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Gold Line Maintenance and Operations Campus

Monrovia, California

Stormwater Management


Metro Gold Line Foothill Extension Construction Authority


Parsons Corporation



Technical Description:

  • (108) ChamberMaxx® stormwater chambers
  • (3) CDS® hydrodynamic separators


The Foothill Gold Line (also known as the Gold Line Foothill Extension) is a 24-mile extension of the Metro Gold Line light rail corridor in Los Angeles, California. The expansion necessitated the need for a new Maintenance and Operations (M&O) Campus, which was built on 24 acres in the city of Monrovia. The M&O facility will be used for servicing, cleaning, painting, and storing light rail vehicles for Metro's growing fleet.

The M&O will be one of the largest facilities in the entire Los Angeles County Metropolitan Transportation Authority (Metro) system and the only facility thus far that meets the U.S. Green Building Council’s Leadership in Energy and Environmental Design Gold standards.

Engineers from Parsons designed a comprehensive stormwater management system that contributed to the sustainability of the site and contributes to the LEED certification standards. Stormwater from runoff from roofs, parking lots, and other impervious surfaces will be captured, treated, and infiltrated for groundwater recharge.

Corrugated Metal Pipe (CMP), often the material of choice for underground infiltration, could not be used due to concerns about conductivity from the many rail lines within the site. Hence, Contech’s plastic solution, ChamberMaxx, was selected by the design team at Parsons Corporation.  ChamberMaxx is a corrugated, open-bottom plastic infiltration chamber system that allows the treated water to be detained and infiltrated into the groundwater aquifers below.

Parsons worked with Contech engineers to design a system using three underground infiltration systems, two of which were constructed from Contech ChamberMaxx infiltration chambers.

Each system utilized 54 chambers to provide an infiltration volume of 5000 CF per system but were arranged in different layouts to accomodate specific site restraints.   One system was long and narrow (15.7 x 135.6) in the back of the facility and the other was rectangular (29.8 x 71.5), placed under a rear parking area.

All three infiltration systems were pretreated using CDS hydrodynamic separators. CDS uses swirl concentration and continuous deflective separation to screen, separate and trap trash, debris, sediment, and hydrocarbons from stormwater runoff. Pretreating with CDS will prolong the life of the ChamberMaxx infiltration systems by removing debris and sediment that can collect within the stone backfill voids. Pretreatment with CDS also aides in maintenance, as the CDS units are easier to clean and maintain compared to the infiltration system itself.

A community open house and dedication for the new facility took place in May 2015. The event was attended by elected officials at all levels of government, transportation officials, and hundreds of community stakeholders. The open house included exhibits of the technology used within the new facility, including an exhibit of the technology used in the stormwater management system. 

Technical Description:

  • (108) ChamberMaxx® stormwater chambers
  • (3) CDS® hydrodynamic separators



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