Summer 2009 - The Cavanaugh Pond Beavers

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Whispers in the Forest
Newtown Forest Association
Connecticut's Oldest Private Land Trust
Over the last 10 years the presence of beavers at the NFA’s Cavanaugh Pond property off of Echo Valley Road have required minimal annual
maintenance by the Board, however, as with all good things – change happens.  The Cavanaugh Pond property is a 15 acre parcel with an
abandoned raised rail bed separating the property into two distinct sections; a small seasonal pond and wetland area to one side and a 5 acre pond
with a vintage fieldstone spillway on the other.  The raised, long-abandoned, rail bed was built in the 1860’s with the material that was dug out from
either side; creating these watershed areas.  Deep underneath the rail bed was a 4 foot x 4 foot stone tunnel built to drain the small pond into the
larger.  There actually used to be an old railroad station in this immediate area.

Back to the issue.   The beavers were not content with the size of the small seasonal pond and from time to time tried to block off the tunnel to
improve their habitat.  The beavers had done so without applying for the proper permits or getting the approval of the wetlands commission.  These
could be overlooked; however, they did not consult with the NFA board, who vehemently disapprove of such behavior and use of NFA property.  Big
picture - the beavers actions are somewhat expected, and in most situations the NFA lets nature take its course.   At this property, the railroad
altered the properties original natural drainage properties, thereby requiring the tunnel to correct this imbalance.  In this case, the tunnels blockage
also could create a public safety hazard by evidence of localized road flooding.

Over the years, the Town has helped the NFA’s efforts to keep the debris from blocking the tunnel.  Earlier this year the Town, unbeknownst to the
NFA, partially restored the flow and replaced the old tunnel grating with a new design.  The Town also restored some of the tunnel stones to their
original location after their having fallen due to a combination of erosion.  

Shortly thereafter, vandals unfortunately removed this grating thereby providing the beaver’s unfettered access to the tunnel.  The beavers not only
plugged up this tunnel but also plugged up a secondary overflow pipe which proved to raise the water level over 4 feet.  Within 24 hours of our
clearing the overflow pipe, the beavers would plug it back up.  We needed the water level to lower significantly before we could even start to
remediate the tunnel blockage.  This routine went on for several weeks at which point it time, we needed to attack the blockage at the tunnel itself.  
This required the NFA to hire a contractor with a specialized excavator to reach into the water and lift out the debris.

If it were only that simple.  The blockage was not just infront of the tunnels entrance.  As we unearthed tunnel to clear the debris we found that the
blockage protruded 25 feet into the tunnel.  This required significantly more time and money than initially estimated. After 2 long days of hard work,
the blockage was cleared sufficient to permit the water level to drop 2-3 feet.  After a week of draining, this also permitted the water level to drop
sufficiently for NFA’s caretaker, Steve Maksel, to stand in the tunnels opening and reach in another 6-8 feet to clear most all of the large debris.  
Within a few hours the water level on both sides of the rail bed had equalized at a level which the tunnel and spillway were initially designed to

Believe it or not every single day until the water level was ultimately equalized, the beavers came back nightly serving to raise the water level
slightly.  The beavers are quite ingenious; and I have a new appreciation for these creatures.  When we removed their evenings work it was clear
the beaver’s instinctual logic provided specific positioning of sticks and materials to minimize the waters flow and catch other debris they floated in.  
The beavers are apparently attracted and driven to stop the sound of flowing water.  Once the flow stopped – they appeared defeated and went
away for several weeks.

A few weeks later the NFA was called and informed that the road was flooding and that beavers came back to impose their wrath – yet again – on
the NFA.  We investigated and to our good fortune found out that the beavers moved across the street onto a neighboring property and started
“doing what beavers do” – they plugged up the pipe going under the road.  This caused the neighbors property to flood and flooded the road.  
Good for the NFA this time – not good for the neighbors.  The Town helped this time unplugging the pipe – flushing enormous volumes of water to
flow back onto our property.  Guess what – the flow of water returned to the tunnel again – only to invite back our friends the beaver.

We have identified many solutions, including the obvious; however, no solution appears to be maintenance free.  All solutions will require some level
of maintenance while active beavers are residing on our property.  With limited resources we need to allocate a lot less time to this 15 acre preserve
and focus on the other 1,000 plus acres we own and care for.   If you are an expert or want to share some civil engineering expertise with us for
some ideas we would love to hear from you.  Please email or call 203-270-3650 to leave a message
and we will call you back.