permanent pool extends way back into inlet pipe,inlet is 7 ft submerged

Discussion in 'Environmental Engineering' started by jcirish, Mar 2, 2017.

  1. jcirish

    jcirish Novice

    Thanx for any help.

    Quick question. If permanent pool of wet detention pond extends way back into the inlet pipe..... inlet pipe of Pond 1 for SR 415 is 2.2 ft submerged always. It's top elev is 5.5 ft and permanent pool elev is 8.7.

    I believe a backwater is created in the inlet pipe up to the 8.7 ft elevation.

    This is HUGE problem cause flat inlet drain on SR 415 S side has 54 in or 4.5 ft inlet pipe whose invert is ONLY 3 ft, thus top of pipe is 7.5. This pipe is thus ALWAYS full due to perm pool elevation of pond 1.

    Issues: water stagnates in inlet pipe, breeds mosquitoes (zika and other dangers), drainage from SR 415 will NOT work properly due to high tailwater behind curb inlets..... pipes close to pond are 100 full and the design calculations reports did NOT state they addressed a high tailwater condition for the pipes close to pond 1.

    They reused a borrow pit for pond 1 should have put it further N at higher elevation and used exfiltration trenches in low spots near Reed Ellis rd like they did in flood plain of river.

    I suspect under 25yr/24 hr storm water may bubble up out of some flat inlets.

    Pond 2 of SR 415 has similar issue with ALWAYS submerged inlet pipe. They enlarged pond by raising teh perm. pool NWL and drowned the inlet.

    thanx, john
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