LOUISA COUNTY, Va. -- Louisa County officials have concluded that the cause of last month’s water contamination was likely caused by a methane gas release from the sewer system.
The conclusion was reached by the Louisa County Water Authority after a number of tests and consultation with outside experts.
Last month, the town issued a ''Do Not Use' order for water within and in the vicinity of the town of Louisa. The town also took the drastic step of evacuating people living and working in a half a mile radius around the Glen Mayre Shopping Center at 406 E. Main Street as the gas level neared the level of creating an explosion.
Officials say the water has been tested many times since the contamination and has been determined safe by the Virginia Department of Health and the EPA.
In a press release Tuesday, officials explained what happened:
The methane entered several locations in the Town through dry “p-traps.” Water was the initial focus of the investigation as gas levels were initially tested using atmospheric meters which indicated a positive reading while water was running. However, when water runs into the sewer system, it can create turbulence which forces additional methane gas out of dry traps, leading to a rapid gas increase in those spaces. “P-traps” are p-shaped piping which is required by building code in drains. Water collects in them preventing the backflow (into a structure) of methane gas which normally occurs in sewer/septic systems. Good maintenance practices call for water to be poured into seldom used p-traps of floor drains and sinks to prevent them from becoming dry when water evaporates. Since Thursday, p-traps in the primary area of the issue have been discovered to be dry. This would allow methane gas to vent from the sewer system into buildings.
In the days following the event, authorities evaluated numerous theories in an effort to identify the cause. Increased attention focused on sewer gas as other causes were ruled out. Town officials sent out notices and conducted smoke and camera tests last week on the sewer system. These revealed: 1) dry p-traps which can contribute to the situation; and 2) grease, likely from food service sources, which causes slow-flow situations in the sewer and can contribute to increased methane production. Due to significant flushing after last week’s situation, methane levels in the sewer system were nearly nonexistent at the time of last week’s tests, but town officials remind all users that grease should be disposed of properly and never be placed in a drain.
Officials tried diligently to expeditiously perform tests on the water itself during the event. However, only a few pieces of equipment (called mass spectrometers) able to perform such tests exist in the state, and they are not portable. The state’s Division of Consolidated Labs in Richmond agreed to perform the water tests. Samples were transported to Richmond shortly after midnight Friday morning and a second sample was transported at 5:30am. During the event, state Hazmat and local personnel were initially compelled to rely on atmospheric air test readings and field equipment for the presence of the suspected contaminant.
“The initial air readings had everyone very concerned that it was possibly a water system-based delivery vector,” said Keith Greene, Chief of Fire and Emergency Services. “Increased gaseous levels occurred in the problem areas when water was running. We now believe that was caused by dry traps allowing methane out as water entered. To see if the contaminant was spreading, we atmospherically tested at other locations during the event, including hydrants. For some reason, some of the older hydrants gave off very low positive readings. At the time however, and given the suspicion regarding the water system, it was initially concluded that those results indicated the problem was potentially in the water, and that it could be spreading.”
LCWA General Manager Pam Baughman agreed. “When Friday’s sample results of the water revealed no contaminants, we began rethinking theories about the water system as a source, but we didn’t want to rule anything which might jeopardize the public’s health, safety, and welfare out too early,” she said.
Early warnings and the safety of town citizens were critical to the decision-making process. While the gas did not reach potentially explosive levels, readings rose rapidly during a short time period (and neared levels determined to be an Immediate Danger to Life and Health by the National Institute for Occupational Safety and Health) while oxygen decreased to unsafe levels. This, coupled with the fact that: 1) the identity of the gaseous contaminant was unknown; and 2) the fact that the possibility of an intentional/criminal/terrorism event had not been ruled out, led to the decision to evacuate within a ½ mile radius of the Glen Marye shopping center. These factors also led to further water tests by state officials.