management Plan
HSG Hydrologic Soil Group
MS4 Municipal Separate Storm Sewer System
N/A Not Applicable
NRCS Natural Resources Conservation Service
PDP Priority Development Project
PE Professional Engineer
SC Source Control
SD Site Design
SDRWQCB San Diego Regional Water Quality Control Board
SIC Standard Industrial Classification
SWQMP Storm Water Quality Management Plan
12/31/2023
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
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City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021

PDP SWQMP PROJECT OWNER'S CERTIFICATION PAGE
Project Name: Gran Vista
Permit Application Number: TSM21-0003 | MFS21-0001 | SP 21-0003

PROJECT OWNER'S CERTIFICATION
This PDP SWQMP has been prepared for WPI-LAS POSAS/MISSION, LLC by Hunsaker and Associates SD, Inc.. The PDP SWQMP is intended to comply with the PDP requirements of the City of San Marcos BMP Design Manual, which is a design manual for compliance with local City of San Marcos and regional MS4 Permit (California Regional Water Quality Control Board San Diego Region Order No. R9-2015-0100) requirements for storm water management.

The undersigned, while it owns the subject property, is responsible for the implementation of the provisions of this plan. Once the undersigned transfers its interests in the property, its successor-ininterest shall bear the aforementioned responsibility to implement the best management practices (BMPs) described within this plan, including ensuring on-going operation and maintenance of structural BMPs. A signed copy of this document shall be available on the subject property into perpetuity. ________________________________________________________ Project Owner's Signature
________________________________________________________ Print Name
________________________________________________________ Company
____________________________
Date
John Young
2/25/2022
Andrew Sun WPI-LAS POSAS/MISSION, LLC
DocuSign Envelope ID: 8E9FFDB1-F33D-41A4-ACFA-2F935F280AE4 DocuSign Envelope ID: EC2FE7EE-5C58-46F9-BFCA-C2FC1D40B987 City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
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City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021

SUBMITTAL RECORD
Use this Table to keep a record of submittals of this PDP SWQMP. Each time the PDP SWQMP is resubmitted, provide the date and status of the project. In column 4 summarize the changes that have been made or indicate if response to plancheck comments is included. When applicable, insert response to plancheck comments behind this page.

Submittal
Number
Date Project Status Summary of Changes
1 8/26/2021 Preliminary Design /
Planning/ CEQA
Final Design
Initial Submittal
2 Preliminary Design /
Planning/ CEQA
Final Design
3 Preliminary Design /
Planning/ CEQA
Final Design
4 Preliminary Design /
Planning/ CEQA
Final Design
02/21/2022 Address City comments
05/20/2022 Address City comments
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021

PROJECT VICINITY MAP
Project Name: Gran Vista
Permit Application Number: TSM21-0003 | MFS21-0001 | SP 21-0003 City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Applicability of Storm Water Best Management Practices (BMP) Requirements (Storm Water Intake Form for all Development Permit Applications) For detailed information please visit:
http://www.san-marcos.net/departments/development-services/stormwater/development-planning Form I-1
[March 15, 2016]
Project Identification
Project Name: Gran Vista
Description: Proposes 120 three story, for-sale townhome units (Occupancy: R3 Townhome/U; Construction Type V-B) with a maximum permitted density of 15.7 units per acre with associated parking areas, streets and utilities.

Permit Application Number (if applicable): Date: 8/25/2021 Project Address: 219-121-15-00 and 219-121-16-00
Determination of Requirements
This form is required as part of the City’s application process. The purpose of this form is to identify potential land development planning storm water requirements that apply to development projects.

Development projects are defined as construction, rehabilitation, redevelopment, or reconstruction of any public or private projects. In addition, the identification of a development project, as it relates to storm water regulations, would truly apply to development and redevelopment activities that have the potential to contact storm water and contribute a source of pollutants, or reduce the natural absorption and infiltration abilities of the land.

To access the BMP Design Manual, Storm Water Quality Management Plan (SWQMP) templates, and other pertinent information related to this program please refer to:
http://www.san-marcos.net/departments/development-services/stormwater/development-planning Please answer each of the following steps below, starting with Step 1 and progressing through each step until reaching "Stop".

Step Answer Progression
Step 1: Based on the above, Is the project a
"development project" (See definition above)?
See Section 1.3 of the BMP Design Manual for
further guidance if necessary.

Yes Go to Step 2.

No Permanent BMP requirements do not apply. No
SWQMP will be required. Provide brief discussion
below. STOP.

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, Priority
Development Project (PDP), or exception to PDP
definitions?
To answer this item, complete Form I-2, Project
Type Determination. See Section 1.4 of the BMP
Design Manual in its entirety for guidance.

In addition to Section 1.4, please refer to the
City’s SWQMP Submittal Requirements form.

Standard Project Only Standard Project requirements apply, including Standard Project SWQMP. STOP.

PDP Standard and PDP requirements apply, including
PDP SWQMP. Go to Step 3 on the following page.

Exception to PDP
definitions
Standard Project requirements apply, and any
additional requirements specific to the type of
project. Provide discussion and list any additional
requirements below. Prepare Standard Project
SWQMP. STOP.

TSM21-0003 | MFS21-0001 | SP 21-0003
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Discussion / justification, and additional requirements for exceptions to PDP definitions, if applicable:

Form I-1 Page 2, Form Date: March 15, 2016
Step 3 (PDPs only). Please answer the list of questions in this section to determine if hydromodification requirements reply to the proposed PDP. Does the project:

Step 3a. Discharge storm water
runoff directly to the Pacific Ocean?
Yes STOP. Hydromodification requirements do not apply.

No Continue to Step 3b.

Step 3b. Discharge storm water
runoff directly to an enclosed
embayment, not within protected
areas?
Yes STOP. Hydromodification requirements do not apply.

No Continue to Step 3c.

Step 3c. Discharge storm water
runoff directly to a water storage
reservoir or lake, below spillway or
normal operating level?
Yes STOP. Hydromodification requirements do not apply.

No Continue to Step 3d.

Step 3d. Discharge storm water
runoff directly to an area identified in
WMAA?
Yes STOP. Hydromodification requirements do not apply.

No Hydromodification requirements apply to the project. Go to Step

4. Discussion / justification if hydromodification control requirements do not apply:

Step 4 (PDPs subject to
hydromodification control
requirements only). Does protection
of critical coarse sediment yield areas
apply based on review of WMAA
Potential Critical Coarse Sediment
Yield Area Map?
See Section 6.2 of the BMP Design
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.

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Project Type Determination Checklist Form I-2
[March 15, 2016]
Project Information
Project Name/Description: Gran Vista/ 120 three story residential units Permit Application Number (if applicable): TBD Date: 8/25/2021 Project Address:

Project Type Determination: Standard Project or Priority Development Project (PDP) The project is (select one): New Development Redevelopment The total proposed newly created or replaced impervious area is: 188530 sf (4.328 ac) Is the project in any of the following categories, (a) through (f)? Yes No (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 No (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 No (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 (Standard Industrial Classification (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.

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-2 Page 2, Form Date: March 15, 2016
Yes No (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 San Diego Water Board; State Water Quality Protected Areas; water bodies designated with the RARE beneficial use by the State Water Board and San Diego Water Board; and any other equivalent environmentally sensitive areas which have been identified by the Copermittees. See BMP Design Manual Section 1.4.2 for additional guidance.

Yes No (e) New development projects, or redevelopment projects 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 (RGOs). This category includes RGOs that meet the following criteria: (a) 5,000 square feet or more or (b) a projected Average Daily Traffic (ADT) of 100 or more vehicles per day.

Yes No (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 BMP Design Manual Section 1.4.2 for additional guidance.

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

Yes – the project is a Priority Development Project (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):
less than or equal to fifty percent (50%) – only new impervious areas are considered PDP OR
greater than fifty percent (50%) – the entire project site is a PDP City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Site Information Checklist
For PDPs
Form I-3B (PDPs)
[March 15, 2016]
Project Summary Information
Project Name Gran Vista
Project Address
Assessor's Parcel Number(s) (APN(s)) 219-121-15-00, 219-121-16-00 Permit Application Number TBD
Project 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
Project Watershed
(Complete Hydrologic Unit, Area, and Subarea
Name with Numeric Identifier)
San Marcos Creek-Frontal Gulf of Santa Catalina,
Carlsbad, San Marcos, Richland #904.52
Parcel Area
(total area of Assessor's Parcel(s) associated
with the project)
_7.59_ Acres (_330,787_ Square Feet)
Area to be Disturbed by the Project
(Project Area) _6.12_ Acres (_266,737 Square Feet)
Project Proposed Impervious Area
(subset of Project Area) 4.36 Acres (190,295 Square Feet) Project Proposed Pervious Area
(subset of Project Area) _1.76 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.

TSM21-0003\MFS21-0001\ SP 21-0003
76,666
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-3B Page 2 of 10, Form Date: March 15, 2016
Description of Existing Site Condition
Current Status of the Site (select all that apply):

Existing development
Previously graded but not built out
Demolition completed without new construction
Agricultural or other non-impervious use
Vacant, undeveloped/natural
Description / Additional Information:

The site is previously graded into two separate development pads. The pad located in the northerly portion of the planning is elevated above North Las Posas Road and is higher than the remaining portion of the planning area. The lower pad, located in the southerly portion of the site, is elevated above West Mission Road.

Existing Land Cover Includes (select all that apply):

Vegetative Cover
Non-Vegetated Pervious Areas
Impervious Areas
Description / Additional Information:

Vegetation on the site is limited to grasses and small shrubs. A few trees are located along the periphery of the site, adjacent to the channel and North Las Posas 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 (GW):

GW Depth < 5 feet
5 feet < GW Depth < 10 feet
10 feet < GW Depth < 20 feet
GW Depth > 20 feet
Existing Natural Hydrologic Features (select all that apply):

Watercourses
Seeps
Springs
Wetlands
None
Description / Additional Information:

There is no hydrologic feature onsite
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-3B Page 3 of 10, Form Date: March 15, 2016
Description of Existing Site Drainage Patterns
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) Is runoff from offsite conveyed through the site? if yes, quantify all offsite drainage areas, design flows, and locations where offsite flows enter the project site, and summarize how such flows are conveyed through the site;
(3)Provide details regarding existing project site drainage conveyance network, including any existing storm drains, concrete channels, swales, detention facilities, storm water treatment facilities, natural or constructed channels; and
(4) Identify all discharge locations from the existing project site along with a summary of conveyance system size and capacity for each of the discharge locations. Provide summary of the pre-project drainage areas and design flows to each of the existing runoff discharge locations.

Describe existing site drainage patterns:
.

The runoff from the project site, in its existing conditions, flows from the north and the east to the southwest corner where it is routed via an existing 12” CMP riser to a 12” existing corrugated metal pipe. After comingling with the total flow from the commercial parcel south of the project, total flow is conveyed to the storm channel west via 12” pipe which ultimately discharges into Lake San Marcos The existing drainage conveyance is natural and there is no runoff from offsite conveyed through the site. Runoff onsite is mostly sheet flow discharging into the channel along the western boundary of the project site
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-3B Page 4 of 10, Form Date: March 15, 2016
Description of Proposed Site Development
Project Description / Proposed Land Use and/or Activities:

The post-developed condition of the site will consist of 120 three story, townhome units (Occupancy: R3 Townhome/U; Construction Type V-B) with a maximum permitted density of 15.7 units per acre, streets and associated utilities including a storm drain system necessary to convey site runoff through the project area. In addition, two underground vaults located southwest and southeast of the site will be constructed for hydromodification, and peak flow detention purposes.

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

The impervious features onsite will consist of the building roofs, roads, sidewalks and parking lots .

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

Landscaped areas
Does the project include grading and changes to site topography? Yes
No
Description / Additional Information:

The site topography will be very close to the existing conditions. However, a cut of approximately 9,335 CY and fill of 9,335 CY will be needed for the earthwork City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-3B Page 5 of 10, Form Date: March 15, 2016
Description of Proposed Site Drainage Patterns
Does the project include changes to site drainage (e.g., installation of new storm water conveyance systems)?
Yes
No
If yes, provide details regarding the proposed project site drainage conveyance network, including storm drains, concrete channels, swales, detention facilities, storm water treatment facilities, natural or constructed channels, and the method for conveying offsite flows through or around the proposed project site. Identify all discharge locations from the proposed project site along with a summary of the conveyance system size and capacity for each of the discharge locations. Provide a summary of pre- and post-project drainage areas and design flows to each of the runoff discharge locations. Reference the drainage study for detailed calculations.

Describe proposed site drainage patterns::

The stormwater runoff will be collected by inlets , and routed via storm drain pipes towards the vaults and Modular wetland units.

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-3B Page 6 of 10, Form Date: March 15, 2016
Identify whether any of the following features, activities, and/or pollutant source areas will be present (select all that apply):

On-site 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
Description / Additional Information:

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-3B Page 7 of 10, Form Date: March 15, 2016
Identification and Narrative of Receiving Water and Pollutants of Concern Describe flow path of storm water from the project site discharge location(s), through urban storm conveyance systems as applicable, to receiving creeks, rivers, and lagoons as applicable, and ultimate discharge to the Pacific Ocean (or bay, lagoon, lake or reservoir, as applicable):

The site will discharge to an existing channel at the southwest corner of the site. The discharge from the site will enter the enclosed storm drain system via 3X8 box culvert that runs southerly crossing W Mission Rd. The site discharge will be conveyed via lined channels and enclosed storm drain to ultimately discharges into the HMP exempted Lake San Marcos , except for a small portion of unlined open channel with a medium erosion susceptibility. The Channel analysis was prepared by Delane Engineering and approved by the City. The study is saved in the City files.

