1. Creating a water quality credit generating facility and accounting program for MS4 permit compliance flexibility: results of a case study analysis in Orange County, CA
Mark Grey, Ph.D
Director of Environmental Affairs and Technical Director
Building Industry Association of Southern California
Construction Industry Coalition on Water Quality (CICWQ)
With support from:
Daniel Apt & Jeremy Hohnbaum, P.E.
Michael Baker International
Richard Haimann, P.E., D.WRE
Haimann Engineering

2. Creating a water quality credit generating facility and accounting program for MS4 permit compliance flexibility
Regulatory Backdrop
Water quality credit generation and use scenarios and spatial relationships
Case Study Description to Develop a Water Quality Credit Generating Facility (WQCGF)
Routing analysis
BMP selection and sizing; performance
Cost to construct and maintain

3. Creating a Water Quality Credit Generating Facility within Orange County -Regulatory Backdrop- -Credit Generation Fundamentals- -Spatial Relationships-

4. Regulatory Backdrop for LID BMP Alternative Compliance
Santa Ana RWQCB: W. Riverside Co., SW. San Bernardino Co., N. Orange Co.
Implementing Requirements
San Diego RWQCB: Southwest Riverside Co., South Orange Co.
Implementing Requirements
Order Nos. R ; R ; R
Water Quality Improvement Plan (WMAA optional) Preparation
Water Quality Equivalency Guidance Document (2015)
LID AC Program partially “defined” within WQIP-WMAA; Independent ACP locations, for example, may be identified
WQIP-WMAA addresses TMDL areas, plus possible focal areas for LID BMPs
Order Nos. R ; R ; R
Section E. Alternatives and In Lieu Programs—Waiver of BMPs
“Urban Runoff Fund” and “Water Quality Credit System” allowed with approval from EO
Implementing guidance in Orange County Model WQMP (Section 7.II-3.0 – 4.0) and Technical Guidance Document, Appendix I, III, and VI

5. Credit User = Credit Generator
Process for a Priority Development Project to Use LID BMP Alternative Compliance
North Orange County Example
Alternative Compliance Program Process Flow Chart (Model WQMP Figure 7.II-9)
START
Remaining design capture
volume after LID BMPs
implemented to the MEP
Does Project Qualify for Water Quality Credits?
Water Quality Credits
Account for any water quality credits that are applicable to the project.
7.II – 3.1
Yes
Credit User
No evaluation
necessary if
Watershed
Plan is prepared No
Is there still design capture volume remaining after credits applied?
Evaluate On-site Treatment Control BMPs
Evaluate on-site treatment control BMPs to achieve equivalent level of compliance.
7.II – 3.2
Yes No
Would the cost of implementation greatly outweigh the pollution control benefits?
Implement On-site Treatment Control BMPs
Utilize treatment control BMPs to achieve equivalent level of compliance.
7.II – 3.2
Submit Waiver Request to Regional Board Executive Officer
Include documentation of feasibility analysis.
7.II – 3.3 No
Yes
“Documentation” =
City-wide Model WQMP or
Watershed Plan
Credit
Generator
Implement Off-site Watershed Based Treatment Control BMPs
Utilize off-site treatment control BMPs to achieve equivalent level of compliance.
7.II – 3.2.1
Contribute to Runoff Mitigation Fund
Contribute to local/watershed runoff fund to achieve equivalent level of compliance.
7.II – 3.4
Continue WQMP Development Process by Selecting Applicable Source Control BMPs
7.II – 2.4.6

6. What is water quality credit trading?
Water quality credit trading is a method to achieve stormwater
(MS4) permit compliance for new and redevelopment projects
Credit
User
Generator
Example Area:
User
Public or private projects
which can’t comply with MS4 permit
on-site LID retention requirements
use water quality credits
Generator
A project accepts runoff from an adjacent tributary drainage area using a
runoff retention facility--installed underground--and the facility generates credits

7. How would a water quality credit be generated
How would a water quality credit be generated? Facility assumptions and performance standards
Planning and Design
Operations and Maintenance
Manage a Design Capture Volume in excess of the facility’s own requirement
Demonstrate, through an engineering analysis that facility can feasibly install LID retention BMP appropriately sized to accept runoff from a tributary drainage area
Provide assurances that the credit generating facility will continue in perpetuity to accept runoff from the design tributary area
Provide BMP operating and maintenance and monitoring assurances
Point of Note: Orange County Technical Guidance Document addresses BMP O&M accounting and tracking

