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Request for Qualifications 61st Pl. W. Retaining Wall Project


61st Place West Retaining Wall Project
Project# ST110003/Grant #D15-067

Deadline: November 30, 2015

The City of Mukilteo is requesting qualifications (RFQ) from qualified professionals or firms to provide professional services for the design and engineering, with the option of construction management and inspection services, for the 61st Place West Retaining Wall Project. The design and engineering includes an alternative analysis, geotechnical investigation, right of way easement acquisition, repairing and/or replacing a 190 foot failing segmental block and soldier pile retaining wall, the installation of a roadway drainage system, and the partial rebuilding and overlay of the existing roadway. This project will be designed and constructed using FEMAís Severe Repetitive Loss Program Hazard Mitigation Grant funds.

In 1996 during a storm event which resulted in a presidential declaration of a disaster, there was a roadway failure on 61st Avenue West. The City received $314,000 in FEMA funds to repair the failed roadway. The repair included the construction of segmental block walls with a soldier pile wall in the middle. A landslide took place on the hillside below and north of 61st Place West on or shortly before March 29, 2011. The main scarp of the landslide was located at the base of two of the retaining walls constructed on the north side of the road in 1998. The ground at the base of the eastern segmental block wall and roughly the eastern two-thirds of the middle soldier pile wall dropped several feet incrementally since initial construction and then rapidly in March 2011. The soil movement resulted in the collapse of the eastern block wall and several feet of soil exposure below the soldier pile wall timber and plywood lagging face. The ground displacement also resulted in the loss of the backfill material placed behind the timber and plywood lagging; the backfill was completely lost between two pairs of piles and partially lost between others. The 61st Place West pavement has been undermined as a result of the backfill lost behind the lagging. The western segmental block wall and about the western third of the soldier pile wall appears intact, but the landslide main scarp appears to be within several feet these structures. The goal of the project is to reduce the risk of loss of 61st Place West. This roadway is the only public access to residential properties as well as the Mukilteo Water and Wastewater Districtís sewer lift station.

Project Description
Phase I of the project will be an alternatives analysis, including geotechnical investigation, to determine if the current retaining walls can be repaired or will need to be replaced by reviewing existing reports and conducting further analysis. Based on the outcome of Phase I, Phase II of the project will obtain right of way easements, repair or replace the current retaining wall structures, install a stormwater conveyance system, partially rebuild the roadway section that has failed, and overlay of the existing roadway.



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