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 and/or Highest Priority Pollutants from the WQIP for the impaired water bodies:
303(d) Impaired Water Body Pollutant(s)/Stressor(s)
TMDLs / WQIP Highest Priority
Pollutant
San Marcos Creek Benthic Community Effects, DDE,
Indicator Bacteria, Phosphorus,
Selenium, Toxicity
Bacteria and Nutrients
Batiquitos Lagoon Toxicity Bacteria and Nutrients
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 expected from the project site based on all proposed use(s) of the site (see BMP Design Manual Appendix B.6):

Pollutant
Not Applicable to the
Project Site
Expected 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
Pesticides
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-3B Page 8 of 10, Form Date: March 15, 2016
Hydromodification Management Requirements
Do hydromodification management requirements apply (see Section 1.6 of the BMP Design 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 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 BMP Design Manual been performed?

6.2.1 Verification of Geomorphic Landscape Units (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 2.b 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:

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-3B Page 9 of 10, Form Date: March 15, 2016
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.

There will be one point of compliance (POC 1) located at the southwest corner of the site at the Box Culvert
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)
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-3B Page 10 of 10, Form Date: March 15, 2016
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 This space provided for additional information or continuation of information from previous sections as needed.

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Source Control BMP Checklist
for All Development Projects
(Standard Projects and Priority Development Projects)
Form I-4
[March 15, 2016]
Project Identification
Project Name: Gran Vista
Permit Application Number: TBD
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 Model BMP Design 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 Model BMP Design 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, Run-On, 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
Discussion / justification if SC-4 not implemented:

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-4 Page 2 of 2, Form Date: March 15, 2016
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)
On-site 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
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.

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Site Design BMP Checklist
for All Development Projects
(Standard Projects and Priority Development Projects)
Form I-5
[March 15, 2016]
Project Identification
Project Name: Gran Vista
Permit Application Number: TBD
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 Model BMP Design 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 Model BMP Design 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:

Where applicable
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
Discussion / justification if SD-4 not implemented:

Where applicable
SD-5 Impervious Area Dispersion Yes No N/A
Discussion / justification if SD-5 not implemented:

Impervious areas throughout the site will be collected via inlets per SD-6 below. Dispersion will occur at the discharge location.

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-5 Page 2 of 2, Form Date: March 15, 2016
Site Design Requirement Applied?
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:

Where applicable
SD-8 Harvesting and Using Precipitation Yes No N/A
Discussion / justification if SD-8 not implemented:

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Summary of PDP Structural BMPs Form I-6 (PDPs)
[March 15, 2016]
Project Identification
Project Name: Gran Vista
Permit Application Number: TBD
PDP Structural BMPs
All PDPs must implement structural BMPs for storm water pollutant control (see Chapter 5 of the BMP Design 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 BMP Design 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 and engineer of record to certify construction of the structural BMPs (see Section 1.12 of the BMP Design Manual). PDP structural BMPs must be maintained into perpetuity, and the local jurisdiction must confirm the maintenance (see Section 7 of the BMP Design 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).

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
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 BMP Design 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.

STEP 1: Evaluate at DMA Scale
1a: After delineating the DMAs, SM-C has been identified as a self mitigating area ( landscaped area that drains directly offsite and to the public Storm drain), and it meets all the requirements per section

5.2.1 from the BMP manual, and 208 sft of de minims sidewalk at the entrance has been delineated and meets the requirements per section 5.2.2.

Determine and delineate the remain areas the DMAs are not "Self-mitigating" or "De minimis" or "Selfretaining", to 1b. 1b: Break down pervious and impervious area, DCV for all DMAs were calculated using worksheet B.2-1.

To Step 2.

STEP 2: Harvest and use is infeasible according to Form I-7. To Step 3.

STEP 3:
3a: Using Form I-8 to conduct a prelimary feasibility screening determined that no infiltration to be feasible.
3b: volume-based Proprietary Biofiltration MWS BMPs and flow-based Modular wetland (or equivalent) chosen.
3c: using Worksheet B.2.1 to calculate the DCV from each DMA.

For the proprietary biofiltration BMP, an underground storage is proposed upstream of the BMP to provided the 1.5 DCV for DMA-1 and DMA-2 . B-5-2 was used to calculate min retention The MWS units BF-3-1 and BF-3-2 were sized to provide the required 1.5 design captured volume and to drawdown in 36 hrs. The unit is hydraulicly disconnected to the vaults The generated flow from DMA-1 and DMA-2 will be routed to the vaults which have internal riser.

The vaults are utilized as a storage for the water qulaity design captured volume (1.5 DCV), in addition to the required storage for HMP and peak flow attenuation. The very low orifice in the risers is sized to draw down the 1.5 DCV (design captured volume) in 36 hrs. The flow from this orifice will be directed to a downstream volume based MWS unit to address water quality requirements. An internal surface control weir will be built inside the riser with an invert elevation set at the water surface elevation associated with the water quality volume in the vault. The riser internal weir will divert the flows below its invert towards the modular wetland unit downstream of the vault.

The low flow orifice that directs the flow to the MWS unit is modeled in the SWMM with a rating table up to the water quality HGL in the vault and labeled as WQ orifice.

The BF-3-3 flow-based is sized using B.6-1 Worksheet to replace the sand filter whic was treating the exisitng Drive (DMA3-C EX and DMA3-D-EX) and treat additional 0.09 acres (treat the undisturbed area that commingles with the proposed area)
BF-3-4 flow-based is sized using B.6.1 to treat WQ flow that is generated from DMA 4 BF-3-5 flow-based sized to treat flow from the onsite area DMA-5 STEP 4:
4a: Proposed BMPs treats 1.5 DCV and drawdown n 36 hrs and the flowbased unit treat 1.5 of the required water quality flow. Project meets pollutant control standards. To Step 6.

STEP 6: SWQMP prepared as step 6.

STEP 7:HMP volumes provided within proposed vaults and SWMM model has been prepared for the project
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-6 Page 2 of X, Form Date: March 15, 2016
(Page reserved for continuation of description of general strategy for structural BMP implementation at the site)
(Continued from page 1)
Runoff generated from DMA 2 will be directed toward the underground Vault HMP-2 east and a volume based MWS unit BF-3-2 for pollutant control, HMP and detention, then conveyed west to commingle with the treated flow from DMA-5.

The flow from DMA-5 will be treated via MWS BF-3-5 which will address the pollutant control requirements, and will meet the hydromodification and detention requirements when measured at POC-1 by over detaining in the proposed two vault . The treated flow will be conveyed west to commingle with the treated flow from vault HMP-1\BF-3-1.

Runoff generated from DMA 1 will be directed towards the underground Vault HMP-1 and a volume based MWS unit BF-3-1 to address pollutant control, HMP and detention requirements, then conveyed to commingle with the treated flows from Vault HMP-2\ BF-3-2 and BF-3-5.

The flow then continues westerly to commingle with the existing treated and bypassed flows, and the treated flow from BF-3-3.

The BF-3-3 will treat the flow that is generated from the proposed DMA3 which includes sidewalk and driveways drain southerly and the existing undisturbed drive that was previously treated via sand filter. The sand filter will be removed and the flows from the DMA3-EX will commingle with the DMA3 proposed and drains towards the BF-3-3 that will treat the total generated runoff (Existing and proposed) and connects to the existing storm drain.

The flow from the DMA 4 (driveway, sidewalk and existing pavement that commingles with it) is routed via proposed BF-3-4 which will treat the WQ flow generated from the newly proposed area and existing area that commingles with it. The discharge from the site and the proposed BF-3-4 will continue towards the historical discharge location on the Las Posas Creek POC1.

Continues Simulation analysis (SWMM) has been provided at the POC1 location to confirm that the proposed project meets the HMP requirements.

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-6 Page 3 of X (Copy as many as needed) Form Date: March 15, 2016 Structural BMP Summary Information
(Copy this page as needed to provide information for each individual proposed structural BMP) Structural BMP ID No. BF-3-1
Construction Plan Sheet No. TBD
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)
Biofiltration with Nutrient Sensitive Media Design (BF-2) Proprietary Biofiltration (BF-3) meeting all requirements of Appendix F 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 BMP Design Manual)
Alisa S. Vialpando, RCE #47945
Hunsaker & Associates San Diego, Inc. 9707
Waples Street
San Diego, CA 92121
Telephone: (858) 558-4500
Who will be the final owner of this BMP? WPI-Las Posas/Mission, LLC Andrew Sun c/o World Premier Investments, Inc.

Who will maintain this BMP into perpetuity? WPI-Las Posas/Mission, LLC Andrew Sun c/o World Premier Investments, Inc.

What is the funding mechanism for maintenance? HOA
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-6 Page 4 of X (Copy as many as needed) , Form Date: March 15, 2016 Structural BMP ID No. BF-3-1
Construction Plan Sheet No. TBD
Discussion (as needed):

Using B-2-1, DCV has been calculated to be 3,441 CFT

1.5 DCV = 5,161 CFT’
Vault1 (HMP1) provides the required volume with 2.5 ft associated WSE

1.6” water quality orifice in the riser within the vault1 at elevation 0 (measured form the vault’s bottom) has been sized to drawdown the 1.5 DCV in 36 hrs.

The flow from this orifice will be directed to a downstream volume based MWS unit BF-3-1 to address water quality requirements. An internal surface control weir will be built inside the riser with an invert elevation set at the water surface elevation associated with the water quality volume in the vault. The riser internal weir will divert the flows below its invert towards the modular wetland unit downstream of the vault.

The BF-3-1 has been sized to be L-8-8 per the sizing letter and MWS detail from bioclean see attachment 1e.

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-6 Page 3 of X (Copy as many as needed) Form Date: March 15, 2016 Structural BMP Summary Information
(Copy this page as needed to provide information for each individual proposed structural BMP) Structural BMP ID No. BF-3-2
Construction Plan Sheet No. TBD
Type of structural BMP:

Who will maintain this BMP into perpetuity? WPI-Las Posas/Mission, LLC Andrew Sun c/o World Premier Investments, Inc.

What is the funding mechanism for maintenance? HOA
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-6 Page 4 of X (Copy as many as needed) , Form Date: March 15, 2016 Structural BMP ID No. BF-3-2
Construction Plan Sheet No. TBD
Discussion (as needed):

Using B-2-1, DCV has been calculated to be 5,859 CFT

1.5 DCV = 8,789 CFT’
Vault2 (HMP2) provides the required volume with 2.6 ft associated WSE

2.3” water quality orifice in the riser within the vault1 at elevation 0 (measured form the vault’s bottom) has been sized to drawdown the 1.5 DCV in 36 hrs.

The flow from this orifice will be directed to a downstream volume based MWS unit BF-3-2 to address water quality requirements. An internal surface control weir will be built inside the riser with an invert elevation set at the water surface elevation associated with the water quality volume in the vault. The riser internal weir will divert the flows below its invert towards the modular wetland unit downstream of the vault.

The BF-3-2 has been sized to be L-8-12 per the sizing letter and MWS detail from bioclean. see attachment 1e
WPI-Las Posas/Mission, LLC
Andrew Sun c/o World Premier Investments, Inc.

WPI-Las Posas/Mission, LLC
Andrew Sun c/o World Premier Investments, Inc.

Privately maintained by WPI- Las Posas/Mission, LLC
X X X
X
X
X X
sizing letter and MWS detail from bioclean, see
attachment 1e
WPI-Las Posas/Mission, LLC
Andrew Sun c/o World Premier Investments, Inc.

WPI-Las Posas/Mission, LLC
Andrew Sun c/o World Premier Investments, Inc.

Privately maintained by WPI- Las Posas/Mission, LLC
X X X
sizing letter and MWS detail from bioclean, see
attachment 1e
WPI-Las Posas/Mission, LLC
Andrew Sun c/o World Premier Investments, Inc.

WPI-Las Posas/Mission, LLC
Andrew Sun c/o World Premier Investments, Inc.

Privately maintained by WPI- Las Posas/Mission, LLC
X X X
sizing letter and MWS detail from bioclean, see attachment 1e City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-6 Page 3 of X (Copy as many as needed) Form Date: March 15, 2016 Structural BMP Summary Information
(Copy this page as needed to provide information for each individual proposed structural BMP) Structural BMP ID No. HMP-1
Construction Plan Sheet No. TBD
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) Proprietarily Biofiltration (BF-3)
Biofiltration with Nutrient Sensitive Media Design (BF-2) Proprietary Biofiltration (BF-3) meeting all requirements of Appendix F 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:

Who will maintain this BMP into perpetuity? WPI-Las Posas/Mission, LLC Andrew Sun c/o World Premier Investments, Inc.

What is the funding mechanism for maintenance? HOA
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-6 Page 4 of X (Copy as many as needed) , Form Date: March 15, 2016 Structural BMP ID No. HMP-1
Construction Plan Sheet No. TBD
Discussion (as needed):

SWMM 5.1 Was used to size the vault to meet flow control requirements. Vault-1 has been sized to detain the flows from DMA-1 and over detain for DMA-5,4 and 3, so the proposed project meets the HMP requirements when measured at the POC1.

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-6 Page 3 of X (Copy as many as needed) Form Date: March 15, 2016 Structural BMP Summary Information
(Copy this page as needed to provide information for each individual proposed structural BMP) Structural BMP ID No. HMP-2
Construction Plan Sheet No. TBD
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) Proprietarily Biofiltration (BF-3)
Biofiltration with Nutrient Sensitive Media Design (BF-2) Proprietary Biofiltration (BF-3) meeting all requirements of Appendix F 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:

Who will maintain this BMP into perpetuity? WPI-Las Posas/Mission, LLC Andrew Sun c/o World Premier Investments, Inc.

What is the funding mechanism for maintenance? HOA
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Form I-6 Page 4 of X (Copy as many as needed) , Form Date: March 15, 2016 Structural BMP ID No. HMP-2
Construction Plan Sheet No. TBD
Discussion (as needed):

SWMM 5.1 Was used to size the vault to meet flow control requirements. Vault-2 has been sized to detain the flows from DMA-2 and over detain for DMA-5,4 and 3, so the proposed project meets the HMP requirements when measures at the POC1.

