Hello from California,
About 10 years ago I designed site improvements for a school on a 4 acre property with an existing church. This is considered fairly large property-"near downtown"-- for an area with some of the highest land values in the US.
Since construction, I've monitored performance on my own, and I have my own ideas of what I would do differently / better. But we were not required to contain an event anywhere near a 25-year reoccurrence interval--I believe our requirement was say a 1-inch storm in 24 hours.
We currently have another site ---much smaller-which requires 5-year containment; this is an expensive undertaking--fortunately church members have deep pockets and determination to see their dream built.
And we just finished construction of a what I consider a sophisticated system for an industrial customer including underground storage tanks, pumps, controls and wiring like you'd see in a sewage treatment plant.
But it seems to me you folks face a very large challenge if you must absolutely contain a 25-year event, unless you a) are blessed with building on very permeable soil, b) have a huge site for retention basis, or c) have a huge budget.
Are you sure that containment of a "25-year storm" is the case? Even a 10-year event totally contained will be a substantial undertaking.
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Scott Onishuk M.ASCE
Santa Barbara CA
(805)563-0788
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Original Message:
Sent: 02-20-2019 13:30
From: Jesse Kamm
Subject: Owner/user experiences with parking facilities designed for 25yr storm detention
I have a facility owner that is interested to talk with other facility owners about their user experiences with parking lots designed to flood in intense storm events. Like most projects, they have quite a few compounding constraints and are looking at cost effective design alternatives to the fully contained UG detention system as currently designed. The CE of record has suggested a mix of the UG system and use of the parking area for 25 yr storms. I'm encouraged by the idea as I've seen projects throughout the western U.S. use this technique.
The owner will operate a religious facility and a day school and is curious if other owners with similar designs would do it again or if they are burdened by the occasional standing water in the parking areas. Are there any good resources or personal testimonies I can point them towards?
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Jesse Kamm PhD, PMP, A.M.ASCE
Senior Vice President of Construction Management
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