Low Impact Development Training Module 4: Bioretention Design Exercise Neil Weinstein

Sponsors 2 District Department of Transportation U.S. Department of Transportation Federal Highway Administration The Low Impact Development Center, Inc. University of the District of Columbia Funding for this project was provided through a grant from the Federal Highway Administration, U.S. Department of Transportation

Contributors 3 The Low Impact Development Center, Inc. John Shorb Landscaping, Inc. Logo Groundwork Anacostia River, D.C.

Copyright 4 Unless otherwise noted, Low Impact Development Training, funded by DDOT & DDOE, is licensed under a Creative Commons Attribution-NonCommerical- ShareAlike 3.0 Unported License. Content provided by cited entities remains the property of those entities and may not be used without their explicit permission.

Overview Group exercise to design bioretention cell(s) to capture and treat stormwater runoff from an office park Divide into groups of 2-4 5

Expected Outcomes Design a bioretention cell to meet District retention requirements Design a planting plan for bioretention cell 6

Materials DC Guidebook Printouts of site – with scale Calculator Rulers 7

Site Plan Ignore existing storm drains Plan Courtesy of The Low Impact Development Center, Inc.

Redevelopment Design bioretention cells to intercept retention volume from parking lot 9 Plan Courtesy of The Low Impact Development Center, Inc.

Design Delineate drainage area Calculate required retention volume Find most suitable location(s) Select most appropriate bioretention design variation Calculate size of bioretention required 10

Retention requirements Retain a volume equal to post- development rainfall from 90th percentile event (1.2 inches) 11

Step 1 Estimate the area of the parking lot using the geometric method 12 LIDC Plan Courtesy of The Low Impact Development Center, Inc.

Step 2 13

Step 3 Select a bioretention profile 14 Ponding depth Media depth Gravel depth

Step 4. Calculate Bioretention Surface Area 15

Step 5. Map out Flowpaths 16 Plan Courtesy of The Low Impact Development Center, Inc.

Step 6. Determine where to place bioretention Considerations: –Intercept stormwater flows (water doesn’t flow uphill!) –Minimize loss of parking capacity 17

Step 7. Planting Plan Use plant lists from bioretention specification in the Guidebook Create a planting plan using spacing guidelines in the specification Take sunlight and optimal location within the bioretention cell into consideration 18

Group Presentations 19