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Section 319
NONPOINT SOURCE PROGRAM SOCGESS STORY
Stakeholders Cooperate to Reduce Sediment Loading and Restore
Recreational Uses in Cains Pond '
\A/citprhnH\/ Imnrnx/prl Sediment from stormwater runoff accumulated in Cains Pond,
an old mill pond, and reduced its depth to the point that sec-
ondary contact recreation (such as boating) was no longer possible. As a result, the New
Hampshire Department of Environmental Services (NHDES) included Cains Pond on the
state's 2010 Clean Water Act (CWA) section 303(d) list of impaired waters for not meet-
ing its secondary contact recreation use. Stakeholders reduced sediment inputs from the
developing watershed by installing a sediment trap chamber system and coordinating with
the New Hampshire Department of Transportation to reduce winter sand application. After
the sediment sources were addressed, the pond was dredged of accumulated sediment,
which restored recreational use. As a result, NHDES will remove Cains Pond's secondary
contact recreation use impairment from the CWA section 303(d) list in 2012.
Problem
Cains Pond, a three-acre impoundment on Cains
Brook in the New Hampshire coastal town of
Seabrook, was historically created for mill opera-
tion, ice harvesting, fire suppression and recreation.
The pond is bounded by a residential area to the
west and a major highway (U.S. Route 1) and urban-
ized commercial area to the east.
This watershed experienced a commercial develop-
ment boom around the year 2000. Construction
activities are thought to have contributed much of
the sediment that accumulated in the pond during
that time. Increased development also resulted
in a greater number of impervious surfaces.
Traditional stormwater infrastructure transported
untreated stormwater directly to the pond. Local
residents used Cains Pond for fishing, boating, and
other recreational pursuits; however, those uses
became increasingly restricted as the pond filled
in with sediment. Bathymetric surveys indicated
deep sediment shoals that reduced water depth to
non-navigable depths of 1 to 2.2 feet. In addition
to shallow water, the sediment accumulation likely
contributed to excessive aquatic plant growth,
further hindering recreational uses (Figure 1). The
shallow depths also allowed the pond to freeze to
the bottom in winter, which inhibited fish survival.
As a result, the NHDES included Cains Pond on the
2010 CWA section 303(d) list of for not meeting its
secondary contact recreation use.
Figure 1. Before restoration efforts, Cains Pond was filled with
sediment and supported an overgrowth of aquatic plants.
Project Highlights
In 2007 Seabrook, acting through its conserva-
tion commission, received a U.S. Environmental
Protection Agency (EPA) CWA section 319 grant to
address the sources of sediment inputs to Cains
Pond. A 2008 CWA section 319 grant built on that
effort and ultimately resulted in restoring the pond
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Figure 2. Project partners controlled sediment inputs and
dredged Cains Pond, allowing the pond to once again
support its secondary contact recreation use.
so it attains its secondary contact recreation use.
The Cains Pond restoration projects included
developing assessments, planning, permitting,
implementing best management practices, con-
ducting outreach, dredging accumulated sediment,
and improving recreational access.
Project partners modified the primary stormwater
outfall to the pond to incorporate a sediment trap
chamber that captures sediment from U.S. Route 1.
The chamber removes an estimated 1.9 tons of
sediment per year. The chamber will be cleaned and
maintained by the town. The state's Department
of Transportation reports that it no longer applies
winter road sand to that section of Route 1, further
reducing sources of sediment to the pond.
In-pond dredging was carefully planned and con-
ducted to restore the secondary contact recreation
function. The main basin of the pond was dredged
to an average depth of seven feet (an increase of
approximately five feet over pre-dredge depths). A
deeper "hole" (ten feet) was dredged in the north-
eastern section of the pond to provide a cool, deep
spot for fish habitat. The narrower, west end of the
pond was also dredged to an average depth of four
feet (an increase of three feet deeper than pre-
dredge depths). Those depths allow for navigation
and provide fish habitat (Figure 2). Additionally, the
dredge depth is sufficient to prevent the pond from
freezing to the bottom in winter. It is anticipated
that the deeper conditions will also limit the growth
and spread of invasive aquatic plants, thereby
reducing the accumulation of decaying vegetation.
The project included installing an American
Disabilities Act-compliantfishing platform and car
top boat launch on an access easement at the north-
east shore of the pond; those improvements will
further promote the recreational use of Cains Pond.
Results
Project implementation took place between 2007
and 2010. Approximately 12,000 tons of accumulated
sediment, plus leaf litter and decaying vegetation,
were dredged from the pond to achieve target
depths averaging six to seven feet. The post-dredge
bathymetric survey confirmed that target depths
were attained. Non-motorized boats can once
again navigate Cains Pond. Because the waterbody
(assessment unit NHIMP600031004-05) now meets
applicable standards for secondary contact rec-
reation use, the impairment will be removed from
the state's 2012 CWA section 303(d) list. The pond
remains on the impaired waters list for aquatic life
use impairment due to pH and low dissolved oxygen.
Partners and Funding
The work to restore recreational uses at Cains Pond
involved the cooperation of numerous stakehold-
ers including Seabrook, Waterfront Engineers LLC,
Maritime Construction & Engineering LLC, Doctor
John Maloney, Riverbend Masonry, the Seabrook
Department of Public Works, NHDES and EPA.
EPA CWA section 319 funds provided $68,240 for
the first phase of the project and $91,800 for the
second phase. The funds contributed to planning,
administering and implementing the restoration
project. Project coordination was provided by the
Town of Seabrook Conservation Commission, in
close cooperation with NHDES staff. The town
contributed $253,000 in matching cash to imple-
mentation funds and continues to provide required
maintenance.
I
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-11-001LL
September 2011
For additional information contact:
Barbara McMillan
New Hampshire Department of Environmental
Services
603-271-7889 • Barbara.mcmillan@des.nh.gov
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