HUDSON VALLEY REGIONAL COUNCIL. 3 Washington Center, Newburgh, NY

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1 PROJECT AREA: YONKERS HUDSON VALLEY REGIONAL COUNCIL 3 Washington Center, Newburgh, NY GREEN INFRASTRUCTURE CONCEPT PLAN - BECZAK ENVIRONMENTAL EDUCATION CENTER Project type: Urban Environmental Education Center Retrofits DECEMBER 2011 Proposed practices: 1- Tree plantings. 2- Rain barrels. 3- Stormwater planter 4- Rain garden

2 The following report describes a schematic landscape design proposal using green infrastructure practices for stormwater management. The illustrated plan, report and appendices combined are intended to give practical guidance for the owner, design professionals, contractors, and other interested parties to use in developing a final design. They are not intended to be used as final design and construction documents. OVERVIEW Beczak Environmental Education Center is a nonprofit organization dedicated to educating people about the ecology, history and culture of the Hudson River. The site occupies approximately two acres along the Hudson River in Yonkers near the Sawmill River daylighting project at Larkin Plaza. A constructed tidal marsh on the site and regular educational programs draw student groups from the broader region. Executive Director Clifford Schneider would like to include stormwater best management practices on th site as demonstration projects, especially for homeowners. This report includes three plans that could be installed with the help of volunteers. Documentation of the installations could then be incorporated into further educational materials for visitors to the site. Three independent green infrastructure plans are proposed: Tree plantings in parking lot islands: Planting areas in the parking lot would be expanded and improved. Rain barrels A small demonstration project would be set up for rainwater harvesting from a portion of the roof at one end of the rear pergola. Stormwater planter and rain garden Downspouts for part if the rear roof would be connected to a stormwater planter discharging to a rain garden. While the rain barrels and stormwater planters can be installed in separate phases, the gutter reconfiguration necessary for both projects should be designed at the same time. The stormwater planter and rain garden would be designed and constructed together. The parking lot islands could be implemented separately. LOCATION Street Address: 35 Alexander St, Yonkers, NY Section, Block, Lot and part of OWNERSHIP The property is owned by Westchester County. Figure 1 Parcel Map Yonkers GIS s.htm) 2

3 EXISTING CONDITIONS SURFACE COVER/CONTRIBUTING AREA The site includes a 3,800 square foot building, parking lot, and open lawn and landscaped areas. A tidal marsh has been constructed along the waterfront, and the stormwater infrastructure was designed to capture and treat roof and parking lot runoff in the in a polishing trench. Impervious parking lot, terrace, and path Approximately 28,000 SF Roof Approximately 3,800 SF Lawn and landscaped areas Approximately 40,000 SF SOILS AND TOPOGRAPHY The site is generally flat, sloping very gently toward the river. It is a remediated brownfield. The soil is 100% Urban Land with a thin layer of topsoil added in the lawn area and a somewhat deeper layer along the edges of the property where trees and shrubs have been planted. The soil conditions at the Beczak site appear to severely limit the number tree species that will thrive there, and call for careful attention to species selection and soil amendment. SOLAR AND WIND EXPOSURE The site is generally open to sun and wind. A pergola covers the terrace on the west. Prevailing winds are generally from the west. VEGETATION Trees have been planted along the north and south sides of the property and at the entrance. The two parking lot islands in the front of the building are underutilized for planting. The narrower island along the sidewalk includes two pin oaks that are in very poor condition. The larger island includes one pin oak that appears to be in better condition, and the rest is turf. The trees in the parking lot islands would be further assessed as part of the final design development. 3

