Northeast Interceptor Sewer (NEIS)

The Northeast Interceptor Sewer (NEIS) is a major sewer tunnel approximately 8.5-km long, extending northward from the east terminus of the NOS-ECIS sewer located just east of the Los Angeles River, near Mission Road to the intersection of San Fernando Road and Eagle Rock Boulevard. The NEIS corridor is located within the densely developed and populated area of the City of Los Angeles. It was built to provide a downstream outlet for the proposed Eagle Rock Interceptor Sewer (ERIS). An extensive geotechnical instrumentation program was in place during construction.

Group Delta Consultants installed the instrumentation equipment for TSFKK JV, who monitored the construction. GDC's responsibilities included the geotechnical instrumentation and installation of 23 multipoint extensometers, 24 inclinometers, 220 borros-type settlement points, and 12 piezometers. In addition, tiltmeters were installed at critical historic bridge structures and buildings. The extensometers and inclinometers were concentrated at the shaft excavations and freeway crossings. 

North Outfall Sewer -
East Central Interceptor Sewer

The North Outfall Sewer – East Central Interceptor Sewer (NOS-ECIS) is a major sewer tunnel approximately 11.5 miles long furnished with an 11 feet inside diameter pipe. The NOS-ECIS corridor is located in a densely developed area within the central and southern sections of the City of Los Angeles. An extensive geotechnical instrumentation program was set in place during construction.

Group Delta Consultants installed and initialized the instrumentation equipment for the design-build contractor. Group Delta installed 270 multipoint extensometers, 19 inclinometers, and 8 observation wells. Our responsibilities included initial readings of each instrument before turning instruments over to the City of Los Angeles for monitoring except for the strain gages at the shaft excavations which we monitored until the completion of the project. We were also responsible for the instrumentation of the shaft excavation struts with strain gages and monitoring stresses on the struts. The monitoring of strain gages had been accomplished by using remote digital transmission of data from the excavation sites to our offices.

Middle Fork Surge Shaft

The 17-kilometer long Middle Fork Tunnel is a hydro-power/water pressure tunnel in northern California. The tunnel has a 10 feet diameter, 600 feet deep surge shaft at the tunnel downstream, located in a remote area of the Sierra Mountains. The shaft, made out of 2-ft thick non-reinforced concrete, had been deteriorating and leaking. The project consisted of preventing the leakage by placing an 8-ft diameter, 550-ft long, 0.75-inch thick steel liner inside of the existing surge shaft, then filling the void with concrete.

Group Delta Consultants provided installation, monitoring and interpretation of the recorded data for this unique project. Monitoring of the steel liner movement after the installation was conducted with 72 strain gauges. Six piezometers were installed between the existing concrete shaft and new steel liner to monitor any changes of water level in the annulus, and verify that the leakage of the surge shaft has stopped. The liner load that was supported by a steel frame during installation and grouting was monitored with 4 load cells. The monitoring was achieved with systems of multiplexers and data loggers.

Brightwater East Project

This project is part of a $705 million wastewater conveyance system named Brightwater which will include the East tunnel, the Central tunnel and a West tunnel totaling 13 miles of conveyance in King County, Washington. The East Tunnel Contract of the conveyance system consists of 14,050 feet of precast concrete segmentally-lined tunnel with an inside diameter of 16 feet 8 inches ID tunnel containing four pipes & three fiber optics cables; construction of launch & receiving shafts; pump station excavation & shoring; 2,400 LF micro tunnel connecting the North Creek tunnel shaft to the existing pump station.

Group Delta Consultants provided geotechnical instrumentation installation for this project. Instrumentation included observation wells, piezometers, three point rod extensometers inclinometers and technical submittals.

Eastside LRT

The Eastside LRT is a southeasterly extension of the Pasadena Gold Line (formerly Blue Line) from Union Station passing through the cities of Los Angeles and East Los Angeles, and is 5.8 miles long. The project consisted of an at-grade alignment, four existing bridges, one 456-ft long new bridge across US 101, and a tunnel section (1.8 miles). Group Delta Consultants provided geotechnical instrumentation installation for this project. Geotechnical instrumentation included:

• Technical Submittals;
• 2900 feet of borehole Extensometers (3 points);
• 1500 feet of Inclinometers Tape Extensometers;
• Strain Gauges (12 load instrumentation zones and 4 levels);
• Over a 1000 Building and Ground Settlement Reference Points;
• 295 feet of Deep Bench Marks; 660 feet of observation wells; and
• Data loggers

In addition to geotechnical instrumentation we have provided full range of geotechnical investigation foundation recommendations and seismic design. Our work has been reviewed and accepted by City of Los Angeles and Caltrans.