charles county, md low impact ... - govt.co.charles.md.us · low impact development (lid)/...

Presentation HighlightsPresentation Highlights

BackgroundBackground

What is LID / ESD?What is LID / ESD?

Why adopt LID/ESD Why adopt LID/ESD

MD SWM Act 2007MD SWM Act 2007

Planning ProcessPlanning Process

Design ObjectivesDesign Objectives

ESD PracticesESD Practices

How we got hereHow we got here

Grant award: By the National Fish and Wildlife FoundationPartners:

Charles County Government, Town of La Plata, and Town of Indian Head

Grant objective: Wide scale implementation of low impact development practices in Charles County.Basis:

U.S. Army Corps of Engineers Mattawoman Creek Watershed Management Plan;Port Tobacco River Watershed Restoration Action Plan; andMaryland Stormwater Management Act of 2007

Final ProductsFinal Products

Stormwater Management OrdinanceDrainage OrdinanceStormwater Management Polices and Procedures ManualLID /ESD Supplement to Design Manual

TimelineTimeline

Public Kick-off Meeting (January 2009)Focus Groups to Review Discuss Draft (April/May 2009)Informational Notices (June/July 2009)Briefings to Planning Commission and County Commissioners (July/August/September 2009)Submittal to Maryland Department of the Environment for their review (TBD)Public Adoption Process (public meetings and work sessions)Engineer/Inspector Training (at completion)

What is LID / ESD?What is LID / ESD?

LID DefinedLID Defined

A A stormwaterstormwater management strategy to maintain or restore the management strategy to maintain or restore the natural hydrologic functions of a site to achieve natural resournatural hydrologic functions of a site to achieve natural resources ces protection objectives and fulfill environmental regulatory protection objectives and fulfill environmental regulatory requirementsrequirementsLID employs a variety of natural and built features that reduce LID employs a variety of natural and built features that reduce the the rate of runoff, filter out pollutants, and facilitates the infilrate of runoff, filter out pollutants, and facilitates the infiltration of tration of water into the ground.water into the ground.LID incorporates a set of overall site design strategies as wellLID incorporates a set of overall site design strategies as well as as highly localized, smallhighly localized, small--scale decentralized source control scale decentralized source control techniques known as Integrated Management Practices (techniques known as Integrated Management Practices (IMPsIMPs))IMPsIMPs may be integrated into buildings, infrastructure, or may be integrated into buildings, infrastructure, or landscape features.landscape features.

Bottom LineBottom Line

LID and ESD now have pretty much the same meaning in MDLID and ESD now have pretty much the same meaning in MD

The two terms will be used interchangeably in the rest of the The two terms will be used interchangeably in the rest of the presentationpresentation

Why Adopt LID / ESD?Why Adopt LID / ESD?

MD SWM Act 2007MD SWM Act 2007Prevent soil erosion from development projects. Prevent soil erosion from development projects. Prevent increases in nonpoint pollution. Prevent increases in nonpoint pollution. Minimize pollutants in Minimize pollutants in stormwaterstormwater runoff from both new development and runoff from both new development and redevelopment. redevelopment. Restore, enhance, and maintain chemical, physical, and biologicaRestore, enhance, and maintain chemical, physical, and biological integrity l integrity of receiving waters to protect public health and enhance domestiof receiving waters to protect public health and enhance domestic, c, municipal, recreational, industrial and other uses of water as smunicipal, recreational, industrial and other uses of water as specified by pecified by MDE. MDE. Maintain 100% of the average annual predevelopment groundwater Maintain 100% of the average annual predevelopment groundwater recharge volume. recharge volume. Capture and treat Capture and treat stormwaterstormwater runoff to remove pollutants. runoff to remove pollutants. Implement a channel protection strategy to protect receiving strImplement a channel protection strategy to protect receiving streams. eams. Prevent increases in the frequency and magnitude of outPrevent increases in the frequency and magnitude of out--ofof--bank flooding bank flooding from large, less frequent storms. from large, less frequent storms. Protect public safety through the proper design and operation ofProtect public safety through the proper design and operation of stormwaterstormwatermanagement facilities. management facilities.