4 Figure 2 Concept Plan (11x17 plan included at the end of the report) 4

5 CONCEPT PLANS 1 PARKING LOT ISLANDS AND TREE PLANTINGS Since runoff from the parking lot is treated in the polishing trench and flows to the river, converting the parking lot islands to bioretention areas was considered unnecessary. Establishing appropriate tree species in good quality soils with adequate space for the roots, and protection from compaction are the key features of the plan. In addition to stormwater quality benefits and runoff reduction, the trees would provide shade on the adjacent impervious surfaces and beautify the street and parking lot. Figure 3 Island A :Two separate planting areas along Alexander Street that would be connected Figure 4Island B: Larger tree island with existing oak to be evaluated With detailed guidance and assistance from landscape nurseries and contractors, volunteers could plant the trees and provide the important initial maintenance. The site assessment and final design could also be carried out as a student project. In fact, a worthwhile study for an advanced student project would extend beyond the Beczak site to the nearby neighborhood where many of the tree plantings that have been installed as part of the redevelopment of the waterfront have been unsuccessful. The plan indicates the removal of two trees that are in poor condition in the tree island (Island A) along Alexander Street. A wide concrete path that separates this island from a smaller raised bed would be removed to establish a continuous tree pit. In the larger island (Island B) the concept plan shows two new trees to supplement the one existing oak. This tree would be retained or replaced based on the findings in the complete assessment. The turf area around the trees would be developed into a low maintenance planting of grasses excluding a wide ring of mulch around the base of each tree. The mulch would have multiple benefits related to the soil, protect against damage from mowers and trimmers, and suppress weeds. 2 RAIN BARRELS A location in an open area on the concrete terrace provides an ideal site for a group of rain barrels and signage for public education focused on homeowners. The downspout on the southwest corner of the building would be fitted with a diverter that would allow some rainwater to flow to a series of three rain barrels. The harvested rainwater could be used in the nearby lawn or non edible garden areas. Overflow from the last barrel would discharge to the lawn. Commercially available rain barrels from a nearby supplier could be installed by the manufacturer or the construction and installation could be a carried out by volunteers. 5

6 Figure5 Proposed rain barrel and sign location Figure 6 Rain barrel examples home made and prefabricated 3 STORMWATER PLANTER AND RAIN GARDEN Two practices designed as a treatment train to capture, channel, and treat runoff from a portion of the rear roof are proposed. The storm drain system from the roof and parking lot has been designed to channel runoff to the stormwater polishing trench, but the culverts can be obstructed by plants and shifting sand. During heavy rain, roof runoff can back up from the pipes on the rear terrace and roof runoff overflows the gutters and ponds briefly in the lawn adjacent to the terrace. While increased maintenance could help to mitigate this, a stormwater planter and rain garden are proposed to contribute to the solution and serve as an educational feature useful for homeowners. A variety of approaches to capturing and treating the runoff for educational purposes could be used here. The concept illustrated in the plan emphasizes a simple planter design that could be replicated on small residential properties in Yonkers. Figure 71 Rain Chain hains.html The two roof gutters that drain to northwest part of the rear roof would be retrofitted to connect to a discharge point at the north end of the pergola, as shown in the plan below. The rainwater would flow down a rain chain into a waterproof planter containing a well drained soil mix. The planter would be designed with a shallow ponding area that would drain within one to two days. An overflow pipe would carry water down to an opening in the lower part of the container and out to a brick or stone runnel leading to the rain garden, which would be designed to allow short term ponding and excess water would flow westward across the lawn to and into the landscaped area. 6

7 Figure 7 Plan view diagram Stormwater planter and rain garden Figure 8 Northwest corner of the building. Existing condition (left) and visualization of stormwater planter, rain chain and runnel (right) 7

8 Figure 9 Stormwater planter at Audubon Society Center, Portland, OR Figure 10 Planter by Nigel Dunnett, Adrian Hallam and Chris Arrowsmith (photo at 8

9 DESIGN, CONSTRUCTION, MAINTENTANCE 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). The green infrastructure techniques include 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 Yonkers this 90% rainfall number is 1.3 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. 1- TREE PLANTING. DESIGN The specific location and strategy for the plantings would follow the outline given previously. MATERIALS Soil and Soil Amendments Siite preparation would be based on soil conditions revealed in the site assessment, including drainage, ph range, compaction levels, texture and other factors. The soil analysis may indicate the need for removing existing soil and replacing with a good quality growing soil or amending with compost, and may severely limit the list of species recommended. Plants Trees. Specific selections would be based on the site analysis, which would include climate, soil, space limitations, and visual factors. Two small trees would be selected that would be appropriate for the limited soil volume in the small island. There would be adequate soil for small street trees with a mature canopy diameter of around 25. For the larger island, trees that would ultimately achieve a canopy spread in the 40 range could be selected. The calculation of soil volume is discussed further in the section on sizing below. All selections should be species that can withstand urban stress. Grasses Native grasses that are suitable for the soil and microclimate conditions in the parking lot would be selected. A simple planting based one to three species that have a neat appearance all year is recommended. Other Materials An organic mulch layer 3-4 deep would be provided around the trees 9

