From the Department of Environmental Quality Permit
Water Withdrawal and Instream Flow Conditions
editors note:
The current volume of useable water in the Ragged Mountain Reservoir is 0.46 billion gallons (BG).
The permit stiplulates stream release from SUGAR HOLLOW based on the volume of water in RAGGED MOUNTAIN RESERVOIR of
volumes below, equal to or between 0.66 BG, 1.1 BG, and 1.53 BG
The current volume of useable water in the entire system is 1.6 BG.
The permit stiplulates stream release from SOUTH FORK based on the volume of water in THE ENTIRE SYSTEM of
volumes below, equal to or between 1.36 BG, and 2.36B gallons (= full)
DEFINITIONS:
Operational
With respect to the expanded Ragged Mountain Reservoir, the facility shall be deemed
"operational" upon issuance of a temporary operation and maintenance certificate by the
Virginia Department of Conservation and Recreation, even though the Reservoir may not
fill with water to its full normal pool elevation until some time thereafter.
Initial Fill:
With respect to the Expanded Ragged Mountain Reservoir, "initial fill" refers to the
period of time beginning when the facility becomes operational (as defined above), and
ending when either (a) the water level at the facility for the first time reaches the normal
pool elevation, or (b) a permanent operation and maintenance certificate is issued for the
facility by the Virginia Department of Conservation and Recreation, whichever is later.
Useable Storage:
"Useable storage" is the volume of water in a reservoir that is
available for withdrawal to use for water supply purposes and is generally that
volume of water located above the dead storage pool of the reservoir. It is less than total volume.
- Total downstream flow provisions before the expanded Ragged Mountain Reservoir is operational (editors note: =current state)
- From South Fork Rivanna Reservoir (SFRR)
- When the water level at SFRR is at or above the spillway elevation of 382 feet, SFRR will be spilling water on a daily basis and no additional total downstream flow is required
- When the water level at SFRR is below the spillway elevation of 382 feet total downstream flow will be at least 8 mgd or natural inflow, whichever is less
- From Sugar Hollow Reservoir: (SHR)
- When the water level at SHR is at or above the spillway elevation of 975 feet, SHR will be spilling water on a daily basis and no additional total downstream flow is required
- When the water level at SHR is below the spillway elevation of 975 feet, total downstream flow past the dam will be at least 0.4 mgd or natural inflow, whichever is less.
- From Ragged Mountain Reservoir (RMR), there are no new requirements.
- Total downstream flow provisions after the expanded RMR is operational but before the Pipeline from SFRR to RMR is operational
- From South Fork Rivanna Reservoir: (SFRR)
- If total useable storage available to the Urban Water System is equal to or greater than 2.36 billion gallons (editors note: = full) , total downstream flow past SFRR must be at least 70% of the natural inflow or 1.3 mgd, whichever is greater, subject to the following exceptions:
- No total downstream flows in excess of 20 mgd shall be required
- If useable storage in SFRR has been exhausted (i.e., the water level is at or below the lowest operable water supply intake), then total downstream flow past SFRR shall be whatever volume of water enters that intake unless or until the total downstream flow past SFRR equals or exceeds 1.3 mgd.
- If total useable storage available to the Urban Water System is between 1.36 billion gallons and 2.36 billion gallons, total downstream flow past SFRR must be at least 50% of the natural inflow or 1.3 mgd, whichever is greater, subject to the exceptions as above.
- If total useable storage available to the Urban Water System.is less than 1.36 billion gallons, total downstream flow past SFRR must be at least 30% of the natural inflow or 1.3 mgd, whichever is greater, subject to the exceptions as above.
- From Ragged Mountain Reservoir, there are no new requirements.
- From Sugar Hollow Reservoir, when the water level in Sugar Hollow Reservoir is above the lowest operable water intake and the Expanded Ragged Mountain Reservoir has not completed its initial fill:
- If the useable storage in Ragged Mountain Reservoir is equal to or greater than 1.53 billion gallons total downstream flow past Sugar Hollow Reservoir must be at least 100%.of the natural inflow to Sugar Hollow Reservoir; or 10 mgd, whichever is less
- If the useable storage in Ragged Mountain Reservoir is equal to or greater than 1.1 billion gallons but less than 1.53 billion gallons, total downstream flow past Sugar Hollow Reservoir must be at least 100% of the natural inflow to Sugar Hollow Reservoir; or 2 mgd, whichever is less
- If the useable storage in Ragged Mountain Reservoir is equal to or' greater than 0.66 billion gallons but less than 1.1 billion gallons, total downstream flow past Sugar Hollow Reservoir must be at least 100% of the natural inflow to Sugar Hollow Reservoir; or 1 mgd, whichever is less
- If the useable storage in Ragged Mountain Reservoir is less than 0.66 billion gallons, total downstream flow past Sugar Hollow Reservoir must be at least 100% of the natural inflow to Sugar Hollow Reservoir; or 0.4 mgd, whichever is less
- From Sugar Hollow Reservoir when the water level in Sugar Hollow Reservoir is above the lowest operable water intake and the Expanded Ragged Mountain Reservoir has completed its initial fill
- If the useable storage in Ragged Mountain Reservoir is equal to or greater than 1.53 billion gallons, total downstream flow past Sugar Hollow Reservoir must be at least 100%.ofthe natural inflow· to Sugar Hollow Reservoir; or 10 mgd, whichever is less.
- If the useable storage in Ragged Mountain Reservoir is less than 1.53 billion gallons, then total downstream flow must be at least 100%·of the natural inflow to Sugar Hollow, or 2 mgd, whichever is less.
- When the water level in Sugar Hollow Reservoir is at or below the lowest operable water intake, RWSA must fully open the total downstream flow control device supplied from the lowest operable water intake and leave it in the fully open position until the water level in Sugar Hollow Reservoir is again higher than the lowest water intake
- From Ragged Mountain Reservoir, RWSA must provide a total downstream flow past the dam· of at least 23,800 gpd