2009 maryland stormwater ordinance & design manual updates environmental site design presented...

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.)

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.)

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

Submerged Gravel Submerged Gravel WetlandWetland

Landscape InfiltrationLandscape Infiltration

Rain GardenRain Garden

Micro-BioretentionMicro-Bioretention

Micro-Bioretention (cont.)Micro-Bioretention (cont.)

SwalesSwales

Infiltration BermInfiltration Berm

Dry WellsDry Wells

Rainwater HarvestingRainwater Harvesting(Cisterns & Rain Barrels)(Cisterns & Rain Barrels)

Enhanced FiltersEnhanced Filters

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

2009 maryland stormwater ordinance & design manual updates environmental site design presented...

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