FROM: Robert Thompson, General Manager
Originator: Mike Dorman, Director of Engineering
SUBJECT:
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DIGESTER GAS FACILITIES REPLACEMENT, PROJECT NO. J-124
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GENERAL MANAGER'S RECOMMENDATION
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RECOMMENDATION:
Approve a contingency increase of $9,400,000 (79.86%) to the existing Professional Design Services Agreement (PDSA) with Brown and Caldwell for Digester Gas Facilities Replacement, Project No. J-124, for a total contract amount of $11,770,000 and a new total contingency amount of $10,577,000 (89.86%).
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BACKGROUND
The digester treatment process at both Orange County Sanitation District's (OC San) plants produces a methane-rich digester gas that is compressed and used in the central generation (CenGen) facilities to produce electricity. Flares are utilized to burn the digester gas when CenGen is not operating, or the capacity is limited. The Plant No. 1 facilities were built in 1992 and the Plant No. 2 facilities were built in 1990.
The original scope for this project was to replace the gas compressors and flares at both plants, rehabilitate the existing gas compressor building at Plant No. 1, and construct a new gas compressor building at Plant No. 2.
As this project neared design completion, the construction cost estimate increased significantly. At that time, OC San also created a Heavy Mechanics Group that has become much more proficient at overhauling complex industrial machines like the gas compressors and have completed the overhaul of the existing gas compressors at both plants to maintain proper operation, changing the need to replace them. The project team performed a feasibility study and life cycle costs analysis to determine if replacement or rehabilitation (reuse of the existing gas compressors and replacement of remaining equipment that is at the end of its useful life) would be the most cost effective. The evaluation determined that rehabilitation had a substantially lower construction cost and an o...
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