• DETENTION/RETENTION BASIN NOTES (continued)
  • Slopes within the basin and slopes outside the landscape maintenance assessment district may be as steep as 2:1 at the discretion of the City Engineer.
  • Pipe shall be encased per STD Plan D-6.
  • Trench backfill (including irrigation line trenches) shall be compacted to 90% relative compaction and certified by the soils engineer. Alternatively, trenches may be backfilled with a sand-cement slurry (2 sack mix) or Portland Cement Concrete, upon the recommendation of the geotechnical consultant. Inspection of this operation by the geotechnical consultant and the city inspector is required.
  • Soils engineer shall verify and approve trench bottom soil prior to placement of pipe.
  • OUTLET STRUCTURES
  • The drain pipe encasement shall be placed on a firm foundation approved by the soils engineer.
  • Anti-seep collars are required at 15' intervals for pipe under the embankment, with a minimum of one required in addition to the inlet and outlet erosion protection.
  • Discharge shall be to a paved street, channel, or an approved drainage course with grouted riprap. Ripap shall be 12" minimum size rock. Ripap shall be embedded in a minimum 6" into grout.
  • The drain pipe shall be a minimum of 15" in diameter and shall be constructed with water tight joints.
  • All concrete shall be Portland Cement Concrete 420-C-2000 unless otherwise specified.
  • CITY OF PALMDALE...

BASIN NOTES Std. No.

Approved City Engineer Date D-7.2