Garvey Avenue Grade Separation Drainage Improvement Project, CIP884


SCH Number
Lead Agency
City of El Monte
Document Title
Garvey Avenue Grade Separation Drainage Improvement Project, CIP884
Document Type
MND - Mitigated Negative Declaration
Present Land Use
Public Roadway
Document Description
The City of El Monte is proposing to construct the Garvey Avenue Grade Separation Drainage Improvement Project within City boundaries. The Project will be located just south of the I-10 freeway, and along the Garvey Avenue underpass, which separates vehicular traffic on Garvey Avenue from the Southern Pacific Railroad and Metrolink Railroad. The original roadway underpass was constructed in 1933. Since the original roadway underpass construction, development of nearby commercial and industrial land uses has significantly increased the imperviousness of the surrounding area, leading to significant stormwater accumulation, and has created a flooding problem at the grade separation sump. This project proposes to include the installation of a new storm drain and an infiltration system to alleviate flooding problems during storm events. The proposed storm drain improvements are intended to meet current design standards for a 50-year storm and reduce the occurrence of flooding at the Garvey Avenue Grade Separation. The design objective is to reduce the potential flooding hazards to the general public from multiple times a year to approximately once every 50 years. An additional design objective is to improve the water quality of the San Gabriel River by capturing pollutants from dry-weather flows and stormwater from rain events less than or equal to the water quality storm event, defined as the 85th percentile, 24-hour rainfall event. The proposed improvements include the following key elements: ? New catch basins on Maxson Place will capture the additional flow from Caltrans’ roadway runoff and the outflow from the triple 24-inch culvert crossing under the freeway, as well as runoff captured from the nearby mobile home park and two commercial lots. A proposed 6-foot wide by 2-foot high Reinforced Concrete Box (RCB) storm drain will convey the intercepted flow from these catch basins underground to the intersection of Maxson Place and Garvey Avenue. ? Catch basins on Garvey Avenue will capture flows from areas east of Maxson Place. This includes commercial properties on Garvey Avenue on both the north and south sides of the street, stretching east to Durfee Avenue. The catch basins will connect to the proposed storm drain in Garvey Avenue. ? New underground infiltration basins will be constructed. The basins will be sized to capture a combined 2.2 million gallons of stormwater from dry-weather and storm events. The stormwater captured in the two infiltration basins will recharge the local aquifer. ? A diversion system and a hydrodynamic separator will be installed in Garvey Avenue to route runoff, using a 36-inch reinforced concrete pipe (RCP), to the proposed Infiltration Basin 1. The hydrodynamic separator will provide pretreatment for improved water quality. It will screen, separate, and trap gross solids to remove floatables and neutrally buoyant materials. ? Storm drain and appurtenance will be constructed to convey runoff from the existing Garvey Avenue Underpass storm drain system that is unable to be pumped out by the existing pump system or captured by the proposed Maxson Place Storm Drain. Flows greater than the pump’s capacity will be pretreated and then routed via a proposed 36-inch RCP to the proposed Infiltration Basin 2. ? A 30-inch pump discharge line may be installed conveying the storm water from the existing pump discharge sump to the Basins. The storm drain may be constructed in the existing easement or may require additional easements from Metrolink.

Contact Information

Lee Torres
Agency Name
City of El Monte, City Engineer
Contact Types
Lead/Public Agency

Vik Bapna
Agency Name
Contact Types
Consulting Firm


El Monte
Los Angeles
Southern California
Cross Streets
Garvey Avenue and Durfee
Total Acres
Parcel #
Public street
State Highways
I-10, I-605
Metrolink, UPRR
San Gabriel Valley Airport
Madrid, Payne, El Monte, Twin Lakes, Mountain View
San Gabriel River, Rio Hondo River, Walnut Creek, San Jose Creek

Notice of Completion

State Review Period Start
State Review Period End
State Reviewing Agencies
California Air Resources Board (ARB), California Department of Conservation (DOC), California Department of Forestry and Fire Protection (CAL FIRE), California Department of Parks and Recreation, California Department of Transportation, Division of Aeronautics (DOT), California Department of Transportation, Division of Transportation Planning (DOT), California Department of Water Resources (DWR), California Highway Patrol (CHP), California Native American Heritage Commission (NAHC), California Natural Resources Agency, California Public Utilities Commission (CPUC), California Regional Water Quality Control Board, Los Angeles Region 4 (RWQCB), Department of Toxic Substances Control, Office of Historic Preservation, San Gabriel and Lower Los Angeles Rivers and Mountains Conservancy (RMC), State Water Resources Control Board, Division of Drinking Water, State Water Resources Control Board, Division of Water Quality, California Department of Transportation, District 7 (DOT), California Department of Fish and Wildlife, South Coast Region 5 (CDFW)
State Reviewing Agency Comments
California Department of Transportation, District 7 (DOT), California Department of Fish and Wildlife, South Coast Region 5 (CDFW)
Development Types
Water Facilities (Storm drain and infiltration galleries)(Type Storm drain, MGD 2.5)
Local Actions
Site Plan
Project Issues
Air Quality, Cultural Resources, Flood Plain/Flooding, Geology/Soils, Greenhouse Gas Emissions, Hazards & Hazardous Materials, Hydrology/Water Quality, Noise, Schools/Universities, Transportation


Draft Environmental Document [Draft IS, NOI_NOA_Public notices, OPR Summary Form, Appx,]
Notice of Completion [NOC] Transmittal form

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