One sewage pumping station in East Lyme discharged raw sewage into Bride Brook during Hurricane Sandy, and two Stonington sewage treatment plants in Mystic and Pawcatuck are still on limited treatment because of the coastal storm surge, officials said Tuesday.

Overall, the state's network of sewage treatment plants weathered the storm well. But shellfish beds throughout southeastern Connecticut, from Stonington to East Lyme, remained closed. The beds in the Ledge Light Health District region were ordered closed prior to the storm as a precaution and must be tested before they can reopen, said Steve Mansfield, deputy director of Ledge Light.

Dennis Schain, spokesman for the state Department of Energy and Environmental Protection, said only seven of the state's 250 sewage pumping stations were forced to discharge raw sewage into nearby waterways during the storm. The only southeastern Connecticut location where that happened was the pump station in East Lyme along Bride Brook. That pumping station became fully operational shortly before noon Tuesday, Mansfield said.

Of the state's 89 sewage treatment plants, only four had become flooded or inundated with water and had to resort to limited treatment — called primary disinfectant treatment — during the storm. One of these was the Stonington sewage treatment plant at Mystic. Others were in Fairfield and Bridgeport, Schain said.

Tom Gilligan, director of the Stonington Water Pollution Control Authority, said Tuesday that the Mystic and Pawcatuck plants became overwhelmed overnight Monday, receiving about 2 million gallons of sea water and sewage as opposed to the normal load of 500,000 gallons of sewage per day. Operators were forced to shut off aeration systems to save the plant's mechanisms, he said.

Both the Mystic and Pawcatuck plants are still receiving more than 2 million gallons of day of water. Until that settles down to half that amount, the plants will be on reduced treatment, Gilligan said.

"A lot of streets in Mystic were underwater, and where does that water go but to the treatment plant," Gilligan said.

The two plants have not sustained structural damage, he said.

Schain said many systems had to resort to backup generators during the storm, which preserved full treatment operations. DEEP has been working with sewer system operators since last year's storms to ensure they are equipped with generators.

He said state officials were concerned at one point about a treatment plant in Ledyard that needed a generator, but that facility did obtain one.

In Norwich, the crew staffing the Norwich Public Utilities sewage treatment plant just north of Norwich Harbor was forced to evacuate late Monday when the Falls Avenue access road to the plant flooded with the high tide, said Mark Decker, NPU water and wastewater integrity manager said.

The sewage treatment plant never flooded, did not lose power and remained fully operational throughout the storm, Decker said. Backup generators are in place at all Norwich sewage pumping stations, and two stations — one in the Norwich business park and one on Canterbury Turnpike — resorted to generator power for a time, Decker said.

Drinking water plants at NPU's two main water reservoirs, Deep River Reservoir in Colchester and Stony Brook Reservoir in Montville, lost power but were placed on emergency generators immediately without interruption of service, Decker said.

Groton Utilities Water Division announced Tuesday that the utility's drinking water supply is safe, and the utility's wastewater treatment plant did not sustain any damage from Hurricane Sandy.

For the many homeowners on well water and on-site septic systems, Ledge Light offered tips for problems faced by flooding.

Do not drink the water if there is suspicion that a well may be contaminated or if the cap was partially or completely submerged by floodwater. Ledge Light recommends those homeowners have their wells tested; a list of local certified labs for testing well water is available at www.llhd.org.

If the well is contaminated, the health district website also offers procedures for disinfecting wells.

Septic systems can become inundated and backed up into houses due to the flood. Homeowners in that situation might have to just wait for the water to recede and the septic system's leaching system to dry out and become functional. The district recommends those systems be inspected by a licensed septic installer as soon as possible.

Meanwhile, the state Department of Public Health urged people to stay away from floodwaters because they may be contaminated by sewer system discharges or sewage backups on private properties. The DEEP said the discharges weren't expected to harm the environment.

An Associated Press report was included in this story.

c.bessette@theday.com