The message the Washington Suburban Sanitary Commission wanted everyone to take away from it March 16 informational meeting is that a new pipe will allow the utility to access cleaner water.
WSSC is in the early stages of developing a submerged intake pipe which will extend about 500 feet into the Potomac River from their filtration plant on River Road.
The plant currently processes approximately 130 million gallons of drinking water each day for its customers in Montgomery and Prince George’s County. By building the new intake, WSSC says it does not plan to increase the amount of water per day it removes from the river.
Currently the plant uses an intake which is at the shoreline of the Potomac river. However, that intake is subject to what WSSC calls a disproportionately large influence from the Watts Branch. “Watts Branch flows come out … travel down the shore and end up in our intake,” said Mike Vitagliano, project manager with WSSC.
The problem with this, according to WSSC is that the Watts Branch, which travels through urbanized areas of Rockville, transports a high volume of sediment downstream which the plant then has to filter out.
By moving the intake pipe further into the river, to the other side of an unnamed island, the water utility will have access to cleaner water which is not influenced by the Watts Branch. “We’ll be able to treat it to a lower solids level,” Vitagliano said.
WSSC estimates that moving the pipe out into the river will save them $800,000 per year in operating costs. A preliminary estimate of construction costs for the pipe is $15 million.
In the past, environmental groups have criticized the plan as short-sighted, and questioned why WSSC could not simply clean up the Watts branch. “Instead of addressing the pollution problem at its source, they’re following in the footsteps of the Fairfax County Water Authority,” said Neal Fitzpatrick, of the Audubon Society.
The Fairfax County Water Authority built a new pipe into the Potomac last year, the Audubon society opposed its construction, primarily because of the fear that the Authority would take additional water from the River.
There has never been a study into the amount of water which the River needs in order to maintain an healthy environment. Currently 400-500 million gallons are removed from the river each day, when including all the various institutions which do so. The federal standard is that 100 million gallons must pass by Little Falls each day, but Fitzpatrick says that this number is not based on any science. “We don’t know what this is doing,” Fitzpatrick said. “We would like to have science now. We haven’t had it for 20 years.”
WSSC has repeatedly said that they do not wish to draw any additional water from the River.
Fitzpatrick did not attend the meeting because he did not believe it would be useful. “I don’t think WSSC is going to change their position,” he said.
While conceding the environmental benefits if Watts Branch were to be cleaned up, WSSC does not think that it is the best way to solve the problem of their water quality.
“We can’t rely on that for short-term impacts,” Vitagliano said.
Montgomery County is currently studying ways to rehabilitate the Watts Branch, and WSSC took these studies into account. However, using the most aggressive set of management practices would only result in a 15 percent decline in the amount of solids in the water, said WSSC Senior Scientist Plato Chen. “We did try to model best management practices in the Watts branch and the impacts it would have in the future,” Chen said.
He noted that changes to natural systems take a long time to reach equilibrium. “It’s going to take decades, perhaps, to see changes in raw water quality,” Chen said.
WSSC has hired an outside company, Montgomery Watson Harza, to study the best possible way to construct a new pipe. This is the same company which helped the Fairfax County, Va. Water Authority to construct their new intake pipe which was completed last year.
Since it is so early in the process, there is no favored option for the alignment of the pipe or the method of construction. Gene Gemperline, of Montgomery Watson Harza, laid out many alternatives. He gave several examples of how the pipe might work outlining several methods for taking in water while not taking in fish.
Gemperline also explained possible different alignments and how it would connect to the current facility.
Gemperline also explained construction techniques. Although the Fairfax County intake pipe is not visible now , the cofferdams — dry areas built into the river with access roads which allow the use of heavy machinery and a dry place to work — used during its construction were an eyesore which concerned some residents.
Fitzpatrick concedes that the long term impact of the pipe itself is probably minimal, however, he is concerned about the construction process. “WSSC needs to take every step to limit sediment and pollution that would come from the project,” he said.
Those same sorts of techniques may be used in the construction of this pipe. However, that is just one possibility, and they could also construct a tunnel, float sections of pipe out on barges or construct a pontoon bridge.
The method of construction used, and the other variables will be in part dictated by the permits required at both the state and federal level. “Construction would consider the permitting process,” Gemperline said.
He estimated that the construction of the pipe, if approved, would take from one to two years. If any cofferdaming was necessary, that portion of the construction would likely take four to five months, Gemperline said. However, he cautioned that these estimates are preliminary and subject to change as the construction is studied further.