MDE ESD Planning ProcessMDE ESD Planning Process

Delegated stormwater authorities will be required to use a 3 phase process

1. Concept2. Site Development Plan3. Final

Must be a coordinated local agency effort & includeSCDPlanning and zoningPublic Works

All new developments shall be subject to the design Process for New Developments as outlined in Figure 5.1

Figure 5.1

Concept Design Phase:Concept Design Phase:Site & Resources MappingSite & Resources Mapping

Concept Design Phase:Concept Design Phase:Site & Resources MappingSite & Resources Mapping

Site concept plan shouldidentify and avoid impact to existing site environmental resources

Concept Design Phase:Concept Design Phase:Site Development StrategiesSite Development Strategies

Table 5.2Table 5.2 Summary of Site Development StrategiesSummary of Site Development Strategies

Flexible design criteria to enable use of clustered Flexible design criteria to enable use of clustered developments and conservation designdevelopments and conservation design

Open spaceOpen space

Parking lots required to be landscaped & setbacks relaxed Parking lots required to be landscaped & setbacks relaxed to allow for bioretention islands & other SWM practicesto allow for bioretention islands & other SWM practices

Parking lot runoffParking lot runoff

Max parking ratios Max parking ratios vsvs minimum; shared parking;minimum; shared parking;Stall width & length; parking garagesStall width & length; parking garages

Parking ratios, codes, lotsParking ratios, codes, lotsStructured parkingStructured parking

Grass channels, Grass channels, biofiltersbiofilters for SWMfor SWMOpen vegetated channelsOpen vegetated channels

Small radii Small radii –– 33 ft33 ftLandscape treatment BMP in center (Bioretention)Landscape treatment BMP in center (Bioretention)

CulCul--dede--sacssacs

Street width =22 ft in low traffic volumesStreet width =22 ft in low traffic volumesOpen space design & clustering reduce street lengthOpen space design & clustering reduce street lengthROW reduced with narrow sidewalks, sidewalks on one ROW reduced with narrow sidewalks, sidewalks on one side only, reduce border between street & sidewalkside only, reduce border between street & sidewalk

Using narrower, shorter streets, Using narrower, shorter streets, ROW, sidewalksROW, sidewalks

RecommendationsRecommendationsBetter Site Design Better Site Design TechniqueTechnique

Concept Design Phase:Concept Design Phase:Site Development StrategiesSite Development Strategies

Table 5.2Table 5.2 Summary of Site Development StrategiesSummary of Site Development Strategies

Provide longProvide long--term protection of large tracts of contiguous term protection of large tracts of contiguous forested areas; promote use of native plantingsforested areas; promote use of native plantings

Tree conservationTree conservation

Provide incentives for conservation of natural areas Provide incentives for conservation of natural areas through density compensation, property tax reduction, and through density compensation, property tax reduction, and flexibility in design processflexibility in design process

Conservation incentivesConservation incentives

Use site fingerprinting to reduce clearing, grading & earth Use site fingerprinting to reduce clearing, grading & earth disturbance disturbance

Clearing & gradingClearing & grading

Designate minimum buffer width & provide mechanism for Designate minimum buffer width & provide mechanism for long term protectionlong term protection

Buffer systemsBuffer systems

Direct to pervious surfaces, harvest & reuseDirect to pervious surfaces, harvest & reuseRooftop runoffRooftop runoff

Allow shared driveways & permeable pavementsAllow shared driveways & permeable pavementsDrivewaysDriveways

Relax setbacks & allow narrower frontages to reduce total Relax setbacks & allow narrower frontages to reduce total road & driveway length;road & driveway length;

Setbacks & frontagesSetbacks & frontages

RecommendationsRecommendationsBetter Site Design Better Site Design TechniqueTechnique

Minimization of Development Impacts:Minimization of Development Impacts:Site fingerprintingSite fingerprinting

Large lotsLarge lotsReduced clearing & grading Reduced clearing & grading costscostsPreserves natural soils & Preserves natural soils & vegetationvegetationVegetative bufferVegetative buffer

Design ObjectivesDesign Objectives

The criteria for sizing ESD practices are based on capturing andretaining enough rainfall so that the runoff leaving a site is reduced to a level equivalent to a wooded site in good condition as determined using United States Department of Agriculture (USDA) Natural Resource Conservation Service (NRCS) methods (e.g., TR-55).

