1. City of Bowling Green Implementation of MCM 5 Post Construction Matt Powell

2. Agenda History -Regulatory Background Goals Program Development Documentation New BMPs

3. Program development

4. Bowling Green’s SW Goals Improve the quality of Bowling Green and Warren County’s water resources by: Implementing minimum control measures Providing education to citizens Provide protection of the short-term and long-term public health, safety, and general welfare by: Protecting, and preserving storm water quality and fish and wildlife habitat within Bowling Green. Protecting those downstream from stormwater quality impairment.

5. Defining the Program Determine Pollutant of Concern (POC) Establish Pollutant Load Reduction Develop design requirements that encourage green infrastructure Provide a selection of appropriate BMPs

6. Maximum Extent Practicable To what degree must we implement this minimum control measure and achieve both compliance and unhindered growth and development? Establishment of a second trigger; 10,000ft2

7. Hot Spot Landuses Pretreatment required for following landuses: Automotive Fueling Facilities Automotive Repair Facilities Restaurants with grease collection and disposal Other landuses as determined to have a high potential of pollutant discharge into the MS4 as determined by the City Engineer Typically, oil grease separators, hydrodynamic separators, etc.

8. Conservation Subdivision WQMP = Clearly defined clearing limits Total impervious surfaces for development cannot exceed 15% Minimum lot sizes – 1 acre Disconnected roof drains Stabilized sinkhole basins No additional WQ treatment required

9. Sediment or total suspended solids (TSS) Available BMP research Many other programs using TSS as pollutant of concern Old KYR100000– references 80% TSS reduction Indicator pollutant EPA has stated sediment is no. 1 reason for stream impairment Pollutant of Concern

10. The Presumptive Program The design is as described in BMP Manual + The installation is per the approved plans + The BMP is maintained per the Operation & Maintenance Plan = Compliance. No Performance testing for preapproved BMPs

11. Steps Taken to Date: Ordinance with post construction language BMP storm water stakeholder group BMP Manual revised Ordinance revised Developed plan review and permitting processes Training

12. Never Again Effective date = April 1 2008 If plan has been platted and has approved SWMP, no additional storm water quality treatment required.(The Grandfather Clause)

13. Documentation

14. Asbuilt Certification Need to verify That BMP was installed per approved plans That WQv treatment goals being met Engineer and surveyor Asbuilt must be approved before: Bonds released (S/D) CO issued (non-S/D)

15. O&M Plan Includes the following: BMP Maintenance Agreement Privately owned BMPs only BMP location map BMP schematics BMP maintenance and inspection templates Annual BMP report template Recorded with the deed Privately owned BMPs only O&M Plan The Landings - Agreement - Location map - Schematics - Inspection checklists

16. Maintenance City to maintain BMPs in residential areas on public ROWs Landowner to maintain all other BMPs All BMPs O&M Plan Routine inspections Annual inspection certification

17. A Tale of 2 Methods Volume Based BMPs Calculation WQv = [(P Rv)(A)]/12 Where, WQv is the water quality treatment volume (ac-ft) P is the average rainfall in inches, (in the case of Bowling Green, is 1.1 inches); Rv is the volumetric runoff coefficient, which is: Rv = 0.05 + 0.009(I), where I is the percent impervious cover; and A is the area in acres

18. Manufactured BMPs Treatment mechanisms different from non-manufactured BMPs Must provide 3rd party testing to verify pollutant removal to get approved for use (TARP, NJCAT) Nashville’s list of approved BMPs and reduction capabilities is automatically approved

19. Method 2 Rate Based BMPs Method Qp=C I A Where Qp=unit peak flow in cfs C=runoff coefficient I=intensity, 2.45 inch per hour A=contributing area in acres Automatic 50% credit

20. Modification of Rate Based Method Rate Based BMPs Method Use of TR55 to determine Tc Using synthetic storm curve Tc is used to determine I I declines as Tc increases, thus encouraging green space by reducing the size of the unit required.

21. Treatment Train Bioretention 80% TSS Dry Detention 60% TSS Flow Flow When one BMP discharges into another Discharge from upstream BMP will be “clean” so downstream BMP TSS reduction will be less effective TSS reduction = 80+60 – (80x60)/100 = 92%

22. BMP Selection

23. Ponds Dry ponds Outlet structure Dry storage area 60% TSS reduction

24. Ponds Wet ponds Outlet structure Permanent pool 80% TSS reduction

25. Ponds Variations Micropool Extended detention Multiple ponds Pocket ponds

26. Wetlands Outlet structure Shallow wet treatment area Upland dry storage Plants are key Length of flow (residence time) key 75% TSS reduction

27. Bioretention areas Outlet structure Small storm & large storms Dry treatment area Depressed planting area Specific soils Under drain 80% TSS reduction

28. Open Channel Systems Simple outlet system Treatment area Dry good in most all land use applications Underdrain system Wet Not well accepted in residential Long wetland

29. Sand filters Many variations Best suited for non-residential Typically underground Must receive drainage from only impervious surfaces

30. Infiltration trenches Limited application due to karst topography

31. Questions and Discussion Matt Powell City of Bowling Green matt.powell@bgky.org