DC Stormwater Fee and Impervious Area Charge

How is the stormwater fee charge determined?


The District stormwater fee reflects the amount of impervious, or hard surface, area found on properties. Impervious areas create more stormwater runoff and consequently increase the cost to manage the pollution. The stormwater fee is based on the concept of an Equivalent Residential Unit (ERU), which is based on the average amount (1,000 square feet) of impervious surface on residential properties.

Single family residences are charged based on a tiered system that charges on a number of ERUs that corresponds to their amount of impervious area, as follows:

Square Feet of Impervious Surface / Number of ERUs

100 to 600  / 0.6

700 to 2,000 / 1.0

2,100 to 3,000 / 2.4

3,100 to 7,000 / 3.8

7,100 to 11,000 / 8.6

11,100 and above / 13.5

Each ERU will be charged $2.67 per month.

For all other properties, such as businesses and large multi-family properties, the stormwater fee will be charged $2.67 per month for each 1,000 square feet of impervious area on their lot, reduced to the nearest 100 square feet.

For example, the monthly stormwater fee for a commercial property with 26,500 square feet of impervious area would be calculated as follows:

26,500 square feet / 1,000 square feet = 26.5 X $2.67 = $70.76 per month \

5. Why base the stormwater fee on impervious surface?

Impervious surface relates directly to the amount of stormwater runoff generated from a property. Large, highly impervious properties produce more stormwater than smaller properties, and require the District to do more to treat and reduce stormwater runoff. By basing the stormwater fee on impervious surface, the District can more fairly distribute its stormwater management costs among properties in the District.

6. How does this relate to DC Water's Impervious Area Charge?

Both fees relate to improving the District's water quality. However, DDOE's stormwater fee and the DC Water charge address separate pollution control requirements.
--------------------------------------------------------------
What is an Impervious Area Charge (IAC)? The IAC is based upon the amount of impervious surface on your property. An impervious surface is a man-made surface that cannot be easily penetrated by water, such as rooftops, driveways, patios, tennis courts, swimming pools, parking lots, and other paved or covered areas (regardless of materials used).

Impervious surface areas are a major contributor to rainwater runoff entering the District's sewer system and pollution entering area waterways.
 
How is the amount of the charge determined? The charge is based on an 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 2011 monthly ERU value is $3.45.

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

Impervious Area (Square Feet) / ERU / ERU Rate / Monthly Cost

100-600 / 0.6 / $3.45 / $2.07

700-2,000 / 1.0 / $3.45 / $3.45

2,100-3,000 / 2.4 / $3.45 / $8.28

3,100-7,000 / 3.8 / $3.45 / $13.11

7,100-11,000 / 8.6 / $3.45 / $29.67

11,100 and more / 13.5 / $3.45 / $46.58

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

Why did DC Water develop a Tiered Rate structure for residential customers?

The tiers were developed in order to bill residential customers more equitably, based on the size of their properties. (DCWater)