Repairing the Storm Sewers Will Likely Lower Water Treatment Costs

City Council members became concerned when a contractor said the Metropolitan St. Louis Sewer District (MSD) may have raised prices to treat water from Arnold’s sanitary sewer.

The rates have increased about 50 percent in the last six months, said Gene Fribis, a consultant hired about 13 months ago by the city to investigate leaks into Arnold’s sanitary and from storm sewers. He said City Finance Director Deborah Lewis noticed MSD increased the rate to about .0006 cents per gallon treated from .0004 cents.

MSD sends a sewage bill to Arnold based on the volume of water treated. Extra water that infiltrates the sanitary sewers, from a storm for example, is an additional cost.

An employee for Fribis Engineering provided maps that showed Arnold has two sewer systems, a sanitary sewer and a storm sewer. Sanitary sewer pipes take water from homes and businesses to a treatment plant. Storm sewers carry rain water to rivers or ponds from city streets and neighborhoods.

“The goal is to send as little flow to MSD as possible,” Fribis said during the council work session on June 9.

Between 5.75 and 13 times more water flows through the city’s sanitary sewer after a storm, Fribis said. His firm monitored the volume of water flowing through the sanitary sewers’ pipes during the past year.

That extra water, from rainstorms, should flow through the storm sewer pipes instead of through the sanitary sewer system.

The goal is to reduce the storm water—infiltrating through cracked pipes—to about four times, Fribis said. The federal goal is to reduce water infiltration to about 2.5 times.

“It’s difficult to get that last 20 or 30 percent. You don’t want to spend $50,000 in sewer repairs to save $1,000 in water costs per year,” he said.

Fribis said his role is to help the Arnold find $1,000 repairs, for example, that save $50,000 in annual water costs. 

Broken sewer pipes are part of the infiltration problem, Fribis said. Another factor is that former city planners placed the storm sewer’s pipes near and above the sanitary sewer’s pipes.

The cracked storm pipes leak water into the soil above the cracked sanitary sewer pipes. 

The clay pipes were installed in the 1960s and are crumbling, Fribis said. “The design life of those pipes has expired.”

“Much of the problem could be solved by repairing the storm sewer system,” he said. The city should use modern pipes made of more resilient materials, Fribis said to council members.

Improving the seals around manhole covers would further reduce the volume of storm water entering the sanitary sewer, Fribis said. 

Fribis’ consulting team has tested all the manhole covers in Arnold and has smoke tested about 50 percent of all pipes. Smoke released in the pipes will help the consultants find the cracks.

He said about 90 percent of the survey should be completed by September.

“We will provide Arnold an accurate computer map of the pipes, their condition and location of all the manholes,” Fribis said.

The city will need a new computer system to manage all new sewer information, determine repair priorities, and keep up to date with federal and Missouri Department of Natural Resources regulations, he said.

“Sewers don’t get better they get older, and regulations get tougher,” Fribis said. 

There may come a day when pure water only will be sent to Missouri rivers, he said.

Mayor Ron Counts said, “This is an important issue we are going to be dealing with for a long time.”