PROJECT AREA: Newburgh HUDSON VALLEY REGIONAL COUNCIL 3 Washington Center, Newburgh NY 12550 http://www.hudsonvalleyregionalcouncil.com/ Google 2011 GREEN INFRASTRUCTURE CONCEPT PLAN FOR CERONE PLACE Project type: Municipal storm sewer retrofit DECEMBER 2011 Proposed practices: Bioretention area
The following 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 final design and construction documents. OVERVIEW The City of Newburgh has a combined sewer system that conveys both wastewater and stormwater runoff and is facing the need to address requirements for remediating overflows during wet weather as a regulated combined sewer overflow (CSO). The regulatory agencies involved with this program -- NYS DEC and at the Federal level, the US EPA, are placing an increasing focus on the advantages of using green infrastructure (GI) for meeting these CSO requirements. GI captures water on the landscape and reduces runoff before it reaches the sewer system, thereby reducing the volume of water in the system and helping to reduce overflows during storms. The benefits of GI also include improved air quality, reduced heat island impacts and resulting benefits to public health, and beautification and streetscape improvements that can support walkability and community revitalization. After being contacted about the HVRC s regional GI planning project, the City of Newburgh Engineer, Craig Marti P.E., worked with local architect and planning board member Peter Smith, to consider potential planning sites. Marti suggested looking at areas of the City where stormwater collection sewers had already been installed to separate stormwater from wastewater. In these locations, the stormwater has been separated from wastewater but then flows back into the combined system before it flows to the treatment plant. The plan is to eventually construct a completely separate stormwater system to connect these sections that are already separated. Marti suggested looking for an opportunity to take stormwater from a separated area and divert it out of the sewer system before it s discharged to the combined system, and Cerone Place was selected as a possible location. Smith then evaluated the area with another Newburgh resident, Shabazz Jackson, who is knowledgeable about stormwater remediation, with input from Marti. They identified a City-owned parcel of open land at the north end of Cerone Place and determined that the flow direction and elevation of the existing stormwater pipes at this location could allow stormwater to flow by gravity into this open parcel, which is adjacent to the confluence of the Quassaick Creek and a small tributary that flows out of Crystal Lake nearby. HVRC s outreach team Simon Gruber and Marcy Denker, determined that the full drainage area for the stormwater system at the north end of Cerone Place is difficult to determine without detailed site investigation, and they decided to focus this concept plan on a phase one approach to planning GI at the site. This plan includes capturing runoff from one part of the larger area at the Burton Towers apartment building adjacent to the City-owned open parcel noted above. An existing trench drain at the bottom of this driveway and an adjacent catch basin provide a readily-available opportunity to divert runoff out of the stormwater system into the open parcel, where a bioretention system is proposed. Additional evaluation of the elevation of this proposed bioretention area, the water table elevation, and other factors are needed before final planning and design can be completed for this concept. Initial evaluation indicates that there is enough elevation drop between the proposed bioretention area and the height of the adjacent Creek to allow bioretention to be constructed and to work effectively for runoff reduction and water quality treatment. The Quassaick Creek Watershed Alliance is a local citizen s organization working closely with the Orange County Department of Planning to develop a watershed plan for the Quassaick Creek basin. GI planning in Newburgh has been coordinated with this organization, Alliance members and County staff have provided support and participated in certain aspects of preparing this plan, and their contributions are appreciated. Peter Smith in particular helped to move this concept plan along by producing sketches, helping to coordinate site meetings, and preparing a written summary of the LIDRA modeling results for Cerone Place (included at the end of this report). Other key participants include: Shabazz Jackson, the owner of Greenway Environmental Services, a firm that specializes in manufacturing of specialty soil 2
media, composting, and site remediation; Ian MacDougall, City of Newburgh Acting Director of Planning and Development, a key liaison with the City, who has recognized the economic development and water quality potential of this project; and Chad Wade, RLA, also a member of the City of Newburgh Planning Board and a planner with the Orange County Planning Department. Smith, Jackson and Wade participated in the LIDRA training workshop presented as part of the regional GI planning project in August 2011. They used LIDRA at this workshop to model GI practices for parcels along Cerone Place and this initial simulation found that, see notes below); This group s discussions have included the idea that in addition to the Burton Towers site that s the focus of this concept plan, GI can be implemented for a larger area along Cerone Place that includes three other building projects on and the street itself. Their initial evaluation indicates that the City s open parcel at the north end of Cerone may be large enough to accept all the storm water from roofs and parking lots as well as the street. Craig Marti has noted that other areas in the City have separate storm and sanitary drains already in place, where variations of this approach can potentially be applied. This concept plan has been produced based on the ideas developed by Marti, Smith, Jackson and MacDougall, and their contributions are much appreciated. LOCATION Street Address: Corner of Cerone Place and Little Britain Road, Newburgh NY, and adjoining driveway of the Burton Towers apartment building. OWNERSHIP City of Newburgh Section 33, Block 6, Lot 3.2 EXISTING CONDITIONS SURFACE COVER/CONTRIBUTING AREA The proposed GI site itself is entirely wooded and the drainage area to the site includes grassy slope, a paved terrace, and the north end of the driveway. Part of the runoff from the driveway currently flows over 3
