St.
Paul’s Episcopal Cathedral, at
Ninth and High Streets in downtown Des Moines, is working on a project,
called the St. Paul’s Cathedral and Neighbors’ Rain
Gardens, to transform the current asphalt parking lot into an urban
green-space that will model good water practices and make the site more
beautiful and pedestrian friendly. The project will improve water quality and indirectly reduce stormwater runoff in the southeast corner of 9th and Pleasant Streets in downtown Des Moines while creating a beautiful public space where passersby can relax and enjoy themselves.
The current parking lot has dilapidated asphalt that extends within inches of an existing row of ash trees on Ninth Street, and does little to absorb or filter the water that runs toward Pleasant Street and the alley.
Cathedral Dean Cathleen Bascom voices a spiritual vision for the renovation, “Stewardship is about recognizing the gifts we have from our Creator and responsibly caring for and generously sharing them.” And she reports that in the process of deciding what to do, church leaders began to ask, “What is the most responsible and most generous stewardship of this gift of land?”
St. Paul’s has been involved in flood recovery networks and projects in the city recently which gives them a heightened awareness of the need for good on-site water management. And many people working in the downtown area traverse the land of St. Paul’s daily.
So when the congregation of St. Paul’s considered the necessary repairs of the parking lot they asked, “How can we be a part of the water management and water quality solutions needed in our area and most benefit our many downtown neighbors?”
The resulting vision was to transform the asphalt-covered grounds into a crescent of rain gardens along a porous pedestrian walkway and additional porous elements, including porous asphalt for the area of greatest run-off in the parking lot– all highlighting good water management practices. The tree-lined walkway will border rain gardens and a fountain with seating to allow passersby opportunities for rest and refreshment while bringing environmental healing to the site.
What is a rain garden? A bio-retention cell or rain garden is a depressed area with porous backfill under a vegetated surface. These areas often have an underdrain to encourage filtration and infiltration, especially in clayey soils. They recharge groundwater, remove pollutants, and detain runoff. Rain gardens are an effective solution in parking lots or urban areas where green space is limited.
This physical transformation will also provide educational opportunities for the many downtown workers who traverse these grounds daily and our urban neighbors, particularly the YWCA and PACE Juvenile Center.
The success of the project will be measured in terms of a fairly involved water quality volume formula that is found in the Iowa Stormwater Management Manual and approximated in this project. Good water management practices such as porous pavement and bioretention cells, such as the rain gardens, make up 10% - 15% of the site area. These new measures will manage 100% of the water runoff from the impervious part of the parking lot and from the roof by reducing pollutant concentrations in the runoff and reducing the water impacts from high stormwater flow rates.
Funding for the new rain garden will come from a variety of sources including the Polk County Conservation District and the Iowa Infrastructure Investment Initiative.
In addition, St. Paul’s will receive in-kind assistance from the Polk Soil and Water Conservation District (SWCD), the Polk County Conservation Board, the Friends of the Botanical Center, Drake University urban environmental history faculty, and RDG landscape architects. Assistance with maintenance of the site will be provided by the neighbors of St. Paul’s including the Principal Volunteer Network, the YWCA and PACE Juvenile Center.
All of this and St. Paul’s will still be able to park 40 cars there!
For more information about St. Paul’s plans, contact Dean Cathleen Bascom at Dean@st-pauls-cathedral.com
Resource for more information on best water management practices are available at this EPA website.