8. Some potential reasons for a priority development project (PDP) to enter into an optional water quality credit trading program:
PDP can’t feasibly comply
A watershed plan incorporates an LID BMP alternative compliance program
PDPs are in areas without POCs or TMDL and a WQCGF is in a TMDL area/watershed
Water quality credit generating facility creates multi- benefits, outweighing benefits of on-site PDP compliance
Sub-watershed
Boundary A & B
Receiving Water

9. Water Quality Credit Generating Facility and Relationship to Tributary Area and Receiving Water
Example 1
Tributary Area
To Water Quality
Credit Generating
Facility (WQCGF)
Receiving Water
Key Assumption:
WQCGF must manage DCV of Facility
AND Some Portion of Tributary Area DCV
Water Quality
Credit Generating
Facility (WQCGF)

10. Water Quality Credit Generating Facility and Relationship to Tributary Area and Receiving Water
Example 2
Tributary Area
To Water Quality
Credit Generating
Facility (WQCGF)
PDP
Receiving Water
PDP
Water Quality
Credit Generating
Facility (WQCGF)
PDP
Key Assumption:
WQCGF must manage DCV of Facility
AND Some Portion of Tributary Area DCV

11. Water Quality Credit Generating Facility and Relationship to Credit Users
PDPs meet minimum
on-site performance
standard
Example 3 B
PDP
One watershed consisting of
two sub-watersheds: A & B
PDP
Runoff from Users
To Storm Drain
Tributary Area
to Credit
Generator
PDP
Receiving
Water A
Runoff
Sub-watershed Boundary
Projects in Watershed B use water
quality credits from a Generator
facility located in Watershed A
A water quality credit generating facility (Generator) is built in sub-watershed A, which is designed to accept all or a portion of sub-watershed A’s tributary drainage area runoff, thus creating “credits”
Generator
Receiving Water

12. Water Quality Credit Generating Facility and Relationship to Credit Users
Example 4
Tributary Area
to Credit Generator B
One watershed consisting of
two sub-watersheds: A & B
Runoff
A water quality credit generating facility (Generator) is built in sub-watershed B, which is designed to accept all or a portion of sub-watershed B’s tributary drainage area runoff, thus creating “credits”
Generator A
PDP
PDP
PDPs meet minimum
on-site performance
standard
Runoff from Users
to Storm Drain
PDP
Sub-watershed Boundary
Projects (Users) in Watershed A
use water quality credits generated at
a Generator Facility located in Watershed B
Receiving Water

13. Creating a Water Quality Credit Generating Facility within Orange County -Case Study Analysis-

14. Legacy Campus Plan Project (LCPP) Conceptual Features
~23-acre total new and re-development footprint within City of Orange; Chapman & 55
Medical complex with supporting housing units and commercial and retail space
Use consistent with the Chapman Avenue/Tustin Street Land Use Focus Area, and specifically located within the Yorba North Commercial Overlay
Adjacent to Santiago Creek, tributary to Santa Ana River
241-acre tributary area east of LCPP

15. Legacy Campus Plan Project Area and Land Use

16. Tributary Area to Legacy Campus Plan Project located in Orange, CA

17. Legacy Campus Plan Project Case Study Storm Drain System

18. Generation of Water Quality Credits Using LID Retention BMPs
LID Retention BMPs Evaluated:
Key Criteria for LID BMP Use:
Infiltration Basin
Infiltration Trench
Infiltration Gallery (underground)
Biofiltration/Biotreatment Systems
Harvest and Use Cistern
Combinations of BMPs
Size of tributary area relative to facility generating credit
Hydraulic line and grade of stormwater runoff delivery to facility from tributary area
Soil infiltration suitability/ rate at facility
Ponding Depth
Depth to groundwater
Geotechnical constraints
Area-based LID retention BMPs present challenges to accepting runoff
from a tributary area greater than facility footprint

19. LCPP Tributary Area Characteristics and Runoff Volume
Volume calculated using OC Model WQMP and TGD standards (85th percentile, 24-hour storm event)

20. LCPP Tributary Area Characteristics and Runoff Volume
Volume calculated using OC Model WQMP and TGD standards (85th percentile, 24-hour storm event)

21. EXAMPLE Retention BMP which Generates Water Quality Credits:
Underground Infiltration
Can be located under parking
System is made from 96-inch, 16 gage, perforated aluminized type-2 corrugated metal pipe
Can be as shallow as 4 feet below ground surface, or deeper

