Monday, September 21, 2015

Raspberry Falls and Selma Estates – The Final Water Solution

On Thursday, September 24, 2015 at 7:00 pm Loudoun Water will be holding a public meeting for the Raspberry Falls and Selma Estates water systems. The meeting will be held in the Loudoun Water Boardroom located at 44865 Loudoun Water Way, Ashburn, VA 20147.

Loudoun Water is finally moving ahead with the design and construction of water treatment for Raspberry Falls and Selma Estates building a single water treatment plant to serve both communities. This process began in 2010 when routine testing found total coliform and E. coli bacteria in the untreated raw water from one of the Raspberry Falls wells. That well was determined to be Groundwater Under is the Direct Influence of Surface Water or GUDI by the Virginia Department of Health whose regulations require filtration and disinfection of GUDI water used in a drinking water supply system.

Instead, the well was taken out of service and replaced the following year by a new well at a cost of almost a million dollars. Replacing the well solved the problem for the short term, while Loudoun Water investigated long term solutions. However, experience in the western third of Virginia has demonstrated that the GUDI condition could impact the other wells and it ultimately did.

In the summer of 2014 two of the four wells in Selma Estates and one of the two wells in Raspberry Falls were taken offline after E. coli was detected. The three remaining wells between the two systems could only produce enough water to meet the typical indoor needs, and Loudoun Water requested that residents conserve water and to curb outdoor water use. The communities responded well and reduced their water usage so that the communities could survive the water emergency without mandated water restrictions.

The Raspberry Falls and Selma Estates current water supply systems were constructed by the community developers in 2002 and 2007 respectively, possibly inappropriately considering the underlying geology. After completion they were turned over to Loudoun Water to operate. Raspberry Falls and Selma Estates are clustered developments built in the karst area of Loudoun County in what is now the limestone overlay district. This district was created in 2010 in the area of the county generally north of Leesburg and east of the Catoctin Mountains which is underlain by limestone conglomerate bedrock and runs north along Route 15. The limestone overlay district is really just a zoning change that attempts to ensure that the groundwater supply in that area is capable of supporting needs of current and future residents without creating sinkholes. Karst terrain is fragile and ignoring the limits of natural systems can have serious consequences.

Currently Water is supplied to Raspberry Falls by two community wells. The Selma Estates community drinking water treatment system consists of four wells, water storage, booster pumps, a sodium hypochlorite treatment for disinfection, a greensand filtration unit, a fluoride feed system, an orthophosphate feed system, a standby generator and the pipes for the distribution system.

Though, Loudoun Water considered building separate systems for the two communities the final plan now is to build a combined system with 900 gallon per day per connection maximum flow rate. The plant will be located in Selma Estates and will utilize membrane filtration. This is a water purification technology approved by the Virginia Department of Health and successfully used in dozens of karst locations in the Commonwealth. This technology uses a semipermeable membrane to remove bacteria and microorganisms from the water.

A combined water system is being built because though the initial capital costs are a bit lower for separate smaller system the ongoing operating costs are much lower for a combined system. Selma Estates was chosen as the site for the combined system because it is located at a higher elevation than Raspberry Falls and gravity can be utilized to reduce the cost of water distribution.

The project is currently still in the design stage and will be ready to go out to bid at the end of 2015. Construction is planned to begin and be completed in 2016. The treatment plant is planned to be operational at the beginning of 2017. Loudoun Water will fund the capital costs of the new water treatment system through its general fund. The communities will not be assessed as originally announced last winter. The general fund will be replenished over time through user rate payments collected from all Loudoun Water customers.

Loudoun Water is a political subdivision of the state, just like a town or a county. All income is received is either as ongoing user fees from customers or as availability fees from developers. Loudoun Water receives no tax money. Loudoun County has been one of the fastest growing counties in the country over the past decade and Loudoun Water has capital improvement and expansion projects totaling over $600 million planned over the next 5 years. All of this will have to be paid for by water rates.

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