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FLORIDA
With the passage of the Surface Water Improvement and Management Act (SWIM)
in 1987, the Florida legislature codified its concern over the continued water
quality decline in surface waters and degradation of natural systems. The act
established a framework and provided the initial funding to preserve and
restore waters of regional and statewide importance. The SWIM Act named Tampa
Bay and its tributaries to receive priority attention. Tampa Bay is Florida's
largest open water estuary, with 398 square miles of surface area and a
contributing watershed of more than 2,200 square miles. The Southwest Florida
Water Management District has undertaken a major initiative--the Urban
Stormwater Analysis and Improvement Initiative--to preserve and restore Tampa
Bay. This initiative established existing and future pollutant loading
estimates for the entire watershed, followed by specific stormwater
rehabilitation projects to improve water quality.
The Bath Club Concourse Stormwater Rehabilitation Project
The Bath Club Concourse is located in North Redington Beach, a small
barrier island community in Pinellas County. This combination roadway and
parking area-- connecting Bath Club Circle and Gulf Boulevard--was an
impervious slab of concrete pavement. Since Bath Club Concourse could not
absorb falling rain, stormwater runoff flowed directly into a single storm
sewer, carrying its full load of nonpoint source pollutants directly to Boca
Ciega Bay. In August 1990, the Water Management District and the town agreed to
construct a stormwater rehabilitation project using pervious concrete pavement
at the Bath Club Concourse. Half of the $48,000 cost was funded by the Water
Management District and half from a section 319 grant.
The state has designated Boca Ciega Bay as an "outstanding Florida water"
and determined that it has been adversely affected by urban stormwater runoff.
Therefore, the Bath Club Concourse Stormwater Rehabilitation Project's main
objective was to reduce nonpoint pollutant loading by reducing the volume of
runoff discharging directly into Boca Ciega Bay. A second objective was to
demonstrate an innovative way to treat or improve the quality of stormwater
runoff in highly urbanized areas. These areas pose particular problems because
vacant land is not readily available, and acquiring land to construct a
conventional stormwater treatment best management practice (e.g., wet detention
pond) is often too expensive.
The project's goal was to maximize infiltration of stormwater runoff to
reduce the amount of untreated runoff discharging directly into storm sewers.
Therefore, the design directed drainage toward two pervious concrete parking
areas, separated by an unpaved island, in the center of the concourse. To
maximize infiltration, engineers installed two 150-foot underdrains so
subsurface soils could drain beneath the pervious concrete parking areas. The
project required some 9,120 square feet of pervious concrete, making an
8-inch-thick slab with 20 percent porosity. Table 4-1 summarizes pollutant
loadings and predicted reductions for seven water quality parameters. In
addition, Figure 4-1 graphically illustrates the reduction in total nitrogen as
a result of the BMP.
These results show that a properly designed, constructed, and maintained
stormwater treatment system using pervious concrete pavement (with or without
an underdrain system) is a viable alternative to traditional best management
practices for stormwater treatment.
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