The project work plan consists of an integrated design process, heavy construction (site preparation), rain garden installation, rain garden maintenance, and green infrastructure information and educational sessions.
Final design, engineering, and construction budgeting will be completed as part of an “integrated design process” involving each of the project partners. This process will facilitate maximum value engineering and smooth the transition from design to construction. We will seek a project manager and general contractor for the site preparation portion of the construction, including providing all necessary permits.
Double 8 Foods and IndyTilth will be present at all design meetings to represent the interests of and communicate progress back to the community through various means, including neighborhood meetings, email announcements, and a blog that tracks project progress.
Project design considerations that must be finalized include size, type and placement of the cistern; extent of the rain garden area; how the recycling bin will be positioned with respect to the rain garden area; placement of the curbs and openings to maximize stormwater catchment; necessary depth of excavation, growing medium, and rain garden ponding capacity given anticipated stormwater volume; and appropriate plant material.
Cistern size will be primarily determined to minimize CSO events within the constraints of the budget. Cistern size will be determined to minimize CSO events while following budget constraints. Factors in determining cistern size to achieve the goal of minimizing CSO events include assumed amounts of (1) rainfall, (2) water infiltrated and stored by rain garden planting medium, and (3) water utilized by plantings. Over one million gallons of stormwater fall on the Double 8 Foods site each year, with approximately 26,000 gallons in a one-inch rain storm (Figure 5). The rain garden as proposed for this application (1856 ft2) would have the capacity to infiltrate approximately 25,000 gallons (assuming 0.9”/hour absorption rate, varies by site conditions including native soil and planting medium) and store approximately 28,000 gallons below the overflow (assuming a 2’ ponding capacity). Based on these assumptions, a cistern with a capacity of at least 1800-2000 gallons would enhance the effect of the rain garden in helping avert or partially reduce the magnitude of CSO events at least once per year. A larger cistern would further reduce the likelihood of CSO events. In addition, the cistern would also allow fresh water to hydrate vegetation while plants are getting established, particularly in the first two to three years. Given a one-inch per week water need for plants while getting established (native plants chosen for a rain garden may require less) and no rain for two weeks, the water requirements would be approximately 2300 gallons per week. For a longer drought, the volume needed would increase accordingly. There are many cistern types and sizes. In order to reduce maintenance and health hazards, a closed system cistern is necessary. The cost of a galvanized steel 2000-gallon cistern is approximately $950 and a polyethylene 1800-gallon cistern is $1100. These costs do not include installation, pedestal, or installation of intake (downspout revision) and overflow piping. Placement on the south side of the Double 8 Foods grocery would accommodate the majority of existing downspouts, minimizing downspout revisions.
However, the extent of the rain garden area may largely be determined by available funds. The project budget has been arranged in terms of linear feet of 8’ wide rain garden; thus, the project may be scaled up or down depending on available funding.
In order to maximize educational opportunities, IndyTilth proposes to retain the recycling bin adjacent the rain garden. Placards or other signage could explain aspects of the rain garden, including its purpose and resources for additional information, and announce upcoming events relating to the rain garden, including on- and off-site educational sessions. The recycling bin area needs ample room so that an empty bin can be dropped off next to the filled bin that will subsequently be taken away. This may necessitate positioning the bin along North Park Avenue rather than along East 34th Avenue as it is now.
The depth of excavation will depend on several factors including the depth of overlying asphalt, underlying native soil (or other found materials), chosen planting medium, drainage and/or overflow system, and plant selection. These will all be discussed in the next section and further addressed by a design expert and other team members during the integrated design process.
Heavy construction (site preparation)
We will place sedimentation control, cut and remove asphalt, install a new concrete pad for the cistern, install new concrete curbs and openings, excavate the rain garden retention area, excavate for cistern overflow piping, install cistern overflow piping, install rain garden under-drain system, backfill and rough grade, and patch asphalt. We will also arrange the work site in such a way as to maintain free and clear access to the Double 8 Foods loading dock as required throughout construction.
The assumed depth of excavation is three feet below grade. The surrounding soil indicates that there will be a high clay content (soil type B), necessitating a larger excavated area for planting medium to assure adequate drainage and ponding capacity.
The overlying asphalt is likely thin given that the weeds easily grow through the many cracks. It is difficult to predict, however, what lies underneath the asphalt. Based on review of aerial photography and Sanborn maps, earlier use of this parcel includes an open field (1937) prior to construction of the building that now houses Double 8 Foods between 1937 and 1956. Also, a recent assessment of the Mapleton-Fall Creek neighborhood did not identify this parcel as ever having been a potential brownfield site. Thus, we anticipate need to excavate primarily soil in preparing the site along East 34th Street and North Park Avenue for a rain garden.
In addition to excavating the bioretention area, excavation for cistern overflow will be completed and overflow piping installed.
Depending on available funds, concrete for curbs with appropriate openings will be formed and poured. This is often not necessary for rain gardens adjacent to a parking lot, depending on the site contour and design. Likewise, an under-drain system may not be necessary depending on the native soil drainage and planting medium used.
