Sustainable Sites Initiative
Bio-retention system after heavy rain event
John Burroughs School Bio-retention System
Size & Type of Project:
10,156 square feet; School; Greyfield and greenfield development
Location:
Ladue, Missouri
Budget:
$267,479 for the Bio-retention System; $5 million for the total cost of Phase 1A of the project
Project Phase:
Fall 2007
Project Overview
John Burroughs School (JBS)*, a private college preparatory day school in the St. Louis suburb of Ladue, Missouri, is currently implementing a facilities master plan over the next five years. As a result of the construction of a parking lot, theater and a field hockey field, additional detention was required by the local agency, Metropolitan Sewer District (MSD). At the time of construction, water quality standards were not required by MSD and an existing small pond (0.38 acre) was to be used for the additional required retention.
The client and the design team recognized the impact on the water quality of the lake, a natural area on the site which is integral to the science curriculum. As a direct result of an educational seminar on water quality, the client made a commitment to a substantial change order to protect the lake and contribute to down-stream protection. Late in the construction schedule, a 3-cell bio-retention system was designed and installed in the fall of 2007. Due to space constraints of the school campus, the 3-cell bio-retention system needed to fit within the available space, accommodate the volume of stormwater generated from the drainage area, and provide a learning environment for the school. The bio-retention project successfully led to the pond protection, flood protection and met MSD new water quality requirements.
As part of the science curriculum, students are participating in all areas of the bio-retention system - from selecting the appropriate plants to ongoing monitoring and maintenance. The integration of the facilities into the science curriculum provides hands-on learning opportunities for the students and the community.
Site Context
The City of Ladue is a residential community located minutes from St. Louis. The area resides in the Interior River Valleys and Hills ecoregion, just north of the Ozark Highlands. The biome of the area is primarily midlatitude deciduous forest with rolling hills topography. The average annual precipitation of the St. Louis region is 39 inches per year and the average high temperature is 77.5 degree F while the average low temperature is 33.6 degree F.
Student planting for bio-retention system
Sustainable Practices
Manage and cleanse stormwater: The bio-retention system is primarily a plant- and soil-based filtration facility for parking lot stormwater runoff. Stormwater runoff flows downhill from the driveway and south parking lot into the highest cell, from which it slowly progresses into two lower cells until finally ending up in the pond. Initially, much of the water passes first through an underground vortex filter that spins under the power of the falling water. The cleaned water is then diverted from the vortex filter into the first bio-retention cell while the debris and impurities removed from the water collect at the bottom of the filter. Once a year, the collected sediment from the bottom of the vortex filter is pumped out for disposal. Water then flows into the three cells of the bio-retention basin, each of which has its own underground water holding chamber as well as above-ground plants and soil. Stands of native grasses and wildflowers in each cell help prevent evapotranspiration by shading the water, enhance soil composition, encourage biological activity, and promote the removal of pollutants before stormwater enters the pond. Another important benefit of the system is the prevention of rapid filling and flushing of the pond. Completion of the bio-retention pond will bring natural beauty and a thriving Missouri ecosystem to the south side of the JBS campus.
Promote sustainable awareness and education: As a student-driven project, students researched and selected the appropriate native plants for each environment, including the bottom and sides of the retention basins as well as the adjacent slopes of the basin. A second planting and an adjacent prairie were planted in the fall of 2008. Students were responsible for the labor involved in the planting, initial weeding, and future maintenance of the bio-retention plantings.
In addition, students documented the process by mapping the areas and collecting and analyzing data to assess the performance of the bio-retention system. The following information is on the school website (http://science.jburroughs.org/sdeken/bioretention.htm).
- Data from water chemistry tests done by students on the pond into which water from the bio-retention area eventually flows.
- Data from soil chemistry tests done by students on the soil in the three separate cells of the bio-retention system.
- A guide to the flora that was selected and planted by students in the bio-retention areas.
- Results of a community survey (small animals) and a measure of the biodiversity found at the pond and in the cells of the bio-retention area.
- Results of a population study to estimate the size of the grasshopper population in the newly planted prairie near the pond and bio-retention area.
Construction Cost
This bio-retention project represented a significant change order ($267,479) during construction. The majority of this cost was in the retaining walls and hand labor to place rocks. The large rocks were salvaged from the site but additional rock was brought in for the bottoms of the basins. If more site area had been available, the use of vegetative swales, grading and berms would have reduced the cost significantly. The "fear of the unknown" played a role in the high cost for construction as well as the need to expedite the project within the construction schedule.
