State Route 120 / Guthmiller Road Interchange Improvement

project approval & environmental document (pa&ed) phase

The City of Lathrop, in cooperation with Caltrans, the San Joaquin Council of Government (SJCOG), and the Federal Highway Administration (FHWA) proposes to improve local and regional circulation and reduce existing and future congestion by improving the I-5 /Louise Avenue Interchange. The project is locally sponsored. Interchange improvements are needed to enhance traffic operations and mobility which will accommodate future traffic demands as a result of the growth planned in the City of Lathrop’s General Plan. The I-5 / Louise Avenue interchange is a Type L-1 tight diamond configuration, with single lane on and off-ramps. Recent improvements have provided for turning movements by widening at the ramp termini. River Islands Parkway has been improved and widened to provide access to the Mossdale Landing, River Islands, and Central Lathrop developments. The reconstruction of the interchange (Alternative 2) may close Manthey Road at River Island Parkway. The remaining properties will be accessed from Golden Valley Parkway. Golden Valley Parkway is a major arterial that parallels I-5 and replaces Manthey Road within this area. The project proposes to replace the existing tight-diamond (L-1) I-5 / Louise Avenue Interchange with one of the following two (2) project alternatives: Alternative 1 – Diverging Diamond Interchange (DDI) Alternative 2 (from PSR) – L-1 (east side) / L-9 (west side) Partial Cloverleaf-Tight Diamond Interchange (PC-TD)