10 CONSTRUCTION STEPS Amend soil as required by final design Plant trees Plant grasses Apply mulch MAINTENANCE Well-prepared planting areas designed with appropriate plants and soils require routine maintenance. During the establishment period 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 for the trees would include occasional pruning and replacements, twice yearly clean up and yearly application of mulch and inspections and treatment for damage and disease. SOIL VOLUME CALCULTATION Soil Volume and Tree Size The tree pit design and tree selection should reflect careful consideration of the available soil volume. Soil volume calculations should take into account a variety of specific factors including the soil type, whether the tree is growing in an open space or surrounded by paving, local climate conditions such as reflected heat and from cars, and other factors revealed in the complete site assessment. For the purpose of this plan, a good quality loam soil 3 feet deep is assumed, and healthy, large canopy trees are the goal. The chart shown below, developed by James Urban, shows that the soil volumes exceeding 1600 cubic feet would be required for trees with an ultimate crown projection over 1200 square feet, or about 40 feet in diameter. A general rule of thumb is a ratio of 2 CF of soil to 1 SF of mature crown spread. (Grabosky and others, 1999; Urban, 1999). 1 Another factor to consider is the positive effect of extended pits for multiple trees -- when trees share soil, the volume of soil per tree is reduced. The soil volume required for various size trees assumes a soil depth of 3 feet. (Source: James Urban) in Urban Watershed Forestry Manual - Part 3 page 26.) 1 In Urban Watershed Forestry Manual Part 3: Urban Tree Planting Guide, United States Department of Agriculture Forest Service Northeastern Area State and Private Forestry NA-TP-01-06,September 2006, page

11 The planting island along the sidewalk has two parts: A narrow rectangle 6 wide and 55 long (area 330 SF) and the wider part that would be created at the south end, with an area of 350 SF..With a depth of 3 feet, the available soil volume in each area is similar (990 SF and 1050 SF), Uisng the upper and middle ranges on the chart, a tree with a mature canopy in the range of 400 to 640 SF, or a diameter of 22 to 28,would have adequate soil volume. The larger island is approximately 2100 square feet. With a depth of 3 the available soil volume is 6300 cubic feet. For each of the three trees shown or 2100 cubic feet of soil would be available, which would allow for trees in the medium to large range. Two new trees with a mature canopy of approximately 40 are indicated on the plan. 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

12 2 - RAIN BARRELS CONSTRUCTION STEPS The following excerpt from the City of Portland Environmental Services fact sheet on Rain Barrels gives the basic steps for rain barrel construction. Overflow from the barrels would drain to the adjacent lawn. A rain garden similar to the one for the stormwater planter could also be designed to capture this excess runoff. 1- Inlet: Create an opening with fine screening through which the rain barrel will collect water from the downspout elbow. This can be a single screened opening large enough to accommodate the downspout elbow (as shown in the photo), or a series of smaller screened openings directly in the top of the barrel. 2- Overflow: Drill a hole near the top of the barrel to accommodate an overflow pipe that is at least 2 inches in diameter. If the overflow pipe elbow seals and seats securely, it can be threaded directly into the barrel opening. If not, it should be secured with washers on both sides of the barrel and a nut on the inside. Use Teflon tape around the threads and a bead of silicon caulking around the opening to ensure a tight seal. 3- Foundation: Create a raised, stable, level base (like concrete blocks) for the rain barrel to sit on. You might want to test stability by filling the rain barrel with water before attaching to your structure. A full rain barrel is very heavy and tipping is a risk if it s unsecured or on an uneven surface. 4- Downspout: Cut the downspout with a hacksaw so that the elbow will sit just above the rain barrel inlet. Attach the elbow over the downspout with a screw and secure the downspout to the house with the strap. 5- Attach Barrel: Set up the barrel beneath the elbow and secure the barrel to the house with a strap. Cut and attach the overflow pipe to the overflow elbow and direct to the existing discharge location. 6- Outlet: Drill a hole near the bottom of the empty barrel to attach the drain spigot. If the spigot seals and seats securely, it can be threaded directly into the barrel opening. If not, it should be secured with washers on both sides of the barrel and a nut on the inside. Use Teflon tape around the threads and a bead of silicon caulking around the opening to ensure a tight seal. 2 MATERIALS Two good sources of information on construction with materials lists: Rainwater Harvesting 101 Council on the Environment of NYC How to Manage Stormwater: Rain Barrels Environmental Services City of Portland MAINTENANCE Rain barrels should be drained routinely between rainfall events during the wet season (usually spring) and other periods of frequent rain events in order to maximize stormwater runoff reduction benefits. When the water will not be used in the garden, it can be drained to the nearby bioretention area 48 hours after the end of the rain event. Routine draining as described above. Drain and disconnect rain barrels in fall to prevent freezing, and reconnect in spring. Inspect periodically for leaks, especially spigots and other connection points. Make sure debris does not clog the system. Screen all vents to prevent mosquito breeding. Clean the interior of the barrels by brushing or disinfecting with vinegar or other non-toxic cleaner annually and dispose of well-diluted washout in planting areas. 2 How to Build A Rain Barrel, page

