West Chester, PA 19382 Cape May, NJ 08204 Cahill Associates Environmental Consultants Stormwater Management: Making Sure Green Is Green

West Chester, PA 19382West Chester, PA 19382Cape May, NJ 08204Cape May, NJ 08204

Cahill AssociatesCahill AssociatesEnvironmental ConsultantsEnvironmental Consultants

Stormwater Management: Stormwater Management: Making Sure Green Is Green Making Sure Green Is Green

Critical Link between Critical Link between Land and Water:Land and Water:

Two Sides of the Same CoinTwo Sides of the Same Coin

What happens on the land….

…has everything to do with what happens in and to the water.

Jersey City Reservoir, Morris County

Components of Sustainability Components of Sustainability Water-Related:Water-Related:

• Comprehensive StormwaterComprehensive Stormwater ManagementManagement• Recycled WastewaterRecycled Wastewater• Water Conserving Water UseWater Conserving Water Use• Just for StartersJust for Starters

The Problem - From Smart The Problem - From Smart Growth…Growth…

““The only thing new in the world is the The only thing new in the world is the history we’ve forgotten….” history we’ve forgotten….” Harry TrumanHarry Truman

Sustainability…Sustainability…

• Relates to private residential subdivision and retail and office and industrial centers….

• Also relates to public facilities like schools and parks and recreational facilities and roads….

This could be a new park next to you!

Stormwater Impacts of Conventional Stormwater Impacts of Conventional Development (including Parks and Development (including Parks and

Rec!)Rec!)

• Not just Increased Flooding!• Increased Runoff Volume• Decreased Evapotranspiration and

Groundwater Recharge• Increased Frequency of Runoff Events• Faster Conveyance of Water• Erosion and Stream Channel Changes• Decreased Baseflow• Impacted Aquatic Life• Pollutants and Temperature Impacts

……not to mention other impacts of not to mention other impacts of conventional development conventional development practices…practices…

Habitat Loss/BiodiversityHabitat Loss/BiodiversityWetlands/Floodplains/Other Wetlands/Floodplains/Other

AreasAreasSoils/Special Geologic FeaturesSoils/Special Geologic FeaturesAir Quality/MicroclimateAir Quality/MicroclimateNoiseNoiseHistorical/ArchaeologicalHistorical/ArchaeologicalAesthetics/ScenicAesthetics/ScenicQuality of LifeQuality of LifePublic HealthPublic Health

BalancinBalancing the g the Water Water CycleCycle

Annual Hydrologic CycleAnnual Hydrologic CycleFor an Average YearFor an Average Year

Altered Hydrologic CycleAltered Hydrologic Cycle

InfiltrationInfiltrationInfiltration

Surface RunoffSurface RunoffSurface Runoff

Conventional Development Conventional Development Water Cycle Impacts:Water Cycle Impacts:

• Increased Peak Runoff Rate• Increased Runoff Volumes• Decreased Infiltration• Decreased Groundwater Recharge• Decreased Stream Baseflow• Decreased Evapotranspiration• Temperature

All of which translate into many more related hydrologic, ecologic, other impacts.

Conventional (Detention) Conventional (Detention) Stormwater ManagementStormwater Management

• Controls Peak Rate of Runoff to Predevelopment Conditions

• Fails to Control Volume of Runoff

• Fails to Control Nonpoint Pollutant/Temperature Loadings

We all live downstream….We all live downstream….We haven’t understood the We haven’t understood the

basic hydrology of stream and basic hydrology of stream and river systems.river systems.

Average Annual Rainfall Volume that Occurs by Storm Magnitude for Harrisburg, PA

(PA State Climatological Office, 1926 – 2003)

Average Annual Rainfall Volume that Occurs by Storm Magnitude for Harrisburg, PA(PA State Climatological Office, 1926 - 2003)

1%1%

6%

27%

65%

4" +

3" - 4"

2" - 3"

1" - 2"

0.1" - 1"

0.1” - 1”

Stormwater management has Stormwater management has focused only on the largest focused only on the largest

storms…we haven’t paid storms…we haven’t paid attention to annual water attention to annual water balance and the reality of balance and the reality of

smaller storms.smaller storms.