A bioretention overflow system and soil grading will be completed prior to rain garden installation.
All aspects of heavy construction will be completed and managed by Smock-Fansler.
Rain garden installation
KIB will coordinate site delivery of rain garden materials, including planting medium, appropriate native vegetation, and organic mulch. Double 8 Foods will provide a dedicated material staging and work area in their parking lot. IndyTilth will coordinate with community partners to provide volunteer labor to install rain garden materials.
After site preparation is complete, IndyTilth will coordinate with KIB and project partners to install the rain garden planting medium, vegetation and mulch over two six-hour work sessions. The planting medium will be an engineered soil mix that provides stormwater treatment through filtration and provides needed nutrients for plant growth. This medium will be purchased in bulk and dumped in the Double 8 Foods parking lot to be spread on top of the graded native soil and sub-drainage system by volunteers to a depth of between two and four feet. Given access to volunteer labor and in an effort to minimize soil compaction, we will distribute planting medium by wheelbarrow and hand rakes rather than heavy equipment.
We will irrigate the planting medium for at least one day prior to actual installation of rain garden plants. The irrigation will allow the planting medium to settle and at the follow-up work day, more planting medium will be added to the specified levels per design recommendations (generally within two inches of final design elevations).
Native vegetation with the following qualities will be selected: suited for rain garden applications (allow maximum infiltration and evapotranspiration), high drought tolerance, and visual interest over four seasons. These plants aid in removing stormwater pollutants, allow maximal water to evaporate and create effective drainage pathways via their root network. We will plant a variety of species to promote biodiversity and avoid susceptibility to diseases. Species will include groundcovers, grasses, shrubs, understory trees, as well as larger trees, each of which will be selected to reduce weed growth and maintenance needs.
After the vegetation is planted, we will spread organic hardwood mulch and hand-grade to final elevations per design guidelines. The mulch will provide sustained release of nutrients for plant growth (in addition to planting medium) and promote increased surface area for absorption and evaporation of stormwater. The mulch also retains water for plant use during dry periods, reducing the need to water. The shredded mulch is less likely to wash out into the above-grade drainage system, reducing the need to replace mulch in subsequent years.
Volunteers will be recruited through a rich network of community partners as discussed in Local Support.
Rain garden maintenance
IndyTilth and Double 8 Foods will coordinate and provide rain garden maintenance as needed.
Rain garden maintenance will be handled by the Double 8 Foods on a daily and weekly basis and IndyTilth on a monthly basis. Specifically, Double 8 Foods will remove litter and debris as necessary from the rain garden and monitor the cistern water levels, ensuring there is adequate space for stormwater accumulation during wet months and filled levels of captured stormwater in dry months for plant irrigation as needed. Volunteers, coordinated by IndyTilth through collaborations with community partners, will aid with remaining maintenance, under the guidance of the Steering Committee and other experienced gardeners, at the monthly work parties.
IndyTilth has convened a Steering Committee for developing this application and overseeing the installation and maintenance. The Steering Committee includes Sarah Wiehe (nearby resident, IndyTilth director, Mapleton-Fall Creek Neighborhood Association board member), Isaiah Kuperstein (Double 8 Foods owner), Doressa Breitfield (Mapleton-Fall Creek Development Corporation (MFCDC) staff), Terri Coleman (nearby resident, gardener, MFCDC board member), and Tyson Domer (nearby resident, green building consultant, MFCDC board member). We have commitments from the following organizations to recruit volunteers for the monthly work parties: MFCDC, Historic Meridian Park Neighborhood Association, Watson-McCord Neighborhood Association, Constitution Gardens, and Mid-North Church Council (see letters of support). Sarah Wiehe, Terri Coleman and Tyson Domer, who all live within one block of Double 8 Foods and can see their parking lot from their homes, will take responsibility for maintenance not completed by other community members and volunteers and will also monitor the rain garden weekly. Double 8 Foods will provide food and water for volunteers during the rain garden installation phase and for monthly work parties. The CDC will provide the tools for the monthly work parties, including wheelbarrows, shovels, rakes, hoes, and trowels.
Maintenance of the rain garden will include the following activities: watering from the cistern (weekly as needed for the first year and as needed during drought periods); weed and prune, keep overflow free and clear of leaves, repair eroded areas, inspect trees and shrubs and replace if necessary (monthly during growing period); re-mulch as needed and inspect for sediment build-up, erosion, and vegetative conditions (annually); and maintain records of all inspections and maintenance activity (ongoing).
Green infrastructure information and educational sessions
IndyTilth will coordinate with local organizations such as Marion County Soil & Water Conservation District and The Children’s Museum of Indianapolis to provide informational sessions, both on-site and at community meetings, and highlight the project and educational events on our website www.indytilth.org.
These educational efforts will be implemented through on-site community meetings of the surrounding neighborhood associations, local churches, and apartment communities with the support of Marion County Soil and Water Conservation (discussed via phone on 8/10/10, Clean Water Indiana grant which supports these types of educational outreach sessions) and The Children’s Museum. IndyTilth will maintain web site detailing all aspects of this project.