the edge towards the site. For this concept plan part of the grassy slope is included in the estimated drainage area since it steep and rocky. SOILS AND TOPOGRAPHY The site itself slopes gently to the north, towards the creek, and the adjacent lot is steeply sloped towards the site and the trench drain. The NRCS Web Soil Survey shows RMD Rock outcrop-farmington complex, hilly, RSB Rock outcrop-nassau complex, undulating, and UF Udifluvents-Fluvaquents complex, frequently flooded. 1 Test pits should be dug on this site where the rain garden and bioretention areas are proposed prior to developing the final design. SOLAR EXPOSURE AND VEGETATION The site is covered with bushy growth, and large deciduous trees shade it during the warm months. There is a relatively large open area between trees on the south side of the site. BIORETENTION GARDEN DESIGN Bioretention gardens capture and treat runoff on site. They are slightly depressed below the surrounding grade and allow runoff to pond temporarily, providing detention and pollutant removal benefits. They are used for larger drainage areas and for areas such as parking lots where an additional level of filtration is required. Figure 2 Concept Plan An 11x17 version of the plan is included at the end of the report. 1 1 Soil Survey Staff, Natural Resources Conservation Service, United States Department of Agriculture. Web Soil Survey. Available online at http://websoilsurvey.nrcs.usda.gov/. Accessed [12/11/2011]. 4
The proposed bioretention areas would capture the runoff from a portion of the residential site, including the north part of the driveway and some areas adjacent to it that currently flow to the trench drain at the low end of the driveway. The drain would be retrofitted so that it would no longer discharge to the catch basin next to it except as an overflow. An extension would channel the runoff onto a stone covered outfall that would slope gently toward the bioretention garden. If possible, a grass filter strip would be provided between the outfall and the garden. An overflow device above the ponding area would be installed to direct larger volumes of water back to the catch basin, and an underdrain would be provided. Soil infiltration tests would be provided prior to developing a final design. Figure 2 Typical bioretention design. NYS Stormwater Mangement Design Manual, page 6-49. 5
MATERIALS PLANTS Plants with well-established root systems would be required in order to establish the garden quickly and effectively. Masses of low maintenance native grasses and shrubs would be used for the bioretention plantings. A list of plants appropriate for the wet and dry environment in bioretention areas and a list of local sources for native plants can be found in Appendix H of the New York State Stormwater Management Design Manual 2010 (Design Manual). SOIL AND MULCH Figure 9 Bioretention area in parking lot (Photo:NRCS http://www.ia.nrcs.usda.gov/features/urbanphotos.html) Components and proportions would be specified in the final design. Recommendations in the Design Manual for bioretention area soils and mulch are as follows: Planting Soil Bed Characteristics The characteristics of the soil for the bioretention facility are perhaps as important as the facility location, size, and treatment volume. The soil must be permeable enough to allow runoff to filter through the media, while having characteristics suitable to promote and sustain a robust vegetative cover crop. In addition, much of the nutrient pollutant uptake (nitrogen and phosphorus) is accomplished through adsorption and microbial activity within the soil profile. Therefore, the soils must balance soil chemistry and physical properties to support biotic communities above and below ground. The planting soil should be a sandy loam, loamy sand, loam (USDA), or a loam/sand mix (should contain a minimum 35 to 60% sand, by volume). The clay content for these soils should by less than 25% by volume. Soils should fall within the SM, or ML classifications of the Unified Soil Classification System (USCS). A permeability of at least 1.0 feet per day (0.5"/hr) is required (a conservative value of 0.5 feet per day is used for design). The soil should be free of stones, stumps, roots, or other woody material over 1" in diameter, including brush or seeds from noxious weeds. Placement of the planting soil should be in lifts of 12 to 18", loosely compacted (tamped lightly with a dozer or backhoe bucket). Mulch Layer The mulch layer plays an important role in the performance of the bioretention system. The mulch 6
