Dredging Lake Ripple
Grafton, MA
Phase 1
July-November 1999
Dredging began July 1999. Although the lake didn't smell as bad as it
had many years ago, (thanks to environmental and pollution controls in recent years) it's
finally getting cleaned.
Click any image for a larger view
(Please be patient when opening any of the 5 panoramas...they're
large !)
Overview
This rough sketch gives an overview of the lake area,
to where the mud is pumped and how the water returns to the lake.
The Equipment
A "weedeater" was brought in to remove many of the weeds at the beginning of the
project. It was found that the lake was choked with weeds, hampering the dredging
equipment by clogging it's cable pulleys.
Here's the dredging equipment used. It moves slowly along a steel cable strung from shore
to shore or to an anchored object so that it follows a straight path as it moves across
the water.
 A view of the business end,
and an example of the stuff they have to deal with 
Near the middle of the dredge boat in the suction line is an area which
clogs whenever large ogjects enter it. It is cleaned often (especially near the shore) as
chunks of wood and debris frequently block it.
Mostly just mud and silt is being removed.
If gravel or sand is encountered (meaning the original lake bed) it is left in place.
The Process
An auger and suction pipe is mounted to a hydraulic boom which is lowered to the bottom of
the lake. The auger rotates and gathers the mud towards the suction pipe in the center,
just in front of it. A diesel engine provides power for the pump and pumps the mud and
water at 75-80 psi. to the far side of the lake and into a large gravel basin.
At the basin, the mud settles to the bottom and the excess water flows toward the drain at
the other side of the basin.
A LARGE 360 degree panorama taken from the center of the empty basin as the dredging
began.
The basin is a large pit built to contain the mud pumped there. It is on a
portion of the Grafton Lions Club property and is accessible from their driveway or a nice
15-20 minute walk along a trail beginning at the bottom of Wheeler Rd. The property along
the trail belongs to the Grafton Land
Trust and is part of the Gummere Wood/Marsters Preserve.
The water rises until it reaches the drain seen at the far end.
Note that boards are able to be added to the drain to hold back the mud as the level
rises,
yet allow the water to flow over.
After the water enters the drain, it flows through a pipe into a small weedy area
(upper left in picture) before reaching the "settling pond" and the second drain
seen here.
After reaching the second drain, the water flows through a final pipe and back into the
lake.
Except, without the mud
As of Sept.7, no water had yet overflowed into the
drains
Except for the trickle of leakage, the basin had collected / absorbed everything.
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