WELL

STREAM

AQUIFER

BEDROCK

SOIL

Green Valleys Association

Cahill AssociatesEnvironmental Consultants

Manage Stormwater as a Manage Stormwater as a Precious Resource… not a Precious Resource… not a Disposal ProblemDisposal Problem

for Stream Baseflow/Low Flowfor Stream Baseflow/Low Flowfor Wells and Springsfor Wells and Springsfor Wetlandsfor Wetlands

Nonpoint Source PollutionNonpoint Source Pollution

• Transported by and dissolved in runoff• Petroleum Hydrocarbons• Metals• Nutrients (Phosphorus and Nitrate)• Organic matter• Sediment• Synthetic Organics (pesticides,herbicides)

Impacts on:Impacts on:

Stream MorphologyStream MorphologyAquatic HabitatAquatic HabitatBank Erosion and UndercuttingBank Erosion and UndercuttingStreambed ScouringStreambed Scouring

Dry Channels…

Eroded Streambanks…

Land Development Impacts on Stream Morphology:

• Channel widening, downcutting, scouring

• Stream bank erosion

• Imbedded substrate with benthic impacts

• Loss of pools, riffles

Land Development Impacts on Stream Ecology:

• Reduced diversity of aquatic insects

• Reduced diversity of fish

• Decline of amphibians

• Degraded wetlands, riparian zones

Land Development Impacts on Land Development Impacts on VegetationVegetation

Trees:Trees:the Perfect the Perfect BMPBMP

Land Development Impacts on Soil:Land Development Impacts on Soil:A Living FoundationA Living Foundation

Soil Horizons• Layer of Soil Parallel

to Surface• Properties a function

of climate, landscape setting, parent material, biological activity, and other soil forming processes.

• Horizons (A, E, B, C, R, etc)

Image Source: University of Texas, 2002

Dramatic increases in soil compaction…

Common Bulk Density Measurements orCommon Bulk Density Measurements orHow compacted is this soil?How compacted is this soil?

David B. Friedman, District Director -- Ocean County Soil Conservation District

Golf Courses, Parks, Athletic Fields1.69 to 1.97g/cc

Undisturbed Lands:Forests & Woodlands

1.03g/cc

CONCRETE2.2g/cc

ResidentialNeighborhoods

1.69 to 1.97g/cc

Bulk Density is defined as the weight of a unit volume of soil including its pore space (g/cc or grams/cubic centimeter). Water and air are important components of soil and we must frame our soil concepts so that factors affecting water and air dynamics are included. Thus, we are primarily interested in bulk density and pore space as they affect water and aeration status, and root penetration and development.

Effects of Soil DisturbanceEffects of Soil Disturbance

Measurements of Sampled Soil within 20 inches of surfaceSITE Bulk Density (g/cm³) Permeability (in/hr)

Woods 1.42 15Pasture 1.47 9.9

Single House 1.67 7.1Subdivision Lawn 1 1.79 0.14

Garage Lawn 1.82 0.04Cleared Woods 1.83 0.13

Subdivision Lawn 2 2.03 0.03Althletic Field 1.95 0.01

CONCRETE 2.2 - 2.4 0

Adapted from Impact of Soil Disturbance During Construction on Bulk Density and Infiltration in Ocean County, New Jersey (2001) - www.ocscd.org/soil.pdf

http://www.ocscd.org/soil.pdf

Getting Stormwater Right:Getting Stormwater Right:

Structural BMPs Structural BMPs MitigativeMitigative

Non-Structural BMPsNon-Structural BMPsPreventivePreventive

Site Planning & Design ProceduresSite Planning & Design Procedures

STORMWATER CALCULATIONS

STORMWATERMANAGEMENT

PLAN

Zoning Guidanc

e

SLDO Guidance

Township Comprehensive

Plan

Minimum Disturbance, Minimum Maintenance

Lot Configuration & Clustering

Impervious Coverage

Disconnect, Distribute, Decentralize

Source Control

SITE ANALYSIS NON-STRUCTURAL BMPsSTRUCTURAL BMPs

Site Analysis: Constraints vs. Opportunities

BackgroundFactors:

EnvironmentalConstraints

BackgroundFactors:

