The request of staff for the City Council to review and consider for approval is Task Order No. 1 from Stroud Engineering Consultants, Inc. in the amount not to exceed $90,500 for engineering services associated with the Wastewater Treatment Plant’s facility pipe deficiency analysis phase 2.

As City Council may recall, on May 4, 2019 the City’s WWTP had a section of buried 20” ductile iron pipe rupture resulting in a significant sewer spill.  Subsequent to staff’s inspection of the pipe, it was determined that the interior of the pipe contained major corrosion characteristics that caused the pipe failure.  Upon further investigation of additional sections of pipe, it was identified that these sections contain corrosion characteristics as well.  The pipe was installed in 1988 and is used to transfer effluent from aeration basin/tank #1 to the plants headwork’s for preliminary treatment of the effluent. The project scope of work for phase 1 included subsurface utility engineering (SUE), to determine the location of existing utility lines, electric power cables, and potential utility facilities that were not identified in the plant’s as-built drawings.  The installation of a shut off valve directly on the outside of the aeration tank and installation of temporary piping to get aeration basin/tank No. 2 back on line.  Once the plant was operating at full capacity, work started on replacement pipe runs from aeration basins/tanks No. 1 and No. 2 and the installation of valves.  Once completed, all of the original pipes were either removed or left in place, capped and filled with grout to avoid soil collapse below the newly installed replacement pipes.  Finally, existing pipes connected to aeration basin/tanks No. 3 and No. 4 and the Schreiber tank were visually inspected and ultrasonically field tested to determine what type of work if any, might be needed such as pipe lining and/or pipe replacement. Subsequent to the Water Reclamation Facility Gravity Main Condition Assessment completed in April of 2020 by Reiss Engineering, it was recommended that the remaining pipes on the east side of the plant should  be monitored annually utilizing the ultrasonic field testing process or lined with cured in place pipe (CIPP).  Staff has elected to proceed with the recommendation to City Council to proceed with the CIPP.

As City Council may recall, consultants familiar with the plants design layout and operational process recommended to staff the inclusion of performing pipe condition assessments for all pipes installed on the west side of the plant due do the age of the pipes as well as the corrosive environment the pipes have been installed in.