Page 81 - Yucaipa Valley Water District - Board Workshop
P. 81
Workshop Memorandum 16-008
Date: January 12, 2016
Subject: Status Report on the Digester Cleaning and Cover Replacement
Project at the Wochholz Regional Water Recycling Facility
The Yucaipa Valley Water District operates and maintains four anaerobic digesters for sludge
conditioning, each with a diameter of 45 feet and a side water depth of 22 feet, yielding a working
capacity of approximately 262,000 gallons per digester. The digesters treat sludge drawn from
both the primary clarifiers and from the dissolved air flotation thickeners. Digested sludge flows
by gravity and can be stored temporarily in a sludge holding tank before being conveyed to the
belt presses for dewatering. To keep the digesters functioning properly they should be cleaned
every 8-10 years in order to remove the accumulated build-up of sand, grit, and other debris.
When the digesters were cleaned in 2005, the District staff assessed the condition of the digesters
and related equipment. Based on corrosion identified at this time, the District made a decision to
replace at least two covers the next time the digesters were scheduled to be cleaned.
In 2015, the District staff worked with RMC to develop a construction bid schedule that included
a series of construction alternatives for cleaning and/or replacement of the digester covers. After
carefully evaluating the cleaning/construction bids received for this project, the Board of Directors
decided to award a construction contract to Pascal & Ludwig for the cleaning and replacement of
four digester covers for a sum not to exceed $2,175,000. [DM 15-041]
The purpose of this agenda item is to provide an update on the status of the construction project.
Yucaipa Valley Water District - January 12, 2016 - Page 77 of 279
Date: January 12, 2016
Subject: Status Report on the Digester Cleaning and Cover Replacement
Project at the Wochholz Regional Water Recycling Facility
The Yucaipa Valley Water District operates and maintains four anaerobic digesters for sludge
conditioning, each with a diameter of 45 feet and a side water depth of 22 feet, yielding a working
capacity of approximately 262,000 gallons per digester. The digesters treat sludge drawn from
both the primary clarifiers and from the dissolved air flotation thickeners. Digested sludge flows
by gravity and can be stored temporarily in a sludge holding tank before being conveyed to the
belt presses for dewatering. To keep the digesters functioning properly they should be cleaned
every 8-10 years in order to remove the accumulated build-up of sand, grit, and other debris.
When the digesters were cleaned in 2005, the District staff assessed the condition of the digesters
and related equipment. Based on corrosion identified at this time, the District made a decision to
replace at least two covers the next time the digesters were scheduled to be cleaned.
In 2015, the District staff worked with RMC to develop a construction bid schedule that included
a series of construction alternatives for cleaning and/or replacement of the digester covers. After
carefully evaluating the cleaning/construction bids received for this project, the Board of Directors
decided to award a construction contract to Pascal & Ludwig for the cleaning and replacement of
four digester covers for a sum not to exceed $2,175,000. [DM 15-041]
The purpose of this agenda item is to provide an update on the status of the construction project.
Yucaipa Valley Water District - January 12, 2016 - Page 77 of 279
