People traveling Davenport's West River Drive near Modern Woodmen Park have become used to seeing barricades reducing the roadway to one lane westbound near Gaines Street.

After months of having to merge into one lane during parts of 2016 and this year, the problem finally appeared to have been fixed this fall and the barricades were removed — only to return Nov. 27.

This time, the barricades were in a different spot, east of the Talbot Memorial Bridge (Centennial Bridge), and both lanes of westbound River Driver were blocked, forcing traffic to take a short detour.

The cause of the problem — then and now — is an old storm sewer pipe under the street made of clay that, through the years, has cracked. This allows water, carrying soil, to get into the pipe and over time, wash away the soil above, creating a void and causing the street to sink, Nicole Gleason, Davenport public works director, explained.

To fix this, the city hired a contractor to dig down under the street and slip a new, ductile iron pipe between 30 and 40 feet long inside the cracked clay pipe with a concrete collar at both ends, and then backfill the void and repour the street, Brian Schadt, city engineer, said. The clay pipe itself is too brittle to repair.

The storm sewer pipe in question is about 30 inches in diameter and may date to around the early 1900s, Schadt said. It extends west under the bridge, then turns south and empties into the Mississippi River. At times, the city could not access the pipe to repair it because the river was so high that the water was backing up into the area where contractors needed to work, near Gaines Street. That's why people traveling West River Drive often saw barricades but no work going on.

To avoid this delay in the future, the city is bidding out for a diver to install a temporary metal plate that would cover the storm sewer pipe at its mouth in the river, Gleason said. The pipe would then be pumped out, so workers wouldn't have to wait for river levels to drop. Once the repairs were complete, the plate would be removed.

The first repair earlier this fall cost about $43,000; the current repair — expected to be finished Monday — also is anticipated to be in about that range. The city budgets about $1.2 million annually for these types of repairs, Schadt said.

All told, the city has about 220 miles of storm sewer pipes and 440 miles of sanitary sewer pipes, he said.