This document is the 101G Trench Installation (Flowable Fill) Detail. Pipe detail, chart and notes provide descriptions and measurements.

The detail shows the minimum cover to rigid pavement, final backfill, minimum cover to flexible pavement, flowable fill backfill, springline, bedding, suitable foundation and recommended trench width.

A chart with values for recommended minimum trench widths based on pipe diameter is shown.

Note 1 states that flowable fill should be designed to provide adequate strength to carry all live and dead loading but allow for any future excavation. Note 2 says that if trench is excavated in rock or high-bearing strength soils, trench widths for 24”-60” may be reduced. Note 3 explains that flowable fill should not be placed when temperatures are below 40f, against frozen trench material or where appreciable precipitation is forecasted during placement. Note 4 advises that precautions should be taken to prevent flotation. Note 5 explains foundation requirements. Note 6 is about bedding and suitable material, minimum bedding thickness shall be 4” for 4”-24” or 6” for 30”-60”. Note 7 clarifies that the final backfill should not be placed until a penetrometer reading of at least 500 PSI is met. Note 8 states that minimum cover is 12” up to 48” diameter pipe and 24” of cover for 60” diameter pipe, measured from top of pipe to bottom of flexible pavement or to top of rigid pavement.