Tanks, Pumps & Pipes Suggested for Pine Brook Flooding
by Judy Silberstein
(September 28, 2005) Plowing their way through one of the meatiest
agendas in months, the Larchmont Village Board received recommendations
from engineers on how to handle flooding along Pine Brook
Drive; conducted a public hearing on a new ordinance to require more
scrutiny by the Planning Board over partial demolitions and major additions
to homes; and
heard complaints about the condition of the tunnel leading from the train
station to a parking lot in the Town of Mamaroneck. And that was only
a few of the topics on the board's list.
This Week: Flood Recommendations
Next Week: Reining in Renovations + More on the Train Station Tunnel
Controlling floods in a low-lying
area of Larchmont’s Pine Brook
area could be accomplished with tanks, pumps and pipes, at a probable
cost of more than $1 million dollars. That was the suggestion from
consulting engineers Dolph Rotfeld and Brian Coyne, who presented their
views on Monday, September 26 at a Larchmont Village Board meeting packed
with residents from the impacted neighborhood. The engineers have been
intensively studying the area since November of 2004 and presented an
interim update in July. (See: Engineers
Report on Larchmont Flooding: Interim Update.)
Mr. Rotfeld explained that the storm waters that gush from the
drains on Pine Brook Drive under particular conditions are funneled
from three separate watersheds. In a major storm, known as a “25-year
cubic feet per second can come rushing down from the Beechmont section
of New Rochelle. Another 600 cubic feet per second surge into the pipes
from the Sheldrake area of New Rochelle and Town of Mamaroneck, and
an additional 250 from the Chatsworth Avenue part of Larchmont. A small
tributary contributes 30 to 50.
This amounts to “three trains on one track” said Mr. Rotfeld,
describing the convergence of more than 1000 cubic feet of water, unfortunately,
at a section of pipe that is both low-lying and increasingly narrow.
the problem: during high tides, the pipe is often full even before
any rainwater appears.
His recommendation called for two steps: diverting a portion of the
water away from the choke point and building a storage and pump system
to manage the rest. The “guestimated” price tag ranged
from $1.3 to $1.5 million to handle a “two-year event” and
up to 60% more for the larger storms of a “25-year event.” Mr.
Rotfeld wryly commented that last year there were two “25-year
storms” in the space of three weeks.
Just diverting the Chatsworth
water into a separate pipe starting at Howard Street and Mayhew Avenue
would be far cheaper – perhaps $350,000 to $400,000 - and might
control much of the flooding in a typical storm. However, Mr. Rotfeld
was skeptical that diversion would suffice, particularly in a major
The pump approach would focus on Pine Brook Drive near the intersection
of Beverly Place and would entail digging a large underground storage
tank with three to six submersible pumps powered by an above ground
generator. Three pumps could remove 5000 gallons of water per minute;
six pumps would double the capacity.
Trustee Anne McAndrews asked the engineers about the potential impact
of work at Beechmont Lake in New Rochelle, which for years has been
viewed as a potential mechanism for retaining floodwaters that could
be gradually released. Mr. Coyne rejected that approach. “Even
if it were drained bone dry, it’s too small to make an impact,” he
“I was surprised to hear that,” said Trustee Mike Wiener
in a later interview. He’s been working towards that solution
since coming on the board in 2002. (See: Summer
Storm Damages Area) And New Rochelle is starting to make progress
on fixing Beechmont Lake (see: Engineers
Report on Larchmont Flooding: Interim Update). He noted the major
implication of the Rotfeld study is that: “The
models proved that we are so tide-dependent. When the tide is up, nothing
The engineer's chart indicates
how much water (blue) is in the pipe at different locations at high
tide. At the far right, the pipe near Kilmer Rd. and near Beverly Place
is almost filled - even before any rain water appears.
“”It’s a big project,” said Trustee Wiener. “A
big part of the decision would be how to fund it.” Mr. Rotfeld
indicated that one potential funding source, the Army Corps of Engineers,
had already declined to become involved based on their cost/benefit
What is the next step and what is the timetable, asked Eric Berg,
whose property backs onto Pine Brook Drive.
“I don’t have a step; I don’t have a timetable,” said
Mayor Bialo. “It’s a lot to chew on.