The basic principle is that a reduced runoff curve number (RCN) may be applied to post-development conditions when ESD practices are used.

The goal is to provide enough treatment using ESD practices to address channel protection (Cpv) requirements by replicating an RCN for woods in good condition for the 1-year rainfall event.

This eliminates the need for structural practices (MDE, Chapter 3).

If the design rainfall captured and treated using ESD is short of the target rainfall, a reduced RCN may be applied to post-development conditions when addressing stormwater management requirements.

The reduced RCN is calculated by subtracting the runoff treated by ESD practices from the total 1-year 24-hour design storm runoff.

ESD PracticesESD Practices

Group 1:Group 1: Alternative SurfacesAlternative SurfacesAA--11 Green RoofsGreen RoofsAA--2 2 Permeable PavementsPermeable Pavements

Group 2:Group 2: Nonstructural PracticesNonstructural PracticesNN--1 1 Disconnection of rooftop runoffDisconnection of rooftop runoffNN--2 2 Disconnection of nonDisconnection of non--rooftop runoffrooftop runoffNN--3 3 SheetflowSheetflow to conservation areato conservation area

Group 3:Group 3: MicroMicro--scale Practices to Treat Runoffscale Practices to Treat RunoffMM--1 1 Rainwater HarvestingRainwater HarvestingMM--2 2 Submerged Gravel wetlandsSubmerged Gravel wetlandsMM--3 3 Landscape InfiltrationLandscape InfiltrationMM--4 4 Infiltration Infiltration BermsBermsMM--5 5 Dry wellsDry wellsMM--6 6 MicroMicro--bioretentionbioretentionMM--7 7 Rain gardens Rain gardens MM--8 8 Swales Swales MM--9 9 Enhanced FiltersEnhanced Filters

AA--1 Green Roofs1 Green Roofs

Also known as vegetated roofs, roof gardens, or eco-roofs.May be used in place of traditional flat

or pitched roofs to reduce impervious cover and more closely mimic natural hydrology. Green roofs produce less heat than conventional systems. Therefore, they may be used to help mitigate stormwater impacts and temperature increases caused by new development.There are two basic green roof designs that are distinguished by media thickness and the plant varieties that are used:

ExtensiveIntensive

Hamilton Apartments Ecoroof Hamilton Apartments Ecoroof -- 1999 first 1999 first large scale stormwater monitoring and large scale stormwater monitoring and

education site in USAeducation site in USA

Extensive Green RoofsExtensive Green Roofs

Extensive green roofs more common lightweight system media layer is 2-6 inches thick. limits plants to low-growing, hardy herbaceous varietiesmay be constructed off-site as a modular system with drainage layers, growing media, and plants installed in interlocking grids. Conventional construction methods may also be used to install each component separately

AA--1 Green Roofs1 Green Roofs

Design ConsiderationsInfrastructureStructureWaterprooofingDrainageConveyanceTreatmentLandscaping

Construction ConsiderationsWaterproofingSlope stabilizationInstallationInspectionMaintenance

AA--2: Permeable Pavements2: Permeable Pavements

Permeable pavements are alternatives that may be used Permeable pavements are alternatives that may be used to reduce imperviousnessto reduce imperviousnessMDE groups into 3 categoriesMDE groups into 3 categories

Porous bituminous asphaltPorous bituminous asphaltPorous concretePorous concreteInterlocking concrete paving blocks (grid pavers)Interlocking concrete paving blocks (grid pavers)

BenefitsBenefitsReduce impervious coverReduce impervious coverProvide water quality and groundwater recharge benefitsProvide water quality and groundwater recharge benefitsMitigate temperature increasesMitigate temperature increases

