Commission approves contingency increase for SR‑71/91 interchange after differing site conditions

The Riverside County Transportation Commission committee approved an increase in the construction contract contingency for the SR‑71/91 interchange improvement project to address additional costs from differing site conditions encountered during foundation construction.

John Terracio, senior capital projects manager, said the construction contract originally awarded to Skanska USA Civil in October 2022 was for $120,500,000 with a 12% contingency ($14,460,000) for a total not-to-exceed $134,960,000. During construction, subsurface conditions materially different from contract documents — including large cobbles and boulders, higher-than-anticipated groundwater, and buried manmade objects — impacted 10 of the 13 CIDH (cast‑in‑drilled‑hole) foundations.

Terracio said the differing site conditions (DSCs) drove the majority of change orders: "78% of the CCOs for the project are just over $13,000,000 were related to differing site conditions," and staff now forecasts a contingency shortfall of just over $2,300,000. He recommended increasing contract contingency from $14,460,000 (12%) to approximately $16,800,000 (about 14%) to produce a final contract total slightly over $137,000,000 and to authorize contingency work as needed.

Vice Chair Conner asked whether the cost increase was due to supply‑chain issues or global material-price rises; Terracio replied the cause was the subsurface conditions encountered during drilling, not supply‑chain impacts, and that core drilling had not revealed the full extent of the DSCs. Staff said the overall project remains within its originally approved $137,300,000 allocation and that no additional project funding is required.

Commissioners moved and seconded the recommendation, and the clerk recorded affirmative votes; the committee approved the contingency increase and authorization to approve contingency work to close out the contract.