HomeMy Public PortalAboutMSD Stormwater Regulations Spring 2011 Update (PDF)MSD Storm Water Regulations Spring 2011 Updatewww.stlmsd.comJohn Grimm, P.E. Principal Engineer jcgrim@stlmsd.com
Storm Water Quality?
Presentation OutlineDesign Methods are changing – change is GOODSome Phase II Permit Items & MSD Regulations, Amendment No. 3Some New MSD Plan Review ItemsA Quick Native Plant Seeding – Prairie Detention Basin Update…
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Stay Tuned…
MSD Regs Amendment No. 3 -wording added to match Ph II permit wording
Amendment 3, date issued January 1, 2011
Volume Reduction BMPs –Hierarchy, in Order of Preference –To Try to “Lose” 1.14” of rainfall (& maybe even more???)1.) Bioretention (Raingardens)2.) Permeable Pavements3.) Rainwater Harvesting4.) Green Roofs
Post-Constructed BMPs Permitted for Construction1043 Total Items Permitted (1/21/11)Infiltration BMPs2%Engineered Swales8%Permeable Pavement11%Cisterns2%Ponds3%Storm Credits1%Surface Sand Filters15%Underground Sand Filters4%Underground Manufactured Filters4%HDS Units10%Other1%Bioretention39%
TSS Metals (Cu, Zn, Pb) TKN (Nitrogen) Total-P BacteriaBioretention 40% 90% 93-98% 68-80% 70-83% 90%Sand Filter 0% 70% 45% 46% 33% 76%a: Volume Based Hydrology. Reese, A.J. Stormwater Magazine. September 2009.b: USEPA Fact Sheets EPA 832-F-99-007 (Sand Filters) and EPA 832-F-99-012 (Bioretention).Pollutant Removal RatebAnnual Volume ReductionaBMP TypeWHY BIORETENTION?POLLUTANT ANDVOLUME REMOVAL CAPABILITIESCosts vary, $3 to $20 per cubic foot captured, (Average $7 to $8)
Use NATIVEPlants•Deep Root Systems•Rainfall Infiltration Benefits•Rainfall Interception Benefits•Better Nutrient Removal•Minimal Irrigation - Conserves Water•Minimal or No Fertilizing, also help to Uptake Excess Fertilizer from Upstream Drainage Areas•Less Maintenance •Better Survivability•Enhance Biodiversity (Mosquito Control) and Promote a Conservation Culture•Control Erosion•Very Wet or Very Dry Conditions
Revised August 2010…and Still Revising…
Runoff Volume Reduction Tool8479751.68581781.58682801.48784821.38885831.28986851.189888619089880.99190890.89291910.79392920.69493930.59594940.49595950.39696960.29797970.19898980100-year2-year1-yearModified Curve Number (for Impervious Areas)Rainfall Reduction (in.)*MSD StandardBMP DetailsCurve Number (CN) Reductions
Who has the Ball???Plan reviews until approval, try for maximum of 3 (goal is 85% of projects)MSD is tracking plan review iterations until approval, this is an MSD Strategic Plan measurable goalGoal is 3 reviews or fewer, then approveIN-REVIEW-OUTIN-REVIEW-OUTIN-REVIEW-OUTIN-APPROVERejection if comments not addressed, (discussed with Principal Engineer first)
For initial submittals with Runoff Volume Reducing BMPs , MSD will try to expedite the reviewSome jobs have recently been sent in this way and we have done so alreadyINCENTIVES !!!
Some Suggestions on Street ProjectsRoughly 10% of all our impervious area is Streets, this alone is enough to produce water quality impairmentBioretention alongside roadwaysRoof drain disconnectsAdd bioretention/raingardens at disconnect locationsSwap areas may not be allowed (i.e. most polluted surface isthe street)
Area SwapsOn some redevelopmentsites it is sometimes difficult to capture and treat runoff only from disturbed area portions of a project. In some cases a trading or swapping of disturbed area for other existing, non-disturbed area to be treated by BMPs is a more practical approachStrive to meet area treated for area disturbed. The swap should result in an equally or more polluted existing surface being treated by BMPs.If not practicable MSD might consider a water quality volume (WQv) swap (for the 1.14” – 90th % rainfall). Volume provided to be at least 1.5 times the calculated WQv required for disturbed area.
Area Swaps Example
Native Plant Seeding
Propagating the prairie, andPropagating the idea of water quality…
Thank You! Questions?