Cooperator: Wisconsin Department of Natural Resources
Project Chief: William R. Selbig
Location: Cross Plains
Project Number: BQY25
Period of Project: July 1998–September 2007
updated 2/20/07
Problem
Farmland in Wisconsin is rapidly being converted to urban land uses. This urban
development, with the associated increase in impervious area, generally impacts
the water quality and increases the runoff volume that is delivered to the receiving
water body. When new site plans are proposed, many of the plans use “end-of-pipe” structural
best-management Practices (BMPs) such as wet and dry detention ponds. However,
these structural BMPs are primarily designed to reduce the flood peak of a runoff
event. They have limited water quality and quantity benefits.
Low-impact development
is designed to reduce the volume and improve the quality of runoff while attempting
to preserve the natural hydrology of the site. Low-impact practices include
the reduction of impervious surfaces and installation of infiltration devices,
such as rain gardens.
A detention pond (foreground) serves as one
stormwater-runoff control device during construction of a residential subdivision
using low-impact development practices in Dane County, Wis. |
Objective
To evaluate the effectiveness of low-impact practices for reducing runoff quantity
and improving runoff water quality.
Approach
Test and control sites have been selected in Cross Plains, Wisconsin. The control
site, which was developed from 1988 to 1991, used traditional urban design practices
such as storm sewers, curbs and gutters, and a wet detention basin. The second
site began development in May 1999 and is implementing low-impact development
practices. Both sites are finger valleys that are approximately a quarter mile
apart.
Equipment at both sites is maintained to continuously monitor
water level, precipitation, and water temperature, and is housed in a monitoring
station that has phone telemetry and electrical power. An automated water-quality
sampler at each site is programmed to take flow-proportional samples from runoff-producing
storm events.
Comparisons in the performance of BMPs in the control and study
area will be made based on unit-area runoff and unit-area loads. Trends in water
quality and quantity will also be analyzed to further characterize the construction
cycle (from platting to site closeout).
Progress (January 2006 to June 2006)
All event summary statistics were computed for the test sites at Cedar
Hills and the north detention pond for the period 1998 – 2005. A regression was
created using dye tracer data to estimate discharge at the control site on Bourbon
Road for the period 1998-2005. Removal of monitoring equipment was initiated.
Plans (July 2006 to December 2006)
The remainder of instrumentation will be removed and the site restored
to natural conditions. Event statistics for the control site at Bourbon Road
will be computed and compared to the test site. All data will be tabled and summarized
for inclusion in draft report.
Reports
Scientific Investigations Report is planned for September 2007. |
