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Edmund Bennett
6 years ago
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1 Assessing the Development Costs of LID vs. Traditional Stormwater Management for a Commercial and Single-Family Residential Site Mike Schlegel, Triangle J Council of Governments Hunter Freeman, Withers & Ravenel Presentation Outline Background & Goals Project Team What are we trying to do? Who is involved? Approach & Methodology How did we do it? Site Designs What did we do to the sites? Commercial Site Single-Family Residential Site Next Steps What s left to do? 1

2 Background (what are we talking about?) Low impact development (LID) is designed to maintain and restore the hydrologic regime by creating a landscape that mimics the natural hydrologic functions of infiltration, runoff, and evapotranspiration. (NCSU 2009) an array of site planning practices and micro-scale stormwater treatment techniques that manage runoff volume and water quality. (NCSU 2009) claimed to be cost effective for developers compared to traditional development. (EPA, 2007) still rare in North Carolina Project Purpose & Partners The purpose of this project is to shed light on the relative development costs of LID vs. traditional development approaches because the lack of local information related to the development costs of LID has been cited as a primary barrier to wider LID implementation in NC. Project funding provided by: 2

3 Project Advisory Team Kevin Boyer, Stormwater Utility Division, City of Raleigh Matt Flynn, Water Resources Department, Town of Cary Chris French, Filterra Bioretention Systems Jason Hunt, Stormwater Services, City of Charlotte Dave Mayes, Public Services Department, City of Wilmington Jonathan Page, Bio & Ag Engineering, NCSU Peter Raabe, American Rivers Mike Randall, Stormwater Permitting Program, NC DEMLR Pete Schneider, Dept. of Water Resources, City of Greensboro Case Study Objectives Use real sites that have been permitted in the Traingle. And ensure same restrictions now that applied at the time of permitting. Consider an average developer, and be realistic in the designs, with the aim of showing developers that LID is within reach (as opposed to maximizing LID). Avoid putting BMPs in the ROWs other than swales or a bioswale, and avoid setback changes or variances as much as possible that could complicate permitting. 3

4 Site Selection PAT considered a commercial site, multi-family residential and single-family residential. The commercial site selected because of the potential for rain water harvesting and pervious pavement. Single-family residential site selected for interesting issues to explore such as downspout disconnection, permitting complexities, overall variety. Raises many issues that are outside the scope of this study, especially related to potential postconstruction issues for follow-up study. Design Approach 1) Conventional Site Design (as originally permitted) 2) Conventional Site Layout with LID Stormwater Controls Apples to Apples comparison 3) Expanded Site Layout made possible by LID Stormwater Controls Maximize return on investment 4

5 Storm-EZ Permitting Tool Commercial Site 5

6 Commercial Site - Redesigned 6

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8 SFR Site (Single- Family Res.) SFR Site Redesigned 8

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10 Cost Assessment Approach Focused on Developer Costs Design Permitting Construction Unit Cost Approach Cost per unit x # of units Actual costs from similar projects E.g., Bioretention cell: $30/sf x 3800 sf = $114,000 10

11 Commercial Site - Apples to Apples ~ $30,000 Commercial Site - Max. Use ~ $378,000 11

12 SFR Site - Max. Use ~ $55,000 Next Steps Review final drawings and costs with PAT Final report and cost memo Outreach and Presentations Future study SFR barriers and opportunities Easements/access Public vs. private streets HOA responsibilities Homeowner responsibilities 12

13 Questions Mike Schlegel (919) Hunter Freeman, P.E. (919)

Green Infrastructure & Low Impact Development

Green Infrastructure & Low Impact Development CITY OF COVINGTON STORMWATER MANAGEMENT WHAT IS GREEN INFRASTRUCTURE? Green infrastructure uses vegetation, soils and natural processes to manage water and