Monitoring Information
The bio-retention system and pond are being regularly monitored by students in the science department. Water chemistry testing and soil chemistry testing are already a part of the science curriculum and the school already had the hardware to perform these tests. The only cost is the restocking of the chemicals and replacement of equipment and glassware that breaks. The cost estimate for this expense is less that $100 per year.
Students are monitoring dissolved oxygen, water temperature, phosphorus and nitrate levels, pH, and turbidity. These factors were chosen in order to monitor the succession (aging) of the pond. Each of the tests will also allow the students to analyze the overall pond health. Nitrogen and phosphorus levels are deemed to be the most important indicators for pollution and eutrophication.
The soil is also being tested for nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur and soil pH. The students are mainly concerned with the top soil and its living and nonliving role in supporting the plants in the bio-retention system.Nitrogen, phosphorus and potassium are considered most significant to promote healthy plant growth. Measures of nitrogen and phosphorus taken during the first year fell within acceptable ranges, with nitrogen readings tending to be on the lower end of the range and potassium readings at the higher end of the range. Potassium readings were unusually high, with most readings being much greater than the acceptable value. All of the five nitrogen and phosphorus readings measured by students during the first year of operation (October 2007 - October 2008) fell below the maximum level considered safe for drinking water, which is <10 mg/L for nitrogen (EPA) and <5 mg/L (WHO). All but one of the measurements for the percent saturation of oxygen in the pond fell with the acceptable range to support life in the pond (60 - 100% saturation). This was true for pH readings as well.
Maintenance
John Burroughs has an on-site maintenance staff that will monitor and maintain the basins and lake. During this first year, ending fall of 2008, the staff monitored the cells for siltation, erosion and plant establishment. An adjacent site is still under construction and is contributing silt to the lower basin. The basins are currently being monitored for durability during the rainy spring season. Maintenance strategies will be better defined during the first couple of years but currently include trash removal, silt removal, weeding, mowing or burning of prairie plants, and cleaning of vortex filters and drainage pipes. Quantitative data is not available at this time but will be tracked as a matter of the schools maintenance budget.
Since the bio-retention area is so new, more plants and seed will be planted in the spring of 2009. The anticipated cost of these plants and seed is $200 - $300. After this, few additional plants will be needed so no additional cost is anticipated.
Receiving pond
Issues/Constraints of the Site
- The constraints of an established construction budget and schedule were substantial obstacles to this initiative. Due to the conviction of the client, this project was accomplished. They showed that it is never too late to do the right thing.
- Space constraints are not unique to many projects. However, a client with a land-locked campus needs to make careful choices about the allocation of land. John Burroughs chose to allocate this land to a sustainable strategy instead of parking.
Lessons Learned
- Sustainable practices that are integral to curriculum are the best outdoor classrooms.
- It is never too late to consider a sustainable strategy in your project or to retrofit a site for a sustainable strategy.
- In stormwater systems, segmental block walls are not ideal for the containment of water or management of the force of water. (Portions of the segmental block walls were grouted solid. The original design had poured concrete walls)
- It is difficult to predict the exact impact of water on structures and stacked natural stone. Water will find small holes in which to by-pass the system.
- Construction contingencies need to cover the cost of on-site refinements.
More project details
Data from JBS science curriculum: http://science.jburroughs.org/sdeken/bioretention.htm
Planting plan: http://science.jburroughs.org/sdeken/bioretention/JBSbioretentionflora.htm#map
JBS master plan: http://masterplan.jburroughs.org/images/pics/firstfloor1.jpg.
(This drawing was made before bio-retention system was added to the construction plans.)
Project Consultants
Project Manager:
Randall Moskop
Project Manager
Christner, Inc
Landscape Architects:
Ronen Wilk
Peter Gisolfi Associates
Steven Wheeler
Christner, Inc.
Civil Engineer:
Mark Meyer
Principal Engineer
Intuition and Logic
Dan Koziatek
Director of Engineering
Volz, Inc
Educators:
Dr. Scott Deken
Science teacher
John Burroughs School
Margaret Bahe
Science Department Chair
John Burroughs School
Upkeep and Maintenance:
Ed Philipp
Head of Plant Operations and Grounds
John Burroughs School
*Project made possible in part by a gift from the E.E. Ford Foundation in memory of Julia Ford Menard. John Burroughs School Class of 1941.