The San Gabriel Basin has been the subject of environmental investigation since 1979 when groundwater contaminated with volatile organic compounds (VOCs) was first detected. In May 1984, four areas of groundwater contamination within the San Gabriel Valley were listed on the U.S. EPA National Priorities List (NPL).
Geosyntec’s Scope of Services
In 2002, Geosyntec was retained by a multi-party PRP group to provide overall technical strategy for Good Faith Offer and Consent Decree Statement of Work negotiations. Our work focused on the remedial design and action implementation to address a dissolved chlorinated plume for the eastern shallow and southern deep groundwater portions of the El Monte Operable Unit (EMOU) of the San Gabriel Valley NPL Site.
Geosyntec prepared the detailed designs of the environmental infrastructure to be installed at the site. This work included the engineering design of the extraction and reinjection piping throughout the site. Due to the location of the site, we also performed extensive surveying and investigation to design pipeline routes around existing utilities that were in operable condition. The groundwater system included over 9,500 feet of below grade double walled high density polyethylene conveyance piping for the shallow system and over 10,000 feet of ductile iron piping for the deep system. The pipeline design included a railroad and bridge crossing. Our design team drew upon their railroad engineering experience to prepare the design of the railroad crossing in accordance with railroad standards and their structural engineering experience to design a suspended pipeline for the bridge crossing. Geosyntec developed detailed design drawings including the plan and profile drawings; electrical and single line diagrams; civil, mechanical and structural details; and the detailed specifications for procurement and installation of the designed systems. We prepared all drawings and specifications in the Construction Standards Institue (CSI) format, and submitted all designs for construction permitting.
In addition to the environmental piping, Geosyntec designed the pumps and treatment system for the site. The design included pumping and treatment for both the shallow and deep aquifers as separate systems. Groundwater from the shallow aquifer is pumped to the treatment plant where it is treated by a granular activated carbon (LGAC) system, then re-injected into the aquifer. Groundwater from the deep aquifer is pumped to the treatment plant where it is also treated by a LGAC system and chlorine, then introduced into the City of El Monte’s water distribution system for domestic use.
By applying sustainable design principles, Geosyntec’s innovative treatment system design for the shallow and deep aquifers allowed the groundwater to be treated and made available for re-used.