HomeMy WebLinkAboutStormwater/Runoff Drainage Proposal Review - PLN General - 5/31/1994 MASON COUNTY
PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER
Shelton, Washington 98584
DATE May 31, 1994
INTER-DEPARTMENTAL COMMUNICATIONS
TO: JASON MANASSEE, Planner - DCD
FROM: ALAN A. TAHTA, Office Tech. - P/W
SUBJ. McDONALD'S - Belfair, Ace Site, Stormwater/Runoff Drainage Proposal
I've reviewed the stormwater/drainage proposal prepared for McDonald's
in Befair, Washington by MAP Ltd. The proposal provides for water quality
treatment of a 6 month storm event and provides for infiltration of the runoff
from a 100 yr storm event. The engineer has employed a flow splitter that
delivers flow quantities less than a water quality design storm to an
infiltrating bio-Swale. Larger storm event runoffs are directed around the
bio-swale and are delivered to an underground infiltration trench.
I expect this arrangement to work well in handling McDonald's runoff and
in helping to alleviate the surface drainage problem that exists in Belfair
under normal operating conditions, but I feel the Engineer should incorporate
an emergency spill separator to pre-treat the parking lot runoff prior to
delivering the stormwater to either the bio-swale or the infiltration gallery.
In the event of a parking lot spill, petroleum products could be delivered
directly to their bio-swale or to their infiltration trench, resulting in the
possibility of introducing petroleum contaminants into the area's
groundwaters. I have been in contact with Mark Eisses, P.E. , a principle of
MAP Ltd. and he understands my concern and will be submitting a revised plan
sheet which incorporates an oil/water separator into one of the catch basins.
I requested that he furnish us with three copies of the revised page of the
Drainage & Grading Plan.
The number of parking spaces appears to be adequate for the building
size and the aisle widths appear adequate for the parking angle chosen.
An Operation & Maintenance document should be prepared and submitted as
part of the proposal. Enclosed please find an edited version of Kitsap
County's standard O&M document. The enclosed document has not been approved by
our County Prosecutor's Office, so if a document fashioned after this example
is submitted, it will need reviewing by the Prosecutor's Office before final
acceptance. I have furnished Mr. Eisses a copy of this same document for
editing and submittal.
Attached you should find a four page Drainage and Grading Plan, a 16
page calculation brief, and a sample O&M agreement.
IV'rAA4 Jr7l;L_z-
TARJA
File: H:\WP\LETTERS\MAC-D.IDC