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Controlling Nonpoint Source Pollution from Agricultural Areas
Restores Tappahanna Ditch

Waterbody Improved Run°ff from agricultural areas caused high bacteria levels in

Delaware's Tappahanna Ditch of the Choptank River. As a result,
the Delaware Department of Natural Resources and Environmental Control (DNREC) added the
watershed to the 1996 Clean Water Act (CWA) section 303(d) list of impaired waters for bacteria
and nutrients. Watershed stakeholders provided technical assistance and installed agricultural best
management practices (BMPs) in the watershed, which led to reduced bacteria levels. As a result,
DNREC removed Tappahanna Ditch from the state's list of impaired waters for bacteria in 2018.

Problem

Tappahanna Ditch is in the Choptank River watershed
on the western edge of Delaware in Kent County
(Figure 1). The Choptank River watershed consists of
the Tappahanna Ditch in the northern portion of the
watershed, Culbreth Marsh Ditch in the center, and
Cow Marsh Creek in the lower portion. The drainage
area of the Choptank River watershed within Delaware
is approximately 97 square miles. Primary sources
of nonpoint source pollution in the watershed likely
include runoff from agricultural activities (e.g., fertilizer
and manure application) and concentrated areas of
animal production.

Monitoring data collected in the late 1990s indicated
that Tappahanna Ditch failed to meet the state's
enterococcus bacteria numeric criterion, which
requires that the annual geometric mean be less than
100 colony-forming units (cfu) per 100 milliliters (ml_).

Tappahanna Ditch did not support its freshwater
primary contact designated use, prompting the state
to add the watershed to Delaware's 1996 CWA section
303(d) list of impaired waters for bacteria.

in 2006 the U.S. Environmental Protection Agency
developed a total maximum daily load (TMDL) to
address the nutrients and bacteria loading through-
out the Chesapeake Bay watershed, which includes
Tappahanna Ditch. Nutrient TMDLs for the Choptank
River watershed include a yearly-average cap on total

nitrogen at 1,359 pounds per day and a 40% reduction Figure 1. Tappahanna Ditch is part of the Choptank
in phosphorus levels. Also, the TMDL requires a 29%	River watershed In the Delaware portion of the

reduction in nonpoint source bacteria loads in the	Chesapeake Bay basin.

Choptank River watershed.

Watersheds

Tappahanna Ditch
Piedmont
Delaware Bay
Chesapeake Bay
Inland Bays

Su'dex Corp. 2017


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Tappahanna Ditch 305(b) Report Enterococcus Geomeans
By Year

Figure 2. Bacteria geomean levels have dropped and
now meet standards.

Story Highlights

The Kent County Conservation District (KCD) offered
technical assistance to the farming community by
providing nutrient management planning and cost-
share funding for agricultural BMPs. The conservation
districts also partnered with the U.S. Department of
Agriculture's (USDA's) Natural Resources Conservation
Service (NRCS) to develop conservation plans and
Environmental Quality Incentive Program (EQIP)
contracts. Watershed partners worked with landown-
ers to enroll 4,500 acres of cover crops and implement
nutrient management planson approximately 3,000
acres from 2013 to 2017.

In addition, several BMPs were installed on poultry
operations within the watershed, including 17 manure
storage structures, 11 poultry carcass composters,
30 heavy-use area protection pads, one animal waste
iquid handling system, and the transfer of 115 tons
of manure during 2013-2017. The KCD planning staff
continue to work with farmers throughout the water-
shed, providing ongoing technical assistance to ensure
improved water quality.

Delaware's USDA Conservation Reserve Enhancement
Program (CREP) was established in 1999 to protect
and enhance environmentally sensitive land and
waters in the coastal plain geographic areas of the
Delaware, Chesapeake, and inland Bays watersheds
by establishing voluntary land retirement agreements
with agricultural producers. To assist in CREP program
development and implementation, in 1999 Delaware's
Nonpoint Source Program committed CWA section

319 funds to create a full-time Delaware CREP Program
Coordinator position. The CREP Program Coordinator
helped install 62 acres of grass buffers, 1 acre of ripar-
ian buffers, 25 acres of wildlife plantings, and 54 acres
of hardwood trees in the Tappahanna Ditch watershed.

Results

Bacteria levels have decreased in response to the more
than 10 years of water quality protection and restora-
tion efforts in the Tappahanna Ditch-Choptank water-
shed. DNREC collected monitoring data at STORET
Station 207081 in Tappahanna Ditch between January
2012 and December 2016. The geometric mean of
the 45 samples collected over the 5-year period was
72 cfu/100 ml, down from a high of 137 cfu/100 mL.
in 2014 (Figure 2). Because the 2018 geomean of
72 cfu/100 mL was well below Delaware's freshwater
bacteria water quality standard of 100 cfu/100 mL,
DNREC removed the 7.5-mile segment of Tappahanna

Ditch (DE-l 10-001)
from the state's list of
impaired waters in 2018
per its Assessment and
Listing Methodology. The
2018 Integrated Report
shows the segment
continues to meet the
applicable water quality
standards for bacteria
due to ongoing resto-
ration efforts in the
watershed (Figure 3).

Figure 3. Tappahanna
Ditch water quality has
improved, thanks to
restoration efforts.

Partners and Funding

Key partners included KCD, NRCS, and the Delaware
Nonpoint Source Program. In 2005-2017, NRCS sup-
ported implementation efforts within the watershed
for $2.5 million. Over $236,400 in federal CWA section
319 funds supported the costs of the Tappahanna
Ditch restoration effort. Because of the nature of
the funding and enrollment procedures, much of the
funding provided by watershed partners has been
extremely important. Implementation efforts within
the watershed are continuing with the collabora-
tions and working relationships that our partners and
producers have formed.

&

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U.S. Environmental Protection Agency
Office of Water
Washington, DC

EPA 841-F-22-001I
June 2022

For additional information contact:

Mark Hogan
DNREC NPS Program

302-739-9922 • Mark.Hogan@delaware.gov


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