Do I Need a Stormwater Management (SWM) Plan in Washington DC?

The requirement for a Stormwater Management (SWM) Plan in Washington DC depends on whether the project is considered a “Major Land Disturbing Activity” or a “Major Substantial Improvement Activity.”

As your Civil Engineer in Washington DC, we can help answer the following questions to determine if your project will require us to prepare a Stormwater Management Plan.

1. Is the total project land disturbance over or under 5,000 square feet? 

  • If the project’s total land disturbance (footprint of building area plus area of land disturbance) can be kept under 5,000 square feet, we can avoid stormwater management requirements in Washington DC.  
  • If the project’s land disturbance will be over 5,000 square feet, then the project will be considered a “Major Land Disturbing Activity” and will require stormwater management plans. 

2. Is the cost of the proposed renovation or addition greater than 50% of the pre-project value of the existing structure? 

  • If the proposed cost of construction is greater than 50% of the pre-project building value AND land disturbance is greater than 5,000 square feet, then the project is considered a “Major Substantial Improvement Activity” and will require stormwater management plans.

decision tree for stormwater management plan
Page 16, DOEE Stormwater Management Guidebook

What is a Stormwater Management (SWM) Plan in Washington DC?

Simply put, a Stormwater Management (SWM) Plan is a detailed engineering plan outlining how a property will minimize the discharge of its stormwater runoff, typically done by utilizing Best Management Practices (BMPs).

As previously mentioned, the requirement for a stormwater management plan in Washington, D.C. falls under two categories, Major Land Disturbing Activities and Major Substantial Improvement Activities. Each of these categories have their own performance standards and will necessitate more or less infrastructure to meet these requirements.

For a Major Land Disturbing Activity, SWM plans must demonstrate the site’s ability to retain the first 1.2” of rainfall from a design storm on-site; whereas, SWM plans for a Major Substantial Improvement Activity only have to retain the first 0.8” of rainfall (i.e., less stormwater design).

Stormwater Management Plan prepared by DeMarr Engineering
Example of a Stormwater Management (SWM) Plan prepared by DeMarr Engineering for a Major Land Disturbing Activity in the Columbia Heights Neighborhood of Washington, DC.

Stormwater Management facility design by DeMarr Engineering
Example of a profile view of a Stormwater Management facility designed by DeMarr Engineering.

Does the Installation of a Stormwater Management System Require Inspections?

Stormwater Management Systems require several inspections throughout the construction process. Before any land disturbance on-site, DC requires the property owner, permittee, or designated agent to complete an on-site or virtual Department of Energy and Environment (DOEE) pre-construction inspection. The assigned DOEE inspector is also expected to be contacted by the appropriate individual prior to the start of construction of the Stormwater Management Plan.

Additionally, DOEE is authorized to inspect construction activities on an on-going basis after land disturbance begins. A final construction inspection will need to be scheduled with the DOEE inspector within 1 week from the completion of construction activities related to a Stormwater Management Plan.

Is a Stormwater Management As-Built Plan Required?

All Stormwater Management Plans require the registered professional engineer for the project to submit the As-Built Plan within 21 days after the final construction inspection and completion of all construction of the site, BMPs, land covers, and stormwater conveyances. A Stormwater As-Built Plan ensures that the proposed facilities have been installed correctly and will function effectively.

Stormwater Management Facility As-Built Plan by DeMarr
Example of a profile view of a Stormwater Management facility inspected and as-built by DeMarr Engineering.

For a quote on a Stormwater Management (SWM) Plan for your next project in the Washington, DC area, contact our civil engineers today.

References:

The post Do I Need a Stormwater Management (SWM) Plan in Washington DC? first appeared on DeMarr Engineering.

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