DIVISION 1 - GENERAL REQUIREMENTS - IDEAS-EC

D. Observe following trenching criteria1. Trench size. Excavate only sufficient width to accommodate free working space. In no caseshall trench width at top of pipe or conduit exceed the following dimensionsOverall Diameter of Utility ServiceExcess Dimension8 inches and less Max. 24-Inch trench2. Where soil conditions permit, cut trench walls vertically from bottom of trench to 1 FT abovetop of pipe, conduit, or utility service.3. Keep trenches free of water. Include cost of dewatering in original proposal.4. Brace and sheet trenches as soil conditions dictate and in full compliance with OSHArequirements. Do not remove sheeting until backfilling has progressed to the stage that nodamage to piping, utility service, or conduit will result due to removal.5. Brace trenches running near walls or columns, to prevent any settlement or other disturbanceof walls or columns.6. When a wheel blade trenching technique is employed the minimum trench width can bereduced to 6-inches for water lines having an outside diameter of 3-inches or less.3.03 PREPARATION OF FOUNDATION FOR PIPE LAYINGA. If over-excavation occurs, backfill and compact to 95 percent of maximum dry density per ASTMD4253 or backfill with granular bedding material.B. In case of rock excavation, carry excavation minimum of 6 IN below established grade and backfill tograde with suitable earth or granular material. Form bell holes in trench such that only barrel of pipeis supported by bedding material.C. Subgrade stabilization: Provide subgrade stabilization when directed by the Contracting Officer inaccordance with these specifications. Observe the following requirements when unstable trenchbottom materials are encountered.1. Notify Contracting Officer when unstable materials are encountered and define by Drawingstation locations and limits. Contracting Officer will evaluate the trench conditions anddetermine the quantity of stabilization and the amount of additional compensation.2. Remove unstable trench bottom caused by Contractor failure to dewater, rainfall, orContractor operations. Replace with subgrade stabilization with no additional compensationfrom the Government.3.04 BACKFILLINGA. Do not backfill until tests to be performed on system show system is in full compliance to specifiedrequirements. Partial fill, over the barrel of pipe only, may be permitted to restrain the system duringtesting.B. Methods: Provide backfill and compaction methods of following types1. Granular Bedding (pipe zone) material. Furnish compacted bedding where indicated on thedrawings or specified up to 12 IN above top of pipe or conduit. Comply with the followinga. Place backfill in lifts not exceeding 8 IN (loose thickness).b. Hand place, shovel slice, and pneumatically tamp all bedding (pipe zone) material.02320 - 404/08 UTILITY TRENCHING AND BACKFILLING