EnvironmentalOpportunities

WATERSHED ANALYSIS

BUILDING PROGRAM

ISSUES

PRE-SUBMISSION

MEETING

APPLICANTSUBMISSION

Design Phase 2MITIGATIVE

BMPs

RestorationBMPs

Runoff Quality BMPs

Volume Reduction

BMPs

Soil Infiltration-

based BMPs

Design Phase 1PREVENTIVE

BMPs

Sensitive Areas

Site Factors Inventory

WATERSHEDANALYSIS

SITE ANALYSIS

Structural Best Management Practices

Runoff Volume/Infiltration-Oriented Vegetative and Soil-Based

1. Rain/recharge gardens/Bioretention2. Vegetated filter strips3. Vegetated Swales (Bio-infiltration, Dry, Wet)4. Porous pavement with infiltration beds5. Infiltration basins6. Subsurface infiltration beds7. Infiltration trenches8. French drains/dry wells9. Outlet control (level spreaders, etc.)

10. Retentive grading techniques, bermsRunoff Volume/Non-Infiltration-Oriented

11. Vegetated roofs12. Cisterns/Rain Barrels/Capture Reuse

Runoff Quality/Non-Infiltration13. Constructed wetlands14. Wet ponds/retention basins15. Filters16. Water quality inserts17. Detention/Extended Detention

18. Special Storage: Parking Lot, Rooftop, etc.Restoration BMPs

19. Riparian Corridor Restoration

20. Revegetation/Reforestation

21. Soils Amendment

One size no longer fits all…One size no longer fits all…

Structural BMPs Structural BMPs Runoff Volume/Infiltration-Oriented Vegetative and Soil-Based

• Porous Pavement• Infiltration Basin• Infiltration Bed• Infiltration Trench• Rain Garden/Bioretention• Dry Well / Seepage Pit• Constructed Filter• Vegetated Swale• Vegetated Filter Strip• Berm

Pollutant Removal EffectivenessPollutant Removal Effectiveness

POLLUTANT INFILTRATION PRACTICES

Stormwater Wetlands

Stormwater Ponds Wet

Filtering Practices

Water Quality Swales

Stormwater Dry Ponds

Total Phosphorus

70 49 51 59 34 19

Soluble Phosphorus

85 35 66 3 38 -6

Total Nitrogen 51 30 33 38 84 25

Nitrate 82 67 43 -14 31 4

Copper N/A 40 57 49 51 26

Zinc 99 44 66 88 71 26

TSS 95 76 80 86 81 47

Water quality benefits of porous pavement with infiltration from “National Pollutant Removal Performance Database for Stormwater Treatment Practices” Center for Watershed Protection, June 2000 \

Porous Porous PavemePaveme

ntnt

Porous Paving w/ InfiltrationPorous Paving w/ Infiltration

Rams Head Plaza at University of North Rams Head Plaza at University of North CarolinaCarolina



DuPont Barley Mills Office DuPont Barley Mills Office ComplexComplex



• Precipitation is carried from roof by roof drains to storage beds.• Stormwater runoff from impervious and lawn areas is carried to storage

beds.• Precipitation that falls on porous paving enters storage beds directly• Stone beds with 40% void space store water. Continuously perforated

pipes distribute stormwater from impervious surfaces evenly throughout the beds.

• Stormwater exfiltrates from storage beds into soil, recharging groundwater.

Costs of Porous PavementCosts of Porous Pavement

• Generally costs the same or less for the site• Actual asphalt slightly more expensive (special gradation and higher grade binder)• Reduces Piping Infrastructure and Basins • Penn State Berks Campus – 320 spaces 1999

- $3500 / space budgeted for standard pavement

- $2700 actual cost for porous

Swarthmore College

Permeable Patios, Terraces, Permeable Patios, Terraces, CourtyardsCourtyards

Infiltration BasinsInfiltration Basins

Infiltration Basin – Commerce Plaza 1983

Vegetated Infiltration BedsVegetated Infiltration Beds

Distributing Water in Sub-Surface Bed

Penn New School Penn New School 4343rdrd and Locust Streets and Locust Streets

• PaDEP Growing Greener & Philadelphia Water Department

• Porous Pavement Play Yard• Infiltration Bed Beneath Athletic Field• Rain Gardens and Native Vegetation • Environmental Education

Previous impervious parking lot at site

Completed Porous Pavement PlayfieldCompleted Porous Pavement Playfield

Infiltration TrenchesInfiltration Trenches

Rain Gardens / BioretentionRain Gardens / Bioretention

Rainwater can support the landscape and soils, reducing pipes and basins.

