Gravity Line Down Murphy Road

Purpose
The Murphy Road segment of the Southeast Interceptor is the first segment to be designed. As described in the City's Collection System Master Plan, the Southeast Interceptor will “intercept” wastewater flow that is currently routed through the City's downtown core system, and route it around the south and east side of the City to a connection with the existing Plant Interceptor pipeline in Northeast Bend.
Schedule

The City has completed 60% design and preparation of construction bid documents is expected to be complete by early Fall 2009. The project is expected to be bid in Fall/Winter 2009/2010 and construction is expected to begin in March 2010.

Design Details
Existing buried utility coordination

The City's design team has evaluated existing buried utilities within the project areas and is closely coordinating with Roats Water System and other franchise utilities within the City's right of way to plan and accomplish the required utility relocations.

Geotechnical Investigation
Citizens may have noticed the project team performing geotechnical borings in September 2008 at locations along Murphy Road. This investigation provided information to designers and will be provided to contractors bidding the project. The boring logs confirmed the presence of rock at relatively shallow depth and the project design and construction schedule is expecting rock excavation, blasting, and use of rock hammers to accomplish the required excavation.
Pipe plan and profile

This segment will be constructed from Parrell Road to Brosterhous Road and will require deep excavations to allow existing pump stations to be taken off-line and to provide future ability to provide sewer service to existing and future development north and south of Murphy Road. Within this segment the pipe diameter ranges from 18-inches to 24-inches and is designed to be installed at depths of 9 to 23 feet below the existing roadway. Trunk sewer line extensions will be extended within Parrell Road, Tapadera, Benham, Broadmoor, Country Club Drive, and Brown Trout Place.
Improvements to existing pump stations

The Southeast Interceptor solves immediate sewer service problems in the area by disconnecting two of the City's existing sewer pump stations (and many private home sumps) from a small 6-inch forcemain (pressurized sewer pipe) and routes these flows by gravity to a single large existing pump station. This will immediately reduce the City's operation and maintenance costs associated with the pump stations (by reducing equipment wear and long pump run times when pumps “compete” with each other to pump flow down the forcemain) and reduce property owner risk associated with failure of home sump components such as check valves.

Construction Phase Impacts

Traffic Control
The requirements to relocate existing utilities and to install the interceptor at the required depths will require temporary detours around the localized construction area. Only emergency traffic (fire, ambulance, police) and local traffic (residents of properties accessed directly off of Murphy Road) will be allowed to pass. The construction is expected to take place in a “segment by segment” manner. Once pipeline construction within a segment is complete, that section of road will be reopened to normal traffic. This segmented approach will limit the length of Murphy Road and connecting roads that are closed to normal traffic during construction at any given time.

Detour Routes. The City's design team will define detour routes as the project design advances, and the City's contractor will be required to maintain temporary traffic control signage to direct drivers to the selected routes. Preliminary work indicates that the shortest detour route around the affected areas are acceptable. Local residents can expect to see some increase in traffic on local streets adjacent to Murphy Road as required to accommodate the detours.

Construction Duration, Dates, and Hours of Construction
The City's design team estimates that construction of the interceptor may occur at average production rates of 40 feet of pipe installed per day along the deepest portions of the alignment. At this production rates, work starting in March 2010 may continue for approximately 30 weeks (March 2010 through September 2010). The project team is refining the construction constraints to be included in the bid package, but multiple crews, multiple construction sites, and extended work hours may be allowed or required to reduce the total construction duration. Additional information is expected to be available as the project design progresses.