Centuries
of human occupation along the banks of the Neponset River have altered the river, its tributaries and
surrounding lands, affecting the ecosystems along these
waterways.
People
have changed the channels of the waterways, themselves,
making
them straighter
or deeper, for instance, or placing segments in underground
pipes. People have altered the
consistency of riverbanks, replacing the
natural mix of soil, rock and plant-life with concrete walls
or large pieces of rock. People have changed the surrounding vegetation,
replacing woods or marsh with "fill", buildings
and pavement. People have changed the content of river-bottom sediment and the
water-column, adding pollutants from human daily life or
from manufacturing. People have altered water flow,
installing dams and also removing water from the
same groundwater supplies that feeds the river and its
tributaries. People have changed the
array of wildlife using the river system, enabling exotic species
to enter the Neponset River Watershed,
while native species have left because of pollutants, the
exotic, invasive species, and/or other changing conditions.
These
days, we are examining how best to restore the Neponset
River system back to better "health" and
"function". In some cases, this means working
with landowners to remove dams and contaminated sediment
that has gathered behind these structures, and in others, it
may mean "daylighting" waterways - e.g., taking a
stream or the river out of a pipe, and restoring the
waterway, itself, and its surrounding lands to support
diverse native plants and wildlife. A more indirect
restoration method may include installing bioretention cells
or tree-filter-boxes - to catch and filter stormwater runoff
that flows from popular walking paths and also from roads
and parking lots, before it can contaminate local
streams.
Waterway Issues
A
dam built on a waterway obstructs the movement and
migration of aquatic wildlife, like fish. It also slows down
water, causing the water to drop its load of sand, dirt,
pebbles, nutrients and contaminants, yielding "sedimentation"
behind the dam. This can cause an imbalance in nutrient load -
too much above the dam and too few below. The slow-moving water also has more time to
sit beneath the sun and warm up, decreasing the amount of oxygen it can carry. Less oxygen in the water can
stress and kill aquatic organisms in the stream.
Sedimentation
(or "siltation") in a waterway can cause the water to become turbid
(e.g., cloudy, or not
clear), which makes it more difficult for aquatic
organisms to catch prey. Sedimentation also can cover and kill
the eggs of aquatic organisms. How does sedimentation
happen? Sand from nearby roads can travel down into the
stream, or, fast-moving stormwater,
flowing from the street or perhaps from a nearby parking
lot, can erode the streambanks as it joins the stream.
Dams also cause
water to slow down and drop its load of silt, sand, etc.
Application
of road salts during the winter affects
waterways and their aquatic organisms, too.
Removal
of native vegetation (including mowing) from the edges
of a waterway reduces shading of the water, thereby causing
the water to warm up and not be able to hold as much
dissolved oxygen, which can stress or kill the organisms
in the waterway. Also, when there is less vegetation
bordering a waterway, water runoff from the surrounding
landscape is not as well filtered. Therefore, the waterway
receives more
pollutants. Less vegetation along the waterway also means
that less organic debris falls into the water, decreasing
the food supply for small, aquatic organisms.
Adjacent
malfunctioning septic systems, cracked sewer pipes, or
incorrectly piped homes and businesses can leak
untreated wastewater and sewage into streams, either
through over-the-ground flow or through the ground and its
groundwater.
This waste acts like fertilizer,
potentially leading to excessive growth of algae and
plants and then to the corresponding dearth of dissolved
oxygen as the vegetation dies and is broken down by
bacteria. Raw sewage also adds viruses and bacteria to the
water. Toxins in the wastewater also can affect the
inhabitants of the stream.
Excessive
water use and groundwater withdrawal in the
surrounding community can lower a stream's water level
significantly - even dry the stream bed, leading to poor
water quality and wildlife habitat and eventually to the
death of aquatic species.
More
About Neponset Dams
Before the Industrial Revolution and the
exploitation of New England’s rivers for waterpower, the
Neponset River supported a bountiful population of anadromous
fish -- e.g., fish that spawn
in freshwater (Neponset River), refuel in salt marshes (Neponset River
Estuary), and spend most of their
lives in the ocean (Dorchester Bay/Boston Harbor/Atlantic).
Common examples of anadromous fish are herring and
shad.
The industrial
revolution yielded rampant construction of dams throughout
our waterways which blocked migration routes of these local
fish populations and degraded local water quality, and
produced vast amounts of river-borne pollution. The dams -
or their reincarnations - remain to this day for the most
part, and their effects continue. However, now that we are
learning that dams create a whole array of significant negative
effects on rivers and streams, are expensive and
time-consuming to maintain, and have finite lives, we are
beginning to see the intelligence in removing them.
People
spent decades cleaning up the waterways after the Industrial
Revolution, and we continue the cleanup.
After years of vast improvements to the
water quality of the Neponset River, we are now setting our sights
on restoring the aquatic habitat that once supported
well-known fish like Blueback herring and American
shad. Specifically, we are focusing on modifying or removing the Baker Dam and the Tileston and Hollingsworth
Dam (T&H) on the Neponset River in order to restore
water flow and fish passage. Success would mean access for
these fish populations to up to 17
miles of historical migration route along the Neponset!
Under the leadership of the MA Department of Fish & Game
(MA Department of Fisheries,
Wildlife and Environmental Law Enforcement), with the
assistance of the US Army Corps of Engineers, the US
Geological Survey and the MA DCR, and with the support of the Executive Office of
Energy & Environmental Affairs, a process has been underway to examine
Neponset River fish habitat restoration options from a
technical, economic, environmental and community
perspective.
The project has included several components,
starting with the 1996 stocking of Blueback herring and American
shad in the river after it was
determined suitable as anadromous fish habitat.
That same year, the Army Corps of Engineers initiated
a study of options for fish passage and
habitat restoration, focusing on the
T&H and Baker Dams. A draft of their report was released in February of
2002 and indicated modest levels
of contaminated sediments behind the two dams, which led to
the next phase of the project - an expanded
sediment survey. The
survey would characterize the
quantity, quality and transport properties of sediments
behind both dams. Read about the Neponset
River Restoration Project.
NepRWA
also has been surveying and investigating more than 100 dams
in the watershed via a basic inventory of dams and other
obstructions to fish movement. Amazingly, during the pilot
phase of the project, 87 structures were found in just the
river's East Branch watershed, alone.
