BIORETENTION/CISTERN/IRRIGATION TO ELIMINATE STORMWATER RUNOFF AT THE UNIVERSITY OF MARYLAND

Water quality of parking lot (~1,858 m2) stormwater runoff and its treated effluent flow were analyzed for total phosphorus (TP), total nitrogen (TN), total suspended solids (TSS), electrical conductivity (EC), copper, lead and zinc. The novel system under investigation, located at the University of Maryland, College Park, Maryland, includes a standard bioretention facility, underdrained to a cistern to store treated stormwater, and pumped to a vegetable garden for irrigation. The site abstraction, the average bioretention abstraction, and bowl volumes were estimated to be 8500, 4378, and 895 L, respectively; this indicates that rain events of more than 0.45 cm are necessary to produce runoff and more than 0.75 cm will produce system overflow. The cistern water quality indicates good-to-excellent treatment by the system. Compared to local tap water, cistern water has lower concentrations of TP, TN, EC (non-winter), copper, and zinc, indicating a good water source for irrigation.

Water Quality Impacts due to the Addition of Biosolids-Derived Compost to Bioretention

Bioretention is a common stormwater control measure (SCM). While compost, combined with other bioretention soil media (BSM), has the potential for increased pollutant and water uptake and storage, it also may leach harmful nutrients. Limited information is available on the use of compost in SCMs. Therefore, this project seeks to analyze the impacts of the addition of biosolids-derived compost to bioretention. To accomplish this, bioretention mesocosm column studies were conducted to determine the leaching effects of 15%, 30%, and 30% tap water-washed compost, mixed with standard BSM. Synthetic storm runoff was applied to the columns and the effluent was analyzed for total nitrogen (N), phosphorus (P), and their speciation. All three columns leached N and P with maximum total N concentrations of 2,200, 2,100, and 300 mg-N/L and total P concentrations of 12, 4.9, and 4.6 mg-P/L for the 30%, 15%, and 30% washed mesocosms, respectively. Therefore, based on this study, it is not recommended that biosolids-derived compost be added to bioretention media.

Understanding Urban Stormwater Denitrification in Bioretention Internal Water Storage Zones

Free-draining bioretention systems commonly demonstrate poor nitrate removal. In this study, column tests verified the necessity of a permanently saturated zone to target nitrate removal via denitrification. Experiments determined a first-order denitrification rate constant of 0.0011 min-1 specific to Willow Oak woodchip media. A 2.6-day retention time reduced 3.0 mgN/L to below 0.05 mg-N/L. During simulated storm events, hydraulic retention time may be used as a predictive measurement of nitrate fate and removal. A minimum 4.0 hour retention time was necessary for in-storm denitrification defined by a minimum 20% nitrate removal. Additional environmental parameters, e.g., pH, temperature, oxidation-reduction potential, and dissolved oxygen, affect denitrification rate and response, but macroscale measurements may not be an accurate depiction of denitrifying biofilm conditions. A simple model was developed to predict annual bioretention nitrate performance. Novel bioretention design should incorporate bowl storage and large subsurface denitrifying zones to maximize treatment volume and contact time.

1022-013 Dry Run Creek Watershed Final Report

The Dry Run Creek Watershed received a biological impairment in 2002 after sampling conducted by the Department of Natural Resources revealed a lack in the diversity and abundance of aquatic life along a 2.8 mile reach of stream along the Southwest Branch. Among the primary stressors identified were hydrologic change, increased stormsewer inputs, lack of available habitat, and sedimentation. Goals put forth by the Watershed Management Plan and the preliminary Total Maximum Daily Load (TMDL) study center around the reduction in storm sewer inputs. The goal set forth by the TMDL is the reduction of connected impervious surface (CIS) to 10% in each of the creek’s subwatersheds as a surrogate for other stressors. Grant funding is being sought for the construction of two bioretention cells and a green roof to treat the first flush of runoff from a new 400 unit student housing structure and connected parking surfaces totaling 5.16 acres. In addition, a monitoring program will continue to be coordinated through a partnership with the Department of Natural Resources IOWATER program and locally led volunteer efforts which will allow us to track the progress of the watershed. Funding for administration, outreach, and assessment will be provided through existing 319 grants. Implementation of these practices will occur in phases over the course of a two year period.

06017-009 Saylor Creek Watershed Final Report

With the Saylor Creek Watershed Improvement Project, Iowa Heartland RC&D and other area stakeholders have an opportunity to display how "best management practices" (BMPs) can reduce storm water runoff and improve the quality of that runoff in an urban setting. Conservation design is a uew approach to storm water management that addresses the negative impacts of storm water runoff and turns them into a positive. The master plan for the Prairie Trail development surrounding the watershed project will incorporate bioretention cells, bioswales, buffer strips, rain gardens, as well as native plant landscaping to slow storm water runoff and naturally clean sediment out of the water before it reaches Saylor Creek. In addition to conservation design elements, the project will utilize storm water detention ponds and creek bed restoration to develop a complete storm water "treatment train" system within Prairie Trail. The extensive use of conservation storm water management for Prairie Trail is unique for urban development in Iowa.

Hydrologic monitoring of an integrated low impact development (LID) underdrained stormwater management system

In 2005, Wetland Studies and Solutions, Inc. (WSSI) installed an extensive Low Impact Development (LID) stormwater management system on their new office site in Gainesville, Virginia. The 4-acre site is serviced by a network of LID components: permeable pavements (two proprietary and one gravel type), bioretention cell / rain garden, green roof, vegetated swale, rainwater harvesting and drip irrigation, and slow-release underground detention. The site consists of heavy clay soils, and the LID components are mostly integrated by a series of underdrain pipes. A comprehensive monitoring system has been designed and installed to measure hydrologic performance throughout the LID, underdrained network. The monitoring system measures flows into and out of each LID component independently while concurrently monitoring rainfall events. A sensitivity analysis and laboratory calibration has been performed on the flow measurement system. Field data has been evaluated to determine the hydrologic performance of the LID features. Finally, hydrologic models amenable to compact, underdrained LID sites have been reviewed and recommended for future modeling and design.

The Effectiveness of Rain Gardens as a Low-Impact Development Strategy for Storm Water Pollution Reduction in Western Washington

Stormwater runoff is a major cause of surface water pollution in western Washington and cost-effective control measures are needed to reduce contamination of receiving waters. This project evaluated the performance efficiency and costs of installing a residential rain garden by inspecting two gardens and testing water quality samples in one. Infiltration through the garden was effective in reducing metals and nutrients as indicated by reductions in copper and nitrate concentrations of 75% and 97%, respectively. The costs were affordable for most homeowners and cost-effective compared to other options. After doing on-site investigations, the storm water manual for the State of Washington was reviewed and eight recommendations were made for improving it.