13 COST Do-it yourself rain barrels can be constructed for under $30. Readymade 55 gallon to 90 gallon rain barrels generally cost from $100 to $300 installed. A rain barrel and its system components have a lifespan of about 20 years.* SIZING COMPUTATIONS FOR RAIN BARRELS Typical rain barrels hold 55 gallons of water. Therefore, the three rain barrels proposed would capture approximately 20 percent of the WQv for this portion of the roof. Total Impervious Area Draining to Practice (Roof Area) 1100 Ft 2 Step 1: Calculate Water Quality Volume (WQv) WQv = (P) (Rv) (A) / 12 P = 90% rainfall number = 1.3 inches Rv = (I), if Rv < 20%, use Rv = 20% 95% % of Total roof area that drains to practice 100% A = Area draining to practice = 1100 Ft 2 WQv = Ft 3 *Conversion factor 7.5 (gallons/ Ft 3 ) gallons or rain barrels 13

14 3- STORMWATER PLANTER AND RAIN GARDEN PLANTER The planter would be 4 wide, 14 long and 2 ½ deep. The ponding depth would be approximately 6 and planting medium depth would be 2. The excess runoff would flow into the runnel and out to the rain garden. The rain garden would be constructed between the runnel outfall and the existing tree and shrub border along the north end of the property. RAIN GARDEN The rain garden shown has a surface area of approximately 100 square feet. The surface of the planting area would have a 3 mulch layer for filtration, and an outer bench of soil would create a shallow ponding area. The well drained soil mix would be 18 deep. The rain garden would be designed with a length to width ratio of 2:1 with long axis perpendicular to the slope and flow path. Ponding depth above the rain garden bed would not exceed 6 inches. An overflow from the rain garden would flow to the lawn area on the east side. A soil infiltration test should be performed to determine the rate of infiltration of the underlying soils and to inform decisions about the amendment of the rain garden soil. There is a depressed area in the lawn adjacent to the terrace that fills up with roof runoff during heavier rains but drains rapidly, so it would be expected that the rain garden and adjacent overflow area are well drained. The surface area and depth of the rain garden would be more than adequate to treat the part of the WQv for the 1.3 inch storm for the portion of the roof that would not be treated by the stormwater planter. Information about how to conduct a simple soil infiltration test can be found at For a volunteer group seeking to implement this, a step by step approach is recommended, where the stormwater planter would be the first step and the outfall area where the runnel and rain garden are proposed would be observed and tested. MATERIALS Soil amendments Components and proportions to be specified in final design and would follow recommendations in the NYSDECWMDM2010 Soil : The composition of the soil media should consist of 50%-70% sand (less than 5% clay content), 50%-30% topsoil with an average of 5% organic material, such as compost or peat, free of stones, roots and woody debris and animal waste.. The depth of the amended soil should be approximately 4 inches below the bottom of the deepest root ball. Plants Plants with well-established root systems would be required in order to establish the gardens quickly and effectively. Plants would be selected that are adaptable to wet and dry conditions, easy to maintain, and make an attractive contribution to the planter and garden overall. Grasses, perennials, and small shrubs can be used in the planter, The rain garden could emphasize low maintenance shrubs and grasses. Native trees, shrubs, grasses, and herbaceous plants that grow in wetland and upland areas recommended by the New York State Department of Environmental Conservation can be found in Appendix H of the DEC Manual Shredded hardwood mulch Gravel for outfall area 14

