Do you know there your MS4 is?

Transcription

1 Do you know there your MS4 is? Understanding risk Beth Chesson, CPESC, CPSWQ September 14, 2015

2 Understand your MS4 Reduce your risk

3 Nutrient management MS4 Flood management CIP Comprehensive Stormwater Management Program 3

4 Municipal Separate Storm Sewer SYSTEM MS4 is defined as a SYSTEM of conveyances that is 1. Owned by a state, city, town, village, or other public entity that discharges to waters of the U.S.; 2. Designed or used to collect or convey stormwater (including storm drains, pipes, ditches, etc.); 3. Not a combined sewer; and 4. Not part of a Publicly Owned Treatment Works (sewage treatment plant). Not privately owned systems. Not connections to another stormwater system.

5 Outfall Phase 1: Major municipal separate storm sewer outfall (or major outfall ) means a municipal separate storm sewer outfall that discharges from a single pipe with an inside diameter of 36 inches or more or its equivalent (discharge from a single conveyance other than circular pipe which is associated with a drainage area of more than 50 acres); or for municipal separate storm sewers that receive storm water from lands zoned for industrial activity (based on comprehensive zoning plans or the equivalent), an outfall that discharges from a single pipe with an inside diameter of 12 inches or more or from its equivalent (discharge from other than a circular pipe associated with a drainage area of 2 acres or more). Phase 2: Outfall means a point source as defined by 40 CFR at the point where a municipal separate storm sewer discharges to waters of the United States and does not include open conveyances connecting two municipal separate storm sewers, or pipes, tunnels or other conveyances which connect segments of the same stream or other waters of the United States and are used to convey waters of the United States. 5

6 Entire jurisdiction or just MS4? Most MS4 requirements should be applied jurisdiction-wide Construction site runoff control Post construction Education and outreach Illicit discharge program screening Focus on MS4 map your outfalls TMDL expectations: Evaluate your MS4 s contribution to impaired streams Develop TMDL monitoring plans for your MS4 s contribution Implement BMPs to meet WLA 6

7 TMDL load reductions Fecal Coliform Total Maximum Daily Load for the Upper North Buffalo Creek Watershed City of Greensboro, Guilford County 7

8 Fairfax County 8

9 Alexandria, VA 9

10 How to refine? It s all about that data The more data, the better Updated stream layer Parcel data (ownership) Road layer (ownership) Stormwater system map Easements ( owner or operator ) Topo (current, 1-2 contours) Maintenance agreements DOT Other jurisdictions Pond maintenance, other BMPs 10

11 Lexington County, SC 11

12

13 Data analysis Based upon available data ID regulated outfalls Use a corridor as a discriminator (conservative approach) Identify ALL outfalls that are within 300 of a County/Municipal owned parcel with development OR within 300 of a County/Municipal maintained road Of those identified outfalls within 300 of a County/Municipal owned parcel with development OR within 300 of a County/Municipal maintained road, select the outfalls within 150 of the USGS and Lidar derived streams. Identify County maintained ponds within 150 of the merged waterbodies. MS4 outfalls Previously identified 2117 After analysis = 1284

14 Next steps Stream walks to identify true outfalls (versus sheet flow to WOTUS) Collect and/or redefine the level and extent of service for drainage easements Ensure agreements with other MS4s clearly indicated maintenance Level of Service. Drainage area delineation to truly determine MS4 boundaries Extrapolate to other County watersheds Is a 40% reduction in risk worth the effort? 14

15 How to position your MS4 for risk reduction Clear level and extent of maintenance service policies Collect drainage easement information digitally for later use (not just on a recorded plat) Stormwater system inventory, including direction of flow as a minimum Verify streams in field (or via JD) Parcel, roadways, UA, aerial photos, topo Educate your elected officials about the long term risk of taking on maintenance of private systems. 15

16 Questions? Beth Chesson, CPESC, CPSWQ