Small Town Sustainable Stormwater Solutions

Transcription

1 Small Town Sustainable Stormwater Solutions Kathryn Hamilton, RLA, ASLA Westmoreland Conservation District PA/DE ASLA Annual Meeting April 8-9,

2 Urban, Industrial, Residential, Agricultural Flooding, Erosion, Pollution, Degradation

3 The Natural Watercycle

4 Pre-Development: illustrates the NATURAL hydrologic cycle

5 Post Development: illustrates the IMPAIRED hydrologic cycle

6 Stormwater Retrofitting A Stormwater Retrofit provides stormwater treatment in locations where practices previously did not exist or were ineffective Provides runoff capture and treatment Requires data collection Fingerprinted around existing elements Public and private involvement

7 Why use Stormwater Retrofits? Flooding Stream degradation Water quality issues Combined Sewer Overflows (CSOs( CSOs) Regulations

8 Water Pollution Costs $17 billion annually in the USA Causes 14,000 deaths worldwide each day Comes from the land s surface to create Non-Point Source and Point Source Pollution

9 Non-Point Source Pollution When rain falls on the land, the runoff may carry with it sediment, debris, chemicals, or other pollutants. Earth disturbance and land development are big sources of Non-Point Source pollution.

10 Point Source Pollution Water pollution might come from a single point source - as a pipe from a factory dumping pollutants into a river OR Combined Sewer Overflow

11 Over 380 CSO Locations around Pittsburgh!

12 Sewage treatment agencies which have CSO permits across PA

13 Changing Regulations! Why are we required to construct BMP s?? Regulations have been created to reverse the effects of dead zones developing in the Chesapeake Bay and Gulf of Mexico where much of the USA s s polluted stormwater runoff ends up The new SWM regulations have the force of many environmental agencies behind them, each with a different focus.

14 Regulating Agencies! EPA DEP County Conservation Districts PA Fish & Boat Commission Army Corps of Engineers Municipalities PennDOT Utility consent order agreements

15 Regulations Provide Guidance PA DEP regulates: Activities that might reduce water quality including Land development NPDES permits and Erosion + Sediment Control Permits both need Post- Construction Stormwater Management (PCSM) plans and BMP s. PA Stormwater BMP Manual (DEP 2006)

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17 Objectives Fix past mistakes & maintenance problems Solve chronic flooding problems Stormwater demonstration & education

18 Objectives (cont.) Pollutant removal Reduce runoff volumes Stream corridor/watershed restoration

19 Rainfall and Retrofits 98% of Rainfall Events are less than 1 inch

20 BMPs designed to treat 1 1 rainfall

21 Mount Pleasant Residential Rain Gardens stormwater retrofit Mount Pleasant PA Spring 2010 Project Partners: Westmoreland Conservation District Mount Pleasant Borough Residents of Mount Pleasant PA Department of Environmental Protection

22 Typical rain garden scenarios were presented to the homeowners, to encourage them to participate DOWNSPOUT Possible Rain Garden Locations for Roof Water Treatment DOWNSPOUT FLOW OF RUNOFF

23 WCD staff and interns surveyed and evaluated the property of each interested homeowner

24 PA One-Call for Design and Layout Current Downspout Outlet

25 Homeowners were given choices of rain garden planting schemes as well as specific plants for their gardens

26 Each homeowner had to sign a RAIN GARDEN RIGHT-OF OF-WAY AND EASEMENT AGREEMENT Whereas the Grantor owns a certain tract of land Whereas the Grantee received a grant for design, construction and installation of a rain garden Whereas the Grantor desires to be a steward of the land and participate Whereas the Grantee requires certain easements and rights-of of-way to enable construction Whereas Grantor desires to grant and convey to Grantee the easement and right-of of-way

27 RAIN GARDEN RIGHT-OF OF-WAY AND EASEMENT AGREEMENT Grantee shall construct in good and safe condition said rain garden and appurtanances Grantor, its agents, successors and assigns agrees to the sole responsibility of the maintenance of the rain garden after construction for a period of 20 years

28 Each rain garden was marked and approved prior to digging

29 Excavation was done carefully to avoid utilities, protect existing features and minimize disturbance

30 Each rain garden excavation was checked for proper depth to meet design requirements

31 The Contractor was able to minimize disturbance on each property and minimize inconvenience to neighbors

32 An underdrain layer included a perforated pipe surrounded by clean stone and a geotextile wrap

33 A soil mix of 50% topsoil, 30% sand, 20% compost was placed 18 to 24 deep

34 Finished grade of the soil mix was checked to ensure sufficient surface ponding depth

35 A riser pipe is yet to be cutoff to protect soil and mulch from entering the underdrain during construction

36 Completed rain garden: rock dissipater at downspout, landscaping with mulch, basket grate overflow riser

37 Each underdrain outlets safely to the street gutter or to the municipal storm system

38 The location of each rain garden was approved by the homeowner and designed to capture roof water

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43 Scottdale Library Plaza stormwater rain garden Scottdale PA Fall 2009 Project Partners: Westmoreland Conservation District Scottdale Library Scottdale Borough PA Department of Environmental Protection

44 An abandoned street stub provides an opportunity for a stormwater management retrofit utilizing an existing inlet and rooftop runoff

