Exfiltration Dilemma

[jrflyer]

The issue is the depth of the exfiltration system. The exfiltration system is comprised of 24"x35" Aluminum Perforated Steel Type II Gauge Pipe. The pipes are wrapped in Mirafi fabric and have 6" 57 stone coverage on top and bottom per detail. In total the cross section is 6" + 24" pipe +6" for 3'-0". The FF. Elev. is set at 0.0' and per the detail the top of pipe is at -1.5' This only provides 1'0" from top of Mirafi fabric to top of C.I.P. slab. 5" C.I.P. slab and 7" compacted soil. Please advise with any suggestions on depth of top of pipe. Keep in mind that this is under a drive aisle with 3000# point load. Thanks.

 

[civilperson]

Why not thicken the pavement over the trench, (plus a foot extra width on either side), to 12" thick with #5 rebars at 9" centers bothways? This will help bridge across the "57" gravel backfill.

 

[cvg]

commonly called a "concrete blanket" in this neck of the woods - this is a typical detail for protection of shallow utilities and should be done with concrete. It will protect the pipe, however it may or may not prevent differential settlement of pavement in vicinity of the trench.