2009 Maryland Stormwater Ordinance & Design Manual Updates

1. 2009 Maryland Stormwater Ordinance & Design Manual Updates Environmental Site Design Presented by Robert Kane, P.E. & Jen Smith, E.I.T. Stormwater Ordinance Forum

2. Current SWM Practices • No increase in runoff flow rate (Q) from pre-development to post-development conditions • Treat stormwater runoff for water quality (WQv) • Provide groundwater recharge (Rev)

3. Current SWM Practices - Continued • Provide detention of Channel Protection Volume • (Cpv), or 1-year storm event • Not required for Eastern Shore

4. Current SWM and ESD • Non-structural best management practices (BMPs) provided in old Chapter 5 included design options that reduced a site’s WQv, Rev and Cpv requirements • These reductions were optional and considered “stormwater credits”

5. New Maryland SWM Regulations • On April 24, 2007, Governor Martin O’Malley signed the “Stormwater Management Act of 2007” (Act) • The Act requires that Environmental Site Design (ESD), through the use of nonstructural Best Management Practices (BMPs) and other Better Site Design techniques, be implemented to the Maximum Extent Practicable (MEP)

6. Stormwater Design Changes • Woods in good condition • Rainfall targets based on impervious area • Channel protection on Eastern shore • Water quantity requirements determined by local jurisdiction • Small scale practices • Treat impervious at source

7. Maryland SWM Act Update • Deadlines for Localities: • Submit updated local ordinances addressing regulation changes by November 11, 2009 • MDE provided a Model Ordinance • Local Ordinances need to be adopted by May 2010

8. Follow Design Process for New Development (Figure 5.1) Develop Natural Resources Map Field verified by design professional Minimize total site imperviousness ESD has been used to MEP Comprehensive Review Process Incorporate ESC into development plan ESD Implementation

9. County and municipal stormwater authoritiesshallestablish a coordinated approval process among all appropriate local agencies ESC & SWM Any other local agency deemed appropriate Tailored to meet local initiatives Review agencies to provide feedback during: Concept Phase Site Development Phase Final Design Phase Comprehensive ESC & SWM Review

10. Site and Resource Mapping Soils Stream buffers Springs Vegetative cover Stable Outfall Bedrock/Geology Floodplains Topography/slopes Steep slopes Highly erodible soils Critical areas Existing drainage areas Forests and forest buffers Wetlands and wetlands buffers Proposed limits of clearing and grading Major waterways and perennial streams (All field verified by project designer during development)

11. Narrower and shorter: Streets Right-of-ways Sidewalks Open vegetated channels Parking ratios Parking lot runoff Cul-de-sacs Open space Setbacks and frontages Better Site Design Techniques

12. Site Fingerprinting and Development Layout Drainage areas Maintain natural flow paths Provide stable outfall Expand forested, wetland, and stream buffers Maintain sheet flow “Clustering” development Plan building footprint and layout Locate ESD practices

13. Stormwater Management Finalize topography to define drainage boundaries Size ESD practices Erosion and Sediment Control Preservation Phasing and Sequencing Clean Water Diversions Overlay: Stormwater + ESC Final Design Submittal Site Development and Final Design

14. Figure 5.1, Page 5.6

15. Questions?

16. MDE Model Ordinance • Waiver Policy • Redevelopment Policy • Inspection and Maintenance

17. Quantitative Control ESD to the MEP required Watershed Management Plan has been developed Direct discharges to tidally influenced water Circumstances prevent the reasonable implementation of quantity control Waiver Policy

18. Quality Control Infill development projects where ESD has been implemented to the MEP Redevelopment Projects Circumstances prevent the reasonable implementation of ESD to the MEP Waiver Policy (cont.)

19. All Waivers Case by case Consider cumulative effects Will not adversely impact stream quality Waiver Policy (cont.)

20. All Redevelopment Reduce impervious by 50% within LOD Implement ESD to MEP to provide WQ treatment for 50% of impervious within LOD Use a combination of reduction and treatment Redevelopment

21. Alternative Impervious reduction has been maximized and ESD is implemented to MEP On-site structural BMP Off-site structural BMP On-site and off-site combo Redevelopment (cont.)

22. Separate Policies Retrofitting Stream restoration Watershed Management Plan Fees paid Hardship Variance Redevelopment (cont.)

23. Maintenance and Inspection • Regular inspections required, varies per ESD practice • Inspection reports maintained by Municipality • Inspection reports for ESD practices: • Date of inspection • Name of inspector • Quality assessment of SWM system related to ESD to the MEP • Condition of all stormwater structures • Description of needed maintenance

24. Maintenance and Inspection (cont.) • Inspection and Maintenance agreement prior to building permit issuance • Agreement recorded by applicant/owner in county records • Agreement to include corrections of violations within a reasonable time limit • Owner of private SWM facility is responsible for maintenance • Maintenance schedule established for life of SWM facility/ESD system • Easements must be provided

25. Questions?

26. The target for ESD implementation shall be “woods in good hydrologic condition” ESD shall be implemented to the MEP ESD shall be used to address both Rev and WQv requirements Channel Protection practices are designed according to the Reduced Runoff Curve Number Method Unified Sizing Criteria

27. Pe = Rainfall Target from Table 5.3 used to determine ESD goals and size practices Qe = Runoff depth in inches that must be treated using ESD practices = Pe X Rv; Rv = the dimensionless volumetric runoff coefficient = 0.05 + 0.009(I) where I is percent impervious cover ESDv = Runoff volume (in cu. ft. or ac.-ft) used in the design of specific ESD practices = (Pe) (Rv) (A) / 12 Runoff stored in ESD practices may be subtracted from the Overbank Flood Protection and Extreme Flood Volumes (Qp2, Qp10, Qf) ESD practices shall be used to treat the runoff from 1” of rainfall (i.e., Pe = 1”) ESD Sizing Criteria

28. Pe = Rainfall Target from Table 5.3

29. CPv shall be addressed on all sites including those where the 1-year post-development peak discharge is less than or equal to 2.0 cfs Local SWM review agencies will determine whether Qp2, Qp10, and Qf will be required in their jurisdiction QE may be treated using an interconnected series of “treatment train” of practices ESD requirements shall be addressed for the entire limit of disturbance (LOD) ESD Sizing Criteria (cont.)

30. Questions?

31. Green Roofs

33. Permeable Pavements

34. Reinforced Turf

35. Disconnection of Rooftop Runoff

36. Disconnection of Non-Rooftop Runoff

37. Sheet flow to Conservation Area

38. Sheet flow to Conservation Area

39. Submerged Gravel Wetland

41. Landscape Infiltration

42. Landscape Infiltration

43. Rain Garden

44. Rain Garden

45. Micro-Bioretention

46. Micro-Bioretention (cont.)

47. Swales

48. Infiltration Berm

49. Infiltration Berm

50. Dry Wells