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
ATTACHMENT 1

BACKUP FOR PDP POLLUTANT CONTROL BMPS
This is the cover sheet for Attachment 1.

Indicate which Items are Included behind this cover sheet:

Attachment
Sequence
Contents Checklist
Attachment 1a DMA Exhibit (Required)
See DMA Exhibit Checklist on the back of
this Attachment cover sheet.

Included
Attachment 1b Tabular Summary of DMAs Showing DMA
ID matching DMA Exhibit, DMA Area, and
DMA Type (Required)*
*Provide table in this Attachment OR on
DMA Exhibit in Attachment 1a
Included on DMA Exhibit in
Attachment 1a
Included as Attachment 1b, separate
from DMA Exhibit
Attachment 1c Form I-7, Harvest and Use Feasibility
Screening Checklist (Required unless the
entire project will use infiltration BMPs)
Refer to Appendix B.3-1 of the BMP
Design Manual to complete Form I-7.

Included
Not included because the entire
project will use infiltration BMPs
Attachment 1d Form I-8, Categorization of Infiltration
Feasibility Condition (Required unless the
project will use harvest and use BMPs)
Refer to Appendices C and D of the BMP
Design Manual to complete Form I-8.

Included
Not included because the entire
project will use harvest and use BMPs
Attachment 1e Pollutant Control BMP Design
Worksheets / Calculations (Required)
Refer to Appendices B and E of the BMP
Design Manual for structural pollutant
control BMP design guidelines
Included
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Use this checklist to ensure the required information has been included on the DMA Exhibit:

The DMA Exhibit must identify:

Underlying hydrologic soil group
Approximate depth to groundwater
Existing natural hydrologic features ( watercourses, seeps, springs, wetlands) Critical coarse sediment yield areas to be protected
Existing topography and impervious areas
Existing and proposed site drainage network and connections to drainage offsite Proposed demolition
Proposed grading
Proposed impervious features
Proposed design features and surface treatments used to minimize imperviousness Drainage management area (DMA) boundaries, DMA ID numbers, and DMA areas (square footage or acreage), and DMA type (i.e., drains to BMP, self-retaining, or self-mitigating) Potential pollutant source areas and corresponding required source controls (see Chapter 4, Appendix E.1, and Form I-3B)
Structural BMPs (identify location, type of BMP, and size/detail) City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: August 2021
ATTACHMENT 1a

DMA EXHIBIT

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date:August 2021
ATTACHMENT 1b
TABULAR SUMMARY OF DMAs

DMA 1.C DMA 1.D BF-3-1 DMA 2.C DMA 2.D BF-3-2 DMA 3.C DMA 3.D Total Area BF-3-3 DMA 4.C DMA4.D BF-3-4 DMA 5.C DMA5.D BF-3-5 SM-C de Minimis Area Area Area Area Area Area Summation Area Area Area Area (ac.) (ac.) (ac.) (ac.) (ac.) (ac.) (ac.) (ac.) (ac.) (ac.) (ac.) (ac.) (ac.) (ac.) (ac.) Roofs 0.90 0.73 0.10 0.83 0.75 0.13 1.15 1.28 1.15 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.24 0.00 0.24 0.22 0.12 208.00 Concrete or Asphalt 0.90 0.54 0.08 0.62 0.56 0.15 1.02 1.17 1.05 0.03 0.02 0.04 0.04 0.08 0.00 0.08 0.08 0.11 0.00 0.11 0.10 Landscaped area (C Soil) 0.10 0.38 0.00 0.38 0.04 0.14 0.00 0.14 0.01 0.02 0.00 0.02 0.002 0.03 0.00 0.03 0.0030 0.09 0.00 0.09 0.01 Landscaped area (D Soil) 0.10 0.00 0.09 0.09 0.01 0.00 0.87 0.87 0.09 0.00 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1.65 0.27 1.92 1.35 0.43 3.03 3.46 2.31 0.05 0.04 0.086 0.04 0.11 0.00 0.11 0.08 0.44 0.00 0.44 0.33

0.71 0.67 0.52 0.69 0.74
Imp= 77.05% 66.93% 75.65% 66.15% 71.40% 70.75% 59.57% 43.44% 52.27% 73.42% 80.10% 0.00% 80.10% Note: * DMA 2-D impervious area includes 0.023 ac of undisturbed exisitng pavement with runoff commingles with the proposed impervious area ac. SFT
Total Area Total Area
Runoff
Factor
Summation
RF x A
Summation
RF x A
Total Area Summation
RF x A
Total Area Summation RF
x A

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date:August 2021
ATTACHMENT 1c
FORM I-7, HARVEST AND USE FEASIBLITY SCREENING CHECKLIST

land use: Residential use. 36 hr: 9.3 gal/per resident* 120 * 3 people/unit = 3348 gal = 447.5 cubic feet Generate landscape: moderate plant use. 1470 gal/ac * 1.71ac = 2514 gal = 336 cubic feet Total = 447.5+336 = 783.5 cubic-feet
DCV = 10,955 cubic-feet

0.25 DCV = 2,714 cubic-feet

City of San Marcos PDP SWQMP Template Date: March 15, 2016 ATTACHMENT 1d
FORM I-8, CATEGORIZATION OF INFILTRATION FEASIBILITY CONDITION

Based on the USDA Web Soil Survey, Soil C and D has low infiltration rate.& BASED ON INFILTRATION TESTING PER GEOTECHNICAL REPORT DATED 7/15/21.

BASED ON INFILTRATION TESTING PER GEOTECHNICAL REPORT DATED 7/15/21.

Site is underlain by soil type C and D that has low infiltration characteristics, which could result in lateral migration of water into the adjacent roadway improvements and utilities causing settlement and water movement through utility lines.

BASED ON INFILTRATION TESTING PER GEOTECHNICAL REPORT DATED 7/15/21.
2/22/2022
City of San Marcos PDP SWQMP Template Date: March 15, 2016 ATTACHMENT 1e

POLLUTION CONTROL BMP DESIGN WORKSHEETS
DMA#1
1 85th percentile 24-hr storm depth from Figure B.1-1 d= 0.70 inches 2 Area tributary to BMP (s) A= 1.92 acres
3 Area weighted runoff factor (estimate using Appendix
B.1.1 and B.2.1) C= 0.71 unitless
4 Street trees volume reduction ( 15 ft3
x 440 trees) TCV= 0.00 cubic-feet
5 Rain barrels volume reduction RCV= 0.00 cubic-feet
6 Calculate DCV= (3630 x C x d x A) - TCV - RCV DCV= 3,441 cubic-feet

1.5 DCV= 5,161
DMA#2
DMA 2
1 85th percentile 24-hr storm depth from Figure B.1-1 d= 0.70 inches 2 Area tributary to BMP (s) A= 3.46 acres
3 Area weighted runoff factor (estimate using Appendix
B.1.1 and B.2.1) C= 0.67 unitless
4 Street trees volume reduction ( 15ft3
x 26 trees) TCV= 0.00 cubic-feet
5 Rain barrels volume reduction RCV= 0.00 cubic-feet
6 Calculate DCV= (3630 x C x d x A x M ) - TCV - RCV DCV= 5,859 cubic-feet

1.5 DCV= 8,789
DMA3
DMA 3
1 85th percentile 24-hr storm depth from Figure B.1-1 d= 0.70 inches 2 Area tributary to BMP (s) A= 0.09 acres
3 Area weighted runoff factor (estimate using Appendix
B.1.1 and B.2.1) C= 0.52 unitless
4 Street trees volume reduction ( 15 ft3
x 29 trees) TCV= 0.00 cubic-feet
5 Rain barrels volume reduction RCV= 0.00 cubic-feet
6 Calculate DCV= (3630 x C x d x A x M ) - TCV - RCV DCV= 113 cubic-feet DMA 4
1 85th percentile 24-hr storm depth from Figure B.1-1 d= 0.70 inches 2 Area tributary to BMP (s) A= 0.11 acres
3 Area weighted runoff factor (estimate using Appendix
B.1.1 and B.2.1) C= 0.69 unitless
4 Street trees volume reduction ( 15 ft3
x 29 trees) TCV= 0.00 cubic-feet
5 Rain barrels volume reduction RCV= 0.00 cubic-feet
6 Calculate DCV= (3630 x C x d x A x M ) - TCV - RCV DCV= 199 cubic-feet DMA 1 Worksheet B-2.1
Worksheet B-2.1
Worksheet B-2.1
Worksheet B-2.1
2/22/2022 R:\1482\&Hyd\SWQMP\Calcs\1482-Worksheets.xlsx DMA 5
1 85th percentile 24-hr storm depth from Figure B.1-1 d= 0.70 inches 2 Area tributary to BMP (s) A= 0.44 acres
3 Area weighted runoff factor (estimate using Appendix
B.1.1 and B.2.1) C= 0.74 unitless
4 Street trees volume reduction ( 15 ft3 x 29 trees) TCV= 0.00 cubic-feet 5 Rain barrels volume reduction RCV= 0.00 cubic-feet
6 Calculate DCV= (3630 x C x d x A x M ) - TCV - RCV DCV= 837 cubic-feet DMA 3-EX
1 85th percentile 24-hr storm depth from Figure B.1-1 d= 0.70 inches 2 Area tributary to BMP (s) A= 0.453 acres
3 Area weighted runoff factor (estimate using Appendix
B.1.1 and B.2.1) C= 0.79 unitless
4 Street trees volume reduction ( 15 ft3
x 29 trees) TCV= 0.00 cubic-feet
5 Rain barrels volume reduction RCV= 0.00 cubic-feet
6 Calculate DCV= (3630 x C x d x A x M ) - TCV - RCV DCV= 909 cubic-feet Worksheet B-2.1
Worksheet B-2.1
2/24/2022 R:\1482\&Hyd\SWQMP\Calcs\1482-Worksheets.xlsx DMA 3-EX

FLOW BASED BMP SIZING CALCULATION
1 DCV DCV 909 cubic-feet
2 DCV Retained (Treewell Reduction) DCV Retained 0 cubic-feet 3 DCV Biofiltered DCV Biofiltered 0.00 cubic-feet
4 DCV requiring flow-thru (Line 1 - Line 2 - 0.67*Line 3) DCV flow-thru 909 cubic-feet 5 Adjustment Factor (Line 4 / Line1) AF= 1.00 unitless
6 Design rainfall intensity i= 0.20 in/hr
7 Area tributary to BMP(s) A= 0.45 acres
8 Area-weighted runoff factor (estimate using Appendix B.2) C= 0.79 unitless 9 Calculate Flow Rate = AF x (C x i x A)x1.5* Q= 0.107 cfs 1)
2)
3)
4)
*1.5 Times Flow Rate Safety Factor
Flow-thru treatment control BMPs shall be sized to filter or treat the maximum flow rate of runoff produced from a rainfaill intensity of 0.2 inch of rainfall per hour or each hour of every storm event DMA 3-EX: Flow Based BMP Design Flows (BF-3-3) Worksheet B.6-1 Adjustment factor shall be estimated considering only retention and biofiltration BMPs located upstream of flow-thru BMPs. That is, if the flow-thru BMP is upstream of the project's retention and biofiltration BMPs then the flow-thru BMP shall be sized using an adjustment factor of 1.

Volume based (e.g., dry extended detention basin) flow-thru treatment control BMPs shall be sized to the volume in Line 4 and dlow based )e.g., vegetated swales) shall be sized to flow rate in Line 9. Sand filter and media filter can be designed by either volume in :ie 4 or flow rate in Line 9 Propietary BMPs, if used, shall provide certified treatment capacity equal to or greater than the 2/22/2022 R:\1482\&Hyd\SWQMP\Calcs\1482-Worksheets.xlsx

36 Hr
1710
2400
3777
4696
5716
6738
7758
8779
4786
7554
11331
15109
18840
22662
BF-3-1

STANDARD DETAIL

STORMWATER BIOFILTRATION SYSTEM
MWS-L-8-8-11'-0"-V

SITE SPECIFIC DATA
INTERNAL BYPASS DISCLOSURE:

PLAN VIEW

ELEVATION VIEW

RIGHT END VIEW

LEFT END VIEW

GENERAL NOTES

INSTALLATION NOTES
36 Hr
1710
2400
3777
4696
5716
6738
7758
8779
4786
7554
11331
15109
18840
22662
BF-3-2

STANDARD DETAIL

STORMWATER BIOFILTRATION SYSTEM
MWS-L-8-12-8'-9"-V

SITE SPECIFIC DATA
INTERNAL BYPASS DISCLOSURE:

PLAN VIEW

ELEVATION VIEW

RIGHT END VIEW

LEFT END VIEW

GENERAL NOTES

INSTALLATION NOTES
DMA 3

FLOW BASED BMP SIZING CALCULATION
1 DCV DCV 113 cubic-feet
2 DCV Retained (Treewell Reduction) DCV Retained 0 cubic-feet 3 DCV Biofiltered DCV Biofiltered 0.00 cubic-feet
4 DCV requiring flow-thru (Line 1 - Line 2 - 0.67*Line 3) DCV flow-thru 113 cubic-feet 5 Adjustment Factor (Line 4 / Line1) AF= 1.00 unitless
6 Design rainfall intensity i= 0.20 in/hr
7 Area tributary to BMP(s) A= 0.09 acres
8 Area-weighted runoff factor (estimate using Appendix B.2) C= 0.52 unitless 9 Calculate Flow Rate = AF x (C x i x A)x1.5* Q= 0.013 cfs 1)
2)
3)
4)
*1.5 Times Flow Rate Safety Factor
Flow-thru treatment control BMPs shall be sized to filter or treat the maximum flow rate of runoff produced from a rainfaill intensity of 0.2 inch of rainfall per hour or each hour of every storm event DMA 3: Flow Based BMP Design Flows (BF-3-3) Worksheet B.6-1 Adjustment factor shall be estimated considering only retention and biofiltration BMPs located upstream of flow-thru BMPs. That is, if the flow-thru BMP is upstream of the project's retention and biofiltration BMPs then the flow-thru BMP shall be sized using an adjustment factor of 1.

