HUDSON VALLEY REGIONAL COUNCIL 3 Washington Center, Newburgh NY

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1 PROJECT AREA: Newburgh HUDSON VALLEY REGIONAL COUNCIL 3 Washington Center, Newburgh NY Google 2011 GREEN INFRASTRUCTURE CONCEPT PLAN FOR NORA CRONIN PRESENTATION ACADEMY Project type: School playground DECEMBER 2011 Proposed practices: 1- Permeable paving 2 -Tree planting

2 The following draft report describes a schematic landscape design proposal using green infrastructure practices for stormwater management. This plan is intended to give practical guidance for the owner, design professionals, contractors, and other interested parties to use in developing a final design. It is not intended to be used as a final design or construction documents. OVERVIEW The Nora Cronin Performance Academy is a Catholic middle school for girls that opened in 2011 in the City of Newburgh. Sister Yliana Hernandez, PBVM, the founder and Principal, worked with her board to develop this school over a period of years through dedicated fundraising and planning efforts. Renovation of the building included volunteer contributions by contractors and other donors. The Academy does not have adequate funding to finalize and implement the green infrastructure concept plan described in this report, but they are interested in the potential to incorporate this approach in the final site design and construction. The goals for the backyard area are to have a playground that has a hard, relatively smooth surface so it can be easily maintained in all seasons, including removing snow. The original site plan submitted to get City approval for renovating the building and the site shows a relatively small playground area and an adjacent walking path leading to a stairway to the sidewalk along the southern property boundary. The green infrastructure concept plan described below incorporates a significantly larger playground area, based on discussions with Sr. Hernandez about the school s goals. A permeable paved playground surface is proposed, which would allow for a paved surface with no increase in runoff. Tree plantings are proposed for the south and west sides of the yard to shade the pavement and provide stormwater benefits including runoff reduction and water quality protection. LOCATION Street Address: 69 Bay View Terrace, Newburgh NY Section 48, Block 7, Lot 2 OWNERSHIP Presentation Education Foundation Inc. EXISTING CONDITIONS SURFACE COVER/CONTRIBUTING AREA The site is mostly disturbed earth and new fill. 2

3 SOILS AND TOPOGRAPHY The rear yard is flat and elevated about four feet above street level. The Web Soil Survey Report indicates Mardin gravelly silt loam 1 This is classified in hydrological soil group C. Soil infiltration tests would be conducted prior to final design. SOLAR EXPOSURE AND VEGETATION The rear yard where the playground is proposed is open and exposed to sun on the south and west. There are some trees on the north side, which is shaded by the building. Figure 1 View of west property line where trees are proposed Figure 2 View of rear yard where paving is proposed, facing east Figure 3 View of south property line where trees are proposed, facing southeast 1 Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at Accessed [12/12/2011]. 3

4 CONCEPT PLAN A paved area (approximately 35 x 50 feet) in the rear of the building that could be paved with permeable paving is shown on the plan. A strip about 9 wide along the west property line would be left unpaved and prepared for a planting of large canopy shade trees as would the open area on the south side. If desired for aesthetic reasons, the proposed permeable paving could incorporate a final design that includes a different paving pattern to visually delineate the walking path design shown in the original site plan, which leads from the northwest corner of the building to a stairway leading to Bay View Terrace on the south side of the property. This walking path, in other words, would be at the same elevation and would essentially be part of the same surface as the rest of the playground, but could be made of different materials or just a different color for visual interest and to provide a visual cue that the stairway is present. Based on the experience of site owners, managers and design professionals who have installed and monitored permeable paving, it can have advantages over conventional paving that go beyond its infiltration and reducing runoff benefits. One advantage may be particularly important for this project in freezing conditions, snow and ice are reportedly less likely to accumulate and persist on permeable paving. This has been observed and documented at the University of New Hampshire s Stormwater Center, where pervious paving and other green infrastructure practices are installed and monitored in scientific tests lasting several years or longer, and has been reported by many others as well. Given this project site s use as a schoolyard, the potential to reduce the number of days when snow or ice are present, and therefore to reduce maintenance and increase safety, seems like an important factor. Figure 4 Green Infrastructure Concept Plan shown superimposed on the architectural site plan prepared for the Nora Cronin Presentation Academy by Minuta Architecture PLLC and dated Thanks to Joseph Minuta, AIA, for providing a PDF copy of this site plan. (An 11x17 version of the GI concept plan above is included in the pdf version of this report.) 4

