SW_Review_Comments2.pdf
City of Edmonds
TH
121 5 AVENUE NORTH
EDMONDS, WA 98020
(425) 771-0220
FAX(425) 771-0221
Website: www.ci.edmonds.wa.us
DEVELOPMENT SERVICES DEPARTMENT
Planning Building Engineering
Stormwater Review Comments
Permit : Date:
# PLN20060141 1/02/2008
st
Project Name/Address:
Arnhold Short Plat 24310 101 Ave. W.
Contact Person/Address/Fax:
Jesse Jarrell, EIT./13000 Highway 99 South, Everett,
_
WA, 98204/ (425)356-2708
Reviewer: Division:
Blaine Chesterfield Engineering
During review of the subject submittal it was found that the following information,
corrections, or clarifications will need to be addressed:
1.
The infiltration test was completed just below the grade of the existing ground
bottom
but needs to be below the of the proposed infiltration trench. Please
redo the infiltration tests and resubmit the calculations. The calculations for
the infiltration facility will be affected by any change in the infiltration rate.
2.
The acceptable method for testing to determine the percolation rate of soils on
your property is the sub-surface maximum infiltration test. This test is used to
estimate the maximum sub-surface vertical infiltration rate at a particular level
lowest
in the soil horizon that corresponds with the finished grade elevation of
(this is at or below the bottom of the
a proposed infiltration facility
infiltration trench)
. The test is designed to simulate the physical process that
will occur during design storm event conditions; therefore, a saturation period
is required to approximate the soil moisture conditions that would occur
during a major storm event. A pipe is employed to allow only the vertical
infiltration rate to be measured so that the computed maximum infiltration
may be used to compute the rate of seepage over the area of interest for
varying head.
Testing Procedure:
(below the bottom of the
a.A hole is dug to the finished grade elevation
proposed infiltration facility)
of a proposed infiltration facility and of
sufficient diameter to allow a 6-inch diameter section of pipe to be placed
in the hole and driven a depth of 6 inches into the soil at the test elevation.
b.The pipe is filled and kept to a minimum depth of one foot of water above
the test elevation at the bottom inside of the pipe, for a period of not less
than 4 hours (the saturation period).
c.Following the saturation period, the pipe is filled to the top and the time
required for the water to fall every inch, down to 6 inches below the top of
the pipe, is recorded.
d.The rates for all on-inch times are then averaged to estimate the maximum
infiltration rate (I). This process is repeated three times, and the results
m
of the three tests are averaged to compute the maximum infiltration rate
(I).
m
Please resubmit three copies of the revised plans/documents to a
Development Services Coordinator. You may contact me at 425-771-0220
if you have specific questions regarding these plan corrections.