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Rainwater garden demonstration projectsProviding beauty to the neighborhood and clean water
The City of Bloomington has partnered with the Nine Mile Creek Watershed District to build six residential rainwater gardens on Thomas Avenue in 2009 and plans for 26 more in a neighborhood just north of Old Shakopee Road and west of Nine Mile Creek. The rainwater gardens are a demonstration promoting clean water, adding wildlife habitat and beauty and recharging groundwater. Construction of the gardens has been in conjunction with the City's Pavement Management Program (PMP) Street Reconstruction Projects. In 2009, 25 residents on Thomas Avenue, between 106th and 108th Streets, were contacted about voluntarily participating in Bloomington's first residential Rainwater Garden Demonstration, six households elected to participate. Barr Engineering assisted the Engineering Division in the design and construction oversight of the gardens. Barr's Landscape Architect assisted in personalized plant selection and placement to promote infiltration performance and individual flower and native grass coloring and characteristics. Due to poor weather in October, construction was put back later into fall and the planting schedule moved into November. On a sunny fall day, a small group of enthusiastic residents, Engineering staff and Barr's Landscape expert planted over 240 plants in the six gardens in a couple hours. The plants were entering dormancy and a high survival rate is expected. A slow drive down this block in mid summer should be a joy to those who enjoy colorful flowers and whispery native grasses. To expand on 2009's success, the Engineering Division stepped up the size of the demonstration neighborhood to a possible 100 residents, of which 26 volunteered to participate. The streets include Washburn, Vincent, Upton and Thomas Avenues between Old Shakopee Road and Bailiff Place. A special meeting was held during the PMP public information process informing the residents of the benefits of rainwater gardens and the opportunity to participate in another rainwater garden demonstration project during the 2010 street reconstruction project. A typical good yard for a rainwater garden has a gentle slope, is not covered by a large tree canopy, has generally sandy soils (typical of this whole neighborhood) and is occupied by a resident with a tendency towards gardening. Engineering staff is working on individual rainwater garden designs and will tailor each to the residents' yard and drainage area, with resident input. Street construction is anticipated for mid to late summer with planting in fall. Fall planting reduces the stress of planting in the hot and dry conditions of summer. Rainwater gardens are six to twelve inches deep, and are designed to capture one inch of runoff from the contributing area. Since they drain down within 24-48 hours, they do not promote mosquito breeding, which typically has a six to seven day cycle. Residents will be responsible for regular maintenance, which includes weeding and watering during the early years, including trash or debris removal. In succeeding years, maintenance will decrease other than the shredded wood mulch may need replacing as it decays, and thick plants may need separating. The typical pollutants that come with runoff from residential streets, such as fertilizers, oils, metals, etc. are treated through the biological processes in the plants and soils. Each garden is designed with a sediment trapping system near or at the street, City Crews will clean these periodically. The residents were not asked to sign into any lengthy contract but are asked to maintain the gardens for a minimum of five years to show the long-term viability and beauty of residential rainwater gardens. While no areas have been identified for the 2011 season, Bloomington Engineering will again be looking to partner with the Nine Mile Creek Watershed District Cost Share Program for a future rainwater garden project neighborhood. The City will be working to identify the next PMP streets in late summer 2010. More information about rain gardens and sustainability
More information about the Pavement Management Program
For more information, contact:
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