SFPUC Digester Covers & Biosolids Cake Bins Construction

Location: San Francisco, CA

Owner: San Francisco Public Utilities Commission

Contract: $13.1 Million

Role: Design-Builder

Delivery Method: Integrated Project Delivery and Design-Build

Result and Benefit to Client

This award-winning project was successfully delivered on schedule and under SFPUC’s budget, and met all criteria established by SFPUC. During construction, a minimum of six digesters were always in-service meeting compliance requirements for the EPA Class B Biosolids permit.

Project Description

After several of the SFPUC’s 64-year old digesters began to experience catastrophic failures in 2012, Monterey Mechanical was retained as the design-builder to design and construct five new digester replacement covers and two new biosolids replacement cake bins, as well as to make as-needed digester repairs.

Work included sludge removal and disposal, selective concrete demolition and corbel reconstruction, digester cover erection, gas system modifications, cake bins and conveyor systems and protective coatings.

We worked with the SFPUC to select the equipment that provided performance and reliability.

Challenges | Solutions

With the 64-year old digesters in a critical state of failure, the emergency design-build project was fast-tracked. To ensure maximum efficiencies for design and construction, Monterey Mechanical engaged stakeholders in a collaborative approach.

It was mandatory that full compliance with the EPA Class B Biosolids permit was maintained during construction. Monterey Mechanical developed and implemented a sequencing plan, in consultation with operations staff, that included contingency plans.

There was a health-hazard risk with lead paint abatement as well as other high-risk work tasks. Monterey Mechanical collaborated with SFPUC staff and Cal/OSHA to develop an alternative method of steel-cover demolition to eliminate costly lead abatement work traditionally performed by sandblasting.

The site is in a congested urban area with restricted site access. Working closely with the SFPUC, Monterey Mechanical developed and facilitated implementation of a robust communications plan that included informing the local community of temporary road closures.

Awards and Commendations

Karen Kubick
SFPUC Sewer System Improvement Program (SSIP)
Program Director

“Replacing our existing biosolids digester covers is certainly not the sexiest or biggest project – but it was urgent as we were on the edge of permitting issues, storage was critical, calculated risks were taken, innovation was incorporated, and local firms got work. That to me is an award-winning project.”

Design-Build Institute of America

Design-Build Institute of America Merit Award, 2017