Green infrastructure policy for stormwater infiltration

• 1. An Overview of NEW STORMWATER RULES (PENDING June adoption) Evan N. Pratt, P.E. Water Resources Commissioner

2. OUTLINE A. Why Change? B. Value of Infiltration C. 3 Main Changes D. Development Benefits and Concerns E. Community Benefits and Concerns F. Case/Cost Studies and Examples G. Summary Talking Points Lets be consistent 3. WHY ARE WE HERE? THESE PEOPLE CANT CHANGE POLICY BUT HAVE TO LIVE WITH IT 4. WHY CHANGE? 5. WHY CHANGE? 6. WHY CHANGE? 7. IT ALL ADDS UP 8. Q: Why Infiltration? A: TSS Removal Efficiencies SOURCE: 2005 DATA REPORT, UNH STORMWATER CENTER 9. Top 5 TSS Removal Efficiencies POROUS PAVEMENT 100% GRAVEL WETLAND 100% STORAGE BASIN INFILTRATION 100% TREE FILTER 93% BIORETENTION 92% RETENTION POND 65% SWALE 55+% 10. WCWRC RULES: WHAT IS CHANGING? 3 KEY CHANGES 1. PROCESS: MANDATORY PRE-APPLICATION MEETING 2. TECHNICAL APPROACH a. METHOD OF CALCULATING RUNOFF: NO IMPACT b. STORMS HAVE GOTTEN BIGGER 3. INFILTRATION REQUIREMENT a. First 1, OR b. Must prove that soils are unsuitable for infiltration 11. OVERVIEW OF CHANGES 12. 1. PROCESS: PRE-APPLICATION MEETING GENERAL EVALUATION Purpose: Engage Owner, clarify changes and benefits Soil types Information on geology and hydrology including estimate of groundwater table elevation Topography Land cover Other pertinent natural or man-made features Potential locations for infiltration BMPs 13. 2. TECHNICAL: 1% STORM Current MDEQ 24 hour 1% storm = 4.36 inches NOAA Atlas 14, Volume 8 Published 2013 Provides data for discreet locations Ann Arbor, Milan & Ypsilanti Stations Range for the 24 hour 1% storm at these stations varies minimally All indicate the 24 hour 1% storm = 5.11 inches Chelsea Station 24 hour 1 % storm = 5.21 New WCWRC Rules 24 hour 1 % storm = 5.11 inches 14. 2. TECHNICAL: Method of Calculation SUMMARY: Method yields about the same results for detention on several sites. The Oakland County Method vs. NRCS Curve Number Peer Review Comparisons WCWRC Deputy WRC -- Dennis Wojcik, P.E. verifications 705 N. Zeeb Road Two Other Site Developments 15. 3. INFILTRATION MDEQ NPDES Permit Application Require that post-construction runoff rate and volume of discharges not exceed the pre-development rate and volume for all storms up to the two-year, 24 hour storm at the site. At a minimum, pre-development is the last land use prior to the planned new development or redevelopment. WCWRC Rules will require infiltration of the greater of the first flush volume or difference between pre-settlement and post-development 24 hour 50% storm. 16. HOW DOES DEVELOPMENT BENEFIT? Many developers are finding lower cost for GI when used in greenfields. Case studies at http://tinyurl.com/streetrunoff Less concrete infrastructure needed. Less surface area of storage needed if doing infiltration Less impact to developable area with co-location It will always be more costly to develop unsuitable land This is why poorly suited land (soils, etc) is cheaper Public cost of developing poorly suited land Whose job is it to look at total cost of a site? 17. COMMUNITY BENEFITS and CONCERNS Reduction in community costs related to development Soils have always been integral to land use decisions. Now on County GIS NRCS Soils layer under Soils Collaboration during pre-application process HOW WILL YOUR COMMUNITY FUND LEGACY COSTS OF DEVELOPMENT? 35% GENERAL FUND (OLD WAY) OR MORE LIKE WCRC? 18. DEVELOPER CASE STUDY: GI COST SAVINGS 19. Case Study: Boulder Hills Pelham, NH 2009 -- 900 OF PRIVATE RESIDENTIAL PAVING IN NE SITE GOAL OF ZERO DISCHARGE 55+ ACTIVE ADULT COMMUNITY SANDY SOILS (NOT A MUST) 20. COST AVOIDANCE 1616 CONCRETE CURB 785 PIPE 8 CATCHBASINS 2 DETENTION BASINS & 2 OUTLET STRUCTURES SAVED 1.3 ACRES IN LAND CLEARING/CONSUMPTION CONVENTIONAL = $789,500 vs. LID SWM= $740,300 INFILTRATION COST SAVINGS = $49,000 = (6.2%) O/M DISCUSSION LATER ALSO LESS 21. Comparison of Unit Costs 22. HOW POROUS O/M IS MUCH LESS WHAT IF PAVEMENT NEVER CRACKED? 23. HOW POROUS O/M IS MUCH LESS AND IS SUPPOSED TO HAVE WATER IN THE BASE 24. HOW POROUS O/M IS MUCH LESS $- $10,000 $20,000 $30,000 $40,000 $50,000 $60,000 $70,000 $80,000 $90,000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 HMA Maintenance With Sweeping Cumulative Porous Sweeping Costs 25. WHY CHANGE: LETS ALL GIVE THE SAME ANSWERS SOAKING WATER INTO THE GROUND IS SIMPLER AND CAN COST LESS WCWRC WILL WORK WITH OWNERS BEFORE A PURCHASE DECISION. OWNERS RESPONSIBILITY TO EVALUATE DEVELOPMENT COSTS OF CHEAPER PROPERTY. GOVERNMENT AGENCIES ARE ALREADY INVESTING 26. GOVERNMENT AGENCIES ALREADY INVEST IN GREEN INFRASTRUCTURE 27. WCWRC OFFICE 705 N. ZEEB 13 years old 42,000+ sft. Detention (2) Bioswales Level Spreader Infiltration Bed Solar Panels Native Veg. BUT No Credit 28. WASHTENAW COUNTY BUILDING Current method detention volume = 45,000 c.f. Revised method detention volume = 60,000 c.f. Reduction in volume utilizing BMPs installed = 11,000 c.f. Revised method required detention volume = 49,000 c.f. 29. 705 ZEEB ROAD REDUCED CONSTRUCTION COST 8 structures @ $2,000 ea. = $16,000 425 ft.-12in. RCP @ $40/ft. = $17,000 265 ft.-15 in. RCP @ $50/ft. = $13,250 Savings = $46,250 (FIRST FLUSH ONLY) BUT SOILS ARE SUITABLE FOR 100% INFILTRATION Extra Savings: 1,950 cyd earthwork @ $10/cyd = $19,500 NET SAVINGS = at least $65,750 (plus additional pipe savings, offset by need to add bioswale) -Will be estimating porous asphalt option in future version 30. EMU Student Housing 31. After planting still standing water 32. Eastern Michigan University, InSite Design Studio Plants mature no standing water 33. InSite Design Studio, Inc. 34. ITS SIMPLE: WHICH IS BETTER?? 35. http://tinyurl.com/streetrunoff TAKE AWAY MESSAGES 1. Human activity is the #1 cause of many problems. The purpose of the New Rules is to: A. Reduce long term cost impacts to communities and taxpayers B. Reduce water quality and flooding impacts of development 2. Good sites with good soils will result in less costly projects Owners responsibility during site selection & due diligence. 3. WCWRC is available to work with communities and the Owner on challenging sites. 36. QUESTIONS?