Dry Well / Seepage PitDry Well / Seepage Pit

Vegetated Swales (simple & Vegetated Swales (simple & inexpensive)inexpensive)

Vegetated Swale (Enhanced)Vegetated Swale (Enhanced)

Vegetated Filter Vegetated Filter Strip Strip

Infiltration BermsInfiltration Berms






Runoff Quality/Non-Infiltration13. Constructed wetlands14. Wet ponds/retention basins15. Filters16. Water quality inserts17. Detention/Extended Detention18. Special Storage: Parking Lot, Rooftop, etc.

Restoration BMPs19. Riparian Corridor Restoration

20. Revegetation/Reforestation21. Soil Amendment

Vegetated RoofVegetated Roof

Vegetated RooftopsVegetated Rooftops

• Reduce the Volume of Stormwater Runoff (typically 50% or more annually)

• Reduce the Rate of Stormwater Runoff

• Increase the Lifespan of a Conventional Roof Surface by 2 to 3 times

• Reduce heating and cooling costs

• Enhance property values and Aesthetics

Fencing Academy of PhiladelphiaFencing Academy of PhiladelphiaRoofmeadowRoofmeadowTMTM

Before

After

Stuttgart’s “Green Space”Stuttgart’s “Green Space”

Capture / ReuseCapture / Reuse

• Volume Control

• Reduced potable water consumption

• Cost savings

UNC-Chapel UNC-Chapel HillHill

• $1.5 billion construction program, largest in 211-year history of UNC-CH

• Funded in part by biggest higher education bond in U.S.

• Guided by award-winning 2001 Campus Master Plan

• Included an Environmental component which set rigorous goals

UNC-Chapel Hill Campus Master PlanAyers Saint Gross, Architects

Image Source: Andropogon Associates

Rams Head Stormwater System

•40,000 SF Green roof plaza•Cistern•Vegetated swale w/ check dams

•Reinforced-turf fire lane•Storage/infiltration bed under artificial turf athletic field•Re-created ephemeral stream•Water quality inserts•Manages runoff from project area and additional 17 acres

Vegetated Vegetated Roof PlazaRoof Plaza

Unique, non-proprietary system design, including:• 56,000-gallon cistern under pathways• Additional 32,000-gallon water storage zone under

soil to support trees• Visual stormwater connections and overflows• 12 to 24 inches of soil for native trees and

groundcovers• Perforated pipe and Rainstore distribution system

Green Roof Plaza with Cisterns

• Cistern constructed of recycled plastic “Rainstore”

• Overflow to Storage Layer under soil

Bricks being placed above cistern Flood test of cistern area

•56,000 gallon cistern filled by 2.7 inches of rainfall (in one or more storms)•On average, it will fill and empty 9 times per irrigation season•Provides 3 weeks irrigation without replenishment

…And then into an Infiltration Bed beneath an Artificial Turf Athletic Field

Returning Springs

and Stormwater Flow to Daylight







Restoration BMPs19. Riparian Corridor Restoration

20. Revegetation/Reforestation21. Soil Amendment

Constructed WetlandsConstructed Wetlands

Wet Pond / Retention BasinWet Pond / Retention Basin

Water Quality Inserts/FiltersWater Quality Inserts/Filters







Restoration BMPs19. Riparian Corridor Restoration20. Revegetation/Reforestation21. Soil Amendment

Riparian Buffer Restoration and ReforestationRiparian Buffer Restoration and Reforestation

Lawn to Sustainable Meadows

Seeding 1st year

2nd year

3rd year

Landscape RestorationLandscape Restoration

Images courtesy of Rolf Sauer and PartnersImages courtesy of Rolf Sauer and Partners

Landscape Restoration (cont.)Landscape Restoration (cont.)

