Overview

A project that was four decades in the making – construction on a new $59.6 million, 40,893-square-foot Bay Area Water Treatment Plant was completed in July 2015. The facility provides water to nearly 38,000 customers from a state-of-the-art membrane water treatment plant. Result: increased capacity, dual transmission lines, best in class technology.

Project scope included a new water treatment plant, two finished above ground water tanks, yard piping and equalization basin, plus two miles of new dual transmission lines.

Challenges/Solutions:

• The compacted, three-month project design schedule hinged on completion of the geotechnical investigation and design. G2 expedited all aspects of work to maintain the overall schedule.
• The overall site was raised five feet to elevate new buildings and tanks above the floodplain. Approximately three to four feet of undocumented fill existed below building and tank locations.  G2 recommended removal/replacement of undocumented fill with engineered fill to enable use of shallow foundations, instead of an expensive deep foundation system.
• G2 assisted the design team in developing drawings and specifications for the proposed geotechnical instrumentation, dewatering and drainage, backfill and compaction, excavation support and compaction, and granular materials to address the project challenges.
• Groundwater was as shallow as three feet below existing grades. G2 performed extensive analyses to evaluate site dewatering to lower the groundwater table and allow undercutting/ backfilling, trenching and deep excavations in dry conditions.
• Existing structures and utilities were vulnerable to damage during construction of new facilities.  G2 recommended hydro-excavating at existing utilities to determine their as-built location, avoiding damage to existing structures.