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DEC/DEP published Interim Release Protocol

In October, the DEC and DEP agreed upon an Interim Ashokan Reservoir Release Protocol (Protocol), which is available here for download.

  Interim Release Protocol (135.8 KiB, 1,484 hits)
DEC/DEP Interim Ashokan Release Protocol

  Water Quality Monitoring for Releases (68.7 KiB, 1,401 hits)
Water Quality Monitoring Plan for Release Channel Operations

The Lower Esopus Watershed Partnership, as part of the Ashokan Release Working Group, is compiling comments on the protocol from participating municipalities to provide DEC and DEP with feedback.

The protocol includes provisions for community beneficial releases, flood mitigation releases, and turbidity control releases. The interim protocol is driving recent reservoir releases as the DEP aims for a 90% Conditional Seasonal Storage Objective outlined in the protocol to create a void in the reservoir for flood mitigation and turbidity control. Since storms Irene and Lee filled the reservoir with turbid runoff, recent releases in the lower Esopus Creek have been noticeably turbid with fine colloidal clay sediment.

Snapshot of Rainfall and Gauge Data for Irene

Hurricane Irene: The Storm Event of August 28-29th, 2011

Rainfall
The storm event experienced in Ulster County during August 28-29 was greater than a 100 year rainfall event at some locations. Almost all of Ulster County received more than six inches of rain and some places exceeded eight inches of precipitation. The rainfall at Slide Mountain (11.53 inches) was considered at least a 200 year event while rainfall at Mohonk and in Rosendale was considered at least a 100 year event.

Stream Flooding- Accordingly, many streams also set flood records. Record flood levels were experienced across the County including along the Upper Esopus Creek, the Stony Clove Creek in Phoenicia, the Rondout Creek in Rosendale, and a near record crest at the Walkill River in Gardiner. This storm event is estimated to be an 80 year storm event on some of our larger streams and greater than a 100 year event in our mountain streams.

Lower Esopus
Although flooding was severe on the Lower Esopus Creek, flood elevations did not exceed the record flood of 2005. This is due in part to the void in the Ashokan reservoir which captured some flood water and delayed (attenuated) the flow from the Upper Esopus to the Lower Esopus. The storage and attenuation of the reservoir is evidenced by the gage data below.
 
The first peak is the rapid rise in water levels associated with the actual rainfall event. The second peak is associated with spill from the reservoir. The second flood peak was not as high as the first. This indicates that spill from the reservoir did not create the highest flood elevations. The highest flooding experienced along the Lower Esopus was from the actual rainfall event in the lower watershed and sub-watersheds (Sawkill, Plattekill), not from the spilling of the reservoir. Additional storage void in the reservoir would not have had any effect on lowering the first peak of the storm.

Irene crests at Mt. Marion:
08/28/2011 16:15 EST 25,200 cfs 25.39 ft
08/29/2011 14:45 EST 19,100 cfs 23.95 ft

Historical crests:
(1) 26.46 ft on 04/03/2005
(2) 25.10 ft on 04/26/1977

This storm demonstrated the protective ability of the reservoir to mitigate flooding on the lower Esopus. Coldbrook gauge on the upper Esopus Creek was 2.76 feet higher during Irene than in 2005 and 1.4 feet higher than its previous record (1980). Given the flood levels experienced on the Upper Esopus Creek, if the reservoir had been at capacity at the beginning of the rain fall event, we would have likely seen peak flood elevations of up to three feet higher on the Lower Esopus. Flood peaks at this level would have significantly exceeded the record flood of 2005 and caused even more damage. 

The Ashokan Waste Channel was releasing at 600 MGD during the first peak in creek level. The Waste Channel was shut off at 8/28/2011 18:35:00. As the stage of the Mt. Marion gauge rises, the contribution of 600 MGD release to stage height decreases as follows (600 MGD = 930 cfs):

@ 17 ft, 930 cfs = 0.75 ft of additional height
@ 18 ft (Action Stage), 930 cfs = 0.6 ft of additional height
@ 20 ft (Flood Stage), 930 cfs = 0.5 of additional height
@ 22 ft (Moderate Flood Stage), 930 cfs = 0.27 ft of additional height
@ 24 ft (Major Flood Stage), 930 cfs = 0.22 ft of additional height

At the crest of 25.39 ft, Ashokan Release was contributing less than 3 inches of additional height at Mt. Marion. Of the 25,200 cfs at peak flow, the release was contributing 3.69%.