Soil Amendment / RestorationSoil Amendment / Restoration

Non-Structural Strategies Non-Structural Strategies

aka Low Impact aka Low Impact DevelopmentDevelopment

aka Conservation Designaka Conservation Designaka Green Infrastructureaka Green Infrastructure

Even for Community Parks!Even for Community Parks!

Site Planning & Design ProceduresSite Planning & Design Procedures

STORMWATER CALCULATIONS

STORMWATERMANAGEMENT

PLAN

Zoning Guidanc

e

SLDO Guidance

Township Comprehensive

Plan

Minimum Disturbance, Minimum Maintenance

Lot Configuration & Clustering

Impervious Coverage

Disconnect, Distribute, Decentralize

Source Control

SITE ANALYSIS NON-STRUCTURAL BMPsSTRUCTURAL BMPs

Site Analysis: Constraints vs. Opportunities

BackgroundFactors:

EnvironmentalConstraints

BackgroundFactors:

EnvironmentalOpportunities

WATERSHED ANALYSIS

BUILDING PROGRAM

ISSUES

PRE-SUBMISSION

MEETING

APPLICANTSUBMISSION

Design Phase 2MITIGATIVE

BMPs

RestorationBMPs

Runoff Quality BMPs

Volume Reduction

BMPs

Soil Infiltration-

based BMPs

Design Phase 1PREVENTIVE

BMPs

Sensitive Areas

Site Factors Inventory

WATERSHEDANALYSIS

SITE ANALYSIS

Non-Structural BMP Categories with Specific Non-Structural BMP Categories with Specific Non-Structural BMPsNon-Structural BMPs

1.0 Protect Sensitive and Special Value Resources1.0 Protect Sensitive and Special Value ResourcesBMP 1.1BMP 1.1 Protect sensitive/special value featuresProtect sensitive/special value featuresBMP 1.2BMP 1.2 Protect/conserve/enhance utilize riparian areasProtect/conserve/enhance utilize riparian areasBMP 1.3BMP 1.3 Protect/utilize natural flow pathways in overall Protect/utilize natural flow pathways in overall

stormwater stormwater planning and designplanning and design2.0 Cluster and Concentrate2.0 Cluster and Concentrate

BMP 2.1BMP 2.1 Cluster uses at each site; Build on the smallest Cluster uses at each site; Build on the smallest area possiblearea possible

BMP 2.2BMP 2.2 Concentrate uses areawide through Smart Concentrate uses areawide through Smart Growth practicesGrowth practices3.0 Minimize Disturbance and Minimize Maintenance3.0 Minimize Disturbance and Minimize Maintenance

BMP 3.1BMP 3.1 Minimize total disturbed area – grading Minimize total disturbed area – grading BMP 3.2BMP 3.2 Minimize soil compaction in disturbed areasMinimize soil compaction in disturbed areasBMP 3.3BMP 3.3 Re-vegetate and re-forest disturbed areas, using Re-vegetate and re-forest disturbed areas, using

native speciesnative species4.0 Reduce Impervious Cover4.0 Reduce Impervious Cover

BMP 4.1BMP 4.1 Reduce street imperviousnessReduce street imperviousnessBMP 4.2BMP 4.2 Reduce parking imperviousnessReduce parking imperviousness

5.0 Disconnect/Distribute/Decentralize5.0 Disconnect/Distribute/DecentralizeBMP 5.1BMP 5.1 Rooftop disconnectionRooftop disconnectionBMP 5.2BMP 5.2 Disconnection from storm sewersDisconnection from storm sewers

Non-Structural BMP Categories with Specific Non-Structural BMP Categories with Specific Non-Structural BMP’sNon-Structural BMP’s

1.0 1.0 Protect Sensitive and Special Value Protect Sensitive and Special Value ResourcesResources

BMP 1.1BMP 1.1 Protect sensitive/special value Protect sensitive/special value featuresfeatures

BMP 1.2BMP 1.2 Protect/conserve/enhance utilize Protect/conserve/enhance utilize riparian areasriparian areas

BMP 1.3BMP 1.3 Protect/utilize natural flow Protect/utilize natural flow pathways in overall pathways in overall

stormwater stormwater planning and planning and designdesign

Non-Structural BMP Categories with Non-Structural BMP Categories with Specific Non-Structural BMPsSpecific Non-Structural BMPs

