Supervisors authorize contract to repair McDonald Road and Rainbow culverts

The San Diego County Board of Supervisors approved the replacement or rehabilitation of between 20 and 24 culverts including three on McDonald Road and three at a Rainbow intersection.

A 5-0 board of supervisors’ vote, Wednesday, Oct. 16, approved the authorization for bid and subsequent award of a construction contract for the culverts. The contract is structured to include a base bid of 20 culverts and an additive alternative, which can be added to the contract if funding permits, of four culverts. The base bid includes the McDonald Road and Rainbow culverts.

The county’s Department of Public Works maintains more than 18,000 drainage facilities including more than 14,000 culverts. Stormwater crews inspect all county-maintained culverts on a cyclical basis and prioritize them for rehabilitation or replacement. Field engineering staff members inspect the culverts nearing the end of their service life to determine whether replacing the culverts or rehabilitating them with new lining would be the more preferable option.

Lining a culvert involves the installation of an internal sleeve. Lining methods include cure-in-place pipe which utilizes resin-impregnated fabric inserted into the existing culvert, slip lining insertion of solid wall surface into the existing culvert and insertion of spiral-wound pipe which will expand and line the culvert. The internal sleeve restores the pipe’s structural integrity while reducing excavation and thus minimizing traffic impacts.

Repair of holes and the restoration of capacity without replacing the culvert can also be accomplished by invert paving which consists of preparing the invert surface area, or the bottom of the culvert, to receive concrete, installing bar reinforcement and anchorage devices and paving the inverted area with concrete on the bottom of the pipe to fill existing holes and restore it to a structurally-sound pipe floor. If the culvert is damaged beyond economical repair, a culvert replacement is more appropriate than rehabilitation in which case the existing culvert is removed and a new one is installed.

Three culverts at 799 McDonald Road and 830 McDonald Road will be replaced. The work will also replace three culverts at Fifth Street and Huffstatler Street in Rainbow.

The estimated cost for the culvert repair contract, including contingency, is $1,520,000. Highway User Tax Account revenue derived from the sales tax on gasoline will provide $1,350,000 while a previous-year balance for the San Diego County Flood Control District will be used for $170,000.

The culvert repair and replacement on a countywide basis is scheduled to begin in spring 2020 and be complete during summer 2020. Before the start of construction residents and businesses will receive mailers or notices on door knobs notifying them of the upcoming work. Traffic control measures will be implemented during the construction to limit impacts to community members and other travelers.