PRIORITY PROJECT

WATER QUALITY TECHNICAL REPORT
FOR:

CVS PHARMACY
Las Posas Rd, San Marcos, CA
PREPARED FOR:

World Premier Investments
3 MacArthur Place, Suite 550
Santa Ana, CA 92707
714-662-6900
714-662-7788 FAX
PREPARED BY:

EXCEL ENGINEERING
440 State Place
Escondido, CA 92029
Tel: (760) 745-8118
Project No: 05-036
DATE PREPARED:

July 10, 2008
Revised: December 19, 2008
January 13, 2009
February 11, 2009
April 27, 2009
July 10, 2009

APPENDIX F

SITE PLAN

TOPOGRAPHIC MAPS

14 9.1.1.2 Proposed design of Sand Filter
The sand filter proposed in this project is located on one side of the parking lot. The street section has a 1% min slope from the high side to the lower side. Instead of a curb & gutter on the lower side, this project will implement a sand filter. This filter is design to be over the minimum requirements for water quality.

TABLE OF REQUIRED MINIMUM CONFIGURATIONS OF THE SAND

FILTERS AND WHAT THE PROJECT IS PROVIDING
Nodes
Volume
Required
(cubic ft)
Min
Bottom
Area
(sq. ft)
Min Length of

1.5 ft Wide
Filter
(ft)
Length
Provided
(ft)
Remarks
7 to 20 4,326.770 432.677 288.45 689.00 Exceeds min req. 15 to 17 699.170 69.917 46.61 54.00 Exceeds min req.
4 to 25 1,275.240 127.524 85.02 86.00 Exceeds min req.
.

9.1.2 Calculation of 85th percentile discharge rates
Use P=0.81 inch the precipitation 85th percentile storm event, and I=7.44P Tc-0.645. The discharge rates that enter to each BMP are:

Tc(mins) C I (in/hr) A (acre) Q (cfs) Flow direction

6.74 0.79 1.7602 0.453 0.630 Node 4 to 25

8.07 0.79 1.5672 0.608 0.753 Node 7 to 9

7.12 0.79 1.6991 0.591 0.793 Node 11 to 13

4.99 0.79 2.1369 0.257 0.434 Node 14 to 22

5.11 0.79 2.1044 0.301 0.500 Node 15 to17
Note: Please refer to BMP site plan for flow direction nodes For BF-3-3
Required flow to be treated =

0.107 +0.015= 0.122 cfs

CURB OPENING

STANDARD DETAIL

STORMWATER BIOFILTRATION SYSTEM
MWS-L-6-8-4'-8"-C

SITE SPECIFIC DATA
INTERNAL BYPASS DISCLOSURE:

PLAN VIEW

ELEVATION VIEW

RIGHT END VIEW

LEFT END VIEW

GENERAL NOTES

INSTALLATION NOTES

DMA4

FLOW BASED BMP SIZING CALCULATION
1 DCV DCV 199 cubic-feet
2 DCV Retained (Treewell Reduction) DCV Retained 0 cubic-feet 3 DCV Biofiltered DCV Biofiltered 0.00 cubic-feet
4 DCV requiring flow-thru (Line 1 - Line 2 - 0.67*Line 3) DCV flow-thru 199 cubic-feet 5 Adjustment Factor (Line 4 / Line1) AF= 1.00 unitless
6 Design rainfall intensity i= 0.20 in/hr
7 Area tributary to BMP(s) A= 0.11 acres
8 Area-weighted runoff factor (estimate using Appendix B.2) C= 0.69 unitless 9 Calculate Flow Rate = AF x (C x i x A)x1.5* Q= 0.024 cfs 1)
2)
3)
4)
*1.5 Times Flow Rate Safety Factor
Flow-thru treatment control BMPs shall be sized to filter or treat the maximum flow rate of runoff produced from a rainfaill intensity of 0.2 inch of rainfall per hour or each hour of every storm event DMA4: Flow Based BMP Design Flows (BF-3-4) Worksheet B.6-1 Adjustment factor shall be estimated considering only retention and biofiltration BMPs located upstream of flow-thru BMPs. That is, if the flow-thru BMP is upstream of the project's retention and biofiltration BMPs then the flow-thru BMP shall be sized using an adjustment factor of 1.

STANDARD DETAIL

STORMWATER BIOFILTRATION SYSTEM
MWS-L-4-6-3'-11"-V

SITE SPECIFIC DATA

PLAN VIEW

ELEVATION VIEW

RIGHT END VIEW

LEFT END VIEW

GENERAL NOTES

INSTALLATION NOTES

DMA 5

FLOW BASED BMP SIZING CALCULATION
1 DCV DCV 837 cubic-feet
2 DCV Retained (Treewell Reduction) DCV Retained 0 cubic-feet 3 DCV Biofiltered DCV Biofiltered 0.00 cubic-feet
4 DCV requiring flow-thru (Line 1 - Line 2 - 0.67*Line 3) DCV flow-thru 837 cubic-feet 5 Adjustment Factor (Line 4 / Line1) AF= 1.00 unitless
6 Design rainfall intensity i= 0.20 in/hr
7 Area tributary to BMP(s) A= 0.44 acres
8 Area-weighted runoff factor (estimate using Appendix B.2) C= 0.74 unitless 9 Calculate Flow Rate = AF x (C x i x A)x1.5* Q= 0.099 cfs 1)
2)
3)
4)
*1.5 Times Flow Rate Safety Factor
Flow-thru treatment control BMPs shall be sized to filter or treat the maximum flow rate of runoff produced from a rainfaill intensity of 0.2 inch of rainfall per hour or each hour of every storm event DMA 5: Flow Based BMP Design Flows (BF-3-5) Worksheet B.6-1 Adjustment factor shall be estimated considering only retention and biofiltration BMPs located upstream of flow-thru BMPs. That is, if the flow-thru BMP is upstream of the project's retention and biofiltration BMPs then the flow-thru BMP shall be sized using an adjustment factor of 1.

CURB OPENING

STANDARD DETAIL

STORMWATER BIOFILTRATION SYSTEM
MWS-L-4-8-4'-8"-C

SITE SPECIFIC DATA
INTERNAL BYPASS DISCLOSURE:

PLAN VIEW

ELEVATION VIEW

RIGHT END VIEW

LEFT END VIEW

GENERAL NOTES

INSTALLATION NOTES

City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
ATTACHMENT 2

BACKUP FOR PDP HYDROMODIFICATION CONTROL MEASURES
This is the cover sheet for Attachment 2.

Mark this box if this attachment is empty because the project is exempt from PDP hydromodification management requirements.

Indicate which Items are Included behind this cover sheet:

Attachment
Sequence
Contents Checklist
Attachment 2a Hydromodification Management Exhibit
(Required)
Included
See Hydromodification Management
Exhibit Checklist on the back of this
Attachment cover sheet.

Attachment 2b Management of Critical Coarse Sediment
Yield Areas (WMAA Exhibit is required,
additional analyses are optional)
See Section 6.2 of the BMP Design
Manual.

Exhibit showing project drainage
boundaries marked on WMAA Critical
Coarse Sediment Yield Area Map
(Required)
Optional analyses for Critical Coarse
Sediment Yield Area Determination

6.2.1 Verification of Geomorphic
Landscape Units Onsite

6.2.2 Downstream Systems Sensitivity
to Coarse Sediment

6.2.3 Optional Additional Analysis of
Potential Critical Coarse Sediment
Yield Areas Onsite
Attachment 2c Geomorphic Assessment of Receiving
Channels (Optional)
See Section 6.3.4 of the BMP Design
Manual.

Not performed
Included
Submitted as separate stand-alone
document
Attachment 2d Flow Control Facility Design, including
Structural BMP Drawdown Calculations
and Overflow Design Summary
(Required)
See Chapter 6 and Appendix G of the
BMP Design Manual
Included
Submitted as separate stand-alone
document
Attachment 2e Vector Control Plan (Required when
structural BMPs will not drain in 96
hours)
Included
Not required because BMPs will drain
in less than 96 hours
City of San Marcos PDP SWQMP Template Date: March 15, 2016 PDP SWQMP Preparation Date: 08/26/2021
Use this checklist to ensure the required information has been included on the Hydromodification Management Exhibit:

The Hydromodification Management Exhibit must identify:

Underlying hydrologic soil group
Approximate depth to groundwater
Existing natural hydrologic features ( watercourses, seeps, springs, wetlands) Critical coarse sediment yield areas to be protected
Existing topography
Existing and proposed site drainage network and connections to drainage offsite Proposed grading
Proposed impervious features
Proposed design features and surface treatments used to minimize imperviousness Point(s) of Compliance (POC) for Hydromodification Management Existing and proposed drainage boundary and drainage area to each POC (when necessary, create separate exhibits for pre-development and post-project conditions) Structural BMPs for hydromodification management (identify location, type of BMP, and size/detail) City of San Marcos PDP SWQMP Template Date: March 15, 2016 ATTACHMENT 2a

HYDROMODIFICATION MANAGEMENT EXHIBITS

ATTACHMENT 2b

MANAGEMENT OF CRITICAL COARSE SEDIMENT YIELD AREAS

CCSYA

ATTACHMENT 2c

GEOMORPHIC ASSESSMENT OF RECEIVING CHANNELS
Prepared by Delane Engineering

Project site location
Open Channel prior to
hitting Las Posas Creek
and Lake San Marcos
Delane Engineering
conducted channel
susceptibility analysis
of this open channel

1 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415

CHANNEL SCREENING ANALYSIS

KARL STRAUSS SAN MARCOS

TASTING ROOM AND GARDEN
ARMORLITE DR.

SAN MARCOS, CA 92069
ASSESSOR' S PARCEL NUMBER(S):
219-163-60
ENGINEER OF WORK:

BRIAN P. WIESE, P.E., LICENSE # C80674
EXPIRATION DATE: 03/31/2021
PREPARED FOR:

Karl Strauss Brewing Co.
5965 Santa Fe Street, Suite E
San Diego, CA 92109
PREPARED BY:

Delane Engineering, Inc.
4909 Murphy Canyon Road, Suite 330
San Diego, CA 92123
619-535-0602
DATE:

November 18, 2019
2 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 TABLE OF CONTENTS:

1.0 Introduction

2.0 Office Assessment

3.0 Analysis Domain

4.0 Field Screening
Vertical Susceptibility
Lateral Susceptibility

5.0 Conclusion
ATTACHMENTS:

ATTACHMENT A: Vicinity Map
ATTACHMENT B: Field Assessment Photographs
ATTACHMENT C: Form 1: Initial Desktop Analysis
ATTACHMENT D: Form 3: Vertical Susceptibility Field Sheet ATTACHMENT E: Form 4: Lateral Susceptibility Field Sheet ATTACHMENT F: Form 6: Probability of Mass Wasting Bank Failure 3 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415

1.0 Introduction
A new brewery with tasting room, garden, food truck staging areas, and an associated parking lot is being proposed by Karl Strauss Brewing Company on a

1.51 acre site at Los Posas Road and Los Vallecitos Blvd inthe City of San Marcos.

Runoff from the site is discharged via lateral into an existing 72” pipe recently constructed as part of the adjacent Palomar Station development. The 72” pipe is part of the public storm drain system that flows in a generally southerly direction before discharging into a vegetated channel, referred to herein as Los Posas Creek. See Attachment A for vicinity map showing project site in relation to Los Posas Creek.

The project is subject to hydromodification requirements as described in Chapter 6 of the City of San Marcos BMP Design Manual, the purpose of which is to minimize the potential of storm water discharges from the MS4 from causing altered flow regimes and excessive downstream erosion in receiving waters. To meet this requirement the project must provide flow control for post-project runoff to meet the flow control performance standard. The flow control performance standard covers flow rates ranging from a lower flow threshold of 10 percent, 30 percent or 50 percent of the pre -development 2-year runoff event (0.1Q2, 0.3Q2, or

0.5Q2) up to the pre-development 10-year runoff event (Q10). The determination of the low flow threshold depends on the erosion susceptibility of the receiving stream with 0.1Q2 for projects discharging to streams with high susceptibility to erosion ( also the default when a channel susceptibility study has not been prepared), 0.3Q2 for projects discharging to streams with medium susceptibility to erosion, and 0.5Q2 for projects discharging to streams with low susceptibility to erosion
As described in section 6.3.4 of the San Marcos BMP Manual, the use of a higher low flow threshold of 0.3Q2 or 0.5Q2 must be supported by a channel screening report based on a tool developed by the Southern California Coastal Water Research Project (SCCWRP), documented in SCCWRP’ s Technical Report 606 TR 606), dated March 2010, “ Hydromodification Screening Tools: Field Manual for Assessing Channel Susceptibility.” This study follows the methodology of the SCCWRP in order to determine the susceptibility of Los Posas Creek, the results of which can be used to establish the required flow control sizing for the project.

2.0 Office Assessment
Although the screening tool presented in TR 606 is predominantly designed for field-based assessment, it requires some preparatory office work to provide context and familiarity with the site prior to conducting the field evaluation. A satellite image is provided in Attachment A which shows features of the overall setting such as vegetation coverage, grade -control locations, human influences, and existing infrastructure.
4 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 The office assessment also requires an initial desktop analysis, the results of which are provided on Form 1 in Attachment C. Inputs for the drainage area and mean annual precipitation where determined from StreamStats, a Web -based GIS application that provides users access to USGS Data (StreamStats report provided in Attachment C). The valley width and valley slope were determined from City of San Marcos bare earth elevation contour information (2 -ft) from 2009.

3.0 Analysis Domain
As defined in the San Marcos BMP Manual, the receiving stream is the location where runoff from the project is discharged to natural or un-lined channels. This occurs at the outfall of Los Posas Creek from a triple box culvert on the west side of Los Posas Road, approximately 500ft south of the intersection of Linda Vista Drive. This is the upstream limit of analysis as it is where the open , unlined channel begins (Photos 1, 2).

