TMWRF operates 5 methane digesters for the treatment of biosolids.  The solids are collected from the primary and secondary clarifiers and held in the digester for approximately 21 days.  During this time the solids are decomposed by microorganisms to make them more biologically stable and thus less impactful on the environment when disposed.  This biological activity exposes the interior of the digester to a harsh chemical environment with the potential to cause corrosion and decay of the steel roof and supporting structure. 

The Digester No. 2 roof is in need of rehabilitation and coating to ensure its continued service.  A capital improvement project was initiated that provided for the design and construction of the needed repairs.  The project was to be managed by the City of Reno engineering staff in accordance with the interlocal agreement to operate TMWRF.  Sparks’ City Council approved the reimbursement to Reno for the construction portion of this project on June 10, 2019. 

  Subsequent to cleaning and sand blasting the interior surfaces, exposed structural steel members were inspected by a Structural Engineer.   The steel roof support columns were found to be significantly more corroded than anticipated, requiring additional work to completely repair the digester roof, including:

• Adding new steel columns to abandon the existing steel tube columns that are corroding on the inside;
• Repair of steel beams that show significant loss of width of the flange or severe pitting;
• Replacing beam bolts and clip angles that corroded to the extent that the anchor nut no longer is in contact;

Offsite coating of the new fabricated steel structural members.

A quote for the extra work was solicited from the current contractor, Farr Construction Corporation dba Resource Development Company.  The quote was reviewed and determined to be reasonable for the scope of work.  There is not adequate funding in the project force account to cover this additional work.  Consequently, staff is now seeking City Council approval of the change order to the contract to allow for the additional work.

1. City Council may approve the change order.
2. City Council may reject change order and direct the Manager to have staff investigate alternatives.

I move to approve the reimbursement to the City of Reno for Change Order No. 1 to the Digester 2 Cover Rehabilitation Project construction contract with Farr Construction Corporation dba Resource Development Company at TMWRF for an amount not to exceed $170,000 with the City of Sparks’ share being $53,329.00.