22. Pollutant Load Reduction Using Regional Stormwater Runoff Retention
Results from two case studies in Orange County:
Subsurface Infiltration & Flood Basin Retrofit
Description
Units
Campus Legacy
Fletcher Basin
Tributary Drainage Area
Acre
241
918
Average Annual Runoff
Acre Feet
154
589
Average Annual Runoff Infiltrated Using Retention
152
267
Average Annual Runoff After Installing Retention
0.82
321
Average Annual Runoff Volume Reduced
Percent 98 45

23. Subsurface Retention System Cost Estimate: Conceptual Project Design – Orange County, CA
48-Inch Diameter System
96-Inch Diameter System
Description
Cost
Capital Construction
$13,535,000
Annual O & M
$178,000
Total Present Value Capital Cost and O & M over 200 Years
$19,454,000
Description
Cost
Capital Construction
$7,835,000
Annual O & M
$103,065
Total Present Value Capital Cost and O & M over 200 Years
$11,261,000
System sized for runoff from a 241-acre tributary area
System located within up to a 5.5-acre footprint
~450,000 cubic feet of runoff (design storm volume)

24. Subsurface Retention System Cost Estimate: Conceptual Project Design – Orange County, CA 48-Inch Diameter System
Description
Unit
Quantity
Unit Price
Item Total
Engineering
Design Plan and Specifications (7.5% of construction) LS 1
$890,325
$891,000
Permitting and CEQA (20.0% of design)
$178,200
$179,000
Subtotal:
$1,070,000
Construction Support
Construction Administration (5.0% of construction)
$593,550
$594,000
Construction
Mobilization (1.0% of construction)
$117,530
$118,000
Excavation & Stockpile CY
98,238 $9
$885,000
Backfill and Compaction
81,778
$53
$4,335,000
Haul and Dispose of Excavated Soil
16,460
$60
$988,000
Shoring SF
50,461
$15
$757,000
Repaving
193,648
$10
$1,937,000
Diversion Structure at Chapman & Wheeler
$235,556
$236,000
Pretreatment Gross Solids Removal Vault
$285,556
$286,000
Diversion Pipe to Retention Storage LF
100
$300
$30,000
48" ID Chamber Retention Storage
(Corrugated Metal Pipe)
35,366
$65
$2,299,000
Construction Subtotal:
$11,871,000
Capital Cost Total:
$13,535,000
Annual O & M Cost:
1.5%
$178,065
PV O & M Cost: 3.0%, 200 years
$5,919,000
Total PV Capital & O & M
$19,454,000

25. Subsurface Retention System Cost Estimate: Conceptual Project Design – Orange County, CA 96-Inch Diameter System
Description
Unit
Quantity
Unit Price
Item Total
Engineering
Design Plan and Specifications (7.5% of construction) LS 1
$515,325
$516,000
Permitting and CEQA (20.0% of design)
$103,200
$104,000
Subtotal:
$620,000
Construction Support
Construction Administration (5.0% of construction)
$343,550
$344,000
Construction
Mobilization (1.0% of construction)
$68,020
$69,000
Excavation & Stockpile CY
54,031 $9
$487,000
Backfill and Compaction
37,571
$53
$1,992,000
Haul and Dispose of Excavated Soil
16,460
$60
$988,000
Shoring SF
37,423
$15
$562,000
Repaving
109,730
$10
$1,098,000
Diversion Structure at Chapman & Wheeler
$235,556
$236,000
Pretreatment Gross Solids Removal Vault
$285,556
$286,000
Diversion Pipe to Retention Storage LF
100
$300
$30,000
96” ID Chamber Retention Storage (Corrugated Metal Pipe)
8,841
$127
$1,123,000
Construction Subtotal:
$6,871,000
Capital Cost Total:
$7,835,000
Annual O & M Cost:
1.5%
$103,065
PV O & M Cost: 3.0%, 200 years
$3,426,000
Total PV Capital & O & M
$11,261,000

26. Findings from Case Study Engineering Analysis
Hydraulic line and grade from a tributary area to a Water Quality Credit Generating Facility is an important feasibility & design element
Surface-based LID BMPs have limited utility for generating volume credits:
May be limited due to routing issues
May be limited by design & placement requirements
May be limited by available space
Underground retention/infiltration systems appear to be most feasible to generate large volume credits
Use influenced by LID BMP engineering feasibility criteria
Use influenced by location characteristics