Serving professionals in engineering, environmental, and groundwater geology
since 1957

MONTHLY DINNER MEETING

Date: Tuesday, November 14th
Location: Stevenís Steak House, 5332 Stevens Place, Commerce, California

Time: 6:00 p.m.-Social Hour; 7:00 p.m.-Dinner; 7:45 p.m.-Presentation

Cost: $30 per person with reservations, $35 at the door, $15 for students with a valid Student ID

Reservations: Please call (323) 889-5366 or email rmunro@mactec.com

SPEAKER: Morton Price, City of Los Angeles, Bureau of Engineering Geotechnical Engineering Division

TOPIC: Mitigation Measures for Tunneling Through a Groundwater Gallery with a Hard Rock Shielded Tunnel Boring Machine, Los Angeles, California

ABSTRACT

The City of Los Angeles is updating the main waste water conveyance system which passes through the Los Angeles Narrows. The recently constructed North East Interceptor Sewer (NEIS) forms a central segment of this system. The Upper Reach of the NEIS tunnel was mined through the shale and sandstone of the Miocene Puente Formation. The geologic investigation showed the Upper Reach of the NEIS tunnel was to be mined through Miocene Puente Formation using an open face TBM. Literature research revealed that a 1906 groundwater gallery in the vicinity of the NEIS tunnel crossed the Upper Reach of the tunnel. A location of the Narrows Gallery was obtained from the 1906 plans, and 25 ft on either side of the Gallery was grouted. Continuous core borings were advanced in the vicinity of the Narrows Gallery to verify its location. These borings were grouted with low mobility grout (LMG) at the Narrows Gallery depth to create a barrier for groundwater flow into the NEIS tunnel. Two monitoring wells were installed to measure the effectiveness of the grout. The presence of the Narrows Gallery was inconclusive. Mining proceeded accompanied by probing ahead. During probing near the extent of the grouted area, the Narrows Gallery was encountered. More continuous rock core borings were advanced, and subsequently filled with LMG. Rock core indicated the geometry of the Narrows Gallery was not completely defined. Mining proceeded with flows of groundwater into the tunnel of 500 GPM. After the TBM passed through the Narrows Gallery, the rest of the NEIS tunnel was successfully mined.

SPEAKER BRIEF BIOGRAPHY

Morton's educational background consists of a BS in Geology (1999) from Cal Poly, Pomona. Currently, he is pursuing an MS in geology from Cal State Los Angeles. His Masters Project is a hydrogeologic evaluation of the Baldwin Lake at the Los Angeles Arboretum. Morton holds a Professional Geologist license and is preparing for the Certified Engineering Geologist License exam. He has worked for the City of Los Angeles, Geotechnical Engineering Division since 2001 working on various projects involving underground construction, landslide investigation and environmental geology. Before his City experience, he spent two years at the Los Angeles Regional Water Quality Control Board investigating water quality impacts from septic systems in the Oxnard Forebay and Malibu areas. Morton Price, City of Los Angeles, Bureau of Engineering Geotechnical Engineering Division, 213-847-0466.