HomeMy WebLinkAboutGrading Plan for Short Plat - GRD Letters / Memos - 8/13/1996 c
GARY YANDO,DIRECTOR
�0N.STgTFO . .
Q. s
OUU DEPARTMENT OF COMMUNITY DEVELOPMENT
o T 2 PLANNING -SOLID WASTE-UTILITIES
N Y y BLDG. I • 411 N. 5TH ST. • P.O. BOX 578
of 1864 �o SHELTON,WA 98584 • (360) 427-9670
August 13, 1996
Dan Holman
P.O. Box 2379
Shelton, WA 98584
RE: Grading Plan for Island West Catfish Lake Short Plat
Dear Dan:
The following comments were generated by Mason County Public Works for the
review of the proposed grading plan for Island West Short Plat.
The plan sheet delivered to Public Works is labeled a "Grading Plan", and though
it contains grading features pertinent to stormwater management, it cannot be considered a
stormwater control plan.
The proponent has proposed armoring the roadside ditches and widening them for
the first 140 feet of road which contains grades from 6 to 8%. The next 150' or so of road
appears to contain grades between 8 and 5%, which, depending on the soil type and expected
flow quantities and rates, may also warrant armoring. A pond area is depicted on the
proposal, but the only dimensions appear to be easement boundaries. The geometry of, and
the function the pond is expected to perform (detention, retention, water quality treatment,
sediment trapping) are not provided, and would be expected to be underlying elements of the
design of a typical stormwater control pond. A stormwater control plan would also typically
contain a report or remarks pertaining to delivery of offsite generated flows onto the site,
their accommodation, and a section or remarks pertaining to the downstream conveyances
that are expected to accommodate the flows generated on this site and other areas served by
the feature (culvert, open channel, streams, wetlands).
As an activity subject to Ecology stormwater control standards, the extent of
proposed road building would classify this as a large parcel development (creating in excess
of 5,000 square feet of imperviousness -- Ecology defines gravel roads as impervious
surfaces). As a large parcel development activity, Ecology requires the stormwater plans be
prepared and stamped by a licensed civil engineer. Mason County's Title 16 requires Public
Works to review short plats for drainage. Though Mason County has not adopted Ecology's
standards, they do provide a standard to compare proposed development activity to.
Recycled '
I have discussed this proposal with Gary Yando, who indicated that Ecology
standards should be applied to this site, therefor, a Stormwater Site Plan (SSP) which
contains an Erosion and Sediment (E&S) control plan and a large parcel permanent
stormwater quality control plan prepared by a civil engineer should be developed for this
proposed short plat.
If you have any questions pertaining to this letter, please contact Alan Tahja, at
427-9670, ext. 363.
Sincer
Andeff
Subdivision Planner
File: H:\WP\STRMWTR\REVIEWS\IW-CTFS.IDC
1
July 29, 1996
To: Alan Tahja
From: Randy Neff /V/p,
RE: Island West Grading Plan
Alan:
Is this enough adequate information to determine if this
plan will address stormwater as per our discussions? Please
review and let me know. I realize that they need to have an
O & M Agreement for the stormwater.