layer helps maintain soil moisture and avoid surface sealing which reduces permeability. Mulch helps prevent erosion, and provides a micro-environment suitable for soil biota at the mulch/soil interface. It also serves as a pretreatment layer, trapping the finer sediments which remain suspended after the primary pretreatment. The mulch layer should be standard landscape style, single or double, shredded hardwood mulch or chips. The mulch layer should be well aged (stockpiled or stored for at least 12 months), uniform in color, and free of other materials, such as weed seeds, soil, roots, etc. The mulch should be applied to a maximum depth of three inches. Grass clippings should not be used as a mulch material (Appendix H, page 6). OTHER MATERIALS Pipe for drain extension and underdrain Stone for inflow path as required in final design Shredded hardwood mulch CONSTRUCTION STEPS Excavate to the depth and regrade as required by the final design Backfill with layer of clean washed gravel Retrofit trench drain and catch basin Install drain and overflow Construct stone outfall Fill to required depth with amended soil Install plantings Apply mulch and stones MAINTENANCE CONSIDERATIONS The bioretention garden would be designed for low maintenance. Weeding and watering are essential in the first year and can be minimized with the use of a weed free mulch layer. Routine maintenance would include the occasional replacement of plants, mulching, weeding and thinning to maintain the desired appearance. The gravel diaphragm would require regular maintenance to clean sediments and debris. Plan by Simon Gruber and Marcy Denker. Thanks to Peter Smith, Craig Marti, Shabazz Jackson, Chad Wade, Ian MacDougall, and Elizabeth McKean for their support and contributions. 7
SIZING CALCULATIONS GREEN INFRASTRUCTURE SIZING AND DESIGN The green infrastructure practices included in these plans are among those considered acceptable for runoff reduction in the 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 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 = 0.05 + 0.009(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. The garden would have a surface area of approximately 2,000sf. Given a depth of 3,feet, this would be more than the surface area of 1608 sf required to capture the WQv of 1,742 cf. 1: Calculate Water Quality Volume (WQv) Available Surface area 2000 ft 2 Total Drainage Area 20000 Ft 2 WQv = (P) (Rv) (A) / 12 P = 90% rainfall number = 1.1 inches Rv = 0.05+0.009 (I), if Rv < 20%, use Rv = 20% 95% I = percent impervious of area draining to planter = 100% % of Total area that drains to planter 100% A = Area draining to practice = 20000 Ft 2 WQv = 1742 Ft 3 2 Bioretention Details WQv*df/k(hf+df)(tf) df = depth of soil medium = 3 ft k = Coefficient of permeability of planting soils 0.5 ft/day hf = Average ponding depth (max depth/2 0.25 ft tf = filter time (days) = 2 days 3. Calculation Af = Required surface area for bioretention 1608 Ft 2 8
COST 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. http://greenvalues.cnt.org/national/cost_detail.php 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. http://www.cwp.org/categoryblog/92-urban-subwatershed-restoration-manual-series.html CERONE PLACE LIDRA MODELING FINDINGS By Peter Smith, Member, City of Newburgh Planning Board, August 19, 2011; edited by Simon Gruber. Peter Smith participated in the LIDRA training workshop held on August 17, 2011 presented as part of the regional GI planning project, along with two other Newburgh residents -- Shabazz Jackson, the owner of Greenway Environmental Services, a firm that specializes in manufacturing of speciality soil media, composting, and site remediation; and Chad Wade, RLA, also a member of the City of Newburgh Planning Board and a planner with the Orange County Planning Department. Together, they ran a LIDRA simulation for GI implementation on parcels along Cerone Place. This model area was suggested by Craig Marti, City Engineer for the City of Newburgh, because it provides an opportunity to divert stormwater collected in a separate storm sewer along Cerone Place before it flows into the combined sewer and to the Cityʼs wastewater treatment plant. However, having limited input data and limited time we ran the LIDRA program only to simulate the benefit of green infrastructure interventions to reduce runoff before it enters this storm sewers, and we did not use it to model the potential for diverting water already collected in the storm sewer to the proposed bioretention site at the north end of Cerone Place.. Green Infrastructure interventions included in the LIDRA simulation: 1. A rain garden at the foot of Cerone Place 2. green roofs 3. permeable paving at parking areas, not at travel ways. Results: 1. 40% reduction in stormwater runoff 2. Estimated cost of $80 - $90,000. per year over a ten year period. Conclusions: Informal discussions with team leaders during the second half of the program, and the running of the individual sites, led us to believe that the Project suggested for Cerone Place is feasible. Even a cursory examination, using merely the green infrastructure substitutions, demonstrate noticeable benefits for a relatively small investment. 9
Other G.I. measures suggested were: Modification of lawn areas using more absorptive soil top dressing. (LIDRA does not address this) Permeable paving along the edges of Cerone Place. Benefits: Reduction in storm-water runoff diverted to the waste water treatment plant. Reduction in untreated sewage flowing directly into the Hudson during storm surges. Increased capacity in wastewater treatment plant, a salable asset for economic development. Action: Explore ways to fund a model project at the Cerone Place catchment to take advantage of the separate storm and sanitary sewer lines and introduce green infrastructure practices that would divert the stormwater out of the combined system and reduce the amount of runoff leaving the catchment. 10
Figure Sketch showing the location of the storm sewer (highlighted in yellow) and the sanitary sewer (parallel and just to the left of the storm sewer) along Cerone Place, produced by Peter Smith on a base map provided by the City, with input from Craig Marti P.E. 11