Construction Cost/Value of Award: $1,834,210
Yerba Buena Engineering & Construction Inc., performed for the NPS at Fort Cronkhite, Golden Gate National Recreation Area, repairs to the foundations of 18 historic buildings, including removal of designated portions of existing foundation piers and existing wiring, piping, ramps, landings and other existing utilities and facilities to access the work areas.
Yerba Buena, as the prime contractor, worked in conjunction with the NPS to review all protective measures including litter control and maintaining a clean work site to prevent attracting animals (such as ants, mice, raccoons, etc) to the construction location. The protection of wildlife including swallows and owls was also a key essential during the performance of this project. Yerba Buena took extra precaution in confining all operations within minimal limits, to prevent damage to the natural surroundings.
The site is located next to a sensitive wetland and lagoon, so a Storm Water Pollution Prevention Plan (SWPPP) was implemented to prevent construction debris and waste from entering the storm drainage system that empties directly into the lagoon. In addition, the project included the abatement of hazardous materials, necessitated preservation of historical/natural features, and performed adjacent to occupied areas requiring a high degree of coordination with the client to minimize disruption to existing facilities. The site had also been determined to be archeologically sensitive due to the existence of artifacts such as charcoal, human bones, ash, fire rocks and building materials. Yerba Buena worked with an Archeological Monitor throughout the project duration to record, collect and protect cultural resources discovered. Yerba Buena maintained excellent communication with the Archeological Monitor of activities, by providing notification 72 hours in advance of new activities (phases) such as ground-disturbing site work.
Yerba Buena Engineering & Construction provided temporary barriers, including straw wattles, hay bales and silt fencing, to protect existing trees and plants as well as root zones. The project required the installation of new reinforced concrete foundation piers, walls and footings, supplemental framing and connectors including shear walls, as well as a new foundation drainage system and a sheet-metal liner. The foundations were rebuilt to address the spall and corrosion-related deterioration of concrete along with restoration of the façade of the foundations to match the historical structures.
To limit the potential for damage to the lifted historical structures and reduce the potential risk associated with winter weather conditions, an accelerated schedule was implemented by revising the concrete specifications. This reduced the cure time from 28 days to three days, allowing for the shoring to be moved three weeks sooner than originally planned. This reduced the total project duration from 360 days to less than 200 days. This project was completed ahead of schedule and within budget.