Permeable Pavement Types

MDE: Typical Sections

AA--2: Permeable Pavements2: Permeable Pavements

Design Considerations:Design Considerations:Space / Topography / Soils / Drainage area / Hotspot RunoffSpace / Topography / Soils / Drainage area / Hotspot RunoffStructureStructureConveyance / treatment / landscaping / setbacksConveyance / treatment / landscaping / setbacks

Construction ConsiderationsConstruction ConsiderationsErosion and sediment controlErosion and sediment controlSoil compactionSoil compactionUnderUnder--drainsdrainsInspectionInspectionMaintenanceMaintenance

Porous PavementPorous Pavement

Permeable Permeable PavementPavement

Eco-Stone

DC Navy Yard

AA--3: Reinforced Turf3: Reinforced Turf

Reinforced turf consists of Reinforced turf consists of interlocking structural units with interlocking structural units with interstitial areas for placing gravel interstitial areas for placing gravel or growing grass. or growing grass.

These systems are suitable for These systems are suitable for light traffic loads and are light traffic loads and are commonly used for emergency commonly used for emergency vehicle access roads and overflow vehicle access roads and overflow or occasionally used parking. or occasionally used parking.

Turfstone

GEOBLOCK

GREEN GEOBLOCK

AA--3: Reinforced Turf3: Reinforced Turf

Design Considerations:Design Considerations:Space / Topography / Soils / Drainage area / Hotspot RunoffSpace / Topography / Soils / Drainage area / Hotspot RunoffStructureStructureConveyance / treatment / landscaping / setbacksConveyance / treatment / landscaping / setbacks

Construction ConsiderationsConstruction ConsiderationsErosion and sediment controlErosion and sediment controlSoil compactionSoil compactionUnderUnder--drainsdrainsInspectionInspectionMaintenanceMaintenance

Group 2: Group 2: Nonstructural Practices

N-1. Disconnection of Rooftop Runoff N-2. Disconnection of Non-Rooftop Runoff N-3. Sheetflow to Conservation Areas


Disconnecting impervious cover and treating urban runoff closer to its source are the next steps in the design process for implementing ESD. Using nonstructural techniques (e.g., disconnection of rooftop runoff, sheetflow to conservation areas) and micro-scale practices (e.g., rain gardens, bio-swales) throughout a development is an effective way to accomplish this goal. Nonstructural practices may be used to disconnect impervious cover and direct runoff over vegetated areas to promote overland filtering and infiltration. Whether runoff is directed over permeable areas or captured in small water quality treatment practices, there are reductions in both volume and pollutants delivered to receiving streams. These practices may be used to address the ESD design criteria


Nonstructural and micro-scale practices are an integral part of the ESD stormwater management plans. The use of these practices must be documented at the concept, site development, and final design stages and verified with “as-built” certification. If practices are not implemented as planned, then volumes used to design structural practices must be increased appropriately to meet the ESD sizing criteria.

NN--1: Disconnection of rooftop runoff1: Disconnection of rooftop runoff

Rooftop disconnection involves directing flow from downspouts onto vegetated areas where it can soak into or filter over the ground. This disconnects the rooftop from the storm drain system and reduces both runoff volume and pollutants delivered to receiving waters. To function well, rooftop disconnection is dependent on several site conditions (e.g., flow path length, soils, slopes).

Disconnected downspout

Connected downspout

MDE: Typical Details

NN--1: Disconnection of rooftop runoff1: Disconnection of rooftop runoff

Design Considerations:Design Considerations:Space / Topography / Soils / Drainage area / ReconnectionsSpace / Topography / Soils / Drainage area / ReconnectionsConveyance / treatment / landscaping Conveyance / treatment / landscaping

Construction ConsiderationsConstruction ConsiderationsErosion and sediment controlErosion and sediment controlSite disturbanceSite disturbanceInspectionInspectionMaintenanceMaintenance

