Sanitation plant undergoing repairs |

Sanitation plant undergoing repairs

by Amy Alonzo
A crane works on a digester that was damaged as a result of a hard freeze at the Minden-Gardnerville Sanitation District.
Brad Coman |

Drivers heading south into Minden may have noticed a large crane looming over the Minden-Gardnerville Sanitation District for the last couple of months, and it won’t be going anywhere soon.

The crane is part of a $1 million project to repair the plant’s largest digester, which was damaged by sub-freezing temperatures in 2015.

Three digesters are located at the Minden-Gardnerville plant. The two smaller digesters each hold about 250,000 gallons of waste, and the larger one holds about 500,000 gallons. The digesters are fed grease from restaurants and sludge, and microorganisms digest the mixture and create methane.

The grease “is like sugar on cereal,” Johnson said. “They (microorganisms) just love it. It’s like candy to them.”

The methane runs through a cogeneration system to create heat and electricity, producing enough power for about 70 percent of the plant’s operations, said Frank Johnson, district manager. That 70 percent of self-generated power saves the towns about $150,000 annually in gas and electric bills, said Ray Wilson, chair of the plant’s board of trustees.

Over the winter of 2015 sub-freezing temperatures froze a relief valve on the largest digester. The digester wasn’t being fed at the time, but when sludge started getting pumped in, the pressure “popped the top,” Johnson said. “It was still operable, but it was leaking methane gas.”

The digester was used until June of 2016, and then it was emptied and cleaned — a process that took an entire month. During that time, insurance claims were filed, and insurance is paying for the bulk of the repairs, Johnson said.

In April Reno-based KG Walters Construction started disassembling the digester’s 15-inch-thick cement and rebar roof. Insulation was added to pipes that feed the digester, and its support columns will be rebuilt before a new roof is installed.

The project is expected to wrap up by October or November.