45 Scottdale s 100 year old street was layers of asphalt, 3 inch brick, 4 inch slag bed and 8 inch poured concrete

46 The rain garden area is excavated to expose the inlet and to provide enough volume for the infiltration layers

47 The rain garden is constructed using the existing street inlet as an emergency overflow

48 A standard concrete curb separates the porous concrete edge from the rain garden soil mix

49 Completed stormwater plaza includes the rain garden, porous concrete and a raised planter

50 Rainwater drains through the porous concrete into a stone base

51 Native plants help with evapotranspiration of stormwater from porous concrete and a rain garden

52 Mount Pleasant Parking Lot Rain Gardens stormwater retrofit Mount Pleasant PA Spring 2010 Project Partners: Westmoreland Conservation District Mount Pleasant Borough Mount Pleasant Parking Authority PA Department of Environmental Protection

53 Mount Pleasant Borough parking lots generated stormwater which ran uncontrolled into the streets, flooding downhill neighbors

54 Five rain garden locations were excavated at the low point in each parking lot

55 Each rain garden has an underdrain layer which includes a perforated pipe and clean stone wrapped in fabric

56 Each rain garden has a rain garden soil mix and an overflow riser connected to the underdrain

57 The rain gardens are landscaped with native plants, mulch and stone to slow and infiltrate runoff

58 Rain water rushes into the rain garden through curb cuts and onto rock energy dissipaters

59 An unsightly paved island with crumbling curbs increased runoff and provided little aesthetic value

60 The paved and curbed island was replaced with porous concrete and trees in over-excavated tree planting pits

61 Columbia Avenue Tree Planting using Silva Cells Vandergrift PA Spring 2010 Project Partners: Westmoreland Conservation District Vandergrift Borough Vandergrift Improvement Program PA Department of Environmental Protection

62 The historic Borough of Vandergrift has wide sidewalks and many street trees, just not in this location

63 A green plan for managing urban stormwater runoff was designed to go under the wide sidewalks, to be soaked up by trees

64 Silva Cell soil containment system is filled with a loose soil mix for stormwater retention

65 Silva Cells supports pavements while protecting soil from compaction for better tree health

66 Porous concrete was placed over the Silva Cells on a bed of crushed stone, leaving holes for planted trees

67 Porous concrete is placed over Silva Cells and trees are planted in the un-compacted soil

68 Greensburg Parking Lots stormwater management retrofit Greensburg PA Spring 2007 Project Partners: Westmoreland Conservation District City of Greensburg Gibson Thomas Engineers PA Department of Environmental Protection

69 An abandoned transmission shop, dilapidated properties and alleyways were demolished by the City to make way for a city parking lot

70 Moore Avenue Lot A green plan for the new parking area included infiltration islands and canopy trees to reduce stormwater runoff to the combined sewer

71 Once fully covered with impervious surfaces, this area is now partially green and manages stormwater

72 2B STONE BACKFILL 2B STONE BACKFILL Wheelstops in the parking area delineate leased spaces and allow runoff to be captured by the grass lined infiltration swales

73 The City demolished residential properties (some dilapidated) to make way for a city parking lot

74 A green plan for the new parking area included a rain garden, porous paving, canopy trees, and underground infiltration chambers

75 Stormwater runs off a portion of the parking area and is captured by a landscaped rain garden

76 Stormwater runs off the parking area below the rain garden and is captured by a porous concrete paver unit system

77 Economics Mt Pleasant Parking Lot Rain Gardens 1,500 sf in (5) rain gardens 1,300 sf porous concrete 4,500 cf runoff capture Bid price: $75,000 Average cost commercial rain gardens*: $20-$30 $30 / sf Average cost porous concrete*: $12 / sf *NOTE: costs include demolition and site preparation

78 Economics Mount Pleasant Residential Rain Garden project 100 sf to 200 sf rain gardens in 14 locations 1,800 cf runoff capture Bid price: $55,000 Average rain garden cost*: $25-$35 $35 / sf *NOTE: costs include site preparation

79 Economics Scottdale Library Stormwater Plaza 300 sf rain garden 960 sf porous concrete 850 cf runoff capture Bid price: $54,600 Average rain garden cost*: $30 / sf Average porous concrete cost*: $22 / sf *NOTE: costs include demolition and site preparation

80 Economics Vandergrift s s Columbia Ave street tree planting 6 canopy trees 1,200 sf porous concrete 2,200 cf structural infiltration soil support system 650 cf runoff capture Project Bid: $75,000 Average structural soil system cost*: $65 / cf Average porous concrete cost*: $10 / sf *NOTE: costs include demolition and site preparation

81 Economics Greensburg City Parking Lot infiltration islands 530 lf infiltration trench 4,700 sf infiltration paver blocks 6,000 cf runoff capture Bid cost: $1.5 M Average infiltration bed cost*: $80 - $100 / lf Average infiltration paver cost*: $7 / sf *NOTE: NOTE: costs DO NOT include demolition and site preparation

82 References: Pennsylvania Stormwater Best Management Practices Manual 2006 Provides guidance on the design and installation of stormwater best management practices and post construction stormwater management plans for NPDES permits Center for Watershed Protection s s Urban Subwatershed Restoration Series - Manual 3: Urban Stormwater Retrofit Practices

83 Questions? Contact: Kathryn Hamilton, RLA, ASLA 218 Donohoe Road Greensburg PA