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Geotechnical Engineering Report <br /> Proposed Flight Line Steam Line Project lrerracon <br /> Boeing Everett Facility• Everett, Washington <br /> January 17, 2012 • Terracon Project No.: 81115085 <br /> saturated, or frozen, the affected soil should be removed prior to placing Foundation Material <br /> Class A. Overexcavation for compacted backfill placement below foundations should extend <br /> laterally beyond all edges of the foundation at least 8 inches per foot of overexcavation depth <br /> ' below foundation base elevation. We recommend that Terracon be retained to observe and test <br /> the foundation bearing materials. <br /> ' 4.4.3 Foundation Drains <br /> In our opinion, the utilidor should be provided with a permanent drainage system to reduce the <br /> risk of future moisture problems. We offer the following recommendations and comments for <br /> drainage design and construction. <br /> ' We recommend that both sides of the utilidor include a perimeter foundation drain to collect <br /> exterior seepage water. The drain should consist of a minimum 6-inch diameter perforated PVC <br /> pipe. We recommend that perforations be approximately 3/8- to 1/2-inch in diameter on <br /> approximately 5-inch centers, with two rows of perforations parallel to the axis of the pipe and <br /> about 120 degrees apart. The pipe should be laid with the perforations facing down. The <br /> perforated drain pipe should be embedded in at least an 18-inch wide envelope of clean, free- <br /> draining, well graded mixture of course sand and gravel. The free-draining materials should <br /> meet the requirements of Section 9-03.12(4), Gravel Backfill for Drains, as presented in the <br /> ' WSDOT Standard Specifications for Road, Bridge, and Municipal Construction. A non-woven <br /> filter fabric such as Mirafi 140N, or equivalent, should envelope the free-draining granular <br /> material. Ideally, the drain invert would be installed at or very slightly below the base of the <br /> utilidor foundations. <br /> Sufficient cleanouts should be provided for the inspection and maintenance of the entire length <br /> of piping. Roof downspouts, parking lot drains, and drains from any other runoff surfaces <br /> should not be tied into the perforated piping system of the foundation drains. Instead, the runoff <br /> water collected from such sources should be routed through a separate tightline piping system <br /> and sent to a catch basin or other appropriate discharge location. <br /> 4.5 Lateral Earth Pressures <br /> Preliminary plans indicate that the cast-in-place and precast utilidor components will include <br /> ' subgrade walls up to about 16 feet tall. The lateral earth pressure recommendations given in the <br /> following paragraphs are applicable to the design of rigid retaining walls subject to slight rotation, <br /> such as cantilever or gravity type concrete walls. These recommendations are not applicable to <br /> the design of modular block - geogrid reinforced backfill walls. Recommendations covering these <br /> types of wall systems are beyond the scope of services for this assignment. However, we would <br /> be pleased to develop recommendations for the design of such wall systems upon request. <br /> Walls with unbalanced backfill levels on opposite sides should be designed for earth pressures <br /> at least equal to those indicated in the following table for the active and at-rest condition. Earth <br /> Responsive • Resourceful • Reliable 15 <br />