EAST CHERRY CREEK VALLEY WATER AND SANITATION DISTRICT

WILLOWS PIPELINE AND WESTERN WELLFIELD CONNECTION PROJECTS

Douglas and Arapahoe Counties, Colorado

Lyman Henn was retained by Camp Dresser & McKee on behalf of the East Cherry Creek Valley Water & Sanitation District (ECCVWSD) to conduct a geotechnical engineering investigation along the alignment of the proposed Willows Pipeline transmission water main and Western Wellfield Connection pipelines in Douglas and Arapahoe Counties , Colorado .

The 13 miles of transmission pipeline includes trenchless crossing of I-25 as well as several heavily traveled paved roads. The alignment also crosses Cherry Creek as well as smaller drainage's by cut and cover methods. The 8.5 combined miles of wellfield connection pipeline includes a trenchless crossing of C-470, Colorado Boulevard , Arapahoe Road , and other paved roadways. The alignment also crosses Little Dry Creek as well as other local drainages by cut and cover methods.

Lyman Henn performed a comprehensive review of previous geotechnical data collected during construction of highway E-470 and adjacent areas and summarized all pertinent previous data a preliminary report. Based on the preliminary report, Lyman Henn planned geotechnical investigations for the Willows Pipeline to augment and verify previously collected data. As a separate effort, Lyman Henn planned geotechnical investigations along the Western Wellfield Connection pipeline alignments. Lyman Henn coordinated and conducted the subsurface investigation programs, which included 39 borings including five groundwater observation wells along the Willows Pipeline and 64 borings along the Western Wellfield Connection pipeline alignments. The purpose of these studies was to determine the general subsurface conditions by conducting geologic reconnaissance and drilling test borings, and to evaluate the subsurface conditions with respect to vault and pipeline design, excavation, pipe bedding, and backfilling. Also included was an evaluation of the site with respect to potential construction problems and recommendations dealing with the earthwork and quality control during construction.

Lyman Henn provided recommendations for pipeline and vault design along with construction considerations for trenchless crossings. Areas of shallow groundwater and potentially unstable subgrade and/or raveling soils were delineated in the geotechnical report. Lyman Henn provided support for the backfill grouting of the trenchless crossings and other earthwork-related issues during construction.