Stormwater Credit Exchange


Mission Statement

The Stormwater Credit Exchange (SCE) is a clearinghouse service that allows participants who reduce their "stormwater runoff footprint," the total stormwater runoff from a property during a storm event, to market those credits. Participants who do not reduce their footprint can make offers to purchase offset credits via the SCE.

The Stormwater Credit Exchange offsets are based on the reduction or elimination of stormwater runoff. The offsets are also based on activities by SCE participants.

See the Instruction and Exchange Board below to particpate in the SCE service.

Review our Legal and Privacy policies.

The Information section includes stormwater taxes and fees in the Washington, DC Metropolitan Area.

Paticipants can submit Offers to sell their credits and buy credits by clicking on the link below.

The SCE is a private sector complement to a public sector program.

DDOE Stormwater Retention Credit

Under the DC Department of the Environment (DDOE) Stormwater Retention Credit Trading Program, all regulated development sites have a net retention requirement, which could be achieved through a combination of on-site and/or off-site practices. All regulated sites would be required to achieve a minimum stormwater reduction amount of their 1.2" retention volume on site. Unregulated sites can generate credits by exceeding existing retention.

Every time a stormwater runnoff credit is purchased or sold via the SCE, the credit holder will be designated with a Stormwater Retention Credit (SRC) certifying that the holder sold or purchased the credit. One SRC = 1 gallon of retention for one year. SCE is establishing a baseline rate for one SRC that equals $1. It is for reference purposes only because the marketplace will establish the true price. SRCs can be bought and sold though the SCE at a miniumum rate of $1 per SRC.

An SRC can be banked indefinitely for future use and its ownership can be transferred. For a transfer of ownership to be complete, DDOE must approve an application for transfer of ownership in order to track the ownership and use of an SRC, including preventing fraudulent use of an SRC. The owner of an SRC may also retire it without using it.



DDOE Stormwater Management Final Rule




Exchange Board

Legal / Privacy

Submit Offer




Certification and Ownership of Stormwater Retention Credits

The DDOE will certify Stormwater Retention Credits (SRCs) for eligible Best Management Practices (BMPs) and land cover changes in the District of Columbia. To be eligible, the retention capacity in a BMP or land cover change must:

A) Achieve retention in excess of the regulatory requirement or existing retention, but less than the SRC ceiling,1 as shown in Figure 1;

B) Be designed and installed in accordance with a DDOE-approved Stormwater Management Plan (SWMP);

C) Pass a post-construction final inspection and ongoing inspections; and

D) Have a current maintenance agreement or contract in place.

1 The SRC ceiling is important to ensure that an SRC provides a comparable benefit to District waterbodies as would be achieved under strict on-site retention. The 1.7 inch storm is the 95th percentile rainfall event in the District of Columbia, meaning that ninety-five percent (95%) of rainfall events are smaller than 1.7 inches. A gallon of retention capacity that is only used by storms larger than 1.7 inches will be used relatively infrequently and therefore provides less retention benefit on an annual basis than a gallon of retention capacity that is filled by smaller storms. Figure 1, showing the size distribution of rainfall events in 2009, helps to illustrate this point.



Generation, Certification, Trading & Retirement of Stormwater Retention Credits


Forms for Stormwater Retention Credit Certification, Trading & Retirement



Figure 1

1: Regulated Sites Exceeding Required Stormwater Retention Volume (SWRv) on Site

SRC Ceiling _________________________ 1.7 Inch Storm



Stormwater Retention Credit



Required SWRv_______________________ 1.2 Inch Storm

(0.8 Inch for Substantial

Improvement Projects)



Stormwater Retention



Post Development Site Without BMPs_______

2. Unregulated Sites Exceeding Existing Retention

SRC Ceiling____________________________ 1.7 Inch Storm



Stormwater Retention Credit



Existing Site Retention Prior To New BMPs_____





Review of stormwater management plan to create retention capacity for DDOE certification of stormwater retention credits Land disturbance of < 10,000 square feet Land disturbance of >10,000 square feet
Initial plan review payment due upon filing for building permit



Final plan review payment due before issuance of building permit



Supplemental review fee due before issuance of building permit




Fee Schedules Associated With Filing a SWMP with DDOE

Stormwater Management Plan Review Land Disturbance of >5,000 sf & ,10,000 sf Land Disturbance of > 10,000 sf
Initial plan review payment due upon filing for building permit



Final plan review payment due before issuance of building permit



Supplemental review fee due before issuance of building permit






Additional fees as applicable Land Disturbance of + 10,000 sf Land Disturbance of > 10,000 sf
Field visit for soil percolation test

$300 for < 10 borings; $600 for > 10

Review of soil percolation test report


Soil characteristics inquiry


Review of geotechnical report


After-hours inspection fee


Stormwater pollution plan review


Dewatering pollution reduction plan review



Application for relief from extraordinarily difficult site conditions






"Major Land-Disturbing Activities"

The proposed rule amendments retain the existing regulatory trigger for sites with activities that disturb 5,000 square feet or more of soil.

