Monitoring river quality for the Savannah harbor deepening

Editor’s Note: This post was written by Brian E. McCallum, Assistant Director with the U.S. Geological Survey (USGS) Georgia Water Science Center. In this post, McCallum explains the USGS role in working with the U.S. Army Corps of Engineers to perform river monitoring in support of the Savannah Harbor Expansion Project (SHEP).

The USGS has been requested by the Corps’ Savannah District to install and operate a hydrologic and water-quality monitoring network within the Savannah River estuary in support of SHEP.

The intent of the SHEP is to deepen the shipping channel by 5 feet to a new authorized depth of 47 feet, allowing larger container ships to use the Port of Savannah.

The primary environmental concern associated with the project is the potential for increased salinity encroachment, which may damage fragile ecosystems and decrease the dissolved oxygen levels within the Savannah River.

After years of field studies by a diverse group of federal, state, and local stakeholders, the Corps, along with its agency partners, developed a vast monitoring network to ensure the project functions as intended. The USGS is responsible for installing and maintaining a network of surface-water sites that will be the primary indicators of change in the estuary.

The Corps and the USGS installed a chloride monitoring network to assess water quality near the City of Savannah's industrial and domestic water intake in the upper Savannah River estuary. Three stations (02198840, 02198820, and 02198810) collect real-time specific conductance and salinity data to monitor the potential for saltwater encroachment in Abercorn Creek.  An automated sampler is installed at station 02198810 to collect water-quality samples over a 28-day high-tide cycle. The data collected will be used to correlate chloride levels to specific conductance. Stations 02198820 and 02198810 also have new chloride probes to test the possibility of providing direct readings of chloride levels in Abercorn Creek.

The Corps and the USGS installed a chloride monitoring network to assess water quality near the City of Savannah’s industrial and domestic water intake in the upper Savannah River estuary. Three stations (02198840, 02198820, and 02198810) collect real-time specific conductance and salinity data to monitor the potential for saltwater encroachment in Abercorn Creek. An automated sampler is installed at station 02198810 to collect water-quality samples over a 28-day high-tide cycle. The data collected will be used to correlate chloride levels to specific conductance. Stations 02198820 and 02198810 also have new chloride probes to test the possibility of providing direct readings of chloride levels in Abercorn Creek.

The SHEP hydrologic and water-quality monitoring network involves installing five new stations with tidal discharge and continuous water-quality instruments, and upgrading eight existing stations to an equivalent data instrument array. Work began in mid-August 2013 and was completed by early November. Corps contractors installed platforms at four of the new stations to protect the equipment from flood waters.

Hydrologic monitoring is designed to occur during all three phases of channel construction: a 1-year pre-construction phase; a 4-year construction phase; and a 10-year post-construction phase. Additionally, a subset of the proposed locations would continue to be operated well beyond the post-construction phase.

All data are available in real-time on the USGS National Water Information System Web Interface (also referred to as “NWISWeb”) located at http://waterdata.usgs.gov. These data will also be provided to the SHEP database managed by the Corps of Engineers.

This monitoring network will allow the Corps to make frequent assessments of river conditions and provide valuable, real-time data they can use to make adaptive management decisions.

~By Brian E. McCallum, Assistant Director, USGS Georgia Water Science Center

A close-up view of one of four water quality monitoring stations that features a raised platform to protect the equipment from high waters

A close-up view of one of four water quality monitoring stations that features a raised platform to protect the equipment from high waters.

 

About US Army Corps of Engineers Savannah District

The U.S. Army Corps of Engineers Savannah District oversees a multi-million dollar military construction program at 11 Army and Air Force installations in Georgia and North Carolina. We also manage water resources across the Coastal Georgia region, including maintenance dredging of the Savannah and Brunswick harbors; operation of three hydroelectric dams and reservoirs along the upper Savannah River; and administration of an extensive stream and wetland permitting and mitigation program within the state of Georgia. Follow us on Twitter @SavannahCorps and on Facebook.com/SavannahCorps
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  • Steve

    My concern is what happens if increased salinity ends up actually happening how will it be mitigated. The obvious answer is increased outflows from upstream and at the expense of the stakeholders upstream. I see no upside for anyone accept for the people in Savannhah. They receive a deeper channel which increases revenue and jobs while everyone else then shares their precious resource to limit damage that is self imposed on Savannah.
    If the decision is to increase outflows can upstream stakeholders expect compensation from Savannah for the loss of jobs, tourist dollars, land values etc?.

    • Thanks for posting a comment Steve. To answer your concern up front, no increase in outflow will be required to mitigate for the Savannah Harbor Deepening Project, (SHEP). We designed the SHEP using the 1996 Savannah River Basin Water Control Manual (without the new drought plan). The design takes into consideration historic droughts and river flows based on current outflows. We will not require additional outflows to support the SHEP. For more details about how we plan to mitigate for the deepening, you can see our post from April 2013, here: . Hope this helps! ~Russell Wicke

      • Mark Welborn

        That’s interesting Russell. It seems logical that a deeper channel would require a larger volume of water….that water would have to come either upstream from the Atlantic or downstream from the upper basins very limited water resource. If salt water is acceptable in that area great. If the usage in that area requires fresh water then it has to come from the reservoirs. Right?

        • You are correct. The water would come from the Atlantic. Given the extreme tide differential, it must be so. In fact, the tide is so influential at the port, the river reverses direction in Savannah every day when the tide comes in. And the port is nearly 30 miles inland. Therefore the harbor is already mostly salty anyway. The channel deepening will only push the salinity spike a bit further upstream. This should have little impact, and even then only during the hottest days, at high tide, and with low river flows. On those occasions there is mitigation in place (that does not include increased releases) to counter the impacts. I hope this answers your question, but don’t hesitate to clarify your question if I missed the mark. ~Russell Wicke

          • John Stokes

            Russell: What and where is the mitigation for those hottest, highest tide, low flow days?

          • Hello John – thanks for your question. Part of the deepening project involves constructing a raw water storage impoundment near Savannah Hilton Head Airport, upstream from Savannah, Ga. The municipality of Savannah withdraws water from the river in this area to supplement its water supply. Our research indicates that on the highest tides and lowest flows of the river, it is possible that near the city’s intake the increased chlorides could raise the cost of water purification. The raw water storage impoundment will solve this issue. It will cover approximately 40 acres and maintain a capacity of 77 million gallons. When the conditions occur where the chlorides become too high (low flow, high tide), the city will draw water from the impoundment until the tide goes back out.

            As for the hottest days, there are concerns that dissolved oxygen levels in the river may decrease. One of the main mitigation features of SHEP is a dissolved oxygen injection system that will maintain the oxygen levels in the harbor at pre-deepening conditions. An interesting note: even if we attempted to control oxygen levels in the harbor via releases at Thurmond, the effort would be insufficient to have an impact at the harbor.

            Hope this helps John. ~Russell Wicke

  • Joyce

    It seems to me you would need to go through the 100 year study before you could accurately make any decisions relating to deepening the channel.

    • Hello Joyce – thank you for commenting. I’m not sure I understand fully. I think you are writing about the flood reallocation study (the one that will provide recommendations on the winter draw down). Am I correct? If so, can you explain further the connection you have in mind between that and the deepening project in Savannah? ~Russell