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FAIRFAX COUNTY, Va. (WUSA9) -- The approaching storm is causing concern at Lake Barcroft, where four sewage spills in the past two months have closed the beaches in the private Fairfax County community. Heavy rain on April 29th caused the largest of the four spills which in total dumped 413,000 gallons of sewage into Lake Barcroft, according to Fairfax County officials.

Three of the spills originated at the pumping station on Sleepy Hollow Road, which was built in 1959. An old 20 inch force main runs from the pump station up a hill underneath Sleepy Hollow Road. It handles overflow in the event of storms, but the line has been leaking. A 1.6 million dollar project is underway to install a liner inside the 20 inch force main. However, the backup line which runs above ground is only 12 inches in diameter.

It's unclear why the backup line is significantly smaller than the mainline, and that could be part of the problem.

Fairfax County has hired several contractors to help solve the problems. A county spokesperson who declined an on camera interview said the level of testing on Lake Barcroft has been "unprecedented." The private lake is owned and accessible only to members of the Lake Barcroft Association. Some residents think more should be done to prevent more spills.

Though The Fairfax County Health Department advises against swimming or wading in any streams or lakes, many residents are confident the Lake has been flushed clear of contamination.

Here is a chronological account of the Lake Barcroft sewage spills from Fairfax County:

On June 16th 2014, there was a sanitary overflow from a county sanitary pump station just upstream of Lake Barcroft. It is estimated that about 6,000 gallons of sewage was discharged. Since April 28th the county has experienced four sanitary sewer overflows up stream or adjacent to Lake Barcroft.

The first one occurred during the major rain storm on April 29th. At this time the county was in the midst of rehabilitating the force main serving the Holmes Run pump station, and the temporary pump-around to allow this work was overwhelmed by the intensity of the storm.

The county had tried to get the station back in service immediately before the storm, but a connection on the force main had failed during testing. This force main connection was repaired immediately. It was estimated that 300,000 to 400,000 gallons was discharged from the sanitary sewer system.

The county estimated that about 80 percent of this flow was attributed to rain water entering the system, and during this event the flows over the Barcroft dam were measured in excess of 500,000 gallons per minute.

The second event occurred during the storm of May 15th and 16th. The pumps at the pump station had failed to turn on. Crews responded immediately and adjusted the pump electrical controls to assure proper operation of the pumps.

They were able to limit the amount of the overflow. It was estimated that approximately 3,200 gallons were discharged and the flows over the dam at the time were measured at 1,200,000 gallons per minute.

The third event occurred at a different pump station located near beach 3 on Lake Barcroft on May 18th. This was the result of a controller in the station malfunctioning and it was not immediately detected because the previous storm had disabled the telephone lines used for automated reporting of pump station malfunctions to the county's maintenance crews. Due to the outages, crews were physically checking stations over the weekend and this station was checked around 2:00 PM on Sunday, May 18th and was in good operating order. The failure occurred after that time. The overflow was estimated to be 3,900 gallons. Since this event, an automated, wireless backup communication system has been installed in the station to report any malfunctions to the county's maintenance crews.

The fourth event occurred on Monday, June 17th. Crews were working on the gravity sewer line near the Holmes Run pump station. Flows were being diverted to the pump station to allow for inspection of the gravity line. When the pumps came on, the crews noted sewage coming up through the ground, indicating a leak from the force main serving this pump station. The pump station was shut off and flows were diverted back to the gravity line and clean-up operations began. It was estimated that 6,000 gallons escaped during this event. The force main had been repaired and tested after the April 29th event, and had been operational for about a month. The force main was in service and used during the storm of May 16th. After each event the county undertook water testing at several locations above, below and around the lake.

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