Under a state mandate, the city of Astoria continues work to separate storm-water run off from the sewer system. Called the "CSO Separation" project, it has been handled in construction phases over a number of years. The next big phase runs through some of the towns busiest streets and looks to be a substantial piece of work. Dubbed the "11th Street" CSO project it will actually involve a number of streets in the downtown area.
According to a memo to the City Council from City Manager Paul Benoit the engineering firm, Gibbs and Olson, hired with council approval in June of this year has completed about 60% of the design work which will involve 8th street from Commercial to Niagra, 9th street from Duane to Harrison, 10th street from Duane to Jerome, 11th street from Exchange to Irving Ave, 12th from Exchange to Kensington, Irving from 11th to 12th and, 9th from marine Drive to the new outfall.
The entire project will involve laying 10,000 feet of new storm-water pipe within the existing infrastructure in the roadways and may require replacing any of the existing pipes that become weakened as a result of the new work.
Benoit notes that the work on 8th street will involve disturbing so much buried infrastructure that it will be necessary to rebuild the entire roadway curb to curb.
Benoit is asking the Council to approve a change in the design contract to account for some additional work that will be necessary after the engineers discovered an existing storm-water diversion on 9th street was not connected to all the lines coming down the hill and instead were only draining a few catch basins and gutter systems. It was never connected to the outfall on 9th street. The diversions are designed to allow a certain amount of storm-water run off to run down the sewer lines but in heavy rainfall the additional amounts would be diverted to the outfall to avoid overwhelming the treatment system. There is no explanation as to why only a few lines lead to this particular diversion or why it was not connected to the outfall on 9th but in order to meet standards this has to be corrected in the new plan.
This would include the installation of a new outfall on 9th street and the engineering firm is suggesting running a new pipe inside the old using trench-less technology which will require additional geotech studies. The company estimates this will increase the planning costs by $29,794.24. Benoit writes that he already approved an additional $9,889.00 to expand the project slightly.
The project must be completed and in operation by December 1,2013 to meet the conditions of a stipulated order signed by the City and the Oregon Department of Environmental Quality