LAGOON AND SEWER LINE WORK COMPLETED
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SYSTEM UPGRADES 10-8-10 LMS

Major steps have been taken towards upgrading the city’s waste water treatment and delivery systems.

City Waste Water Treatment Superintendent Harry Shanafelt reported completion of dredging operations which removed approximately 1.6 million gallons of liquid from the city’s two sewage lagoons. Test results to determine the dry tonnage are not yet available. From the daily samplings done during removal of the accumulated sludge it appeared that the ratio of solids was running around eight percent.

Shanafelt said the purpose of the sludge removal was to make more room in the lagoons for sewage treatment. He said the lagoon efficiency works on ‘detention time,’ the actual amount of time the waste water remains in the lagoons before being flushed on its way. If it can be kept for an optimum of 17 days the lagoon bacteria has a chance to digest a high percentage of the waste. As it was, the sludge was taking up lagoon space and there wasn’t room for the waste water solids to remain long enough for proper digestion.

Problems at the sewage treatment plant are also coming from the amount of water arriving in the lagoons for treatment. Shanafelt said, “In the Winter we are right around a million gallons a day that goes through the plant and in the Summer that goes up to 2.3 to 2.4 millions a day, so more than half of it is infiltration.”

The cause of infiltration is faulty sewer line joints and cracks in the pipes which allow groundwater to enter the lines and join the waste water on its journey into the lagoons. Shanafelt commented, “There’s no sense in cleaning ‘clean’ water down at the plant. It costs money to treat clean water just like it does waste water.” He added that replacement of long neglected city sewer lines is something which just has to be an on-going job.

The city hired Planned and Engineered Construction (PEC) of Helena, Montana to inject liners into the offending sewer pipes located in areas where line replacement would be either extremely expensive or simply impossible. The company completed its last section of line the evening of October 7th.

Shanafelt said PEC lined the 3,809 feet of pipe that runs along Highway 93 north from Courthouse Drive to the lift pump station on Lemhi Road. According to Shanafelt that section of line was an example where inserting a liner was far more cost effective than digging up and replacing the line. He said the area has a network of telephone fiber optic cables and water lines. “Just the chance…if you rip out a fiber optic cable you’re into it for millions of dollars. This is actually the most economical way to do that.” The work can also be done with no surface disturbance or traffic flow interruptions.

PEC did two other sections of line. One was just below Service Grocery where an old clay tile line went underneath a garage and through a yard which prevented any chance of line replacement. Another badly leaking section was identified on Porphyry Street and was also lined. During its stay in Salmon PEC crews lined a total of 4,539 feet of city sewer pipe.

City crews have been at work replacing the more accessible sewer lines which are located in alleyways. This Summer approximately 1300 feet of line have been replaced in the alley between Shoup and Main Street from Warpath to Beech Street and crews are at work in the alley near Service Grocery. In those cases digging and replacing is less expensive than having the pipes lined.

Shanafelt said it will probably take a year of testing at the lagoons to properly evaluate the results of this Summer’s dredging and infiltration reduction. He said that even though the major upgrade projects will definitely help the sewer treatment plant he’s not sure it will put the city in total compliance with Idaho Department of Environmental Quality and U.S. Environmental Protection Agency suspended-solids regulations. The city is currently in the process of researching effluent filters in case more suspended-solids removal is needed. Shanafelt said if it is determined a filter is required it would be located at a point just before the discharge goes into the river.

The cost of Lagoon Bio-solids Removal and Land Application work performed by Merrell Brothers Incorporated as well as the sewer pipe liner project by PEC will be paid with monies generated by the sewer rate increase put into effect last January by the Salmon City Council.


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