The East Basin started spilling at 8/28/2011 17:55:00 at 3100.00 MGD and peaked at 8/28/2011 22:10:00 at 9540.00 MGD, 10 hours after Coldbrook gauge crest. The second crest at Mt. Marion occurred 16.5 hours after spill crest and 26.5 hours after Coldbrook gauge crest.

Coldbrook crest
08/28/2011 12:00 EST 75,800P 23.34P

Historical crests:
(1) 21.94 ft on 03/21/1980
(2) 20.70 ft on 03/30/1951
(3) 20.58 ft on 04/03/2005

Tidal Surge
Flooding along Lighthouse Drive in Saugerties in the tidal portion of the Esopus Creek was primarily due to storm surge that traveled up the Hudson River from the Atlantic Ocean. Based on water level data from observation stations along the Hudson River, storm surge from Irene coincided with high tide at New York Harbor/Battery Park shortly after 8 AM on Sunday, 8/26, and rolled up the Hudson River, reaching Poughkeepsie at about 12:45 PM, Saugerties around 2:00 PM and Albany at roughly 5:15 PM. Storm surge added nearly 4 feet to the high tide height at the Battery. At Poughkeepsie, river levels were 3 feet above normal high tide. At the Saugerties Lighthouse, the crest in water level was measured at 8.15 feet, which was about 3.5 feet above normal high tide. As a general rule, flood runoff is rarely enough to raise the mainstem Hudson River above sea level further south than Catskill. Irene was an exception to this rule but did not affect river levels near as much as surge. Runoff peaked after the surge event and contributed roughly 1 foot of height at the subsequent high tides on 8/29 at the Saugerties Lighthouse.

Public input sought for impact assessment

Impact Assessment Questionnaire Now Available For Public Input.

Kingston, NY- The Ashokan Release Working Group announced today the availability of an Impact Assessment Questionnaire for residents and businesses along the Lower Esopus. The Questionnaire was developed to gather information about impacts or changes that individuals observed or experienced along the stream that they believed may be related to releases of turbid water from the Ashokan Reservoir that occurred from October 7, 2010 through February 1, 2011. The questionnaire may be filled out on-line by visiting the Working Group’s website at http://ashokanrwg.org. Paper copies will be mailed to property owners along the creek and are available at the town and village halls along the lower Esopus and at the Ulster County Department of the Environment, 17 Pearl Street PO Box 1800, Kingston, NY 12402. Questions regarding the content of the questionnaire can be referred to the Ulster County Department of the Environment at 845-338-7287.

The Ashokan Release Working Group, formed in January over concerns about water releases from the Ashokan Reservoir, will use the information gathered from these questionnaires as part of the assessment of the impacts of this past release and to help inform decisions regarding potential future releases. The Working Group urges land owners and others who have observed or experienced impacts to complete the questionnaire. Paper copies should be returned to the Ashokan Release Working Group care of Ulster County Department of the Environment, 17 Pearl Street PO Box 1800, Kingston, NY 12402 by May 31, 2011.

The Ashokan Release Working Group consists of representatives from the Ashokan Foundation, City of Kingston, County of Ulster, Esopus Creek Conservancy, Lower Esopus Watershed Partnership, New York City Department of Environmental Protection, New York Public Interest Research Group, New York State Department of Environmental Conservation, New York State Department of Health, RCAP Solutions, Riverkeeper, Towns of Hurley, Marbletown, Olive, Saugerties and Ulster, United States Environmental Protection Agency and the Village of Saugerties. One of the goals of the Working Group is to assist with the development, implementation and review of an assessment of ecological, physical and economic impacts of the releases.

Ashokan Release Working Group Mission:
The Ashokan Release Working Group (ARWG) will, through a collaborative consensus building process:
·Assist with the development, implementation and review of an assessment of ecological, physical and economic impacts of the releases that occurred from October 7, 2010 through February 1, 2011.
·Develop a protocol for, and ongoing monitoring and evaluation of, releases from the Ashokan Reservoir to advance the protection and improvement of water quantity and quality and provide flood hazard reduction benefits of the lower Esopus Creek.
·Ensure the release protocol is protective of the ecological, physical and economic interests of the lower Esopus and its adjoining communities while remaining protective of the NYC water supply

DEP opens Ashokan waste channel today

The New York City Department of Environmental Protection announced that it will release water from the West Basin of the Ashokan Reservoir starting today for up to one week. The release is for intended for flood-control and drinking water quality. See statement from NYC DEP Deputy Commissioner Paul Rush:

