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Ecosystem Restoration Project Improves Clam Bayou Drain
WatprhnHv lmnrn\/prl Water quality impacts from nutrient loading and polluted
runoff from nonpoint sources led the Florida Department of
Environmental Protection (DEP) to add Clam Bayou Drain to Florida's 1998 Clean Water Act (CWA)
section 303(d) list of impaired waters for annual average exceedances of the historical maximum
nutrient impairment threshold. In response, project partners implemented numerous nonpoint
source pollution management strategies including constructing the Clam Bayou Ecosystem
Restoration Project, which provides habitat for a variety of wildlife and increases water quality,
storm water treatment, flood control and channel stabilization. Improvement in chlorophyll a (chl a)
measurements demonstrates that the project has had a positive impact on water quality for Clam
Bayou Drain, DEP recently acquired updated seagrass coverage information and is scheduled to
propose removal of this waterbody from the 303(d) list of impaired waters in 2021.
Problem
Clam Bayou Ecosystem and Stormwater Treatment Project
Figure 1. The Clam Bayou Drain watershed is on
Florida's Gulf Coast (project area highlighted in blue).
The 44-acre Clam Bayou Drain watershed is in the
Group 5 Springs Coast Watershed in central Pinellas
County between Gulfportand St. Petersburg, Florida
(Figure 1). Clam Bayou Drain is a Class iil estuary
designated for recreation and the propagation and
maintenance of healthy, well-balanced fish and wildlife
populations. The predominant land uses in the Clam
Bayou Drain watershed are 56% urban and 24%
wetlands. Clam Bayou Drain flows into the Boca Ciega
Bay Aquatic Preserve and then into Tampa Bay.
In 1998, DEP placed Clam Bayou on the state's CWA
section 303(d) list for nutrients, bacteria and dissolved
oxygen impairment. There are no point sources within
the Clam Bayou watershed; nonpoint sources include
septic systems and surface water runoff.
Since 1998, DEP adopted the Identification of impaired
Surface Waters Ruie (IWR) Chapter 62-303, Florida
Administrative Code, applying the numeric interpreta-
tion of the narrative nutrient criteria of 11 micrograms
per liter (ng/L) chl a expressed as an annua! average
not to be exceeded in any year.
The Clam Bayou Drain watershed is mostly urbanized
and built-out, which has led to portions of the bayou
to be highly modified and engineered. The hydrologic
modifications altered the natural flow of water within
the bayou, causing the nutrient concentrations to
increase and eventually exceed the state's applicable
water quality standard for Class III waterbodies.

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Story Highlights
In 2005, the ecosystem restoration and stormwater
treatment project with the cities of St. Petersburg
and Guifport were seiected for Florida's CWA section
319(h) funding. The Clam Bayou ecosystem restoration
project was designed and implemented to address
nonpoint source pollution Impacting the Clam Bayou
watershed and provide benefits such as wetland
restoration, flood control, water quality improvement
and recreational opportunities. The project restored/
enhanced 24.14 acres of various estuarine and coastal
habitats for the bayou and created 20 acres of ponds
that now provide stormwater treatment for an esti -
mated 2,558 acres of urbanized watershed (Figure 2).
The 319 funding supported construction of a new
wet detention pond which, in combination with other
stormwater treatment practices funded by project
partners, results in an estimated load reduction of
1,236.79 pounds per year (lbs/year) total nitrogen and
68,510.85 lbs/year total suspended soiids.
These best management practices enhance water qual-
ity by reducing loads of nutrients and other pollutants
delivered to Boca Ciega and Tampa Bay. The restored
wetland areas also provide essential habitat for wild-
life. Facilities built for recreational use include board-
walks and a canoe/kayak launch facility. Additionally,
educational signage depicts the processes used by the
project to treat stormwater runoff. The project work
was initiated in 2005 and completed in 2013.
Results
Data have been collected for the time periods before/
during the construction of the ecosystem restoration
and stormwater treatment project, as well as after
the completion of the project in 2013. The period of
record consists of 6 years of data, collected at multiple
monitoring stations by various agencies, including
Pinellas County, the City of St. Petersburg and DEP.
There has been a decrease in the chl a concentra-
tions from before the ecosystem restoration and
stormwater treatment project was initiated in 2005
and when it was completed in 2013. These decreasing
concentrations can be attributed to the addition of
several immediately adjacent stormwater treatment
areas with connected control structures, as well as the
restoration of a natural wetland area, which created a
more natural flow regime.
er Construction
Before Construction
Figure 2. Clam Bayou project area, before and after
restoration project construction.
In 2013 the threshold expression was updated from
an annual arithmetic mean to an annual geometric
mean. For comparison, data are presented using both
methodologies; both calculations show an improve-
ment in chl a concentrations. In the post-project
time period (2016-2019), the annual arithmetic
mean (AAM) concentrations have decreased below
the state's impairment threshold of 11 |ig/L, with a
maximum concentration of 11 |ig/L in 2019—down
from a maximum value of 18 jj,g/L in 2004 (pre/during
project). The same improvement is seen in the annual
geometric mean (AGM) chl a concentrations, with a
maximum pre-project value of 14 [ig/L and a maxi-
mum post-project value of 7 ng/L. These reductions
demonstrate that the project has had a positive impact
on water quality for Clam Bayou. As a result, DEP is
scheduled to propose removal of this waterbody from
the 303(d) list of impaired waters in 2021.
Partners and Funding
The project was funded through the City of St.
Petersburg Land Acquisition ($1,920,050), Southwest
Florida Water Management District (Pinellas-Anclote
Basin Board, Water Management Lands Trust Fund,
State Appropriation) ($6,926,200), and CWA section
319 grant funding ($898,800 total [$600,000 in 2005
and $298,800 in 2004]). The 319 funds were allocated
to the construction of the Boca Ciega Clam Bayou
Stormwater Treatment Project-Central Pond. Pinellas
County has also implemented multiple environmental
education campaigns, including Be Floridian. and has
partnered with the University of Florida's Institute of
Food and Agricultural Sciences Extension offices.
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-20-0Q1EE
December 2020
For additional information contact:
Amanda Peck
Florida Department of Environmental Protection
850-245-2952 • Amanda.Peck@floridadep.gov

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