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City of Dubuque Forced Sewer Main, Dubuque County, IA– CAP Section 14

Published Sept. 16, 2020
A map of the Dubuque, Iowa, Forced Sewer Study area.

A map of the Dubuque, Iowa, Forced Sewer Study area.

Location
Dubuque County, Iowa

Description
In 1977, the 30" force main that carried sewer flow from the Terminal Street Lift Station under the US Highway 20 Bridge at Dubuque, Iowa to the sewage treatment plant was abandoned and new 9,500 LF 42" prestressed concrete pressure pipe (PCPP) was constructed parallel to and approximately 20 feet west of the 30" force main and east of the railroad tracks along the banks of the river. It is currently not known how the 30” force main was decommissioned.  If it were to break, it is unknown what type of damages could be caused to the environment, but minimal damages would occur to significant infrastructure since the force main is decommissioned.

The 1977 PCPP sewer main, which carriers approximately 80% of the City's daily sewer flow to Dubuque's Water & Resource Recovery Center (W&RRC) is exposed in several locations due to bank erosion.  The most significant force main exposure is located at the southern terminus of the Dubuque floodwall and flood protection system.  Failure of the sewer main in one of the exposed locations would have serious consequences. Due to the close proximity to the river, a break in the pipe would cause the contents to flow directly into the Mississippi River.  A break in the pipe would also cause a shutdown to the W&RRC thereby stopping waste water treatment for the city.  Additionally, with the close proximity to the railroad, a break in the pipe would likely cause disruptions to railroad use in the area.

Background
The city has 2 sanitary sewer mains (1) thirty-inch and (1) forty-inch diameter sanitary force mains and the Terminal Street lift station located adjacent to the Mississippi River at Dubuque, in Dubuque County, Iowa. Loss of riprap protection along the length of the force main is threatening the safety and integrity of the forced main. Opportunities exist to reduce erosion and safety concerns through structural and non-structural measures.

Status
Funds were received in January 2020 to complete a Federal Interest Determination.  Federal Interest Determined in August 2020.

Authority
CA - Continuing Authorities - Section 14

Summarized Project Costs

Estimated Federal Cost $ 190,000
Estimated Non-Federal Cost $ 90,000
Estimated Total Project Cost $ 190,000
Allocations Prior to FY 2020 $ 0
FY 2020 Allocations $ 100,000
FY 2020 Total Capability $ 100,000

 

Major Work Item Current Year
FY 2020: Federal Interest Determined