A site that undergoes a major land disturbing activity may achieve the 1.2 in stormwater retention volume (SWRv) on site or through a combination of on-site retention and off-site retention, under the following conditions:

(a) The site shall retain on site a minimum of fifty percent (50%) of the 1.2 inch SWRv, calculated for the entire site, unless the Department approves an application for relief for difficult site conditions; and

(b) The site shall use off-site retention for the portion of the SWRv that is not retained on site.





Use of Off-Site Retention

A person shall achieve each gallon of Off Site Retention Volume (OSRv) for each year by:

(a) Using one (1) Stormwater Retention Credit (SRC); or

(b) Paying the in-lieu fee to the Department.





In-Lieu Fee

The in-lieu fee shall be $3.50 per year for each gallon of Off-Site Retention Volume (OSRv)

The base in-lieu fee established by the DDOE shall represent the full life-cycle cost for the DDOE to retain to retain one gallon of stormwater for one (1) year, including the following costs:

(a) Project planning;

(b) Project design;

(c) Project management;

(d) Construction and installation;

(e) Operations and maintenance;

(f) Project financing;

(g) Land acquisition;

(h) Administration of the in-lieu fee program; and

(i) Legal support for the in-leu fee program.



Stormwater Retention Volume Calculation Formula


Stormwater Retention Credit Ceiling.- Maximum retention for which the Department will certify an SRC, calculated using the SWRv equation with P equal to 1.7 inches.


A site that undergoes a major land disturbing activity shall:

(a) Achieve a stormwater retention volume (SWRv) equal to the post-development runoff from the ninetieth (90th) percentile railfall event for the District of Columbia, measured for a twenty-four (24) hour storm with a seventy-two (72) hour antecedent dry period (1.2 inch rainfall event);

(b) Calculate the 1.2 inch SWRv in subsection (a) as follows:

SWRv = [P x [(Rvi x %I) + (Rvc x %C) + (Rvn x %N)] x SA] x 7.48/12

SWRv = volume, in gallons, required to be retained

P = 90th percentile rainfall event for the District (1.2 inches)

Rvi = 0.95 (runoff coefficient for impervious cover)

Rvc = 0.25 (runoff coefficient for compacted cover)

Rvn = 0.00 (runoff coefficient for natural cover)

%I = percent of site in impervious cover

%C = percent of site in compacted cover

%N = percent of site in natural cover

SA = surface area in square feet

where , the surface area under a BMP shall be calculated as part of the impervious cover (%I); and

(c) Calculate the 1.2 inch SWRv for the entire site and each drainage area.



SCE Information Chart

Item Price or Sq Ft Gallons
SRC $ 1.00 (or market rate) 1
ERU 1,000  
ERU $ 9.57 (Rate)*  
ERU 1,000 710.75
1.2 Inch Rainfall 1,000 710.75


* Residential Customers: Beginning in FY 2011,all residential customers will be assessed Equivalent Residential Units (ERUs) based upon the amount of impervious surface on their property and the following six-tier rate structure:

The charge is based on Equivalent Residential Unit (ERU). An ERU is a statistical median of the amount of impervious surface area in a single-family residential property, measured in square feet. The FY 2013 monthly ERU is $9.57.


Impervious Area (Sq Ft) ERU Rate Monthly Cost
100-600 0.6 $9.57 $5.74
700-2,000 1.0 $9.57 $9.57
2,100-3,000 2.4 $9.57 $22.97
3,100-7,000 3.8 $9.57 $36.37
7,100-11,000 8.6 $9.57 $82.3010
11,100 + 13.5 $9.57 $129.20

All nonresidential customers are assessed ERUs based on the total amount of impervious surface on each lot. (DC Water)

See also: DDOE Stormwater Fee Discount Program


Source: DDOE



SCE is operated by the Center for Environment, Commerce & Energy (Center). The Center was founded in 1985 and is a national environmental organization dedicated to protecting the environment, enhancing human, animal and plant ecologies, promoting the efficient use of natural resources and increasing participation in the environmental movement. The Center resolves environmental problems through the application of practical environmental solutions.

Copyright  ©  2013,   Center for Environment, Commerce & Energy

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