As stated in the previous City Council request for consideration of approval for engineering services related to this request, on May 4, 2019 the City’s WWTP had a section of buried 20” ductile iron pipe rupture. Subsequent to staff’s inspection of the pipe, it was determined that the interior of the pipe contained major corrosion characteristics that caused the pipes failure. Upon further investigation of additional sections of pipe, it has been identified that these sections contain corrosion characteristics as well. The pipe was installed in 1988 and is used to transfer influent from aeration basin/tank #2 to the plants headwork’s for preliminary treatment of the material. In addition, another 20” ductile iron pipe was installed for aeration basin/tank #1 as part of the 1988 project.
As described in Task Order No. 36 from Stroud Engineering Consultants, Inc. the following is the scope of work included as phase 1 of the project.
1. The installation of a shut off valve directly on the outside of the aeration tank No.2.
2. The installation of temporary 20” ductile iron pipe from the newly installed valve at aeration basin/tank No. 2 to the plant headworks.
3. Cap and fill with grout the existing abandoned 20” pipe.
It should be noted, the temporary pipe will be used as permanent pipe replacement run for the Schreiber tank subsequent to the construction of the permanent aeration basin/tank pipe run. All ductile iron pipe and fittings utilized in all of the construction phases shall have interior protective coating to eliminate the possibility of pipe failure due to the interior metal corrosion process that occurred in the existing pipe.