Treatment Systems

The use of proactive project management, construction phasing, and partnering resulted in a smooth construction process with no litigation and project completion on time and within budget (Dennis and Oskoui, 1997). The complex pipeline project involved dual-use criteria, jacked/tunneled sections; primary pipeline crossings of highways, railroads, a seismic fault, and flood control channel; a complex hydraulic diversion structure; and live sewer tie-ins. Camilleri et al. (1997) discussed the construction of a new 107-cm (42-in.) diameter, interceptor, portions that encountered wetlands, a force main junction, an above-ground creek crossing, and modifications to an existing overflow chamber. To maximize available construction time, a prepurchase contract was developed for the longer lead time items such as large-diameter pipes and manholes. The challenges in the construction of a 3 109-m (10 200-ft) wastewater storage and diversion tunnel were presented by Maiolini et at. (1997). Complex geological issues, reducing constructing effects in sensitive urban areas, and special contracting practices adopted for the project were addressed. Microtunneling, along with a jet-grouting technique for creating soil-cement columns to support the sewer pipe, was selected over the traditional open-cut technique for the Nimitz Highway Relief Sewer Project (Honke et aI., 1997). Construction of the sewer was completed in 1996, ahead of schedule and under budget. Cusack et at. (1997) discussed the relocation of nine different utilities using trenchless technology during the expansion of interstate highways 1-90 and 1-93 in downtown Boston. This crossing of nine tunnels is an example of the "Utilidor" concept that allows access for operations and maintenance with the possibility of adding more infrastructures at a later date. Myhre and Shah (1997) compared tunneling contract costs and average rates of progress for various tunneling methods. New York City's decision to use various tunneling methods resulted in bids that averaged 20% below design and construction estimates. Microtunneling using precast manholes as jacking shafts has been the city's method of choice for sewer installation projects. Singh (1997) explained the way total quality construction can be implemented in tunneling projects. Lasting success was attributed to using two techniques: (I) process mapping and (2) managing process performance. Three case histories using horizontal directional drilling were presented by Robbins et at. (1997). Significant advantages to using the technology include fast and clean installation with little disruption to the environment; however, experienced companies report that, on projects bid as complete installations, the success rate is approximately two out of three. The Englewood Water District used vacuum sewers rather