5 PERMEABLE PAVING OPTIONS Permeable asphalt, permeable concrete interlocking pavers, or permeable concrete would all be options for the playground. The pavers might be more durable, and lighter color pavers and permeable concrete can be significantly cooler because they tend to absorb less heat from the sun. But the continuous surface of the asphalt may be considered preferable. Permeable rubber mats are also a good playground surface. Permeable pavers can be combined with permeable concrete (or asphalt), so part of the playground could be one material and other parts a different material. A photo showing a parking area that uses permeable concrete pavers combined with permeable concrete is shown below. A design that uses one or a combination of these permeable surfaces would include installing an open graded aggregate as a base, which would act as a reservoir. For play surfaces this base would be about 1 foot deep. Figure 5 Example of a permeable paving project carried out in Syracuse as collaboration between the Carmelo K. Anthony Foundation [which] provides funding for the renovations of basketball courts throughout the City of Syracuse, and the City of Syracuse Parks Department and Onondaga County s Save the Rain program. ( the rain Onondaga County Department of Water Environment Protection) 5

6 Figure 6 This photo taken at the Taconic Regional Headquaters of the NY State Office of Parks, Recreation and Historic Preservation, located in Staatsburg, NY, shows permeable concrete pavers for parking stalls combined with permeable concrete for the travel lane in a parking lot. This project received LEED Platinum certification, the highest level, for adaptive reuse of an old school that incorporates green technology in the building and green infrastructure practices in the site design. (Photo by Barbara Restaino, RLA, LEED AP, Restaino Design Landscape Architects PC. ) POROUS ASPHALT Figure 7 Cross section of one design approach for permeable asphalt installations (National Asphalt Pavement Association accessed 11/2011 6

7 CONSTRUCTION STEPS For all permeable paving, the gravel base layer must be protected from sedimentation during construction. Excavate to required depth. Protect subgrade from compaction or decompact as required. Install geotextile Install stone recharge bed Install choker course Install porous asphalt MATERIALS Non woven geotextile Crushed stone with 40% voids Choker course ½ crushed aggregate Open graded asphalt mix --18% voids PERMEABLE CONCRETE INTERLOCKING PAVERS Figure 8 Example of permeable concrete pavers CONSTRUCTION STEPS MATERIALS Excavate to proposed depth and level the bottom of infiltration bed. Place geotextile if required Place sub base and base aggregrates as required by final design Place setting setting bed aggregate Install edge restraint Place permeable interlocking pavers Place joint aggregate Typical manufacture s specifications for permeable interlocking concrete pavers require the following materials. Concrete pavers (permeable and conventional) Granular subbase Granular base Bedding and void opening aggregates Edge restraints Underdrain if required Geotextile fabric (optional) Figure 9 Typical permeable paver cross section 7

8 PERVIOUS RUBBER MATTING Figure 9 Porous rubber installation detail used as part of playground retrofits at Greenfield School, Philadelphia. Viridian Landscape Studio Design and Meliora Environmental Design MATERIALS (The detail provided by Viridian Landscape Studio shows the base course materials listed here.) Rubber mats 8 Clean open graded aggregate 3 Cushion course 3/8 Wearing course 4 Perforated pipe 30 Mil impervious liner (along planting bed) Non woven geotextile fabric MAINTENANCE CONSIDERATIONS Two excellent fact sheets on permeable and porous paving are available from the NC State University Stormwater Engineering Group at 2 Research Update and Design Implications Maintaining Permeable Pavements The paving should be swept frequently to keep it clear of debris. 2 Urban Waterways, NC State University and A&T State University Cooperative Extension

9 COST Generally permeable surfaces materials are comparable in cost to their impervious counterparts, but the added excavation and gravel base increases the cost. However, permeable paving also can reduce or eliminate other costs for conventional stormwater for pipes, basins, and additional land. Two Sources of Cost Data For installation, maintenance costs and lifespan data for the practices discussed here, the Cost Sheet developed by the Center for Neighborhood Technology (CNT) in collaboration with the US EPA Office of Wetlands, Oceans, and Watersheds (OWOW), Assessment and Watershed Protection Division, Non- Point Source Branch, provides useful information based on examples from various locations. It may be found at their website. Another useful source of cost data can be found in the Center of Watershed Protection's Urban Subwatershed Restoration Manual Series. Manual 3: Urban Stormwater Retrofit Practices, pages E- 1 though 14, includes a discussion of costs in terms of the amount of stormwater treated. The information was compiled in 2006, so an increase about 10 percent should be factored in to account of cost of living increases. Plan by Simon Gruber and Marcy Denker. Thanks to Sr. Yliana Hernandez and Joseph Minuta for their support and contributions. 9

