Section 319
NONPOINT SOORGE PROGRAM SOGGESS STORY
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Restoring Streambanks and Floodplain Habitats Improves Water Quality
Waterbodies Improved
Development in the Stony Brook-Millstone (SBM) watershed
led to increases in volume and intensity of stormwater runoff.
The stormwater eroded Streambanks and floodplains, leading to elevated levels of total suspended
solids (TSS). Monitoring data indicate that TSS levels exceeded water quality standards, which
prompted the New Jersey Department of Environmental Protection (NJDEP) to add a large SBM
watershed segment—now composed of three 14-digit hydrologic unit code (HUC) assessment
units—to the state's 2002 Clean Water Act (CWA) section 303(d) list of impaired waters. In partner-
ship with the SBM Watershed Association (SBMWA), NJDEP initiated numerous watershed man-
agement and educational projects and implemented a series of streambank restoration and erosion
control projects within the impaired portion of the SBM watershed. TSS levels dropped, allowing
the impaired portion to meet water quality standards. In 2008 NJDEP removed the segment (three
assessment units) from the New Jersey CWA section 303(d) list for TSS impairment.
Problem
Stony Brook, in the Piedmont region of New Jersey,
is a major tributary of the Millstone River. The SBM
watershed encompasses 265 square miles in cen-
tral New Jersey (Figure 1) and includes portions of
26 municipalities. The 38-mile-long Millstone River
begins in Millstone Township and flows north until it
joins the Raritan River. Stony Brook has headwaters
in East Amwell Township and flows 21 miles east-
ward until it joins the Millstone River at Carnegie
Lake in Princeton. The SBM watershed has a mix of
urban, forest and agricultural land uses.
Extensive development over the past two decades
converted significant rural portions of the water-
shed to commercial and residential land uses. The
increases in stormwater runoff volume and inten-
sity resulted in severely eroded Streambanks and
compromised floodplain habitats, which, in turn, led
to increased TSS concentrations. The TSS impair-
ment was identified when the SBMWA conducted
a watershed-wide characterization and assessment
of all streams and riparian habitats in 1997. The
TSS impairment was confirmed by concurrent and
continuing monitoring under NJDEP's ambient
monitoring network. TSS concentrations exceeded
the state's surface water quality standard of 40 mil-
ligrams per liter (mg/L), with a maximum recorded
value of 152 mg/L in early 1997. Therefore, in 2002
NJDEP added the stream segment Stony Brook at
Princeton to the 2002 CWA section 303(d) list of
impaired waters for TSS.
Stony Brook/
Millstone River
Figure 1. The Stony
Brook-Millstone
River watershed
is in central New
Jersey.
Because NJDEP changed its basis for defining
assessment units from stream segments to HUC
14 subwatersheds, this impaired stream seg-
ment translated into the listing of three HUC 14
assessment units as impaired for TSS on the 2006
CWA section 303(d) list. The TSS impairment was
deemed partially responsible for the assessment
units not supporting the aquatic life designated
use. Arsenic and total phosphorus were also listed
as the basis for nonsupport of designated uses.
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The HUC 14 subwatersheds of Stony Brook include
Province Line Road to 74d46m dam, Route 206 to
Province Line Road, and Harrison Street to Route
206, in Princeton and Hopewell Townships.
Project Highlights
SBMWA worked with the U.S. Department of
Agriculture Natural Resources Conservation Service
(NRCS) and township engineers to identify sites
throughout the watershed in need of restoration,
erosion control and reforestation. SBMWA trained
volunteers with assistance from NRCS, New Jersey
Forestry Service and the Delaware Riverkeeper
Network. CWA section 319 funds were used for six
streambank restoration/stabilization and floodplain
reforestation projects. Four restoration projects
were implemented in Mountain Brook and two in
the upper Stony Brook portion of the watershed.
NJDEP and SBMWA used bioengineering technolo-
gies to stabilize streambanks, minimize erosion and
provide a substrate for native species plantings.
Those technologies include biologs and erosion
(coir) mats made from coconut fiber and wattle cut-
tings. The coir mats provide temporary stability for
native species seedlings and wetland herbaceous
plants on the streambank to help curtail erosion
and to restore the riparian ecosystem. At Great
Road Easement, Mountain Brook, and Princeton
Community Park, scores of tree, shrub and herba-
ceous species were planted to provide a diverse,
site-appropriate plant community.
Having addressed localized bank instability, part-
ners implemented preventive strategies to control
potential TSS input resulting from future develop-
ment. Many of the municipalities in this watershed
have adopted municipal stormwater management
plans and established stormwater control ordinanc-
es. Such plans and ordinances ensure that any new
development is designed to preserve or restore the
natural hydrology of the site and protect the overall
integrity of the watershed.
Results
The six streambank projects addressed several
problem locations and resulted in measurable water
quality improvement. After project implementa-
tion, data collected from downstream monitoring
stations in 2005 and 2006 show TSS concentrations
consistently attaining the TSS surface water quality
standards (Figure 2). On the basis of these data,
NJDEP removed TSS from the 2008 CWA section
303(d) list as a cause of impairment in the three HUC
14 assessment units.
Stony Brook SASMN Site 0141000
August 2005-December 2006
-TSS Concentration
-Standard
Aug-05
Feb-06 Jun-06 Sep-06
Sampling Date
Figure 2. TSS concentrations observed in 2005 and 2006 met
standards, resulting in delisting.
Partners and Funding
In 1998 SBMWA received $132,000 in CWA sec-
tion 319 grant funds to implement six streambank
restoration/stabilization and floodplain reforestation
projects. The NRCS and Townships of Hopewell and
Princeton provided in-kind labor valued at $54,000.
Funding for the earlier characterization and assess-
ment study was obtained from the Mercer County
Green Links Program, the Fund for New Jersey,
Princeton Township, the Schumann Fund for New
Jersey and the William Penn Foundation.
Continuing efforts are planned in the SBM water-
shed under a U.S. Environmental Protection Agency
targeted watershed grant for the Raritan Basin. The
New Jersey Water Supply Authority, SBMWA and
NJDEP were awarded $1 million in CWA section
319 funding for restoration, pollution prevention and
reforestation projects in the lower Raritan Basin.
That federal grant was matched by an additional
$1 million from other funding sources.
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-09-001NN
December 2009
For additional information contact:
Barbara Hirst
Chief, Bureau of Environmental Analysis
and Restoration
New Jersey Department of Environmental
Protection
609-633-1441 • Barbara.Hirst@dep.state.nj.us
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