Jennifer St. John, Watershed Planner

John Hollister, Engineer

Watershed Restoration Program and Watershed Restoration Program and

Purpose of the Spring Street/ Ballard Purpose of the Spring Street/ Ballard

Street Stormwater ProjectStreet Stormwater Project

October 20, 2011

AgendaAgenda

�� IntroductionsIntroductions

�� Project Overview Project Overview

�� Project Tasks and GoalsProject Tasks and Goals

�� Stormwater Management Retrofit Assessment Stormwater Management Retrofit Assessment

�� Storm Drain Analysis Storm Drain Analysis

�� Questions/DiscussionQuestions/Discussion

Project OverviewProject Overview

Sp

ring S

treet

Sp

ring S

treet

Are

aA

rea

�� Located in the Rock Creek Located in the Rock Creek WatershedWatershed

�� Study Point is located behind Study Point is located behind the existing Post Office, east of the existing Post Office, east of the railroad tracksthe railroad tracks

�� Drainage Area to Study Point = Drainage Area to Study Point = 28.2 acres28.2 acres

Study P

oint

Study P

oint

Overall Project TasksOverall Project Tasks

�� Stormwater Management Retrofit AssessmentStormwater Management Retrofit Assessment

�� Identify opportunities for Stormwater Management Identify opportunities for Stormwater Management RetrofitsRetrofits

�� Storm Drain AnalysisStorm Drain Analysis

Effects of Urban RunoffEffects of Urban Runoff

�� Storm drain Storm drain

systems convey systems convey

heated, dirty heated, dirty

water directly to water directly to

streamsstreams

�� Reduced groundwater Reduced groundwater

recharge (infiltration)recharge (infiltration)

�� Impervious (hard surfaces)Impervious (hard surfaces)

= Increased runoff & pollutants= Increased runoff & pollutants

�� Increased storm flows & Increased storm flows &

decreased base flowsdecreased base flows

�� Infrastructure threatenedInfrastructure threatened

�� Streams eroded, incisedStreams eroded, incised

�� Degraded aquatic Degraded aquatic

habitat & water qualityhabitat & water quality

Proposed Stormwater Management Proposed Stormwater Management

Project GoalsProject Goals

�� Maximize stormwater management to improve Maximize stormwater management to improve

conditions in Rock Creek, the Potomac River & the conditions in Rock Creek, the Potomac River & the

Chesapeake BayChesapeake Bay

�� Improve water quality treatmentImprove water quality treatment

�� Encourage infiltration of runoff from parking lots, Encourage infiltration of runoff from parking lots,

roadways and other impervious surfacesroadways and other impervious surfaces

�� Fulfill requirements in the CountyFulfill requirements in the County’’s National Pollutant s National Pollutant

Discharge Elimination System (NPDES) permitDischarge Elimination System (NPDES) permit

Montgomery CountyMontgomery County’’s (NPDES) Permit s (NPDES) Permit NNational ational PPollutant ollutant DDischarge ischarge EElimination limination SSystemystem

�� Montgomery CountyMontgomery County’’s Municipal Separate Storm Sewer System s Municipal Separate Storm Sewer System (MS4) NPDES Permit (issued in 2010) Requires:(MS4) NPDES Permit (issued in 2010) Requires:

�� New stormwater management for New stormwater management for 20% of existing impervious20% of existing impervious area that is area that is currently unmanaged (currently unmanaged (~ 4,100 acres~ 4,100 acres).).

�� Identify pollution sources and improve water quality in all counIdentify pollution sources and improve water quality in all county ty watershedswatersheds

�� Increase use of Environmental Site Design (ESD), or Increase use of Environmental Site Design (ESD), or Low Impact Design (LID)Low Impact Design (LID)

Pervious PaversBioretention Curb Extension

�� Variety of smallVariety of small--scale practices to capture stormwater runoff close to scale practices to capture stormwater runoff close to the sourcethe source

�� Slows rate and reduces volume of runoffSlows rate and reduces volume of runoff

�� Allows stormwater to soak into the ground, replenishing ground wAllows stormwater to soak into the ground, replenishing ground waterater

�� Filters out pollutantsFilters out pollutants

Stormwater ManagementStormwater Management

�� Maryland Department of the Environment (MDE) has set Maryland Department of the Environment (MDE) has set forth a unified approach to stormwater management forth a unified approach to stormwater management throughout the entire state.throughout the entire state.

�� Water QuantityWater Quantity

•• Control runoff from small storms to prevent Control runoff from small storms to prevent downstream erosiondownstream erosion

�� Water QualityWater Quality

•• Treat the first inch of runoff to remove pollutantsTreat the first inch of runoff to remove pollutants

Stormwater Management Stormwater Management

Retrofit AssessmentRetrofit Assessment�� Study Area = 28.2 acresStudy Area = 28.2 acres

�� Dense Urban AreaDense Urban Area

�� Limitations to possible Limitations to possible

facilitiesfacilities

�� Existing infrastructure and Existing infrastructure and

utilitiesutilities

�� Limited open spaceLimited open space

�� Parking requirementsParking requirements

�� Small water quality facilities Small water quality facilities

possiblepossible

�� Low Impact DevelopmentLow Impact Development

�� Provides small % of Provides small % of

required treatmentrequired treatment

Examples of Potential Stormwater Examples of Potential Stormwater

Management FacilitiesManagement Facilities

Underground WaterUnderground Water

Quality StructureQuality Structure

�� Consists of a storage pipe Consists of a storage pipe

and filtering chamber located and filtering chamber located

underground.underground.

Swale with InfiltrationSwale with Infiltration

•• Stone trench underground to Stone trench underground to

provide infiltrationprovide infiltration

Examples of Potential Stormwater Examples of Potential Stormwater

Management FacilitiesManagement Facilities

BioretentionBioretention Curb ExtensionsCurb Extensions

Examples of Potential Stormwater Examples of Potential Stormwater

Management FacilitiesManagement FacilitiesWater Quality InletsWater Quality Inlets Inlet ModificationsInlet Modifications

•• Modifications capture trash Modifications capture trash

and prevent it from being and prevent it from being

carried to downstream carried to downstream

channelschannels

Storm Drain AnalysisStorm Drain Analysis

28.2ac

26.2ac

Limits of

Storm Drain

Analysis

Storm Drain AnalysisStorm Drain Analysis

�� Verified storm drain capacityVerified storm drain capacity

�� Performed inspection of pipe Performed inspection of pipe

located under railroad trackslocated under railroad tracks

�� Pipe changes from a Pipe changes from a

concrete pipe to a stone concrete pipe to a stone

box culvertbox culvert

�� Modeled large storm events Modeled large storm events

through the stone box through the stone box

culvertculvert

�� Stone box culvert is the Stone box culvert is the

limiting factorlimiting factor

Estimated FloodplainEstimated Floodplain

�� Approximate limits Approximate limits

of floodingof flooding

�� Based on aerial Based on aerial

topographytopography

Questions/DiscussionQuestions/Discussion