2015 Issue

43 ABSTRACT The East Layton Pipeline is a critical aging finished waterline of the Weber Basin Water Conservancy District’s (District or Owner) delivery system that serves as the primary source of drinking water supply for the cities of Layton, Kaysville, Fruit Heights, and Farm- ington, which are located along the Wasatch Front just north of Salt Lake City. The original East Layton Pipeline was constructed in 1955 and includes segments of 30-inch-diameter bar wrapped pipe (AWWAC303) and nonstandard 27-inch-diameter centrifugally cast, reinforced-concrete pressure pipe with rubber gasket joints. Starting in 2010, the pipeline experienced an increased number of leaks requiring emergency repairs, which severely jeopardized the District’s ability to provide a reliable water supply. The pipeline operates with limited system storage and could accommodate shutdown periods of no more than 12 hours during low demands. This paper documents the condition assessment of the existing pipeline, evaluation of alternatives for rehabilitation and replace- ment of the pipeline, and design and construction of the East Layton Pipeline using a ConstructionManager/General Contractor (CMGC) arrangement between the owner, engineer, and contractor. The rehabilitation and replacement evaluation resulted in replacing the existing pipeline with a 36-inch-diameter welded-steel pipeline on a separate parallel alignment through residential streets and slip lining the existing pipeline with a 24-inch HDPE pipe to pro- vide system redundancy and ability to meet future demands. Key attributes of the project include construction of a major pipeline in narrow residential streets, crossing of a canyon with steep side slopes and potential landslidematerial, coordinating utility reloca- tions, surge analysis of existing and future pump stations connected to the pipeline, easement and right-of-way acquisitions, and a sig- nificant public involvement effort prior to and during construction. This paper provides a detailed discussion of key issues and project challenges associated with the rehabilitation and replacement of aging infrastructure from the viewpoint of the Engineer and the Contractor and also discusses the use and benefit of a CMGC alternative project delivery method. INTRODUCTION The Weber Basin Water Conservancy District’s (Owner or District) drinking water system is relied upon by a number of cities and water agencies located in northern Utah. The District’s East Layton Pipeline is the primary source of drinking water for multiple cities located along the populatedWasatch Front north of Salt Lake City, including the cities of Layton, Kaysville, and Fruit Heights. It is also a major supply source for Farmington City. For many of these cities this pipeline provides more than 90 percent of their drinking water and currently there would be no alternate or redundant supply for many residents if this pipeline were to be taken out of service. The northern 7000 foot long reach of the existing East Layton Pipe- line has been experiencing an increased number of leaks over the last 5 to 10 years which has increased operations andmaintenance costs. Due to limited system storage, the pipeline cannot be taken out of service for more than 24 hours during low demand periods, making repairs difficult. Currently the pipeline is operating at design capacity during the summer months and is undersized for meeting projected future demands. PROJECT HISTORY AND BACKGROUND The original 7,000-foot reach of the East Layton Pipeline was con- structed in 1955. At the time of construction, very few residences existed in the area, and the pipeline was constructed in the center of a 20-foot-wide easement that crosses Hobbs Ravine and then traversed open ground southeast toward Highway 89. The align- ment was selected so that the pipeline would operate by gravity flow from the Davis North Water Treatment Plant (DNWTP) and to provide a relatively straight align- ment across the open terrain. Fig- ure 1 shows the existing pipeline alignment overlaid on a 1960’s aerial image on the right and the same pipeline alignment overlaid on a 2012 aerial image along with the parallel replacement pipe in- stalled in 2014. As shown in Figure 1, residential development subsequent to the original construction has greatly encroached upon the pipeline easement and some areas of the pipeline, including air vacuum and Rehabilitation and Replacement of the East Layton Culinary Pipeline By Adam Murdock, P.E. 1 , Tim Petty, P.E. 2 , Judd Hamson 3 , Matt Rasmussen, P.E. 4 1 Project Manager, CH2M HILL, 4246 South Riverboat Rd, Suite 210, Taylorsville, UT 84123; Tel: (385) 474-8540; E-mail: adam.murdock@ch2m.com 2 Design Manager, CH2M HILL, 4246 South Riverboat Rd, Suite 210, Taylorsville, UT 84123; Tel: (385) 474-8546; E-mail: tim.petty@ch2m.com 3 Vice President, Whitaker Construction, 44 South 1050 West, Brigham City, UT 84302; Tel: (801) 589-5624; E-mail: juddh@whitcon.com 4 Project Manager, Weber Basin Water Conservancy District, 2837 East Highway 193, Layton, UT 84040; Tel: (801) 771-1677; E-mail: mrasmussen@weberbasin.com Figure 1. 1960’s and 2012 Aerial View of East Layton Pipeline CULINARY PIPELINE | continued on page 44