Section 319
NUNPUINT SUURCE PROGRAM SUCCESS STORY
Implementing Best Management Practices Reduces Nitrogen in Two
Corsica River Tributaries
I H
improved
Algae blooms in the upper tidal reaches of Maryland's Corsica River
prompted the Maryland Department of the Environment (MDE)
to add the river to the state's Clean Water Act (CWA) section 303(d) list of impaired waters in 1996 for
impairment of aquatic life and recreational use. MDE developed a total maximum daily load (TMDL) for
nitrogen and phosphorus. After six years of restoration efforts, water quality monitoring in two nontidal
Corsica River tributaries shows a significant decrease in nitrogen concentrations. These improvements
indicate that project partners are making progress toward meeting the Corsica River nutrient TMDL.
Problem
The six-mile-long Corsica River is a tidal tributary on
Maryland's Eastern Shore. It flows through Queen
Anne's County and the town of Centreville before
entering the Chester River, which discharges into
the Chesapeake Bay (Figure 1). Major land uses
in the 40-square-mile watershed are agriculture
(64 percent), woodland (28 percent) and developed
areas. The nontidal portions of the Corsica River are
designated for aquatic life protection and contact
recreation; most of the estuarine portions are desig-
nated as shellfish harvesting areas.
Algal blooms and other water quality problems in
the tidal portions of the Corsica River prompted
MDE to add this watershed assessment unit to the
CWA section 303(d) list in 1996 for impairment by
nutrients, suspended sediment and fecal coliform
bacteria. Water quality surveys conducted in 1997
found that the local eutrophication problems (the
overenrichment of aquatic systems caused by
excessive nutrient input) tended to be the greatest
slightly downstream of the tidal/nontidal interface.
Data showed chlorophyll a concentrations (a mea-
sure of algal content) as high as 146 micrograms
per liter (jug/L).
MDE developed a TMDL for nitrogen and phospho-
rus, which EPA approved in 2000. According to the
TMDL, the major source of nutrient loading was
agricultural runoff (85 percent); other sources were
forest and urban nonpoint sources and the town of
Centreville's wastewater treatment plant (WWTP).
The TMDL established the following water quality
goals for the Corsica River: (1) chlorophyll a con-
centrations should remain below 50/jg/L, and (2)
dissolved oxygen (DO) levels should remain above
the state's minimum water quality standard, 5 mil-
ligrams per liter (mg/L).
Corsica River
Watershed
Legend
Subwatersheds
CZI Corsica Direct Drainage
CZ1 Mill Stream Branch
CH Three Bridges Branch and Gravel Run
^WRAS Project Area Boundary
— Roads
Streams
Figure 1. The Corsica River's three subwatersheds are part of the
Corsica River Watershed Restoration Action Strategy (WRAS).
Project Highlights
In 1998 the Maryland General Assembly passed the
Water Quality Improvement Act, which required that
all agricultural operations with gross annual income
over $2,500 and any livestock operations with more
than eight animal units develop and implement nutri-
ent management plans. All plans were developed by
2004, helping to reduce nutrient pollutant loading.
In 2004 the town of Centreville, along with several
key local partners and with support and cooperation
from MDE and the Maryland Department of Natural
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Resources (MDNR), finalized the Corsica River
Watershed Restoration Action Strategy (WRAS). The
plan outlined implementation strategies needed
to protect and restore the watershed. In 2005 EPA
accepted the Corsica River WRAS, which was high-
lighted as one of the nation's best watershed plans
at the CWA section 319 nonpoint source annual
meeting. That same year, Maryland's governor
selected the Corsica River for the state's targeted
restoration watershed program.
Watershed partners have worked to implement agri-
cultural best management practices (BMPs) since
2004. Over the last several years, farmers have annu-
ally planted increasing acres of cover crops. Since
2010, annual cover crop coverage has exceeded the
WRAS goal of 3,000 acres per year. Other agricul-
tural BMPs implemented include approximately
5 acres of natural buffer, 30 acres of grassed buffers,
30 acres of riparian herbaceous cover, 3 acres of
grassed waterways and 2 miles of stream fencing.
