C-B Water District casts wary eye to growth's impact
CARROLL COUNTY -- Population growth trends in Harrison and Carroll County will have an impact on future master planning for the Carroll-Boone Water District (CBWD), said Brad Hammond, an engineer with McGoodwin, Williams and Yates.
Hammond and fellow engineer Chris Hall presented a preliminary update to the water district's five-year master plan at its Oct. 17 Board meeting.
If heavy growth trends continue, especially in Harrison and Berryville, CBWD's ability to push water down the line will call for serious expansion measures.
Currently, Carroll-Boone's pumping and storage capacity is 18 mgd (million gallons per day) for its four member cities of Harrison, Green Forest, Berryville and Eureka Springs and their subsidiaries. Water customers use nowhere near that, however, averaging instead about 7 to 8 mgd in the fall and winter and 9 to 11 mgd in the spring and summer.
Even should demand increase to the full capacity, the plant cannot consistently pump 18 mgd, said Hammond. Hydraulics, mechanics of elevations, pumps, pressure and distance all have an impact on that ability.
The biggest problem, however, is the transmission line. Hammond said the 43-mile line was designed to carry 12 mgd.
Although the booster station helps, Hammond said, "it's getting more difficult to pump water to Harrison. You don't really have the capacity to push 18 mgd through."
The 1983 cost of the original 43-mile transmission line was $14 million. At today's prices it would be astronomical to construct a second, parallel line, Office Manager Jim Allison said, an option the water district has discussed.
Hammond presented 20-year population projections for all four cities based on growth from 1983 to the present.
Harrison has shown the greatest steady growth, he said. From a population of 12,000 in 2,000, he expects the city and its areas to have 16,000 to 17,000 residents by 2027.
He said Southwest Boone County, is becoming a "significant user" of water. Not one of the original members of the water district, it buys some Carroll-Boone water from Harrison.
Allison said Southwest Boone would like to shut down its wells and get all its water from Carroll-Boone.
Other communities might also want to tie in to Carroll-Boone in the future.
This is significant, again, Hammond indicated, because of hydraulics.
"The more others take affects how much you can get to Harrison," Hammond said.
His projections didn't included self-produced water from Southwest Boone, Harrison or Green Forest. Chairman James Yates said those figures need to be included in order to get a complete, accurate picture.
Berryville and Green Forest have also had steady growth.
The presence of high water-use industries such as Tyson Foods is also significant, said Hall.
"An industry can have a big impact on projections, whether they reduce or expand," he said. "It's hard to predict."
Hammond said although projection figures are averages, "we never design to averages."
The engineers use a "peaking factor" from the worst day of production to the best day to get an average that they then multiply by the lowest production day.
If they use the lowest peaking factor, he said, they project 16 mgd needed by 2027. If they use the highest, they would need 21 mgd. He suggested a mid-range factor.
Also at issue is the water allocation from Beaver Lake by the Corps of Engineers. Only now is Carroll-Boone getting approval for an additional 6 mgd, although it has been consistently pulling more than that for years.
It will take an act of Congress, Allison said, to get approved for higher allocations.
Hammond said they will recommend a plant expansion within the next 20 years. Yates expressed concern about using a mid-range peaking factor and leaving the water district open to criticism for not building enough capacity to meet future needs.
Hammond said he would get the water production figures Yates requested and come back with another projection at the January 2008 meeting.