Per criteria in TR 606, the downstream extent of analysis is determined to be the closest of the following:

At least one reach downstream of the first grade -control point Tidal backwater/lentic waterbody
Equal order tributary
A 2-fold increase in drainage area
The nearest lentic waterbody is Lake San Marcos, approximately 5,000 ft downstream and an equal order tributary/2 -fold increase in drainage area does not occur until the confluence with San Marcos Creek approximately 2,000 ft downstream. The first grade control point is approximately 400 ft downstream where a small channel discharges from the east and the main channel shows distinct changes, in particular to bank slope. Although analysis is only required for one reach downstream of this location, the downstream extent selected was the crossing beneath San Marcos Boulevard (Photo 14) as this is a logical divide which may offer grade control, cause discontinuities in the conveyance of water or sediment, etc.

Although the 1,200 ft analysis domain is longer than the 656 feet (200m) maximum reach length for assigning a susceptibility rating per TR 606, this section of Los Posas Creek is an engineered channel which aerial photos and field reconnaissance show to be relatively uniform. Dividing the analysis domain into additional subreaches will not produce significantly different results.

4.0 Field Screening
A field assessment of the analysis domain was done on November 8, 2019. Much of the study area contained dense vegetation (Photos 2, 11) which limited access to some areas of the channel. The areas of the channel that were accessible for assessment were typically moderately vegetated (Photo 12). Evaluating just these 5 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 areas errs conservative as additional vegetation helps hold soil together and reduces flow velocity, further reducing susceptibility to erosion. Aerial photographs of the area dating back over 20 years show that vegetation coverage along the channel has increased with time.

The field screening tool uses a combination of relatively simple, but quantitative field indicators as input parameters to a set of decision trees. These decision trees, along with checklists, tables and calculations, follow a logical progression for assigning a susceptibility rating of Low, Medium, High, or Very High to the channel reach being assessed. susceptibility ratings are assigned independently to the vertical and lateral conditions, the more conservative of which is used to determine the erosion susceptibility ofthe channel. Vertical stability is aprerequisite for lateral stability because a stream that incises can increase bank heights to the point of collapse and channel widening. Accordingly, vertical susceptibility is assessed first because it affects the lateral rating in most instances.

Vertical Susceptibility
The decision tree and associated checklists and calculations for determining a vertical susceptibility rating ( Form 3 from TR 606) are in Attachment D. The purpose of the vertical susceptibility decision tree is to assess the state of the channel bed with a particular focus on the risk of incision . There are three potential states of bed material based on broad classes of armoring potential, described in TR 606 as follows:

Labile Bed – sand-dominated bed, little resistant substrate Transitional/Intermediate Bed – bed typically characterized by gravel/small cobble, intermediate level of resistance of the substrate and uncertain potential for armoring
Threshold Bed ( Course/Armored Bed) – armored with large cobbles or larger bed material or highly-resistant bed substrate
The decision tree includes a photographic supplement to help make the determination of bed material. Through field observation it was determined thatthe bed was not sand-dominated nor sufficiently armored. Although the channel is not consistently armored, some larger cobble was observed along the banks adjacent to the initial discharge location into the channel (Photos 3, 4). Concrete armoring of the bed was observed upstream of the culvert crossing beneath San Marcos Blvd, at the downstream end of the analysis domain ( Photos 13, 14). For the majority of the analysis domain, a surface veneer and dense vegetation cause uncertainty in the potential for armoring. Penetration of the soil was difficult and the limited substrate bed material that was able to be observed contained gravel Photo 5), both of which are consistent with a Transitional/Intermediate Bed. 6 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 Intermediate beds require the following additional risk factors to be examined before a vertical rating can be assigned.

Armoring Potential – The channel was determined to have intermediate armoring potential based on Form 3 Checklist 1. This is a result of the unknown condition of the substrate due to surface veneer and vegetation.

Grade Control – The channel was determined to have intermediate grade control based on Form 3 Checklist 2. Man-made grade control is present at each end of the analysis domain in the form of culverts. Both appear in good condition with no apparent undermining, flanking, etc. The dense vegetation between functions as a continuous natural grade control and the flat valley slope determined as part of the desktop analysis mean that grade control will have an affect across a longer distance. The determination of intermediate instead of effective grade control was made to err conservative due to potential evidence of erosion observed on a few short stretches of bank along the channel (Photo 6)
Proximity to incision/braiding threshold – The channel was determined to have a screening index score of B per Form 3 Table 1as the surface veneer and vegetation result in hardpan/d50 that is indeterminate.

The results of the additional risk factors were translated to numeric values and used as inputs into a formula for coming up with an overall vertical rating as shown at the end of Form 3. The vertical rating was determined to be 6, which falls into the range of MEDIUM VERTICAL SUSCEPTIBILITY.

Lateral Susceptibility
The decision tree for determining a lateral susceptibility rating ( Form 4 from TR 606) is in Attachment E. The purpose of the lateral decision tree is to assess the state of the channel banks with a particular focus on the risk of widening. Although the channel is straight and linear, it is laterally adjustabl e due to lack of armoring.

However, the field assessment found no evidence of lateral adjustments occurring.

The banks werefound tobe moderately to highly consolidated basedonthe criteria in TR 606. They are hard when dry with little evidence of crumbling and bank material stratification is not prevalent or contributing to failure. Although there was no evidence of extensive mass wasting occurring along the channel, TR 606 methodology requires thattheprobability of mass wasting bank failurebeanalyzed to determine whether the risk of bank failure is less than or greater than 10%.

This risk threshold determination was made using the Probability Mass Wasting diagram in Attachment F (Form 6 Figure 1 from TR 606). The inputs for bank angle and height were determined based on measurements taken in the field Photos 7-10). Assessment was done in several locations along the analysis 7 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 domain with generally consistent results, with the more conservative of the measurements being used as inputs. Even erring conservation, it was determined that the probability of mass wasting bank failure is less than 10%.

The vertical rating is medium and the VWI (Valley Width Index) was calculated to be greater than 2 during the initial desktop analysis. As a result, the channel was determined to have MEDIUM LATERAL SUSCEPTIBILITY.

5.0 Conclusion
The methodology in the SCCWRP’s Technical Report 606 was used to analyze the section of Los Posas Creek from the initial discharge into an unlined channel west of Los Posas Road to the culvert crossing beneath San Marcos Blvd.

Results of the analysis indicate that the channel has medium vertical and lateral susceptibility. As such, the Karl Straus San Marcos project should design flow control facilities based on a maximum low flow threshold of 0.3Q2 which is indicative of a receiving channel with MEDIUM SUSCEPTIBILITY to erosion.

5 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415

ATTACHMENT A

VICINITY MAP

LAKE SAN MARCOS

HYDROMOD EXEMPT PER WMAA)

SAN MARCOS CREEK
LOW SUCEPTIBILITY PER 2011

SPECIFIC PLAN STUDY)

PROJECT
SITE

LOS POSAS CREEK

UNDERGROUND PIPE)

LOS POSAS CREEK

ENGINEERED CHANNEL)

ANALYSIS DOMAIN

6 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415

ATTACHMENT B

PHOTOGRAPHS

HMENT B

FIELD ASSESSMENT

10 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 Photo 1: Looking upstream at beginning of analysis domain Photo 2: Looking downstream from beginning of analysis domain

11 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 Photo 3: Evidence of bank armoring at beginning of analysis domain Photo 4: Evidence of bank armoring at beginning of analysis domain

12 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 Photo 5: Channel bed material
Photo 6: Evidence of possible erosion

13 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 Photo 7: Typical left bank slope
Photo 8: Typical left bank height

14 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 Photo 9: Typical right bank slope
Photo 10: Typical right bank height

15 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 Photo 11: Typical heavily vegetated section of channel
Photo 12: Typical moderately vegetated section of channel

16 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415 Photo 13: Armoring at downstream end of domain of analysis Photo 14: Armoring at downstream end of domain of analysis

14 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415

ATTACHMENT C
FORM 1: INITIAL DESKTOP ANALYSIS

user: stream:

33.1360
117.1951
FORM 1:

Variable units Value Description & Source

2.6 15.8

0.005
127
350

9.90 0.016

19.08 6.65

INITIAL DESKTOP ANALYSIS
S.CA Hydromodification Screening Tool version 1.0
P
Mean annual
precipitation inches area-weighted annual precipitation via USGS delineated polygons using records from 1900 to 1960 (which was more significant in hydrologic models than polygons delineated from shorter record lengths) Brian Wiese, PE
Symbol
GIS metrics and screening indices (for detailed instructions/examples see ' Field Screening Companion Document') contributing drainage area to screening location via published HUCs and/or 30-m (or better) National Elevation Data serverADrainage NED), USGS seamless Area mi2
Sv Valley slope m/m
valley slope at site via NED, measured over a relatively homogeneous valley segment as indicated by slope, hillslope coupling/ confinement, valley alignment, confluences, etc., over a distance of up to ~500 meters or 10% of the mainchannel length (whatever is smaller) VWI Valley width
index m/m VWI = Wv / Wref
Wv Valley width meters
valley bottom width at site between natural valley walls as dictated by clear breaks in hillslope on NED raster, irrespective of potential armoring from floodplain encroachement, levees, etc. (imprecise measurements have negligible effect on rating in wide valleys where VWI >>2, as defined in lateral decision tree) Q10cfs
10-year mobility
index
Q10 10-year peak
flow m3/s Q10 = 0.0283 * Q10cfs
10-year peak
flow, US units ft3/s Q10cfs = 18.2 * A

0.87 * P0.77 ( Hawley and Bledsoe, In review)
m1.5/s0.5
INDEX = Sv * Q10 0.5
longitude (decimal degrees):
latitude (decimal degrees):

Karl Strauss San Marcos discharge location at Los Posas Creek Wref Reference width meters Wref = 6.99 * Q10 0.438
INDEX

11/13/2019 StreamStats
https:// streamstats. usgs. gov/ ss/ 1/2
039 Los Posas Creek StreamStats Report
Basin Characteristics
Parameter Code Parameter Description Value Unit
BSLDEM30M Mean basin slope computed from 30 m DEM 8 .79 percent DRNAREA Area that drains to a point on a stream 2 .6 square miles PRECIP Mean Annual Precipitation 15 .8 inches
USGS Data Disclaimer: Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey ( USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.

Region ID : CA
Workspace ID : CA20191113182948989000
Clicked Point (Latitude , Longitude ): 33 .13324 , -117 .19614 Time : 2019 -11 -13 10 :30 :07 -0800

15 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415

ATTACHMENT D
FORM 3: VERTICAL SUSCEPTIBILITY FIELD SHEET

FORM 3: VERTICAL SUSCEPTIBILITY FIELD SHEET
Circle appropriate nodes/pathway for proposed site.

Form 3 Figure 1. Vertical Susceptibility photographic supplement to be used in conjunction with Form 3 Bed Resistance above.

Sheet 1 of 4)
B - 6
Form 3 Support Materials
Form 3 Checklists 1 and 2, along with information recording in Form 3 Table 1, are intended to support the decisions pathways illustrated in Form 3 Overall Vertical Rating for Intermediate/ Transitional Bed.

Form 3 Checklist 1: Armoring Potential
A A mix of coarse gravels and cobbles that are tightly packed with < 5% surface material of diameter < 2 mm
B Intermediate to A and C or hardpan of unknown resistance, spatial extent longitudinal and depth), or unknown armoring potential due to surface veneer covering gravel or coarser layer encountered with probe C Gravels/cobbles that are loosely packed or > 25% surface material of diameter < 2 mm
Form 3 Figure 2. Armoring potential photographic supplement for assessing intermediate beds 16 < d50 < 128 mm) to be used in conjunction with Form 3 Checklist 1.

Sheet 2 of 4)
B - 7
X
Form 3 Checklist 2: Grade Control
A Grade control is present with spacing <50 m or 2/Sv m No evidence of failure/ineffectiveness, e.g., no headcutting (> 30 cm), no active mass wasting ( analyst cannot say grade control sufficient if masswasting checklist indicates presence of bank failure), no exposed bridge pilings, no culverts/structures undermined
Hard points in serviceable condition at decadal time scale, e.g., no apparent undermining, flanking, failing grout
If geologic grade control, rock should be resistant igneous and/or metamorphic; For sedimentary/hardpan to be classified as ‘grade control’, it should be of demonstrable strength as indicated by field testing such as hammer test/borings and/or inspected by appropriate stakeholder B Intermediate to A and C – artificial or geologic grade control present but spaced 2/Sv m to 4/Sv m or potential evidence of failure or hardpan of uncertain resistance
C Grade control absent, spaced > 100 m or > 4/Sv m, or clear evidence of ineffectiveness
Form 3 Figure 3. Grade-control (condition) photographic supplement for assessing intermediate beds (16 < d50 < 128 mm) to be used in conjunction with Form 3 Checklist 2.

Sheet 3 of 4)
B - 8
X
Regionally-Calibrated Screening Index Threshold for Incising/Braiding For transitional bed channels (d50 between 16 and 128 mm) or labile beds (channel not incised past critical bank height), use Form 3 Figure 3 to determine Screening Index Score and complete Form 3 Table 1.

Form 3 Figure 4. Probability of incising/braiding based on logistic regression of Screening Index and d50 to be used in conjunction with Form 3 Table 1.

Form 3 Table 1. Values for Screening Index Threshold (probability of incising/braiding) to be used in conjunction with Form 3 Figure 4 (above) to complete Form 3 Overall Vertical Rating for Intermediate/ Transitional Bed (below).. Screening Index Score: A = <50% probability of incision for current Q10, valley slope, and d50; B = Hardpan/d50 indeterminate; and C = >50% probability of incising/braiding for current Q10, valley slope, and d50. d50 ( mm)
From Form 2
Sv*Q100.5 ( m1.5/ s0.5)
From Form 1
Sv*Q100.5 ( m1.5/ s0.5)
50% risk of incising/braiding
from table in Form 3 Figure 3 above
Screening Index Score

A, B, C)
Overall Vertical Rating for Intermediate/Transitional Bed Calculate the overall Vertical Rating for Transitional Bed channels using the formula below.