10 GREEN INFRASTRUCTURE SIZING AND DESIGN The green infrastructure practices included in these plans are among those considered acceptable for runoff reduction in the New York State Stormwater Management Design Manual 2010 (Design Manual). This includes practices that: reduce calculated runoff from contributing areas capture the required water quality volume. The Water Quality Volume (denoted as the WQv) is designed to improve water quality sizing to capture and treat 90% of the average annual stormwater runoff volume. For Newburgh this 90% rainfall number is 1.1 inches. The WQv is directly related to the amount of impervious cover created at a site. The following equation can be used to determine the water quality storage volume WQv (in acre-feet of storage): WQv = (P) (Rv)(A) 12 where: WQv = water quality volume (in acre-feet) P = 90% Rainfall Event Number Rv = (I), where I is percent impervious cover A = site area in acres (Contributing area) A minimum Rv of 0.2 will be applied to regulated sites. SIZING COMPUTATIONS As shown in the calculations below, for 1,700 square feet of permeable paving with a 1 foot deep base the practice would have the capacity to store 680 cubic feet of runoff. Total Drainage Area 1700 Ft 2 Available Surface Area 1700 Ft 2 Step 1: Calculate Water Quality Volume (WQv) WQv = (P) (Rv) (A) / 12 P = 90% rainfall number = 1.1 inches Rv = (I), if Rv < 20%, use Rv = 20% 95% I = percent impervious of area draining to practice = 100% % of Total area that drains to practice 100% A = Area draining to practice = 1700 Ft 2 WQv = 148 Ft 3 Step 2: Calculate required surface area for pavement: Ap = WQv / n x dt where n = assumed porosity 0.4 dt =trench depth 1 ft A P= 370 Ft 2 OR Step 2: Calculate the available storage volume in the storage reservoir: Storage Volume = Ap*n*dt where: n = assumed porosity = 0.4 dt = gravel bed/reservoir depth = 1 Ft Reservoir Storage Volume = 680 cf 10

11 TREE PLANTING Tree plantings intercept rainfall in the canopy and release it through evapotranspiration. Street tree pits with good quality, uncompacted soil will infiltrate runoff, and tree roots and leaf litter enhance the soil conditions for infiltration. In addition to these stormwater management functions, trees can provide many other benefits including shading and cooling, buffering wind and noise, purifying air and beautification. DESIGN Site Assessment and Tree selections Trees are proposed along the west and south sides of the property. The tree selection should reflect careful consideration of the available soil and soil volume. The areas left unpaved as shown on the plan would provided enough soil volume for large canopy trees. A site assessment should be performed to determine the soil conditions, including drainage, ph range, compaction levels, texture and other factors. The local cooperative extension can provide guidance for assessing the soil and selecting appropriate species. In addition, several excellent resources that could be used as the basis for a student project are included at the end. Mulch An organic mulch layer would be provided around the trees to provide multiple benefits related to the soil, protect against damage from mowers and trimmers, and suppress weeds. CONSTRUCTION STEPS Amend soil as required by final design Plant trees Apply mulch MAINTENANCE CONSIDERATIONS Well-prepared planting areas designed with appropriate plants and soils require routine maintenance. During the establishment period just after planting the new tree plantings would be watered using water bags and spot watering with a clear understanding of the requirements of the trees to avoid over- or under-watering. Ongoing maintenance would include occasional pruning and replacements, twice yearly clean up and yearly application of mulch. RESOURCES The following resources on site assessment and tree selection are recommended: From Urban Horticulture Institute of Cornell University at Recommended Urban Trees: Site Assessment and Tree Selection for Urban Tolerance. Urban Horticulture Institute, Department of Horticulture, Cornell University, Ithaca, NY. Visual Similarity and Biological Diversity: Street Tree Selection and Design. Bassuk, Nina,. Trowbridge, Peter. Grohs, Carol. From the Center for Watershed Protection Urban Watershed Forestry Manual,Part 3:.Urban Tree Planting Guide. Cappiella, Schueler, Tomlinson, Wright. Center for Watershed Protection and USDA Forest Service, Sept