Staff report from the May 17, 2023, meeting of the Contra Costa Transportation Authority
The Interstate 680/State Route 4 Interchange Improvements, the Project is being delivered based on available funding. Phase 3 was completed on May 1, 2023. Phases 1, 2A, and 4 will be constructed next and are currently in the final design phase. Phases 2B and 5 will be delivered in the future as funding becomes available.
The overall Project will be implemented in five phases as funding becomes available. Each of the five
phases can be independently constructed and provide incremental benefits. Phase 3 was completed
on May 1, 2023. Phases 1, 2A, and 4 will be constructed next and are currently in the design phase.
Phases 2B and 5 will be delivered in the future as funding becomes available.
Phase 1 – Northbound (NB) I-680 to Westbound (WB) SR4 Connector
This phase will construct a two-lane flyover direct connector from NB I-680 to WB SR4 and remove
the existing NB I-680 to WB SR4 loop, construct auxiliary lanes, a slip ramp, and install a ramp
metering facility. Phase 1 is currently in final design.
Phase 2 – Eastbound (EB) SR4 to Southbound (SB) I-680 Connector and Improvements to SR4
Interchange at Pacheco Boulevard
This phase has been further split into Phases 2A and 2B:
Phase 2A – This phase will extend the SB I-680 collector-distributor ramp and install a ramp metering
facility for the WB SR4 on-ramp. Phase 2A is currently in final design.
Phase 2B – This phase will construct a two-lane diagonal ramp from EB SR4 to SB I-680, a slip ramp
from Pacheco Boulevard to SB I-680, remove the existing diagonal ramp, and construct an auxiliary
lane on EB SR-4 from Morello Road to the new diagonal ramp.
Phase 3 – SR4 Median Widening between Morello Avenue in the City of Martinez and SR242 in the City of Concord – This phase completed construction on May 1, 2023. Phase 3 widened SR4 from four to six lanes for approximately four miles, including the addition of approximately two miles of High Occupancy Vehicle (HOV) lanes in the EB direction. In addition, Phase 3 replaced Grayson Creek Bridge and raised the profile of SR4 from east of I-680 to east of Grayson Avenue.
Phase 4 – SB I-680 to EB SR4 Connector
This phase will replace the SB I-680 to EB SR4 loop ramp with a direct connector and remove the
existing SB I-680 to EB SR4 loop ramp. It will also construct an auxiliary lane on EB SR4 from the connector to the Solano Way off-ramp. Additionally, it will install a ramp metering facility for the EB
SR4 on-ramp. Phase 4 is currently in final design.
Phase 5 – WB SR4 to NB I-680 Connector
This phase will replace the existing one-lane NB I-680 to EB SR4 diagonal ramp with a slightly
relocated two-lane diagonal ramp, replace the WB SR4 to NB I-680 diagonal ramp with a two-lane
diagonal connector, and widen the WB SR4 to SB I-680 loop ramp from a single lane to two lanes.