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hLEf ,NEELDER iOCT S11 ZIM17 eS, PlDelMeS, et Ce£e7 C1 Temporary sloped excavations should not encroach adjoining buildmgs walls or other structures within an area defined by an imaginary 25(h) l(v) line drawn outward anti downward from closest edge of the structure Furthermore, slope excavations should maintain a minimum 1 foot separation from adjacent pipelines and pipeline backfill Where the stability of a structure may be endangered by excavation operations, support systems such as shoring, bracing, or underpinning may be required to provide structural stability and to protect personnel working within the excavation Removal of material in a shored excavation causes a change of stress in the soils beside and beneath the open excavation This change in stress has corresponding lateral deformations inward of the material at the sides of the excavation Likewise, this horizontal movement is accompanied by a vertical settlement of the retained soil mass Even well constructed shoring will experience lateral movement, typically between 4 5 and 2 percent of the excavation depth The average vertical settlement due to lateral movement may be taken as twice the lateral movement Settlement tends to be greatest close to the excavation, but extends over a horizontal distance equal to twice the excavation depth from the top of the shoring The Contractor should anticipate developing a program to continually monitor existing improvements to detect movement and allow for remedial actions In addition, a complete survey of existing utilities, pavements and structures adjacent to those portions of the proposed • excavations that will be shored should be performed The purpose of this review would be to evaluate the ability of the existing features to withstand horizontal and vertical movements associated with a shored and/or dewatered excavation If movements are greater than the tolerance of existing project features, tie-backs, dead-man anchors, cross bracing, or alternative shoring or dewatering systems may be needed to reduce deflections The City of Stockton, San Joaquin County, and Contractor should anticipate repairing cracks in pavements adjacent to shored portions of the excavation due to lateral displacements of the shoring system Bore and Jack Excavations It is our professional opinion that the soils encountered are amenable to jack and bore techniques for construction of proposed pipelines The Contractor should be aware, however, that a majority of the clays encountered were stiff to hard Also, as previously discussed, the native clays are interbedded with layers and strata of loose to medium-dense sands that are potentially susceptible to caving or collapsing when unsupported Accordingly, bore and jacking may require full length shielding (bore liners) and positive face boring to prevent caving and loss of ground The Contractor should become familiar with the condition of the subsurface materials encountered during our field explorations and as-built plans of adjacent utilities However it should be understood that this geotechnical report does not represent a stuav of the ease or aiffculty of bonng and jacking through all subsurface materials and conditions that may be • encountered within the limits of the proposed pipeline The Contractor should inaependently I3639 GOi/2002R369 kprsl 19 3003 D 2002 KIemteiaer Inc page 8 or M