NN--2 Disconnection of Non2 Disconnection of Non--Rooftop RunoffRooftop Runoff

Directs flow from impervious surfaces to vegetated areas where Directs flow from impervious surfaces to vegetated areas where it can it can soak into or filter over groundsoak into or filter over groundDisconnects surfaces from storm drain system, reducing both runDisconnects surfaces from storm drain system, reducing both runoff off volume and pollutants delivered to receiving watersvolume and pollutants delivered to receiving watersCommonly applied to smaller or narrower impervious areas, driveCommonly applied to smaller or narrower impervious areas, driveways, ways, open section roads, small parking lotsopen section roads, small parking lotsDependent on site condition: Permeable flow path length / soilDependent on site condition: Permeable flow path length / soils / slopess / slopescompactioncompaction

NN--2: Disconnection of non2: Disconnection of non--rooftop runoffrooftop runoff

Design Considerations:Design Considerations:Space / Topography / Soils / Drainage area / ReconnectionsSpace / Topography / Soils / Drainage area / ReconnectionsConveyance / treatment / landscaping Conveyance / treatment / landscaping

Construction ConsiderationsConstruction ConsiderationsErosion and sediment controlErosion and sediment controlSite disturbanceSite disturbanceInspectionInspectionMaintenanceMaintenance

NN--3: 3: SheetflowSheetflow to conservation areato conservation area

Flow from pervious and Flow from pervious and impervious surfaces is directed impervious surfaces is directed to vegetated buffers to vegetated buffers (infiltration, filtering)(infiltration, filtering)

Effective when development Effective when development adjacent to adjacent to protected areasprotected areas

Dependent on site conditions:Dependent on site conditions:Buffer sizeBuffer sizeContributing flow path lengthsContributing flow path lengthsSlopesSlopesCompactionCompaction

SheetflowSheetflow to conservation areato conservation area

MM--1: Rainwater harvesting1: Rainwater harvesting

Group 3:Group 3: MicroMicro--scale Practices to Treat scale Practices to Treat RunoffRunoff

MM--1 1 Rainwater HarvestingRainwater HarvestingMM--2 2 Submerged Gravel wetlandsSubmerged Gravel wetlandsMM--3 3 Landscape InfiltrationLandscape InfiltrationMM--4 4 Infiltration Infiltration BermsBermsMM--5 5 Dry wellsDry wellsMM--6 6 MicroMicro--bioretentionbioretentionMM--7 7 Rain gardens Rain gardens MM--8 8 Swales Swales MM--9 9 Enhanced FiltersEnhanced Filters

MM--1: Rainwater Harvesting (Cisterns & Rain Barrels)1: Rainwater Harvesting (Cisterns & Rain Barrels)

Intercept and store rainfall for Intercept and store rainfall for future usefuture useStored water used for outdoor Stored water used for outdoor landscaping irrigation, car landscaping irrigation, car washing, nonwashing, non--potable water potable water supplysupplyPromotes conservationPromotes conservationReduces runoff volumes and Reduces runoff volumes and discharge of pollutantsdischarge of pollutants

Cistern schematic and applications

MM--1: Rainwater Harvesting:1: Rainwater Harvesting:(Design & Construction)(Design & Construction)

Design Considerations:Space Topography Drainage Area OperationConveyance Treatment Distribution SystemDewatering Observation Well SafetyMosquitoes Setbacks

Construction Considerations:Site Disturbance Storage Tanks PressurizationMaintenance Inspection

MM--1: Rainwater Harvesting: Cost1: Rainwater Harvesting: Cost

RainbarrelsRainbarrelsDoDo--itit--yourself rain barrels can be constructed for under $30. yourself rain barrels can be constructed for under $30. ReadyReady--made 55 gallon to 90made 55 gallon to 90 gallon rain barrels generally cost from gallon rain barrels generally cost from $50 to $300 uninstalled. $50 to $300 uninstalled.

CisternsCisternsCosts for a cistern, not including installation, range from abouCosts for a cistern, not including installation, range from about $250 t $250 for a 200for a 200--gallon cistern to $5,000 for a 10,000gallon cistern to $5,000 for a 10,000--gallon cistern.gallon cistern.

