FOR IMMEDIATE RELEASE06-13
March
13, 2006
Contact:
Ian Michaels
(718) 595-6600
City
to Implement Reservoir Spill Control at Gilboa Dam
Program
similar to Pepacton and Neversink to be in place after 2008 reconstruction
projectWaste
channel to open this week at Ashokan Reservoir
New York City Deputy Mayor Dan Doctoroff announced
this morning that the City will implement a comprehensive reservoir
spill control program at the Gilboa Dam after new release works
are installed during the full-scale reconstruction project that
will begin in 2008. Doctoroff made the announcement at a
meeting in Schoharie with Schoharie County and local officials.
Deputy Mayor Doctoroff, Department of Environmental
Protection (DEP) Commissioner Emily Lloyd and others then traveled
with the officials to Gilboa to review the ongoing dam stabilization
project, which will bring the dam up to State standards well before
the full-scale project begins.
“Bringing reservoir spill control to the Schoharie
Reservoir will help protect people and property downstream during
the spring rains and thaw,” said Deputy Mayor Doctoroff. “The
full-scale reconstruction project that will start in two years
will include the new valves and pipes to enable this type of relief,
and New York City is committed to providing that relief to the
residents downstream. On behalf of myself and Mayor Michael
Bloomberg, I would like to thank them for their patience and understanding
during this difficult time.”
Commissioner Lloyd said, “This demonstrates
the City’s commitment to be a good neighbor in and near the
watershed. We’ve taken every step to make the Gilboa
repairs as quickly as possible, we’ve worked with local agencies
to assist in their disaster response planning and we’ve reached
out to residents to help keep them informed. Future reservoir
spill control is another measure to show that we care about their
well-being.”
The reservoir spill control program at Gilboa will
be modeled after the existing measures already in place at the
Pepacton and Neversink reservoirs. During the winter at those
two reservoirs, the New York City Department of Environmental Protection
(DEP) maintains voids in the reservoirs equal to one-half of the
melted snow pack surrounding each reservoir. Absent any significant
snow pack, the DEP maintains the voids at a level equal to the
amount of water that would runoff into each reservoir from a one-inch
rainfall occurring over a six-hour period.
The reservoir spill control measures will be presented
by the DEP to the State Department of Environmental Conservation
(DEC) for approval. Unlike the Pepacton and Neversink reservoirs,
where any changes to the downstream water releases require the
approval of all the Delaware River basin states, reservoir spill
control at the Schoharie Reservoir can be implemented with just
the approval of the State and the City.
Stabilization Project
Doctoroff’s visit came at a time of major progress
in the work at the Gilboa Dam. An $18.3 million contract
to install 79 post-tensioned anchoring cables was awarded to Nicholson
Construction on March 8. The 34 anchors that will be installed
in parts of the dam that are thought to be potentially unstable
will be completed by early August. The other 45 anchors in
more stable parts of the dam will be done by November.
The anchoring work is the final stage of the stabilization
project and will bring the dam into full compliance with DEC standards
for existing dams. Anchoring cables are being installed along
the top of the dam and also on the downstream side near the spillway. Cables
are installed through holes drilled through the dam and then are
anchored both to the dam and to solid bedrock below. The
cables are then tightened, creating tension that helps to hold
the dam in place.
Before the anchoring work, DEP has completed installation
of four large siphons to help decrease water levels in the reservoir. The
four siphons have a capacity of 125 million gallons per day (MGD)
each, and extend over the dam and onto the downstream spillway. The
siphons were completed at a cost of $3.04 million.
Prior to the completion of the siphons, the DEP completed
installation of a 220-foot long by 5.5-foot high notch at the western
end of the dam. The removal of the notch, at a cost of $1.15
million, effectively lowered the capacity of the reservoir, relieved
pressure behind the dam and helped to secure a dry work area for
the current anchoring work.
Full-Scale Reconstruction
Though the Gilboa Dam will meet State standards
for existing dams at the end of the stabilization project, the
$200+ million full-scale reconstruction project will increase the
stability of the dam even more, allowing it to meet DEC standards
for new dam construction when complete in 2011.
The project had been planned to begin in 2010 but
was advanced to 2008 during the recent stabilization project. The
project will include new water release works that will enable downstream
releases to the Schoharie Creek. The project will also include
rehabilitation of the intake structure for the Shandaken Tunnel,
which conveys water south from the reservoir to the Esopus Creek. From
there the water enters the Ashokan Reservoir and eventually the
Catskill Aqueduct.
Ashokan Reservoir Release Channel
Water levels in the Ashokan Reservoir had already
been well above normal because of record rainfall in October 2005. Flows
through the Shandaken Tunnel were then increased in fall 2005 after
the discovery of the stabilization problem at the Gilboa Dam.
To bring water levels down in Ashokan, the DEP will
this week re-activate the Ashokan Release Channel. The channel
runs through the Ashokan Field Campus of SUNY New Paltz and eventually
empties into the lower Esopus below the Ashokan’s spillway
channel. The channel will allow the DEP to make up to 600
MGD in controlled releases from the Ashokan. DEP has leased
the entire Ashokan Field Campus for this purpose through mid-June.
In another attempt to lower water levels in Ashokan,
the DEP has also maximized flow through the Catskill Aqueduct since
the Gilboa stabilization project began. Flow through the
aqueduct would normally be 300 – 350 MGD, but has been maintained
at 580 MGD to increase diversions from Ashokan.
Increased Monitoring
A major part of the Gilboa stabilization project
has involved improvements to monitoring of the dam and other areas. Since
the project began, the DEP has installed 24-hour-a-day lighting,
surveillance and remote video monitoring of the dam. There
is now also automated snow monitoring of the Schoharie watershed,
along with remote computer monitoring of stream gauges at the Gilboa
and Prattsville. Flow monitoring has also been installed
at the Ashokan Release Channel.