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Water / Wastewater

Group Delta Consultants has performed geotechnical investigations for a number of cities, water districts, and public agencies, including the Cities of Arcadia, Burbank, Costa Mesa, Long Beach, Riverside, and San Juan Capistrano, the County of San Diego, Los Angeles Department of Water and Power, Irvine Ranch Water District, and Moulton Niguel Water District. Many of these projects have been reviewed by the State of California Department of Water Resources, Division of Dam Safety.

Take a look at some of the pipeline and reservoir projects we've worked on below or you can also download our statement of qualifications (SOQ) to provide geotechnical services to the water/wastewater market sector in our SOQs Downloads section. If you would like to discuss your existing or upcoming reservoir or pipeline project, please call Senior Geotechnical Engineer Curt Scheyhing, G.E. at (949) 450-2100.

Haynes Generating Station

Haynes Generating Station

The "repowering project" located at the Los Angeles Department of Water and Power's (LADWP) Haynes Generating Station, located in Long Beach, provides 575 megawatts through a new generating system that is up to 94% cleaner in terms of emissions and 40% more fuel-efficient than two older, 1960s-era generating units that it is replacing. LADWP repowered the facility by building a state-of-the-art power plant that operates with new, combined cycle generating units, which include two gas combustion turbine generators that produce enough steam to power one steam turbine generator.

Group Delta Consultants was initially hired to evaluate indicator pile program Pile Driving Analyzer results, provide pile driving criteria, and assist Kiewit in getting piles approved by LADWP. GDC evaluated the results of CAPWAP, performed wave equation analyses and recommendations for driving of over 1,500 14-inch square prestressed concrete piles.

Subsequently, GDC performed evaluation of twin 60-inch diameter intake pipelines supported on 99 30- and 36-inch diameter drilled piles. We performed a field investigation to develop subsurface conditions along the alignment. We then developed representative ground motions for the design earthquake and performed seismic deformation and soil-structure interaction analysis on multiple representative cross sections using the computer Code FLAC. The results of these analyses provided parameters for the design of the drilled pile foundations and convinced the LADWP that a pile supported pipeline will be safe during an earthquake against liquefaction and lateral spreading. Group Delta also provided axial and lateral capacity of the 30- and 36-inch diameter CIDH piles. During construction, GDC provided observation and Gamma-Gamma testing to verify the integrity of the piles.

Westminster Reservoirs

Westminster Reservoirs

The City of Westminster proposed construction of two 190-ft diameter, 40-ft high, 8 million-gallon, circular steel water storage tanks side-by-side on a 4-acre site. A geotechnical investigation by another firm had provided recommendations for tank design. At the request of the tank designer, Group Delta Consultants reviewed the plans and discovered significant geotechnical problems with the site including large settlement and potential for liquefaction and lateral spreading.

Our subsequent investigation, which included drilling, CPTs, and laboratory tests, confirmed that the site had poor soil conditions. Also present were a 10-ft deep channel and a detention pond in close proximity to the tank pad. GDC estimated that with these conditions the potential for static settlements of about 12-inches was present. Also the potential for liquefaction and lateral spreading and resulting tank failure was high.

In lieu of expensive pile foundations GDC proposed an economical site remediation plan, including installation of stone columns and a soil surcharge, to improve the shear strength and bearing capacity of the soft clays, and decrease post-construction settlement of the tanks. The measured settlements during the surcharge ranged from 9- to 15-inches, close to our prediction.

Group Delta saved the City from a potential disaster because if built according to the original plans, the tanks could have settled more than a foot and probably failed during a seismic event.

Brinton Reservoir

Brinton Reservoir

Group Delta Consultants prepared a preliminary geotechnical report for the City of Banning for their new 8-million gallon water storage reservoir and 4700-feet of 30-inch pipeline.  Our preliminary report on the geotechnical investigation of the site for the reservoirs was submitted and the preliminary tank report will be updated. 

The general alignment of the 30-inch lines starts from the intersection of West Wilson Street and Brinton Road, runs north to the reservoir site, then run northwest and west along a subdivision boundary to the intersection with Mountain Avenue.  The total pipeline length is approximately 4700-feet, and the burial depth of the pipeline ranges between 4-and 7-feet below the existing grade.

10 MG Reservoir, Indio

Proposed site of buried reservoir in Indio

The City of Indio proposed to construct a 10-MG buried concrete water storage reservoir in Indio Hills in the City of Indio, California. Associated improvements include a pump station and two pipelines.

This site is located in a highly active seismic area of Southern California, and is located within an Alquist Priolo Special Studies Zone of the Banning Fault (which is a branch of the San Andreas Fault). Due to the location of the site within the Alquist Priolo Zone, and the importance of the reservoir, the primary purpose of the investigation was to perform trenching at the site to determine whether or not active faulting is present under the reservoir. A secondary purpose of the investigation was to estimate the magnitude of secondary movements at the tank site, if anticipated, due to rupture on nearby major fault(s).

The major geologic/seismic issues at the site were potential for fault rupture and associated displacements, and very high seismic shaking. Extensive trenching performed within the tank site indicated that no active faults were present within the tank area and the potential for primary movements due to fault rupture was low. However, it was discovered that movements of up to 4 inches had occurred due to secondary shearing on some surfaces during past earthquakes. Field consultation and office review was provided by fault expert Dr. Roy J. Shlemon concerning the geomorphology, geology, soil chronology and other geological issues.

Based on our work the reservoir will be built on this site.

Santa Ana River Trunk Sewer

Santa Ana Trunk Sewer Alignment

The new Santa Ana River Trunk Sewer in Riverside will be about four miles long beginning at the east end of the Water Quality Control Plant running along a bike path parallel to the Santa Ana River and ending at Tequesquite Avenue east of the Tequesquite Land Fill in Riverside. The proposed sewer trunk is 4- to 5.5-feet in diameter and 10- to 20-feet deep. About 2500-feet of the alignment will be tunneled under the railroad and in the park area.

Group Delta Consultants provided geotechnical recommendations for the design of this sewer pipeline. Our work included a review of existing information (from our preliminary investigation), supplementary field exploration, laboratory testing, and engineering analyses. Due to the presence of loose to medium dense sands and the shallow groundwater along a portion of the alignment and the proximity to the Santa Ana River, we also evaluated liquefaction and lateral spreading potential along the alignment.

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