Numeric values for responses to Form 3 Checklists and Table 1 as follows: A = 3, B = 6, C = 9.

Vertical Susceptibility based on Vertical Rating: <4.5 = LOW; 4.5 to 7 = MEDIUM; and >7 = HIGH.

Sheet 4 of 4)
B - 9

0.016 n/a (d50 indeterminate) B
Vertical Rating = 6 x 6 x 6 = 6
6B= 6 6B=B=
16 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415

ATTACHMENT E
FORM 4: LATERAL SUSCEPTIBILITY FIELD SHEET

FORM 4: LATERAL SUSCEPTIBILTY FIELD SHEET
Lateral Screening Forms
Circle appropriate nodes/pathway for proposed site
OR use sequence of questions provided in Form 5.

Sheet 1 of 1)
B - 10

17 4909 Murphy Canyon Road, STE 330, San Diego, CA 92123 | P. 619.787.5566 | F. 866.579.6415

ATTACHMENT F
FORM 6: PROBABILITY OF MASS WASTING BANK FAILURE

FORM 6: PROBABILITY OF MASS WASTING BANK FAILURE
If mass wasting is not currently extensive and the banks are moderately- to well-consolidated, measure bank height and angle at several locations ( i.e., at least three locations that capture the range of conditions present in the study reach) to estimate representative values for the reach. Use Form 6 Figure 1 below to determine if risk of bank failure is >10% and complete Form 6 Table 1. Support your results with photographs that include a protractor/rod/tape/person for scale.

Bank Angle
degrees)
from Field)
Bank Height
m)
from Field)
Corresponding Bank Height for
10% Risk of Mass Wasting ( m)
from Form 6 Figure 1 below)
Bank Failure Risk
10% Risk)
10% Risk)
Left Bank
Right Bank
Form 6 Figure 1. Probability Mass Wasting diagram, Bank Angle:Height/% Risk table, and Band Height:Angle schematic.

Sheet 1 of 1)
B - 12
35 deg
25 deg

1.5 m

1.5 m
10% Risk
10% Risk

4.7 m

7.6 m

Attachment 2d
Flow Control Facility Design

INTRODUCTION
This HMP analysis for flow control summarizes the approach used to model the proposed Gran Vista project in San Marcos, CA using the Environmental Protection Agency (EPA) Storm Water Management Model 5.1 (SWMM). SWMM models were prepared for the pre and post developed conditions at the site in order to determine if the proposed hydromodification/detention vault facilities have sufficient footprint and volume potential to meet the current Hydromodification Management Plan (HMP) requirements from the Regional Water Quality Control Board (RWQCB).

This HMP analysis addresses areas shown on the Existing and Proposed Condition exhibits located in Attachment 2a.

POC1 is located at the Southwest corner of the project boundary (Discharge location into the 3X8 Box Culvert) as shown on the hydromodification exhibits.

The discharge from the site will enter the enclosed storm drain system via 3X8 culvert per IP1219 crossing W Mission Rd. The discharge will be routed southerly via concrete lined channels and enclosed storm drain, except for a small portion of an unlined open channel that was analyzed to have a medium erosion susceptibility per an approved susceptibility analysis prepared by Delane Engineering and saved in the City files. The flow from the site will ultimately discharge into the HMP exempted Lake San Marcos.

The discharge location is not exempt from flow-control hydromodification since the site does not directly discharge to Lake San Marcos. However, the open unlined channel in the flow-path from the site to the exempt body was determined to have a medium erosion susceptibility.

Therefore, 0.3 Q2 was used as the lower flow threshold for the receiving stream for the project site. POC1 is discussed in the following sections of this Attachment.

SWMM MODEL DEVELOPMENT
Two (2) SWMM models were prepared for this study for POC1, one for pre-developed conditions and the second for the proposed condition. SWMM was used since we have found it to be more comparable to San Diego area watersheds than the more widely used San Diego Hydrology Model (SDHM). For both SWMM models, flow duration curves were prepared to determine if the proposed hydromodification/detention vault facilities were sufficient to meet the current HMP requirements.

The inputs required to develop SWMM models include rainfall, watershed characteristics, and BMP configurations. The Oceanside Rain Gage from the Project Clean Water website was used for this study since it is the most representative of the project site precipitation among the available gages based on the site location and topograpy.

Evaporation for the site is modeled using average monthly values from the San Diego County hourly dataset (Zone 4). The site was modeled with hydrologic soil groups C and D soils as determined from USGS Survey web-based Soil Survey Map. Other SWMM inputs for the subareas are discussed in the subsections to this document where the selection of the parameters is explained in detail.

HYDROMODIFICATION MODELING
Developed storm water runoff is routed through the proposed treatment facilities consisting of Two (2) hydromodification and detention vaults, located southeast and southwest of the project site. Flows from the proposed project drain to these vaults, location of vaults can be found on the Proposed Hydromodification Map. Onsite flow will exit this site to 3x8 Box Culvert at the southwest corner of the site, which is the chosen point of compliance (POC-1).

DMA Discussion:

Runoff from approximately

1. 1.92 acres at the western portion of the project (DMA-1) is directed towards the proposed Vault HMP-1, and BF-3-1 Volume based MWS unit to address water quality

2. 3.46 acres (including 0.023 acres of the existing driveway) at the eastern portion of the project (DMA-2) is directed towards the proposed Vault HMP-2, and BF-3-2 Volume based MWS unit to address water quality

3. 0.11 acres of the developed area is routed to the flow-based MWS unit to address water quality and directly to the POC-1 (DMA-4).

4. 0.44 acres of the developed area is routed to the flow-based MWS unit to address water quality and directly to poc-1

5. 0.11 ac of the self mitigating pervious slopes (per section 5.2.2 from the BMP manual),

0.005 (208 sf) of de minimis area is routed directly to the POC-1

6. 0.453 ac of the undisturbed existing parking and driveway south of the project (DMA3- EX) with additional 0.09 ac of the proposed driveways and sidewalks (DMA-3) will be routed to the flow-based MWS unit to address water quality and directly connected to the POC-1.

Vaults HMP-1 and HM-2 are sized to detain for the direct flows from DMA-1 and DMA-2 and to over-detain for DMA-3,4,5, self mitigation and de minimis areas to meet HMP requirements when measured at POC1
Vault Discussion:

Vaults’ detaining characteristics have been included in the proposed condition hydromodifcation SWMM model per this report. The vaults will consist of storage ( for water quality and HMP volume). Flow control in the vaults is achieved using multiple orifices on a concrete riser box. The size, number and location of the orifices are presented in the vault Table below. Flow will exit the vaults via a 3’ x 2’ and 4’X3’ risers with a rim elevation of 5.4’ for Vault1 and 5.9’ for Vault 2 above the vault base. The emergency overflow riser is utilized in storm events equal to or larger than the 100 year storm. Once flows exceed the rim elevation of the riser, runoff will drain over the riser rim and enter discharge pipe. Sizing and further peak flow discussion is in the Drainage Study.
.

Basin Table
HMP-1
(POC-1)
HMP-2
(POC-1)
Weir Height (ft.)* 5.4 5.9
Weir Length (ft.) 10.0 10
Approx. Dimensions (LxW) 2’x3’ 4’x3’
Top Orifice
No. of Orifices 2 10
Diameter (in) 3 3
Invert Height (ft.)* 4.50 5.0
Middle Orifice
No. of Orifices 2 10
Diameter (in) 4 3
Invert Height (ft.)* 3.5 3.4
Bottom Orifice
No. of Orifices 2 1
Diameter (in) 4 2
Invert Height (ft.)* 2.5 2.6
Water Quaity Orifice
No. of Orifices 1 1
Diameter (in) 1.6 2.3
*to the volume based MWS unit
Once flows have been routed through the respective vaults, flows discharges southwest to the existing 3x8 box culvert which is chosen as POC-1.

FLOW DURATION CURVE COMPARISON
The Flow Duration Curve (FDC) for the site was compared at the Point of Compliance (POC1) by exporting the hourly runoff time series results from SWMM to a spreadsheet. FDC was compared between 30% of the existing condition Q2 (based on accepting an assumption of medium susceptibility for downstream channel erosion as approved by the susceptibility analysis that was prepared by Delane Engineering for the unlined portion of the channel and saved in the City files) up to the existing condition Q10. The Q2 and Q10 were determined using a partial duration statistical analysis of the runoff time series in an Excel spreadsheet using the Cunnane plotting position method (which is the preferred plotting methodology in the HMP Permit). The range between 30% of Q2 and Q10 was divided into 100 equal time intervals; the number of hours that each flow rate was exceeded was counted from the hourly series.

Additionally, the intermediate peaks with a return period “i” were obtained (Qi with i=3 to 9).

For the purpose of the plot, the values were presented as percentage of time exceeded for each flow rate.

FDC comparison at POC1 is illustrated in Figure 1 in logarithmic scale. POC1 corresponds with the point located downstream of the discharge of the discharge pipe. Attachment 10 provides detailed drainage exhibit for the post-developed condition.

As can be seen in Figure 1, the FDC for the proposed condition is within 110% of the curve for the existing condition. The additional runoff volume generated from developing the site will be released to the downstream storm drain at a flow rate below the 30% Q2 lower threshold.

Additionally, the project will also not increase peak flow rates between the Q2 and the Q10, as shown in the graphic and also in the attached table.

SUMMARY
The total project area to POC-1 is identical in pre and post project condition. The proposed biofiltration and hydromodification/detention facilities mitigate increased flow frequencies as a result of development.

Area Summary
Existing (AC) Proposed (AC)
POC 1 6.598 6.598

KEY ASSUMPTIONS

1. C and D Soils are representative of the existing condition site.

ATTACHMENTS

1. Flow Duration Curve Analysis

2. Elevation vs. Area Curves vs. Discharge Curves to be used in SWMM

3. Vault Details

4. SWMM Input Data (Existing and Proposed Models)

5. SWMM Screens and Explanation of Significant Variables

6. Drying Time of the HMP volume

7. Hydromodification Watershed Maps

Flow Duration Curve Analysis, Plot & Table
Flow duration curve shall not exceed the existing conditions by more than 10% neither in peak flow nor duration.

The figure on the following page illustrates that the flow duration curve in post-development conditions after the proposed BMPs is below the existing flow duration curve. The flow duration curve table following the curve shows that if the interval 0.30Q 2 – Q 10 is divided in 100 sub-intervals, then a) the post development divided by pre-development durations are never larger than 110% (the permit allows up to 110%); and b) there are no more than 10 intervals in the range 101%-110% which would imply an excess over 10% of the length of the curve (the permit allows less than 10% of excesses measured as 101-110%).

Consequently, the design passes the hydromodification test.

It is important to note that the flow duration curve can be expressed in the “x” axis as percentage of time, hours per year, total number of hours, or any other similar time variable. As those variables only differ by a multiplying constant, their plot in logarithmic scale is going to look exactly the same and compliance can be observed regardless of the variable selected. The selection of a logarithmic scale in lieu of the normal scale is preferred, as differences between the pre-development and post-development curves can be seen more clearly in the entire range of analysis. Both graphics are presented for reference.

In terms of the “y” axis, the peak flow value is the variable of choice. As an additional analysis performed by H&A, not only the range of analysis is clearly depicted (30% of Q 2 to Q 10) but also all intermediate flows are shown (30% of Q 2, 50% of Q 2, Q 2, Q 3, Q 4, Q 5, Q 6, Q 7, Q 8 and Q 9) in order to demonstrate compliance at any range Q x – Q x+1. It must be pointed out that one of the limitations of both the SWMM and SDHM models is that the intermediate analysis is not performed (to obtain Qi from i = 2 to 10). H&A performed the analysis using the Cunnane Plotting Position Method (the preferred method in the HMP permit) from the “n” largest independent peak flows obtained from the continuous time series.

The largest “n” peak flows are attached in this appendix, as well as the values of Qi with a return period “i”, from i=2 to 10. The Q i values are also added into the flow-duration plot.

