At Wastewater Treatment Plant No. 3 (WWTP 3), solids removed from the wastewater must undergo anaerobic digestion and a dewatering process. The sludge dewatering process results in a sludge cake which is moved from the centrifuges through a system of conveyors and troughs and loaded into sludge hauling trucks. From there, the sludge cake, also known as Class B biosolids, can be safely land applied for reuse.
The conveyor and trough system are in constant use and experience extensive wear and tear. Recently, a number of holes ranging in size from pin-holes to over 12-in gaps have been discovered throughout the length of the trough. Temporary patches have been welded over the holes, but given the extent of damage and loss of steel thickness throughout the trough, City staff recommends replacing over 50-ft of the affected trough.
The City contacted Schwing Bioset (Schwing), the geographical sole source provider and manufacturer of the troughs, and received a quote for the required parts. Given the critical nature of the solids handling process to the operation of the treatment system, staff recommends dispensing with bidding procedures and authorizing the purchase of the required replacement trough and mounting hardware. Per the attached sole source letter, only Schwing can supply the trough and hardware for this repair.
The installation of the trough will be completed by one of the Wastewater Division on-call contractors. Based on previous repairs done to the dewatered sludge conveyance system, staff estimates the installation costs will range between $40,000 and $50,000. There is an existing project within the Capital Improvement Program for sludge dewatering improvements. This scope of work fits within the project description and there are sufficient funds remaining in the project account to complete the purchase and installation of the trough.
Sewer Enterprise funds are budgeted to fund this resolution within the Sewer Enterprise Funds; therefore, there is no General Fund impact associated with this resolution.