Cost-Effective Stormwater Management Retrofit Device

Transcription

1 Cost-Effective Stormwater Management Retrofit Device Dr. Jim Goodrich 1 Dr. Bob Hawley 2, Matt Wooten 3, Craig Frye 3, and Mark Jacobs 4, Dr. Jake Beaulieu 1, Nora Korth 2 1 United States Environmental Protection Agency 2 Sustainable Streams, LLC 3 SD1 of Northern Kentucky 4 Boone County Conservation District

2 Problem Statement Urbanization has altered watershed hydrology and created an erosive flow regime that impacts: Aquatic habitat Water quality Private property Public infrastructure

3 Typical site in Urbanization Causes Stream Degradation undeveloped basin Conventional storm- Q and Aquatic critical stormwater controls can potentially Habitat Destruction water policy break this cycle Typical site in developing basin

4 Urbanization Causes Stream Degradation and Impacts Public Infrastructure

5 Conventional Stormwater Management Typically Exacerbates Channel Erosion Channel erosion likely begins in a range that is less than the 2-yr design storm Peak flow detention typically has little to no attenuating effect on 97-99% of the precipitation volume in a typical year (Emerson et al., 2003; Hawley, 2012) Typical year rainfall and recurrence probabilities for Northern Kentucky

6 Q critical The Critical Flow (Q critical ) for Bed Material Mobility is both Geomorphically and Ecologically Relevant (Poff, 1992; Townsend et al., 1997; Holomuzki and Biggs, 2000; Suren and Jowett, 2006) t > t c

7 Conventional Detention Exceeds Q critical More than Pre-Developed Conditions No Detention Pre-Developed Conventional Detention (Peak Matching) Analysis of the 2-yr, 2-hr storm from Fort Collins, CO by Bledsoe (2002), Journal of Water Resources Planning and Management

8 Conventional Detention Exceeds Q critical More than Pre-Developed Conditions No Detention Pre-Developed Conventional Detention (Peak Matching) Analysis of the 2-yr, 2-hr storm from Fort Collins, CO by Bledsoe (2002), Journal of Water Resources Planning and Management

9 Conventional Detention = More Erosion than Pre-Developed Conditions Pre-Developed No Detention Conventional Detention (Peak Matching)

10 Sediment is One of the Leading Impairments of U.S. Waterways Sediment/Siltation is the #1 Pollutant in Kentucky (KDOW (2008), 305(b) report to Congress) Streambank Erosion is a Dominant Sediment Source in Many Watersheds (Simon and Klimetz, 2008)

11 TMDLs across the US Require Reductions in Stormwater Volume and Pollutants Montgomery County, MD is required to spend ~ $300 million by 2015 on stormwater retrofitting of impervious area King County, WA pilot project recommends BMPs with an average cost of ~ $50,000 per acre to retrofit/build new BMPs Detention basin retrofit device cost ~ $500 per acre

12 Detention Basins Present a Huge Opportunity to Cost-Effectively Retrofit and Improve Stormwater Treatment from Impervious Surfaces

13 Detention Ponds Are Abundant (~ 2,000 in 3 Northern KY counties alone)

14 Project Goal Design and test an inexpensive device that can retrofit existing detention pond outlet structures to optimize their stormwater mitigation potential.

15 Pilot Installation ~ just west of runway Toyota Basin

16 Device Prototype Restricted Release for Most Storms Reduced stream erosion Enhanced water quality treatment Bypass for Large Events Maintain Flood Control Performance Inexpensive No Heavy Equipment or Re-grading Required

17 Large Industrial Property ~31 acres, 52% impervious Pilot Installation Site Conventional Detention Design Peak Matching for 2, 10, 50, 100-year design storms Engineered Spillway

18 Retrofit Optimized to Reduce Downstream Erosion Based on Hydrogeomorphic Data

19 Modeled 40 Years of Precipitation Data to Minimize the Cumulative Exceedance of Q critical Detention Type Cumulative Number of Storm Events Exceeding Q critical Cumulative Hours of Flows Exceeding Q critical Pre-developed No Detention With Detention With Retrofit 8 300

20 Retrofit Expected to Double Residence Time Enhanced Water Quality Performance TSS removal UV treatment Nutrient processing Toyota Basin Cumulative Minutes of Typical Year Storage* Pre-retrofit ~18,000 Post-retrofit ~40,000

21 Basin H/H Modeling All events greater than 3-month, 24-hr storm (1.64 inches) Outflow < Inflow Post-retrofit outflow < Pre-retrofit outflow Should notice an influence whenever inflow is > ~7cfs

22 Device Specifications at Pilot Installation 75% Restriction of 24 Outlet Reduced stream erosion Enhanced water quality treatment 18 Bypass at 3 above inlet of 24 inlet Maintains Flood Control Performance No Heavy Equipment

23 Monitoring Toyota Pond Pipe Flow Inflow 1 Inflow 2 Outflow Precipitation Site Rain Gage NWS Gage (Northern Kentucky/Cincinnati Airport) Inflow2 Outflow Inflow1 Site Rain Gage Off-site Stream Flow & Hydrogeomorphic Surveys Spur Upstream Downstream Downstream Upstream Spur NWS Rain Gage < 1 mile (Airport)

24 Monitoring Began in August 2013 Device installed 12/20/2013

25 Frozen Gage = Poor Outflow Data Outflow Gage 1/9/14

26 Post-retrofit Inflow 4/3/14

27 Toyota Site Data Extended Detention 4/3/14 Basin 4/3/14

28 Total Precip = 2 inches Peak Intensity = 0.39 in/hr Outflow < 6 cfs Post-retrofit

29 Representative Events Device installed 12/20/2013 Precip = 0.6 inches Outflow = 4 cfs Precip = 1.3 inches Outflow = 4 cfs

30 Total Precip = 0.6 inches Peak Intensity = 0.16 in/hr Outflow = 4 cfs Pre-retrofit

31 Post-retrofit Total Precip = 1.3 inches Peak Intensity = 0.55 in/hr Outflow = 4 cfs

32 Post-retrofit

33 Post-retrofit

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35 Post-retrofit

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42 Post-retrofit

43 Summary Post-retrofit data shows positive hydrologic impact. Pre- Retrofit Postretrofit Total Precipitation (inches) Peak Precipitation Intensity (inches/hr) Peak Inflow (cfs) Peak Outflow (cfs) ?

44 Future Work Downstream Data Hydrologic & geomorphic collection and analysis Water Quality Grab Samples Bench-scale Media Tests

45 EPA Acknowledgements Jake Beaulieu, Craig Patterson and Others Sustainable Streams, LLC Katie MacMannis, Nora Korth and Kurt Cooper Strand Associates, Inc. Chris Rust SD1 & Boone County Conservation District Liz Fet, Field Crews Shaw Environmental & Infrastructure Group Rajib Sinha Toyota Coy Kaylor and Others ISCO Donated $25k worth of monitoring equipment

46 Thank You!