15 CONSTRUCTION STEPS Planter: The construction steps would vary according to the final design. Install runnel Install gravel layer and soil mix Install plants and mulch Gutters: Alter gutters and provide new support as required to drain the half of the rear roof to the planter. Install rain chain Rain Garden Excavate to the depth required by the final design Backfill with layer of clean washed gravel Fill to required depth with amended garden soil Install plantings Apply mulch MAINTENANCE Rain gardens and stormwater planter are intended to be relatively low maintenance. Weeding and watering are essential the first year, and can be minimized with the use of a weed free mulch layer. They should be treated as a component of the landscaping, with routine maintenance including the occasional replacement of plants, mulching, weeding and thinning to maintain the desired appearance (Adapted from the Design Manual, page 5-84). 15

16 SIZING CALCULATIONS Stormwater Planter Sizing The drainage area is estimated to be approximately 800 square feet. As shown in the calculations below, the available surface area of approximately 56 square feet provided would be adequate to capture and treat about half of the WQv of 124 cubic feet. STORMWATER PLANTER Available Surface area 56 ft 2 Total Drainage Area 800 Ft 2 Step 1: Calculate Water Quality Volume (WQv) WQv = (P) (Rv) (A) / 12 P = 90% rainfall number = 1.3 inches Rv = (I), if Rv < 20%, use Rv = 20% 95% I = percent impervious of area draining to planter = 100% % of Total area that drains to planter 50% A = Area draining to practice = 400 Ft 2 WQv = 41 Ft 3 Step 2: Calculate required surface area: Af = required surface area in sq ft = WQv*(df) / [k*(hf +df) (tf)] where: WQv = 41 ft 3 df = depth of soil medium = 2 ft k = hydraulic conductivity = 4 ft/day hf = Average height of water above planter bed = 0.25 ft tf = filter time (days) = 0.17 day Af = Required surface area for planter 54 Ft 2 16

17 Rain Garden Sizing The rain garden would be designed to capture half of the roof drainage area that flows to the planter. As shown in the calculations below, the proposed surface are for the rain garden of 100 square feet provided would exceed the WQv of 41 cubic feet.. RAIN GARDEN Total Drainage Area 800 Ft 2 Step 1: Calculate Water Quality Volume (WQv) WQv = (P) (Rv) (A) / 12 P = 90% rainfall number = 1.3 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 50% A = Area draining to practice = 400 Ft 2 WQv = 41 Ft 3 Step 2: Calculate for drainage layer and soil media volume: V SM = A RG x D SM X n SM V DL = A RG x D DL X n DL ARG = proposed rain garden surface area = 100 ft 2 DSM = depth soil media = 2.5 ft DDL = depth drainage layer = 0.5 ft nsm = porosity of soil media = 0.2 ndl = porosity of drainage layer = 0.4 VSM = volume of soil media = ARG * DSM * nsm 50 Ft 3 VDL = volume of gravel drainage layer = ARG * DDL * ndl 20 Ft 3 DP = ponding depth above surface = 0.5 ft WQv less or equal to the soil volume + the gravel volume + the volume of the ponded water, which is VSM+VDL+(DP x ARG)? 120 Ft 3 17

18 A WORD ON COSTS Costs for green infrastructure retrofits are hard to state accurately. In new construction there is often considerably lower cost up front using and green infrastructure practices and planning versus conventional, big pipe systems. But where that gray infrastructure is already in place, assessing the value of adding a gi practice requires a fuller accounting. A recent report by the Center for Clean Air Policy states: The value of green infrastructure actions is calculated by comparison to the cost of hard infrastructure alternatives, the value of avoided damages, or market preferences that enhance value (e.g. property value). Green infrastructure benefits generally can be divided into five categories of environmental protection: (1) Land-value, (2) Quality of life, (3) Public health, (4) Hazard mitigation, and (5) Regulatory compliance. The report sites, for example, New York City s 2010 Green Infrastructure Plan, which aims to reduce the city s sewer management costs by $2.4 billion over 20 years. The plan estimates that every fully vegetated acre of green infrastructure would provide total annual benefits of $8,522 in reduced energy demand, $166 in reduced CO2 emissions, $1,044 in improved air quality, and $4,725 in increased property value. It estimates that the city can reduce CSO volumes by 2 billion gallons by 2030, using green practicesat a total cost of $1.5 billion less than traditional methods. 1 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. Concept Plan by Marcy Denker 18