2.0 Cluster and Concentrate2.0 Cluster and Concentrate

BMP 2.1BMP 2.1 Cluster uses at each site; Cluster uses at each site; build build on the smallest area on the smallest area possiblepossible

BMP 2.2BMP 2.2 Concentrate uses areawide Concentrate uses areawide through Smart Growth through Smart Growth

practicespractices

Cost Comparison:Cost Comparison:Chapel RunChapel Run

Conventional DevelopmentConventional Development$2,460,200$2,460,200Conservation Design-ParkwayConservation Design-Parkway $ $ 888,735888,735

Non-Structural BMP Categories with Specific Non-Structural BMP Categories with Specific Non-Structural BMPsNon-Structural BMPs

3.0 3.0 Minimize Disturbance and Minimize Minimize Disturbance and Minimize MaintenanceMaintenance

BMP 3.1BMP 3.1 Minimize total disturbed area – Minimize total disturbed area – grading grading

BMP 3.2BMP 3.2 Minimize soil compaction in Minimize soil compaction in disturbed areasdisturbed areas

BMP 3.3BMP 3.3 Re-vegetate and re-forest Re-vegetate and re-forest disturbed areas, using disturbed areas, using

native native speciesspecies

Non-Structural BMP Categories with Non-Structural BMP Categories with Specific Non-Structural BMPsSpecific Non-Structural BMPs

4.0 Reduce Impervious Cover4.0 Reduce Impervious Cover

BMP 4.1BMP 4.1 Reduce street Reduce street imperviousnessimperviousness

BMP 4.2BMP 4.2 Reduce parking Reduce parking imperviousnessimperviousness

Table 1: Narrow Residential Street Widths

Jurisdiction Residential Street Pavement Width

Maximum Daily Traffic (trips/day)

State of New Jersey 20 ft. (no parking)

28 ft. (parking on one side)

0-3,500

0-3,500

State of Delaware 12 ft. (alley)


---

---

Howard County, Maryland 24 ft. (parking not regulated) 1,000

Charles County, Maryland 24 ft. (parking not regulated) ---

Morgantown, West Virginia 22 ft. (parking on one side) ---

Boulder, Colorado 20 ft.

20 ft. (no parking)


26 ft. (parking on both sides)


150

350-1,000

350

350

500-1,000

Bucks County, Pennsylvania 12 ft (alley)

16-18 ft. (no parking)

20-22 ft. (no parking)



---

200

200-1,000

200

200-1,000

(Cohen, 1997; Bucks County Planning Commission, 1980; Center for Watershed Protection, 1998)

Non-Structural BMP Categories with Non-Structural BMP Categories with Specific Non-Structural BMPs:Specific Non-Structural BMPs:

5.0 Disconnect/Distribute/Decentralize5.0 Disconnect/Distribute/Decentralize

BMP 5.1BMP 5.1 Rooftop disconnectionRooftop disconnectionBMP 5.2BMP 5.2 Disconnection from storm Disconnection from storm

sewerssewers

Top Ten Stormwater Top Ten Stormwater Management Principles:Management Principles:

-Prevent first, -Prevent first, -Mitigate second. -Mitigate second. -Manage as a resource – not a waste!-Manage as a resource – not a waste!-Maintain water cycle balance, pre- to post.-Maintain water cycle balance, pre- to post.-Integrate early into site design process.-Integrate early into site design process.-Protect/utilize natural systems (soil, -Protect/utilize natural systems (soil, vegetation).vegetation).-Manage as close to the source as possible.-Manage as close to the source as possible.-Disconnect. Decentralize. Distribute.-Disconnect. Decentralize. Distribute.-Slow it down – don’t speed it up.-Slow it down – don’t speed it up.-Achieve multiple objectives; do as much with -Achieve multiple objectives; do as much with asas little as possible. little as possible.

System Balance….System Balance….

“…everything is “…everything is connected to everything connected to everything

else….”else….”



Stormwater Management: Stormwater Management: Making Sure Green is GreenMaking Sure Green is Green

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West Chester, PA 19382 Cape May, NJ 08204 Cahill Associates Environmental Consultants Stormwater Management: Making Sure Green Is Green