FOR IMMEDIATE RELEASE:
March 31, 2011
No. 24

Statement from NYC Environmental Protection Deputy Commissioner for
Water Supply Paul Rush On Tomorrow’s Activation of the Ashokan Waste Channel

“Following a request from the Town of Hurley, and with the agreement of the State Department of Environmental Conservation and Ulster County, DEP will activate the Ashokan Reservoir Waste Channel starting tomorrow morning for up to one week,” said Deputy Commissioner Rush. “Activating the waste channel is being undertaken in response to a snow storm expected to start tonight that will enhance the potential for higher flows due to snowmelt in the coming days. These releases will increase the reservoir’s ability to capture runoff by creating a void in the west basin of the reservoir, providing enhanced flood protection for communities south of the Ashokan Reservoir along the lower Esopus Creek. This will also provide an additional benefit of protecting water quality by reducing the amount and likelihood of spillage from the more turbid west basin into the higher quality east basin, thereby protecting the drinking water of approximately 8 million New York City residents and the roughly 160,000 residents of towns that rely on the Catskill Aqueduct such as New Paltz and High Falls in Ulster County, and New Windsor and Cornwall in Orange County.”

The latest information from the National Weather Service on the coming storm indicates that the reservoir could spill, increasing the potential for flooding in the lower Esopus. The action agreed to today will release up to 600 million gallons per day from the Ashokan Reservoir for the next week, depending on existing flows in the lower Esopus Creek. These releases will be discontinued if the stream gage on the lower Esopus Creek located at Mt. Marion is within one foot of flood action stage (18 feet) and the National Weather Service forecasts potential flooding.

The waste channel is a concrete canal used to convey water released in a controlled manner from the reservoir through the upper and lower gate chambers to the Little Beaverkill stream and the lower Esopus Creek. Located in Ulster County, the Ashokan Reservoir is approximately 13 miles west of Kingston and 73 miles north of New York City. It was formed by the damming of the Esopus Creek, which eventually flows northeast and drains into the Hudson River. The reservoir holds 127.9 billion gallons at full capacity and was opened in 1915.

DEP manages the city’s water supply, providing more than 1 billion gallons of water each day to more than 9 million residents, including 8 million in New York City, and residents of Ulster, Orange, Putnam and Westchester counties. New York City’s water is delivered from the Catskill, Delaware, and Croton watersheds that extend more than 125 miles from the City, and comprises 19 reservoirs, and three controlled lakes. For more information, visit www.nyc.gov/dep or follow us on Facebook at www.facebook.com/nycwater.

Flood-mitigation release announced for Ashokan

Statement from NYS Environmental Conservation Commissioner Joe Martens and NYC Environmental Protection Commissioner Cas Holloway On Today’s Activation of the Ashokan Waste Channel

“Earlier today, after close consultation with and agreement from Ulster County, the State Department of Environmental Conservation, the New York State Department of Health, and the Environmental Protection Agency, DEP activated the Ashokan Reservoir Waste Channel for up to one week,” said Commissioner Holloway. “Activating the waste channel will increase the reservoir’s ability to capture runoff from intense storms by creating a void in the west basin of the reservoir ahead of tonight’s forecasted storm, providing enhanced flood protection for communities south of the Ashokan Reservoir along the lower Esopus Creek. This action, which reduces the amount of spillage from the more turbid west basin into the higher quality east basin, will also help protect the drinking water of approximately 160,000 residents of towns that rely on the Catskill Aqueduct such as New Paltz and High Falls in Ulster County; New Windsor and Cornwall in Orange County; several towns in Westchester County, including Yorktown and Ossining; as well as the residents of New York City.”

“We concur that activation of the Ashokan diversion channel is appropriate at this time to limit adverse flooding in communities along the Lower Esopus Creek and reduce turbidity in water flowing toward the New York City drinking water system,” said Joe Martens, DEC Commissioner. “Flood ‘action levels’ in the Lower Esopus will be actively monitored and adjustments to the diversion channel output will be made as needed.”

The latest information from the National Weather Service on the coming storm indicates that the reservoir could spill, increasing the potential for flooding in the lower Esopus. The action agreed to today will release up to 600 million gallons per day from the Ashokan Reservoir for the next week, depending on existing flows in the lower Esopus Creek. These releases will be discontinued if the stream gage on the lower Esopus Creek located at Mt. Marion is within one foot of flood action stage (18 feet) and the National Weather Service forecasts potential flooding. This is the first activation of the Ashokan Reservoir release since February 1, 2011.