Post on 28-Dec-2015
2009 Maryland 2009 Maryland Stormwater Ordinance Stormwater Ordinance
& Design Manual & Design Manual UpdatesUpdates
Environmental Site Design Environmental Site Design Presented by Robert Kane, P.E. & Jen Smith, Presented by Robert Kane, P.E. & Jen Smith, E.I.T.E.I.T.
Stormwater Ordinance ForumStormwater Ordinance Forum
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)
Current SWM PracticesCurrent SWM Practices
Provide detention of Channel Protection Volume
(Cpv), or 1-year storm event
Not required for Eastern Shore
Current SWM Practices - Current SWM Practices - ContinuedContinued
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”
Current SWM and ESDCurrent SWM and ESD
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)
New Maryland SWM New Maryland SWM RegulationsRegulations
Stormwater Design Stormwater Design ChangesChanges
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
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
Maryland SWM Act Maryland SWM Act UpdateUpdate
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 ImplementationESD Implementation
County and municipal stormwater authorities shall establish 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 & Comprehensive ESC & SWM ReviewSWM Review
(All field verified by project designer during development)
FloodplainsStable OutfallSpringsSoils Stream buffers
Steep slopesCritical areas
Vegetative coverBedrock/GeologyTopography/slopesHighly erodible soilsExisting drainage areas
Forests and forest buffers
Proposed limits of clearing and gradingWetlands and wetlands buffers
Major waterways and perennial streams
Site and Resource Site and Resource MappingMapping
Better Site Design Better Site Design TechniquesTechniques
Narrower and shorter: Streets Right-of-ways Sidewalks
Open vegetated channels Parking ratios Parking lot runoff Cul-de-sacs Open space Setbacks and frontages
Site Fingerprinting and Site Fingerprinting and Development LayoutDevelopment Layout
Maintain natural flow pathsProvide stable outfallExpand forested, wetland, and stream buffersMaintain sheet flow“Clustering” developmentPlan building footprint and layoutLocate ESD practices
Drainage areas
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 Site Development and Final DesignFinal Design
Figure 5.1, Page Figure 5.1, Page 5.6 5.6
Questions?Questions?
MDE Model OrdinanceMDE Model Ordinance
Waiver Policy Redevelopment Policy Inspection and
Maintenance
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 PolicyWaiver Policy
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.)Waiver Policy (cont.)
All Waivers Case by case Consider cumulative
effects Will not adversely impact
stream quality
Waiver Policy (cont.)Waiver Policy (cont.)
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
RedevelopmentRedevelopment
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.)Redevelopment (cont.)
Separate Policies Retrofitting Stream restoration Watershed Management Plan Fees paid Hardship Variance
Redevelopment (cont.)Redevelopment (cont.)
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
Maintenance and Maintenance and InspectionInspection
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
Maintenance and Maintenance and Inspection (cont.)Inspection (cont.)
Questions?Questions?
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 CriteriaUnified Sizing Criteria
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 CriteriaESD Sizing Criteria
Pe = Rainfall Target from Pe = Rainfall Target from Table 5.3Table 5.3
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.)ESD Sizing Criteria (cont.)
Questions?Questions?
Green RoofsGreen Roofs
Permeable PavementsPermeable Pavements
Reinforced TurfReinforced Turf
Disconnection of Rooftop Disconnection of Rooftop RunoffRunoff
Disconnection of Non-Disconnection of Non-Rooftop RunoffRooftop Runoff
Sheet flow to Sheet flow to Conservation AreaConservation Area
Sheet flow to Sheet flow to Conservation AreaConservation Area
Submerged Gravel Submerged Gravel WetlandWetland
Landscape InfiltrationLandscape Infiltration
Landscape InfiltrationLandscape Infiltration
Rain GardenRain Garden
Rain GardenRain Garden
Micro-BioretentionMicro-Bioretention
Micro-Bioretention (cont.)Micro-Bioretention (cont.)
SwalesSwales
Infiltration BermInfiltration Berm
Infiltration BermInfiltration Berm
Dry WellsDry Wells
Rainwater HarvestingRainwater Harvesting(Cisterns & Rain Barrels)(Cisterns & Rain Barrels)
Rainwater HarvestingRainwater Harvesting(Cisterns & Rain Barrels)(Cisterns & Rain Barrels)
Enhanced FiltersEnhanced Filters
Questions?Questions?
2009 Maryland 2009 Maryland Stormwater Ordinance Stormwater Ordinance
& Design Manual & Design Manual UpdatesUpdates
Environmental Site Design Environmental Site Design Presented by Robert Kane, P.E. & Jen Smith, Presented by Robert Kane, P.E. & Jen Smith, E.I.T.E.I.T.
Stormwater Ordinance ForumStormwater Ordinance Forum