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

4.000

4.500

5.000

1.0E-06 1.0E-05 1.0E-04 1.0E-03 1.0E-02 Flow (cfs)
% Time Exceeding
Flow Duration Curve - POC 1
[Pre vs. Post (Mitigated)]
Pre-project Q
Post-project (Mitigated) Q
ATTACHMENT 1 - Flow Duration Curve Analysis, Plot & Table (Logarithmic “x” scale)
Figures 1.a – Flow Duration Curve Comparison & Peak Flow Frequency Curves Comparison

0.00 0.50

1.00 1.50

2.00 2.50

3.00 3.50

4.00 4.50

5.00 0 1 2 3 4 5 6 7 8 9 10
Peak Flow in cfs
Return Period in Years
Peak Flow Frequency Curves
POC1
Pre-project Qpeak
Post-project Mitigated Qpeak
Figures 1.b – Flow Duration Curve Comparison & Peak Flow Frequency Curves Comparison

LAS POSAS
Low-flow Threshold: 30%

0.3xQ2 (Pre): 0.728 cfs
Q10 (Pre): 4.466 cfs
Ordinate #: 100 3
Incremental Q (Pre): 0.03738 cfs POC 1
Total Hourly Data: 497370 hours The proposed BMP: PASSED Interval Pre-project Flow
(cfs) Pre-project Hours Pre-project %
Time Exceeding
Post-project
Hours
Post-project %
Time Exceeding Percentage Pass/Fail
0 0.728 231 4.64E-04 164 3.30E-04 71% Pass
1 0.765 217 4.36E-04 148 2.98E-04 68% Pass
2 0.803 201 4.04E-04 133 2.67E-04 66% Pass
3 0.840 196 3.94E-04 121 2.43E-04 62% Pass
4 0.878 191 3.84E-04 113 2.27E-04 59% Pass
5 0.915 175 3.52E-04 105 2.11E-04 60% Pass
6 0.952 169 3.40E-04 95 1.91E-04 56% Pass
7 0.990 157 3.16E-04 86 1.73E-04 55% Pass
8 1.027 152 3.06E-04 82 1.65E-04 54% Pass
9 1.065 145 2.92E-04 80 1.61E-04 55% Pass
10 1.102 136 2.73E-04 70 1.41E-04 51% Pass
11 1.139 127 2.55E-04 63 1.27E-04 50% Pass
12 1.177 123 2.47E-04 59 1.19E-04 48% Pass
13 1.214 112 2.25E-04 55 1.11E-04 49% Pass
14 1.251 107 2.15E-04 54 1.09E-04 50% Pass
15 1.289 102 2.05E-04 49 9.85E-05 48% Pass
16 1.326 98 1.97E-04 48 9.65E-05 49% Pass
17 1.364 93 1.87E-04 44 8.85E-05 47% Pass
18 1.401 89 1.79E-04 43 8.65E-05 48% Pass
19 1.438 83 1.67E-04 41 8.24E-05 49% Pass
20 1.476 75 1.51E-04 40 8.04E-05 53% Pass
21 1.513 72 1.45E-04 38 7.64E-05 53% Pass
22 1.550 69 1.39E-04 33 6.63E-05 48% Pass
23 1.588 67 1.35E-04 31 6.23E-05 46% Pass
24 1.625 64 1.29E-04 31 6.23E-05 48% Pass
25 1.663 63 1.27E-04 30 6.03E-05 48% Pass
26 1.700 58 1.17E-04 28 5.63E-05 48% Pass
27 1.737 55 1.11E-04 27 5.43E-05 49% Pass
28 1.775 53 1.07E-04 25 5.03E-05 47% Pass
29 1.812 51 1.03E-04 24 4.83E-05 47% Pass
30 1.850 49 9.85E-05 24 4.83E-05 49% Pass
31 1.887 48 9.65E-05 24 4.83E-05 50% Pass
32 1.924 47 9.45E-05 23 4.62E-05 49% Pass
33 1.962 46 9.25E-05 22 4.42E-05 48% Pass
34 1.999 43 8.65E-05 21 4.22E-05 49% Pass
35 2.036 43 8.65E-05 20 4.02E-05 47% Pass
36 2.074 41 8.24E-05 19 3.82E-05 46% Pass
37 2.111 39 7.84E-05 19 3.82E-05 49% Pass
38 2.149 38 7.64E-05 18 3.62E-05 47% Pass
39 2.186 36 7.24E-05 18 3.62E-05 50% Pass
40 2.223 36 7.24E-05 18 3.62E-05 50% Pass
41 2.261 36 7.24E-05 18 3.62E-05 50% Pass
42 2.298 36 7.24E-05 18 3.62E-05 50% Pass
43 2.335 36 7.24E-05 17 3.42E-05 47% Pass
44 2.373 36 7.24E-05 16 3.22E-05 44% Pass
45 2.410 35 7.04E-05 14 2.81E-05 40% Pass
46 2.448 32 6.43E-05 14 2.81E-05 44% Pass
47 2.485 32 6.43E-05 14 2.81E-05 44% Pass
48 2.522 30 6.03E-05 14 2.81E-05 47% Pass
49 2.560 30 6.03E-05 13 2.61E-05 43% Pass

LAS POSAS
Interval Pre-project Flow
(cfs) Pre-project Hours Pre-project %Time Exceeding
Post-project
Hours
Post-project %
Time Exceeding Percentage Pass/Fail
50 2.597 30 6.03E-05 13 2.61E-05 43% Pass
51 2.635 30 6.03E-05 13 2.61E-05 43% Pass
52 2.672 27 5.43E-05 13 2.61E-05 48% Pass
53 2.709 25 5.03E-05 13 2.61E-05 52% Pass
54 2.747 25 5.03E-05 13 2.61E-05 52% Pass
55 2.784 24 4.83E-05 13 2.61E-05 54% Pass
56 2.821 22 4.42E-05 13 2.61E-05 59% Pass
57 2.859 20 4.02E-05 13 2.61E-05 65% Pass
58 2.896 19 3.82E-05 13 2.61E-05 68% Pass
59 2.934 19 3.82E-05 13 2.61E-05 68% Pass
60 2.971 18 3.62E-05 11 2.21E-05 61% Pass
61 3.008 16 3.22E-05 10 2.01E-05 63% Pass
62 3.046 15 3.02E-05 10 2.01E-05 67% Pass
63 3.083 15 3.02E-05 10 2.01E-05 67% Pass
64 3.120 14 2.81E-05 9 1.81E-05 64% Pass
65 3.158 14 2.81E-05 9 1.81E-05 64% Pass
66 3.195 13 2.61E-05 8 1.61E-05 62% Pass
67 3.233 13 2.61E-05 8 1.61E-05 62% Pass
68 3.270 13 2.61E-05 8 1.61E-05 62% Pass
69 3.307 12 2.41E-05 7 1.41E-05 58% Pass
70 3.345 12 2.41E-05 7 1.41E-05 58% Pass
71 3.382 12 2.41E-05 7 1.41E-05 58% Pass
72 3.420 12 2.41E-05 7 1.41E-05 58% Pass
73 3.457 12 2.41E-05 6 1.21E-05 50% Pass
74 3.494 12 2.41E-05 6 1.21E-05 50% Pass
75 3.532 12 2.41E-05 6 1.21E-05 50% Pass
76 3.569 10 2.01E-05 6 1.21E-05 60% Pass
77 3.606 10 2.01E-05 6 1.21E-05 60% Pass
78 3.644 10 2.01E-05 6 1.21E-05 60% Pass
79 3.681 10 2.01E-05 6 1.21E-05 60% Pass
80 3.719 10 2.01E-05 6 1.21E-05 60% Pass
81 3.756 9 1.81E-05 6 1.21E-05 67% Pass
82 3.793 9 1.81E-05 6 1.21E-05 67% Pass
83 3.831 9 1.81E-05 6 1.21E-05 67% Pass
84 3.868 9 1.81E-05 6 1.21E-05 67% Pass
85 3.905 9 1.81E-05 6 1.21E-05 67% Pass
86 3.943 9 1.81E-05 6 1.21E-05 67% Pass
87 3.980 9 1.81E-05 6 1.21E-05 67% Pass
88 4.018 8 1.61E-05 6 1.21E-05 75% Pass
89 4.055 8 1.61E-05 6 1.21E-05 75% Pass
90 4.092 8 1.61E-05 6 1.21E-05 75% Pass
91 4.130 7 1.41E-05 5 1.01E-05 71% Pass
92 4.167 7 1.41E-05 5 1.01E-05 71% Pass
93 4.205 7 1.41E-05 5 1.01E-05 71% Pass
94 4.242 7 1.41E-05 5 1.01E-05 71% Pass
95 4.279 5 1.01E-05 5 1.01E-05 100% Pass
96 4.317 5 1.01E-05 5 1.01E-05 100% Pass
97 4.354 5 1.01E-05 4 8.04E-06 80% Pass
98 4.391 5 1.01E-05 3 6.03E-06 60% Pass
99 4.429 5 1.01E-05 3 6.03E-06 60% Pass
100 4.466 5 1.01E-05 3 6.03E-06 60% Pass
ATTACHMENT 2 - Elevation vs. Area Curves vs. Discharge Curves to be used in SWMM Elevation vs Area
For the receiving detention vault, a storage node is used to route the hydrographs. The elevation vs area curve in the model is calculated in Excel and imported into the model at a 0.1 ft. interval range.

Elevation vs Discharge
The total discharge peak flow is imported from an Excel spreadsheet that calculated the elevation vs discharge of the multiple outlet system.

The orifices have been selected to maximize their size while still restricting flows to conform to the required 30% of the Q2 event flow as mandated in the Final Hydromodification Management Plan by Brown & Caldwell, dated March 2011. While we acknowledge that these orifices are small, to increase the size of these outlets would impact the vaults’ ability to restrict flows beneath the HMP thresholds, thus preventing the BMP from conformance with HMP requirements.

In order to prevent blockage of the orifice, a debris screen will be fitted to the base invert of the lower orifices located within the detention basin. Regular maintenance of the riser and orifices will be performed to ensure potential blockages are minimized. A detail of the orifice and riser structures is provided in Section 5 of this Attachment. The stage-storage and stagedischarge calculations have been provided on the following pages.

Discharge vs Elevation Table
Low orifice: 1.6 " Top orifice: 8 "
Number: 1 Number: 0
Cg-low: 0.61 Cg-low: 0.61
invert elev: 0.00 ft invert elev: 0.00 ft
Middle orifice: 1.5 " Emergency inlet:
number of orif: 0 Rim height: 4.75 ft
Cg-middle: 0.61 Area 6.00 sq ft <--- 3' x2'
invert elev: 0.50 ft Circumference 10.00 ft
h H/D-low H/D-mid H/D-top Qlow-orif Qlow-weir Qtot-low Qmid-orif Qmid-weir Qtot-med Qtop-orif Qtop-weir Qtot-top Qemerg Qtot (ft) - - - (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs)

0.0 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.1 0.75 0.00 0.15 0.012 0.010 0.010 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.010

0.2 1.50 0.00 0.30 0.025 0.030 0.025 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.025

0.3 2.25 0.00 0.45 0.033 0.044 0.033 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.033

0.4 3.00 0.00 0.60 0.039 0.046 0.039 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.039

0.5 3.75 0.00 0.75 0.045 0.060 0.045 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.045

0.6 4.50 0.80 0.90 0.050 0.150 0.050 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.050

0.7 5.25 1.60 1.05 0.054 0.437 0.054 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.054

0.8 6.00 2.40 1.20 0.059 1.113 0.059 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.059

0.9 6.75 3.20 1.35 0.062 2.457 0.062 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.062

1.0 7.50 4.00 1.50 0.066 4.848 0.066 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.066

1.1 8.25 4.80 1.65 0.069 8.781 0.069 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.069

1.2 9.00 5.60 1.80 0.073 14.881 0.073 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.073

1.3 9.75 6.40 1.95 0.076 23.920 0.076 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.076

1.4 10.50 7.20 2.10 0.079 36.828 0.079 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.079

1.5 11.25 8.00 2.25 0.082 54.712 0.082 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.082

1.6 12.00 8.80 2.40 0.085 78.866 0.085 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.085

1.7 12.75 9.60 2.55 0.087 110.792 0.087 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.087

1.8 13.50 10.40 2.70 0.090 152.208 0.090 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.090

1.9 14.25 11.20 2.85 0.093 205.069 0.093 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.093

2.0 15.00 12.00 3.00 0.095 271.576 0.095 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.095

2.1 15.75 12.80 3.15 0.097 354.197 0.097 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.097

2.2 16.50 13.60 3.30 0.100 455.676 0.100 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.100

2.3 17.25 14.40 3.45 0.102 579.052 0.102 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.102

2.4 18.00 15.20 3.60 0.104 727.670 0.104 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.104

2.5 18.75 16.00 3.75 0.107 905.200 0.107 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.107 Vault #1 WQ Discharge to the
MWS BF-3-1 (was not included
in detention calcs)
Vault #1 HMP Discharge
Discharge vs Elevation Table
Low orifice: 4 " Top orifice: 3.000 "
Number: 2 Number: 2.000
Cg-low: 0.61 Cg-low: 0.610
invert elev: 2.50 ft invert elev: 4.500 ft
Middle orifice: 4 " Emergency inlet:
number of orif: 2 Rim height: 5.40 ft
Cg-middle: 0.61 Area 6.00 sq ft <---2' x 3'
invert elev: 3.50 ft Circumference 10.00 ft
h H/D-low H/D-mid H/D-top Qlow-orif Qlow-weir Qtot-low Qmid-orif Qmid-weir Qtot-med Qtop-orif Qtop-weir Qtot-top Qemerg Qtot (ft) - - - (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs)

0.0 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.1 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.2 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.3 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.4 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.5 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.6 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.7 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.8 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.9 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

1.0 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

1.1 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

1.2 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

1.3 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

1.4 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

1.5 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

1.6 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

1.7 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

1.8 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

1.9 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

2.0 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

2.1 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

2.2 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

2.3 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

2.4 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

2.5 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

2.6 0.30 0.00 0.00 0.000 0.037 0.037 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.037

2.7 0.60 0.00 0.00 0.156 0.138 0.138 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.138

2.8 0.90 0.00 0.00 0.312 0.280 0.280 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.280

2.9 1.20 0.00 0.00 0.413 0.442 0.413 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.413

3.0 1.50 0.00 0.00 0.493 0.600 0.493 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.493

3.10 1.80 0.00 0.00 0.562 0.734 0.562 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.562

3.2 2.10 0.00 0.00 0.624 0.830 0.624 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.624

3.3 2.40 0.00 0.00 0.680 0.883 0.680 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.680

3.4 2.70 0.00 0.00 0.732 0.901 0.732 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.732

3.5 3.00 0.00 0.00 0.780 0.906 0.780 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.780

3.6 3.30 0.30 0.00 0.825 0.938 0.825 0.000 0.037 0.037 0.000 0.000 0.000 0.000 0.863

3.7 3.60 0.60 0.00 0.869 1.061 0.869 0.156 0.138 0.138 0.000 0.000 0.000 0.000 1.006

3.8 3.90 0.90 0.00 0.910 1.358 0.910 0.312 0.280 0.280 0.000 0.000 0.000 0.000 1.18981

3.9 4.20 1.20 0.00 0.949 1.944 0.949 0.413 0.442 0.413 0.000 0.000 0.000 0.000 1.36154

4.0 4.50 1.50 0.00 0.987 2.960 0.987 0.493 0.600 0.493 0.000 0.000 0.000 0.000 1.47983