In 2005 the Maryland Department of Agriculture
(MDA) received CWA section 319 funds to promote
and partially reimburse cover crop planting on farm
fields in the watershed. Since then, CWA section
319 funds have also supported efforts by an MDA
agricultural technician to help local farmers select
and target agricultural BMPs.
In 2006 the town of
Centreville and Queen
Anne's County began a
series of CWA section
319-funded projects, includ-
ing urban stormwater infiltra-
tion projects and support
for education and outreach
efforts. Local partners
installed stormwater wet-
land ponds and bio-retention
practices, which capture
and hold excess stormwater
runoff during heavy pre-
cipitation events. The town
installed stormwater retrofits
on 112 acres (Figure 2).
Local residents volunteering
through the Corsica River Conservancy have installed
more than 300 rain gardens.
Maryland legislation established the Bay Restoration
Fund in 2004. It supports upgrading WWTPs with
enhanced nutrient removal technology, improving
on-site septic systems and implementing cover
crops to reduce nutrient loading to the Chesapeake
Figure 2. From 2009-2010 the
town of Centerville and MDNR
converted an existing stormwater
management pond into a multi-cell
pond-wetland complex to more
effectively capture and treat runoff.
Bay. As of May 2012, 13 on-site septic systems in
the Corsica River watershed were enhanced with
nitrogen-reducing treatment capability. In 2010
the town of Centerville completed upgrades of
its WWTP to include biological nutrient reduction
technology. In addition, Centerville now applies its
WWTP discharge to farmland through spray irriga-
tion for nine months each year, which has greatly
reduced the amount of discharge directly entering
the upper tidal reaches of the Corsica River.
Results
Monitoring data from 2005-2011 show decreasing
trends of instream nitrogen and phosphorus con-
centrations in the nontidal tributaries of the Three
Bridges Branch and Gravel Run subwatershed.
Groundwater monitoring conducted on crop fields
in the watershed during 2005-2007 spring sampling
periods indicates that cover crop planting may be
reducing nutrient loadings.
The upgrades to Centerville's WWTP have also
reduced nutrient loading. Comparing discharge
monitoring records from 1997 (before upgrades) to
the period 2007-2012 (after upgrades) shows that
total nitrogen loads from the plant have declined
by 87 percent (from 11,175 pounds per year to
1,424 Ib/yr) and that total phosphorus loads have
declined by 96 percent (from 2,395 Ib/yr to 92 Ib/yr).
Partners and Funding
Key partners have included local government enti-
ties (the town of Centreville, Queen Anne's County
and the Queen Anne's Soil Conservation District),
local watershed groups (Corsica Conservancy and
the Chester River Association), state agencies (MDE,
MDA and MDNR), and federal agencies (EPA and the
U.S. Department of Agriculture's Natural Resources
Conservation Service [NRCS]). To date, partners
have invested almost $3.5 million in nonpoint source
implementation projects. Maryland's agricultural
cost-share program and NRCS have provided fund-
ing to implement BMPs in the watershed. From
2004 through 2012, $450,000 in federal CWA
section 319 funds supported agricultural technical
assistance to local farmers for selecting and target-
ing BMPs. Another $920,000 funded urban BMP
implementation and provided local nonpoint source
program support. As of May 2012, Maryland's Bay
Restoration Fund had provided more than $150,000
for 13 septic system upgrades in the Corsica River
watershed. The WWTP upgrade and capital cost
of seasonal land treatment (farmland application of
discharge) totaled about $4.5 million.
PRO^
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-13-001P
April 2013
For additional information contact:
Eva Kerchner, Watershed Manager/Zoning Officer
Town of Centreville
410-758-1180 • ekerchner@TownofCentreville.org
Ken Shanks, TMDL Implementation Division Chief
Maryland Department of the Environment
410-537-4216 • kshanks@mde.state.md.us
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