How a Permitting Agency’s Proactiveness can Contribute to the Success of a Microtunnel Project

摘要

Occasionally new trenchless construction causes damage to existing infrastructure requiring expensive fixes. Typically the infrastructure owner will protect itself through language in the encroachment permit while some agencies are taking a more proactive approach. Orange County Flood Control District (OCFCD) is one such agency. Motivated by a multi-million dollar repair to channel levees damaged by microtunneling, OCFCD has hired specialist trenchless consultants to monitor projects that could potentially affect County infrastructure. This paper discusses one such project.San Juan Creek is a channelized creek with concrete lined levees. Moulton Nigel Water District (MNWD) has installed a 48 inch steel casing beneath the creek by microtunneling for a 30-inch effluent transmission main, as replacement for the existing line that was exposed by scour in a flood event. Orange County Public Works (OCPW), on behalf of OCFCD retained trenchless specialists from Mott MacDonald to monitor and advise them on the microtunnel elements of the project. OCPW were reimbursed by MNWD as a condition of the encroachment permit.