Over the past several months the occasional fan of Balancing the Basin has voiced concern about the expansion of Plant Vogtle on the Savannah River. Most of the concern focused on the increased water needs (and impacts on reservoir levels) of the two new nuclear reactors currently under construction near Waynesboro, Georgia. Stakeholders can put away those worries because the Corps of Engineers has not been asked nor has any plans to change reservoir release rates to support the new reactors.
In December, the Georgia Department of Natural Resources issued a water withdrawal permit to the consortium building the reactors, according to press reports. The permit allows the plant to withdraw a monthly average of 62 million gallons per day with a maximum daily limit of 74 million gallons, according to the permit issued by Georgia DNR.
This sounds like lots of water until one converts those figures into measurements that readers of this blog find familiar – cubic feet per second.
Avid fans of this blog know the release rates from the Corps’ three reservoir systems vary depending on reservoir levels. These release rates meet the congressionally-mandated purposes of the reservoirs:
- Flood risk reduction
- Water supply
- Water quality
- Fish and wildlife management
- Hydropower production
- Recreation
- Downstream navigation
The Corps manages the basin and owns and operates its dams and reservoirs. The states of Georgia and South Carolina issue withdrawal permits for water usage since the states own that resource. But back to the calculations.
During the permitting process, state regulators received comments directly concerning the amount of water to be withdrawn for the new reactors. “EPD [Georgia Environmental Protection Division] has confirmed that the nominal make-up water usage for [Plant Vogtle’s new] Units 3 and 4 cooling towers to be approximately 86 cfs or 56 MGD and likely not to exceed 136 cfs or 88 MGD,” according to Georgia DNR’s website. Along this point in the Savannah River, removing this much water equates to 1.2 percent of the average flow rates during normal plant operations. During maximum plant operations and low flow conditions the maximum water withdrawal only equals 3.2 percent of the river flow past Plant Vogtle. To see the source for this paragraph, read page 4 of this document.
On a typical summer day, the reservoirs lose much more than 136 cfs simply to evaporation and transpiration. Readers should also note the location downstream of Plant Vogtle. Steven’s Creek and other tributaries below Thurmond Dam contribute water to the river above the nuclear station.
Conclusion: The water withdrawal permits issued to Plant Vogtle will not impact reservoir levels or releases from Thurmond Dam.
~Billy Birdwell, Senior Public Affairs Specialist
Thanks Billy, you inspired additional research. This list shares the information.
1. As noted above, Vogtle is below the several Augusta area locations that require minimum flow rates.
2. Vogtle will mitigate potentially lower harbor DO levels by injecting O2 just above Savannah. These injections are in addition to O2 injections related to SHEP and should eliminate concern over low harbor DO levels resulting from increased Vogtle withdrawal rates.
3. The SHEP report states that the increased Vogtle withdrawal rate is within the range of error for model predictions.
4. The SHEP report states that the hydrodynamic model used to evaluate the wetland mitigation design has a roughly 80 percent chance of over predicting salinity induced wetland impacts from SHEP, which should eliminate concern over wetland salinity issues resulting from increased Vogtle withdrawal rates. Note that a 50% chance is average.
5. As noted above, GA EPD approved and GA DNR permitted the increased withdrawal rate. GA DNR would not have issued the permit if there had been additional DO concerns between the Vogtle site and the planned O2 injection location.
The planned Vogtle DO injections and SHEP wetland design modifications have mitigated any potential downstream flow rate issues related to increased Vogtle withdrawal rates.
~Ferris
Revisiting the withdrawal permits once again, just how many of these permits are out there? While this latest permit does not greatly impact the lake level, what is the sum of ALL the permits? How many of these permits were in existinance, say, 20-25 years ago verus the present?
Hi Hartwell Cove Dweller,
The effect that incremental increases in river withdrawal rates have on lake levels is a valid concern. The significant increase required for the Vogtle expansion does require mitigation. Obviously, the withdrawal does not affect the upstream river flow rate. The expressed downstream concerns are low DO levels in the Savannah Harbor and increased salinity in the estuary. The Vogtle DO injection system mitigates one and SHEP mitigates the other.
The point of Billy’s topic is that the withdrawal will have NO impact on lake levels, not even a little. Vogtle states their DO injection system will deliver twice the estimated oxygen requirement. The SHEP project provides an also overdesigned DO injection system and overdesigned salinity mitigation, the latter of which much more than compensates for a decrease of 1.2 to 3.2 percent in river flow rate past the plant.
DO is also an issue in the river section between the Vogtle plant and the Savannah Harbor, primarily in oxbows and side channels. However, these will be isolated or dry from low river levels long before the Vogtle increased withdrawal affects harbor DO.
Regarding individual permitted withdrawal rates, GA and SC issue these permits and will have the records. They do provide data for HEC models, but remain the record keepers.
I hope this helps.
~Ferris