FROM: Robert Thompson, General Manager
Originator: Mike Dorman, Director of Engineering
SUBJECT:
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PRIMARY SEDIMENTATION BASINS NO. 3-5 REPLACEMENT AT PLANT NO. 1, PROJECT NO. P1-126
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GENERAL MANAGER'S RECOMMENDATION
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RECOMMENDATION: Recommend to the Board of Directors to:
Approve a contingency increase of $849,780 (6%) to the existing Professional Design Services Agreement with Black & Veatch Corporation to provide design services for Primary Sedimentation Basins No. 3-5 Replacement at Plant No. 1, Project No. P1-126, for a total contingency not to exceed $2,266,080 (16%).
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BACKGROUND
Primary treatment is the second of three liquid treatment steps at Orange County Sanitation District (OC San) Plant No. 1 which removes suspended solids using large concrete primary sedimentation basins. Plant No. 1 has 26 rectangular clarifiers constructed in the 1980s and 1990s and three circular clarifiers constructed in the late 1950s and early 1960s. Due to the current degraded condition of the circular clarifiers, they currently provide additional capacity during peak wet weather flows and when rectangular clarifiers are unavailable for maintenance or condition assessments. The project will replace the three circular clarifiers and related primary treatment facilities to restore reliable treatment capacity.
RELEVANT STANDARDS
Ensure the public’s money is wisely spent
24/7/365 treatment plant reliability
PROBLEM
The original Professional Design Services Agreement included a 10% contingency to address changes to the original Scope of Work. A significant portion of the contingency has been used to reevaluate the rehabilitation versus replacement concept, perform system-wide electrical power system studies, review updated structural code requirements, and design a new primary effluent junction box. The new junction box reduces the need for bypass pumping during construction and provides a long-term hydraulic benefit by allowing...
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