MM--2: Submerged gravel wetlands2: Submerged gravel wetlands

A submerged gravel wetland is a A submerged gravel wetland is a smallsmall--scale filter using wetland scale filter using wetland plants in a rock media to provide plants in a rock media to provide water quality treatment. water quality treatment. Runoff drains into the lowest Runoff drains into the lowest elevation of the wetland, is elevation of the wetland, is distributed throughout the system, distributed throughout the system, and discharges at the surface. and discharges at the surface. Pollutant removal is achieved in a Pollutant removal is achieved in a submerged gravel wetland submerged gravel wetland through biological uptake from through biological uptake from algae and bacteria growing within algae and bacteria growing within the filter media.the filter media.Wetland plants provide additional Wetland plants provide additional nutrient uptake and physical and nutrient uptake and physical and chemical treatment processes chemical treatment processes allow filtering and absorption of allow filtering and absorption of organic matter. organic matter.

Gravel Wetland: Gravel Wetland: SchematicSchematic

MM--2: Gravel Wetland:2: Gravel Wetland:(Design & Construction)(Design & Construction)

Design Considerations:Space Topography Soils Drainage AreaHotspot Runoff Conveyance Treatment Flow Splitter Treatment Cells Wetland VegetationObservation Well

Construction Considerations:Site Disturbance Erosion and Sediment Control Gravel Media Inspection Maintenance

Design Example: AsDesign Example: As--builtbuilt

PerformancePerformance

MM--3: Landscape infiltration3: Landscape infiltration

Landscape infiltration Landscape infiltration (planters) uses on(planters) uses on--site site vegetation to capture, store vegetation to capture, store and treat and treat stormwaterstormwaterRainwater is stored, filters Rainwater is stored, filters through the planting soil and through the planting soil and gravel media below, and then gravel media below, and then infiltrates into native soil.infiltrates into native soil.Practices can be integrated Practices can be integrated into overall site designinto overall site designStorage is provided in Storage is provided in constructed planters made of constructed planters made of stone, brick, concrete, or in stone, brick, concrete, or in natural areas excavated and natural areas excavated and backfilled with stone and backfilled with stone and topsoiltopsoil

Landscape Landscape InfiltrationInfiltration

Landscape PlantersLandscape Planters

MM--3: Landscape Infiltration3: Landscape Infiltration

Design Considerations:Space Topography Soils Drainage AreaHotspot Runoff Conveyance Treatment Flow Splitter Infrastructure Observation Well

Construction Considerations:Soil Compaction Erosion and Sediment Control Gravel & Filter Media Planter Boxes Filter ClothLandscape Installation Inspection Maintenance

MM--4: Infiltration 4: Infiltration BermsBerms

A mound of earth composed of soil and stone that is placed along the contour of a relatively gentle slope. This practice may be constructed by excavating upslope material to create a depression and storage area above a berm or earth dike. Stormwater runoff flowing downslope to the depressed area filters through the berm in order to maintain sheetflow. Infiltration berms should be used in conjunction with practices that require sheetflow (e.g., sheetflow to buffers) or in a series on steeper slopes to prevent flow concentration.

MM--4: Infiltration 4: Infiltration BermsBerms

Design Considerations:Space Topography Soils Drainage AreaHotspot Runoff Conveyance Treatment Storage Capacity Plant Materials

Construction Considerations:Soil Compaction Erosion and Sediment Control Gravel & Filter Media Landscape Installation Inspection Maintenance

MM--5: Dry wells5: Dry wells

An excavated pit or structural An excavated pit or structural chamber, filled with gravel or chamber, filled with gravel or stone, provides temporary stone, provides temporary storage of storage of stormwaterstormwater runoff runoff from rooftopsfrom rooftopsStorage area may be a shallow Storage area may be a shallow trench or deep welltrench or deep wellRooftop runoff is stored and Rooftop runoff is stored and infiltrates into soilinfiltrates into soilPollutant removal ability Pollutant removal ability related to volume of flowrelated to volume of flow


MM--5: Dry well5: Dry well

Design Considerations:Space Topography Soils Drainage AreaHotspot Runoff Conveyance Treatment Landscaping Underground distribution systemSetbacks Operation

