11632 EVERGREEN WAY BASE FILE 2018-01-01 MF Import

Proposed Relail Development J-1443 ' l 12'^Street and Hwy.99 Febn�ary 26,2004 � Everett,Washington. Page IS Utility Trenclune and Backfilling Existing on-site, mderground utilities should be removed, relocated or properly abandoned in place in order to prevent possible future settlement problems. Any existing underground utilities should be decommissioned, abandoned, or backfilled in accordance with all applicable State and local regulations. Alternarively, abazidoned utilides may be grouted in place. Underground utililies that aze to be reused should be evaluated by the appropriate engineer and utility backfill should be evaluated by the geotechnical engineer, to determine their potential effect on the new sWcture. If an� exisUng utilities are to be pteserved, grading operarions must be carefully perfotmed so as to not disturb or damage the exisNng utility. All utility subgrades should be firm and unyielding, end frce of all soils that are loose, disturbed, or pumping. Such soils should be removed and replaced, if necessary. All structural fill used to replace overexcavated soils should be compacted as specified and as recommended in tlus report. If water is encountered in the excavarions, it s6ould be removed prior to fill placement. Alternatively, quarry spalls or pea gravel could be used for bac�ll below the water levcl. Native soils are considered suitable for utility trench backfill provided thcy can be adequately compacted. Flowever,much of the native soils contain a significant fraction of cobbles and boulders that can damage buried utilities if placcd direcUy on ihe materials or if the material is placed directly on We utilities. Therefore, we recommend that a minimum of 4 inches of ( bedding material be placcd above and below all uflli6es that are suppoRed on gravelly and cobbly soils or in general accordance with the utility manufacturer's recommendations and local ordinances. We recommend that pipe bedding conform with Section 9-03.12(3), Gravel Backfill for Pipe Zone Bedding, as presented in the 2002 WSDOT Standazd Specifications for Road, Bridge, and Municipal Construction. All excavation, should be wide enough to allow for compaction ar�und the haunches of pipcs and underground tanks. Otherwise, materials such as controlled density fill or pea gravcl could be used to eliminate the compactive effort required. Backfilling for the remaindcr of the trenches could be completed utilizing common fill or select granular fill, depending un soil moisture and weathcr conditions. Compaction of backfill material sliould be accomplished with soils within t2 percent of their optimum moisture content in order to achicve the minimum specified compaction levels set forth in this report and project specifications. However, initial lift thickncss could be incrcased to levels recommended by the manufacturer lo protcct utilities from damage by compacting equipment. Some excavation bank stability problems for foundation and utility construction may occur where excuvations exlend into the unconsolidated cohesionless soils. Pre-bid test pits could assist in cvaluating the most ewmm�ical meeus of site excavation. Relatively flat slopes, benching, or temporary bracing may be necded. Cooventional trench box shoring is also an option for the project. The anticipated utilities will likely be retatively shallow on tfris projecL ' Wc recommend that utiliry trenching, installation, and bac�(ling confomt to all applicable i'ederal, state, and local regulations such as OSHA and WISHA for open excavations. i i J-1443,022604 I�i ;