4.1 4.80 1.80 0.00 1.023 4.584 1.023 0.562 0.734 0.562 0.000 0.000 0.000 0.000 1.585

4.2 5.10 2.10 0.00 1.058 7.028 1.058 0.624 0.830 0.624 0.000 0.000 0.000 0.000 1.682

4.3 5.40 2.40 0.00 1.092 10.542 1.092 0.680 0.883 0.680 0.000 0.000 0.000 0.000 1.772

4.4 5.70 2.70 0.00 1.125 15.420 1.125 0.732 0.901 0.732 0.000 0.000 0.000 0.000 1.8565

4.5 6.00 3.00 0.00 1.157 22.001 1.157 0.780 0.906 0.780 0.000 0.000 0.000 0.000 1.937

4.6 6.30 3.30 0.40 1.188 30.670 1.188 0.825 0.938 0.825 0.000 0.032 0.032 0.000 2.045 0 1
2 0 1 2 3 4 5 6 7 8 9 10
Lower, Middle & Top Orifice
Low Orifice Middle Orifice Top Orifice
0 10
20 30
40 5060
70 80
90 100
0 1 2 3 4 5 6 7 8 9 10
Total Discharge
Combined Total Discharge; Low, Middle, Top Orifice
and Riser
h(ft)
Q (cfs)
h(ft)
Q (cfs)

4.7 6.60 3.60 0.80 1.218 41.866 1.218 0.869 1.061 0.869 0.132 0.112 0.112 0.000 2.199

4.8 6.90 3.90 1.20 1.248 56.080 1.248 0.910 1.358 0.910 0.201 0.215 0.201 0.000 2.358

4.9 7.20 4.20 1.60 1.277 73.861 1.277 0.949 1.944 0.949 0.252 0.316 0.252 0.000 2.478

5.0 7.50 4.50 2.00 1.305 95.817 1.305 0.987 2.960 0.987 0.294 0.391 0.294 0.000 2.586

5.1 7.80 4.80 2.40 1.333 122.620 1.333 1.023 4.584 1.023 0.331 0.430 0.331 0.000 2.687

5.2 8.10 5.10 2.80 1.360 155.009 1.360 1.058 7.028 1.058 0.364 0.439 0.364 0.000 2.782

5.3 8.40 5.40 3.20 1.386 193.789 1.386 1.092 10.542 1.092 0.395 0.449 0.395 0.000 2.873

5.4 8.70 5.70 3.60 1.413 239.840 1.413 1.125 15.420 1.125 0.423 0.517 0.423 0.000 2.960

5.5 9.00 6.00 4.00 1.438 294.116 1.438 1.157 22.001 1.157 0.450 0.738 0.450 0.980 4.025

5.6 9.30 6.30 4.40 1.463 357.648 1.463 1.188 30.670 1.188 0.475 1.249 0.475 2.773 5.899

5.7 9.60 6.60 4.80 1.488 431.549 1.488 1.218 41.866 1.218 0.498 2.233 0.498 5.094 8.298

5.8 9.90 6.90 5.20 1.512 517.017 1.512 1.248 56.080 1.248 0.521 3.930 0.521 7.842 11.124

5.9 10.20 7.20 5.60 1.536 615.336 1.536 1.277 73.861 1.277 0.543 6.636 0.543 10.960 14.316

6.0 10.50 7.50 6.00 1.560 727.878 1.560 1.305 95.817 1.305 0.564 10.717 0.564 14.407 17.836 depth area sft area (ac) elevation volume (cf)
volume
(acft)

0.0 2100 0.05 0.0 0 0.00

0.1 2100 0.05 0.1 210 0.00

0.2 2100 0.05 0.2 420 0.01

0.3 2100 0.05 0.3 630 0.01

0.4 2100 0.05 0.4 840 0.02

0.5 2100 0.05 0.5 1050 0.02

0.6 2100 0.05 0.6 1260 0.03

0.7 2100 0.05 0.7 1470 0.03

0.8 2100 0.05 0.8 1680 0.04

0.9 2100 0.05 0.9 1890 0.04

1.0 2100 0.05 1.0 2100 0.05

1.1 2100 0.05 1.1 2310 0.05

1.2 2100 0.05 1.2 2520 0.06

1.3 2100 0.05 1.3 2730 0.06

1.4 2100 0.05 1.4 2940 0.07

1.5 2100 0.05 1.5 3150 0.07

1.6 2100 0.05 1.6 3360 0.08

1.7 2100 0.05 1.7 3570 0.08

1.8 2100 0.05 1.8 3780 0.09

1.9 2100 0.05 1.9 3990 0.09

2.0 2100 0.05 2.0 4200 0.10

2.1 2100 0.05 2.1 4410 0.10

2.2 2100 0.05 2.2 4620 0.11

2.3 2100 0.05 2.3 4830 0.11

2.4 2100 0.05 2.4 5040 0.12

2.5 2100 0.05 2.5 5250 0.12

2.6 2100 0.05 2.6 5460 0.13

2.7 2100 0.05 2.7 5670 0.13

2.8 2100 ` 2.8 5880 0.13

2.9 2100 0.05 2.9 6090 0.14

3.0 2100 0.05 3.0 6300 0.14

3.1 2100 0.05 3.1 6510 0.15

3.2 2100 0.05 3.2 6720 0.15

3.3 2100 0.05 3.3 6930 0.16

3.4 2100 0.05 3.4 7140 0.16

3.5 2100 0.05 3.5 7350 0.17

3.6 2100 0.05 3.6 7560 0.17

3.7 2100 0.05 3.7 7770 0.18

3.8 2100 0.05 3.8 7980 0.18

3.9 2100 0.05 3.9 8190 0.19

4.0 2100 0.05 4.0 8400 0.19

4.1 2100 0.05 4.1 8610 0.20

4.2 2100 0.05 4.2 8820 0.20

4.3 2100 0.05 4.3 9030 0.21

4.4 2100 0.05 4.4 9240 0.21

4.5 2100 0.05 4.5 9450 0.22

4.6 2100 0.05 4.6 9660 0.22

4.7 2100 0.05 4.7 9870 0.23

4.8 2100 0.05 4.8 10080 0.23

4.9 2100 0.05 4.9 10290 0.24

5.0 2100 0.05 5.0 10500 0.24

5.1 2100 0.05 5.1 10710 0.25

5.2 2100 0.05 5.2 10920 0.25

5.3 2100 0.05 5.3 11130 0.26

5.4 2100 0.05 5.4 11340 0.26

5.5 2100 0.05 5.5 11550 0.27

5.6 2100 0.05 5.6 11760 0.27

5.7 2100 0.05 5.7 11970 0.27
Vault#1 Stage Storage
y = 0.0482x
R² = 1

0.00 0.05

0.10 0.15

0.20 0.25

0.30 0.35

0.40 0.45

0.0 5.0 10.0
Series1
Linear
(Series1)
WQ Volume

0.05 depth(ft)
volume (ac-ft)

5.8 2100 0.05 5.8 12180 0.28

5.9 2100 0.05 5.9 12390 0.28

6.0 2100 0.05 6.0 12600 0.29

6.1 2100 0.05 6.1 12810 0.29

6.2 2100 0.05 6.2 13020 0.30

6.3 2100 0.05 6.3 13230 0.30

6.4 2100 0.05 6.4 13440 0.31

6.5 2100 0.05 6.5 13650 0.31
Elevation QAVG (CFS) DV (CF) DT (HR) Total T

0.1 0.01 210 11.25 37.12

0.2 0.02 210 3.30 25.87

0.3 0.03 210 2.01 22.57

0.4 0.04 210 1.61 20.56

0.5 0.04 210 1.38 18.95

0.6 0.05 210 1.23 17.57

0.7 0.05 210 1.12 16.34

0.8 0.06 210 1.03 15.22

0.9 0.06 210 0.96 14.19

1.0 0.06 210 0.91 13.22

1.1 0.07 210 0.86 12.31

1.2 0.07 210 0.82 11.45

1.3 0.07 210 0.78 10.63

1.4 0.08 210 0.75 9.85

1.5 0.08 210 0.73 9.09

1.6 0.08 210 0.70 8.37

1.7 0.09 210 0.68 7.67

1.8 0.09 210 0.66 6.99

1.9 0.09 210 0.64 6.33

2.0 0.09 210 0.62 5.69

2.1 0.10 210 0.61 5.07

2.2 0.10 210 0.59 4.46

2.3 0.10 210 0.58 3.87

2.4 0.10 210 0.56 3.30

2.5 0.11 210 0.55 2.73

2.6 0.13 210 0.46 2.18

2.7 0.20 210 0.30 1.72

2.8 0.32 210 0.18 1.42

2.9 0.46 210 0.13 1.24

3.0 0.57 210 0.10 1.11

3.1 0.65 210 0.09 1.01

3.2 0.71 210 0.08 0.92

3.3 0.77 210 0.08 0.84

3.4 0.83 210 0.07 0.76

3.5 0.88 210 0.07 0.69

3.6 0.95 210 0.06 0.63

3.7 1.06 210 0.05 0.56

3.8 1.23 210 0.05 0.51

3.9 1.41 210 0.04 0.46

4.0 1.56 210 0.04 0.42

4.1 1.67 210 0.03 0.38

4.2 1.77 210 0.03 0.35

4.3 1.87 210 0.03 0.32

4.4 1.96 210 0.03 0.28
Total Vault Draw Down
WQ Volume

4.5 2.04 210 0.03 0.25

4.6 2.14 210 0.03 0.23

4.7 2.27 210 0.03 0.20

4.8 2.43 210 0.02 0.17

4.9 2.57 210 0.02 0.15

5.0 2.68 210 0.02 0.13

5.1 2.79 210 0.02 0.10

5.2 2.89 210 0.02 0.08

5.3 3.47 210 0.02 0.06

5.4 4.95 210 0.01 0.05

5.5 7.58 210 0.01 0.03

5.6 11.59 210 0.01 0.03

5.7 16.66 210 0.00 0.02

5.8 22.56 210 0.00 0.02

5.9 29.17 210 0.00 0.02

6.0 25.24 210 0.00 0.01

6.1 19.75 210 0.00 0.01

6.2 23.70 210 0.00 0.01

6.3 27.93 210 0.00 0.01

6.4 31.59 210 0.00 0.00

6.5 33.82 210 0.00 0.00
Vault #2 WQ Discharge
Discharge vs Elevation Table
Low orifice: 2.3 " Top orifice: 8 "
Number: 1 Number: 0
Cg-low: 0.61 Cg-low: 0.61
invert elev: 0.00 ft invert elev: 0.00 ft
Middle orifice: 3 " Emergency inlet:
number of orif: 0 Rim height: 5.00 ft
Cg-middle: 0.61 Area 25.00 sq ft <--- 5' x 5'
invert elev: 3.20 ft Circumference 20.00 ft
h H/D-low H/D-mid H/D-top Qlow-orif Qlow-weir Qtot-low Qmid-orif Qmid-weir Qtot-med Qtop-orif Qtop-weir Qtot-top Qemerg Qtot (ft) - - - (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs)

0.0 0.00 0.00 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000

0.1 0.52 0.00 0.15 0.009 0.013 0.013 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.013

0.2 1.04 0.00 0.30 0.046 0.045 0.045 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.045

0.3 1.57 0.00 0.45 0.064 0.079 0.064 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.064

0.4 2.09 0.00 0.60 0.078 0.104 0.078 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.078

0.5 2.61 0.00 0.75 0.090 0.113 0.090 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.090

0.6 3.13 0.00 0.90 0.100 0.114 0.100 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.100

0.7 3.65 0.00 1.05 0.110 0.138 0.110 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.110

0.8 4.17 0.00 1.20 0.119 0.235 0.119 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.119

0.9 4.70 0.00 1.35 0.127 0.494 0.127 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.127

1.0 5.22 0.00 1.50 0.134 1.035 0.134 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.134

1.1 5.74 0.00 1.65 0.142 2.027 0.142 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.142

1.2 6.26 0.00 1.80 0.148 3.686 0.148 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.148

1.3 6.78 0.00 1.95 0.155 6.283 0.155 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.155

1.4 7.30 0.00 2.10 0.161 10.153 0.161 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.161

1.5 7.83 0.00 2.25 0.167 15.695 0.167 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.167

1.6 8.35 0.00 2.40 0.173 23.385 0.173 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.173

1.7 8.87 0.00 2.55 0.179 33.776 0.179 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.179

1.8 9.39 0.00 2.70 0.184 47.508 0.184 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.184

1.9 9.91 0.00 2.85 0.190 65.312 0.190 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.190

2.0 10.43 0.00 3.00 0.195 88.015 0.195 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.195

2.1 10.96 0.00 3.15 0.200 116.550 0.200 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.200

2.2 11.48 0.00 3.30 0.205 151.957 0.205 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.205

2.3 12.00 0.00 3.45 0.210 195.393 0.210 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.210

2.4 12.52 0.00 3.60 0.214 248.135 0.214 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.214

2.5 13.04 0.00 3.75 0.219 311.587 0.219 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.219 Vault #2 WQ Discharge to the
MWS BF-3-2 (was not included
in detention calcs)
Vault #2 HMP Discharge
Discharge vs Elevation Table
Low orifice: 2 " Top orifice: 3 "
Number: 1 Number: 10
Cg-low: 0.61 Cg-low: 0.61
invert elev: 2.60 ft invert elev: 5.00 ft
Middle orifice: 3 " Emergency inlet:
number of orif: 10 Rim height: 5.90 ft
Cg-middle: 0.61 Area 12.00 sq ft <---4' x 3'
invert elev: 3.40 ft Circumference 14.00 ft
h H/D-low H/D-mid H/D-top Qlow-orif Qlow-weir Qtot-low Qmid-orif Qmid-weir Qtot-med Qtop-orif Qtop-weir Qtot-top Qemerg Qtot (ft) - - - (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs) (cfs)