Former Naval Fuel Depot Point Molate Mitigation Wetland Design

Terraphase provided design and construction oversight for a 0.5-acre mitigation wetland at the former Point Molate Naval Fuel Depot in Richmond, California. The project aimed to restore seasonal wetland habitat to offset site-related impacts and support long-term ecological function in an upland area.

Scope of Services

Terraphase prepared both draft and final construction design documents and managed all phases of construction implementation. The team coordinated with resource agencies, developed drainage infrastructure, and oversaw activities including site preparation, earthwork, installation of drainage controls, seeding, planting, and fencing. The objective was to create a rainwater-fed seasonal wetland dominated by native hydrophytic vegetation and shallow surface ponding that would thrive within five years of construction. Ongoing monitoring has confirmed successful wetland establishment. The project included quality control reviews of the wetland design and construction, and the habitat mitigation monitoring plan.

Notable Accomplishments:

• Coordinated with resource agencies and project partners
• Implemented drainage controls for seasonal water retention
• Verified successful wetland establishment through monitoring

Tahoe Cedars Water Line Replacement Design

Terraphase led the development of the 30% design and cost estimate for the Tahoe Cedars Water Line Replacement Program on behalf of the Tahoe City Public Utility District (TCPUD) in Nevada. The project involves significant infrastructure upgrades across a residential community and along California State Route 89. The project will support the development of a progressive design-build program.

Scope of Services

Terraphase’s 30% design scope included the alignment and layout of over 50,000 linear feet of 8- and 12-inch water mains, replacement of more than 100 customer service laterals and meter connections, and over 50 fire hydrants. The design was organized into nine segments, consistent with TCPUD’s Tahoe Cedars Water Master Plan.

Terraphase also developed a detailed engineer’s cost estimate using historical cost data from TCPUD and neighboring agencies. Data from 14 comparable projects were analyzed to develop composite unit rates through time-weighted averages. The estimate accounted for cost escalation using five construction cost indexes and considered variables such as night work, dewatering, and rock excavation.

Notable Accomplishments

• Designed over 50,000 linear feet of water mains and associated infrastructure
• Developed cost estimates based on analysis of 14 similar historical projects
• Created a customized cost database with adjusted unit rates
• Aligned the design with TCPUD’s Water Master Plan to support progressive design-build delivery

Northern California Utility Stormwater Management Design

Terraphase led the design of drainage improvements and stormwater sedimentation basins for a Northern California utility district. The location of the work was a receiving yard for soil generated during construction and maintenance projects and is permitted under the State Water Resources Control Board (SWRCB) Construction General Permit (CGP).

Scope of Services

Terraphase led the engineering design of drainage improvements across the entire stockpile site to accommodate planned upgrades and long-term expansion.

Terraphase completed hydrological analyses of the stockpile site to develop drainage areas and estimate run-off quantities. These analyses supported the design of two new sedimentation basins (totaling over 100,000 cubic feet of capacity) and their tributary drainage channels for detention and sediment reduction of all run-off prior to discharge to the surrounding open space areas. The design was delivered in a design-build approach working collaboratively with the utility district and the earthwork contractor.

Notable Accomplishments

• Collaborated with the utility district and its earthwork contractor to design and construct the drainage improvements before the rainy season
• Met the utility’s operational and compliance requirements
• Incorporated access improvements requested by stakeholders, including utility district operations and maintenance staff, contractors, and rangers for the adjacent park area