Construction Considerations:Soil Compaction Erosion and Sediment Control Gravel Media Landscape Installation Dry well bottom Underground distribution system Inspection Maintenance

MM--6: Micro6: Micro--bioretentionbioretention

Practice captures and treats Practice captures and treats runoff from discrete impervious runoff from discrete impervious areas by passing through a areas by passing through a filter bed mixture of sand, soil filter bed mixture of sand, soil & organic matter& organic matterFiltered Filtered stormwaterstormwater is either is either returned to the conveyance returned to the conveyance system or partially infiltrated system or partially infiltrated into soilinto soilMicroMicro--bioretention practices bioretention practices are versatile and may be are versatile and may be adpatedadpated for use anywhere for use anywhere there is landscapingthere is landscaping


MM--6: Micro6: Micro--bioretentionbioretention

Design Considerations:Space Topography Soils Drainage AreaHotspot Runoff Conveyance Treatment Landscaping Infrastructure

Construction Considerations:Soil Compaction Erosion and Sediment Control Filter Media Landscape Installation Underdrain installation Inspection Maintenance

MM--7: Rain gardens7: Rain gardens

Shallow excavated Shallow excavated landscape feature or saucer landscape feature or saucer shaped depression that shaped depression that temporarily holds runoff for a temporarily holds runoff for a short period of timeshort period of timeConsists of the following Consists of the following components:components:

Absorbent planted soil bedAbsorbent planted soil bedA mulch layerA mulch layerA gravel filter chamberA gravel filter chamberPlanting materials (shrubs, Planting materials (shrubs, grasses, flowers)grasses, flowers)Overflow conveyance systems Overflow conveyance systems

Captured runoff filters into Captured runoff filters into soil over 24 soil over 24 --48 hours48 hours

Functional LandscapeOn Lot BioretentionOn Lot Bioretention

MM--7: Rain garden7: Rain garden

Design Considerations:Topography Soils Drainage AreaLocation Conveyance Treatment Landscaping Infrastructure

Construction Considerations:Erosion and Sediment Control Planting Soil Landscape Installation Inspection Maintenance

MM--8: Swales8: Swales

Channels that provide Channels that provide conveyance, water quality conveyance, water quality treatment & flow attenuation of treatment & flow attenuation of stormwaterstormwater runoffrunoffPollutant removal through Pollutant removal through vegetative filtering, sedimentation, vegetative filtering, sedimentation, biological uptake, & infiltration into biological uptake, & infiltration into soil mediasoil media3 design variants:3 design variants:

Grass swalesGrass swalesWet swalesWet swalesBioBio--swalesswalesMicroMicro--scale practices are small scale practices are small water qualitywater quality

MM--8: Swales8: Swales

Design Considerations:Topography Soils Drainage AreaHotspot runoff Conveyance Treatment Landscaping Location grass swalesbioswales check dams

Construction Considerations:Erosion and Sediment Control Inspection Maintenance

MM--9: Enhanced Filters9: Enhanced Filters

Modification that takes advantage of Modification that takes advantage of soil conditions below a specific soil conditions below a specific practice ( e.g., micropractice ( e.g., micro--bioretention) to bioretention) to provide water quality treatment and provide water quality treatment and gwgw recharge in a single facility.recharge in a single facility.

Uses stone reservoir under Uses stone reservoir under conventional filtering device to conventional filtering device to collect runoff, remove nutrients collect runoff, remove nutrients anaerobicallyanaerobically, and allow infiltration , and allow infiltration into the soilinto the soil

MDE Typical Details

MM--9: Enhanced Filters9: Enhanced Filters

Design Considerations:Space Soils Hotspot runoff Conveyance Treatment Observation wellSetbacks Infrastructure

Construction Considerations:Erosion and Sediment Control Soil compaction Reservoir installation Inspection Maintenance

Comments / Questions ?Comments / Questions ?

charles county, md low impact ... - govt.co.charles.md.us · low impact development (lid)/...

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