Development of a Spatial TMDL Implementation Plan Modeling Tool to Support Washington DC’s MS4 Program

Benjamin Crary, T. Slawecki, A. Savineau, H. Tao, J. ChampionLimnoTech, District Department of Energy and Environment

7/12/2016

What are the goals of the Implementation Plan Modeling Tool?

• Model “Current Stormwater Loading Conditions”

• Compare to Total Maximum Daily Load (TMDL) requirements

• Track future progress

• Present modeling results in an open-source interface

Simple Model –Complex data management

The District’s StormwaterLandscapeThree stormwater conveyance systems in the District:

*Runoff entering the Combined Sewer System is treated at the Blue Plains Treatment Plant.

Conveyance Total Area

Municipal Separate Storm Sewer System (MS4)

19,750 acres

Direct Drainage 7,230 acres

Combined Sewer System 12,220 acres

The District’s MS4 permit requirementsIncludes: • Over 10 TMDL documents• 500+ numeric MS4 Waste Load Allocations

(WLAs)• WLAs that cover daily, seasonal, and annual

time scales• 23 waterbodies• 18 total pollutants • 45 regulated drainage areas (“TMDL Segments”)

Conventional Metals Organics Other

Total Nitrogen Arsenic Chlordane Bacteria

Total Phosphorus Copper Heptachlor Epoxide BOD

Total Suspended Solids Lead Dieldrin PCBs

Mercury DDD, DDE, DDT Trash

Zinc PAH1, PAH2, PAH3 Oil and Grease

The District’s MS4 permit requirements

**Only Annual Waste Load Allocations are depicted.

One of the biggest challenges was to create a single consolidated inventory of all of our numeric WLAs.

Implementation Plan Modeling Approach

• Runoff and pollutant calculations based on Revised Simple Method

• Runoff is a function of precipitation, area, and the runoff coefficient

• Pollutant load is a function of EMC and runoff

• BMP pollutant removal is a function of BMP volume and load efficiency

BMP Module - Overview

Management practice information from a variety of sources:

**Not all sources had equivalent data

BMP Module – Known Design Specs

BMP Type Efficiency at 1.2” Design

Enhanced Permeable Pavement

92%

Enhanced Bioretention

90%

EnhancedBioretention with Underdrain

83%

Standard Bioretention

58%

Green Roof 50%

Standard Permeable Pavement

0%

(Modeled designs for 1988-1990 precipitation)

Unknown Design Specs: Conservative literature based efficiency

SWMM – based BMP Volume Reduction Approach

BMP Module - Challenges

• Updates to external databases are continuous

• Evolving design requirements• Evolving science

• Improved efficiency approximations

• Modified credit allowances

Create a flexible Modeling Tool framework:

IPMT Framework

• No proprietary software or licensing requirements except for Windows

• Can be installed locally on any computer that has Windows

• Databases are in MS Access• Tools are coded using .NET • GUI/mapping supported by DotSpatial (Open

source GIS)

What does the IPMT do?

• Calculate runoff, pollutant loads, and load reductions • Track progress towards WLAs (required by permit)

• Generate report and graphics

• Power is in the integrated databases (TMDL databases, BMP Databases)

Presents complex modeling results in an easy-to-use interface

Geospatial display of stormwaterrelated inventories

**Quickly identify any management type in a given TMDL segment.

Display BMP implementation

**Summarize the BMP load and volume reduction in the ‘Anacostia Lower’ TMDL segment.

Query TMDL Inventory

**Efficiently identify the TN requirement in the ‘Anacostia Lower’ TMDL segment.

Track progress towards WLAs

**Compare newly added 2015 BMPs to 5 year milestones.

IPMT Summary

• Power is in the integrated databases • (TMDL inventory, BMP inventory, etc.)

• Great automated tracking and reporting tools• Graphics and tables that feed into reports to EPA

• Framework for continually adding more information

Only one component of a larger Implementation Plan

• Flexibility is key• This became a reporting tool • This became a BMP integration tool• This became an outreach tool

• Create tools for the average user• This will likely be adopted into a web-based tool• Results and figures are more engaging than efficiency curves

Lessons

Ben CraryLimnoTech

(202) 864-6827bcrary@limno.com

Jonathan ChampionDC Department of Energy and

EnvironmentStormwater Management Division

(202) 535 1722jonathan.champion@dc.gov

www.dcstormwaterplan.org

Design Specifications Unknown: Literature-based efficiency matrix

BMP Module - Efficiencies

Green RoofRainwater Harvesting

Impervious Surface

Disconnect

Permeable Pavement Systems Bioretention

Filtering Systems Infiltration

Open Channel Systems Ponds Wetland

Storage Practices

Proprietary Practices

Arsenic 17 8 9 38 41 43 52 36 33 33 19 5BOD 0 0 0 0 0 40 51 30 0 63 27 0Chlordane 6 3 3 12 13 14 17 12 11 11 6 2Copper 20 10 10 45 48 51 61 43 38 38 22 6DDD 20 10 10 46 49 52 62 44 39 39 23 7DDE 24 12 13 55 59 63 75 53 47 47 28 8DDT 22 11 12 51 54 58 69 48 43 43 25 7Dieldrin 0 0 0 0 0 0 0 0 0 0 0 0Fecal Coliform Bacteria 23 11 12 52 56 60 71 50 45 45 26 7Heptachlor Epoxide 0 0 0 0 0 0 0 0 0 0 0 0Lead 27 13 14 60 64 68 81 57 51 51 30 9Mercury 17 8 9 38 41 43 52 36 33 33 19 5Oil and Grease 0 0 0 0 0 0 0 0 0 0 0 62PAH1 1 0 0 1 1 1 2 1 1 1 1 0PAH2 9 5 5 21 23 24 29 21 18 18 11 3PAH3 29 14 15 66 71 76 90 63 57 57 33 9TN 43 40 13 47 58 40 83 42 20 20 13 5TP 45 40 13 50 68 60 85 43 45 45 15 10TPCB 18 9 9 40 43 46 54 38 34 34 20 6TSS 31 15 16 70 75 80 95 67 60 60 35 10Zinc 23 11 12 52 56 60 71 50 45 45 26 7

*Runoff and load into practice based on drainage area to BMP

BMP Module - Overview

• Reductions driven largely by DOEE’s stormwater regulations for private development

• Most BMPs now designed to regulatory standards

• Steps to quantify BMP load reductions:• 1. Consolidate and curate an inventory of

all BMPs in the MS4• Bioretention, permeable pavement, trees,

etc. • 2. Establish BMP efficiencies for all BMP

types • Known Design Specs: used SWMM-based

efficiency curves• Unknown Design Specs: used literature

based load efficiencies• 3. Locate each BMP geographically and

assign to appropriate TMDL segments

Program Annual Area Projection

Compliance with Stormwater Regulations 187 acres/yr

Direct investment inBMP implementation and programmatic and source control efforts

21 acres/yr

The District’s MS4 permit requirements(As it relates to the modeling tool)

• Schedule for attainment of all 500+ WLAs: Project and track BMP implementation with time

• Establish 5 year reduction milestones: Track annual progress towards enforceable targets

• Narrative for schedule and controls: Provide tools for reports and graphics

Agenda

1. The District’s stormwater permit requirements

2. Modeling of stormwater runoff and pollutant reductions

3. Implementation Plan Modeling Tool built for the Department of Environment and Energy (DOEE)

4. Recap challenges and lessons