06-105381 (2)�1'(XaZar1 & ASSOCIATES,INC.
GEOTECHNICAL ENGINEERING • ENVIRONMENTAL ENGINEERING
CONSTRUCTION TESTING & INSPECTION
January 16, 2007
Mr. Phil Fryberger
2648 South Star Lake Road
Federal Way, Washington 98001
RE: Limited Infiltration Evaluation
Proposed Conners Single Family Residence
2648 Star Lake Road South
Federal Way, Washington
Dear Mr. Fryburger:
This report presents our findings regarding the existing site soils and estimated infiltration rates based on
in place infiltration tests (based on the King County Surface Water Design Manual Section 5.4.1 General
requirements for Infiltration Facilities) within the proposed single family residence parcel, located at 2648
Star lake Road South in Federal Way. One exploratory test pit was excavated within the proposed storm ----
water infiltration system location. The exploratory test pit was excavated to a depth of approximately 5
feet below the existing site grade. One in place infiltration test was performed at this depth.
A Representative sample of the subsurface soils encountered in the test pit, was collected and sealed in
plastic bags. The sample was transported to our laboratory for further visual examination and verification
of the field classifications.
The soils encountered in the exploratory test pit generally consisted of loose to medium dense,
interbedded, silty, fine to medium grained sand with variable amounts of gravel to fine to medium grained
sand with variable amounts of silt and gravel (Weathered Vashon Recessional Outwash). '
The exploratory test pit was checked for the presence of groundwater during and immediately following
the excavation operations. At the date and time of the field infiltration evaluation, groundwater was not
observed.
It should be recognized that water table elevations may fluctuate with time. The groundwater level will
be dependent upon seasonal precipitation, irrigation, land use, and climatic conditions, as well as other
factors. Therefore, water levels at the time of the field investigation may be different from those
encountered during the construction phase of the project. The evaluation of such factors is beyond the
scope of this report.
The soil infiltration rates at the exploratory test pit locations, based on the EPA Falling Head Percolation
Test Procedure, are presented in the following table. RESUBMITTED
JAN 1 8 2007
CITY OF FEDERAL WAY
Eleven Offices Serving The Western United States BUILDING DEPT.
19501 144th Ave. NE #F-300 • Woodinville, Washington 98072 • (425) 485-5519 • Fax: (425) 485-6837
January 16, 2007
Page 2 of 3
INFILTRATION RATE
Test Pit Test Elevation
Infiltration Rate USDA Soil Classification
(min./in.)
Number (feet) No Factor of Safety Based on Visual Classification
TP-1 -5 15 Loamy Sand*
*USDA Soil Classification does not take into account particle sizes greater than the No. 10 sieve (>2mm in diameter).
The Falling Head Percolation Tests and the soil classifications indicate that the weathered Vashon
recessional outwash soils have a moderately rapid rate of permeability (approximately 2 to 6 inches per
hour) in their current condition.
The infiltration rate presented in this report is based on field testing with clear water and does not
incorporate a factor of safety. Therefore, at a minimum the above infiltration rates should be divided by a
factor of safety of two for the infiltration system design to account for possible soil clogging, which may
result from water impurities.
We hope that this letter report provides the information required at this time. If you have any questions,
or if we can be of further assistance, please do not hesitate to contact our office.
Respectfully submitted,
KRAZAN & ASSOCIATES, INC.
C-- ) L
ChrisBehrens, L.G., E.G.
Senior Engineering Geologist
CB/cb
CHRIS J BEHRENS
RESUBMITTED
JAN 18 2007
CITY
I B�LDING DEP WAY
Eleven Offices Serving The Western United States
19501 144th Ave. NE #17-300 • Woodinville, Washington 98072 • (425) 485-5519 9 Fax: (425) 485-6837
6" MIN. NATIVE EXISTING
BACKFILL OR W GROUND ELEV.=
TOPSOIL
W�2
PROPOSED FINISH
GRADE ELEV.=
o w-
LIIII
Q No1-17
'I INVERT ELEV.=
F- I I :I
O BOTTOM ELEV.=
I!-1 I I I Ij - '� I 1I IIc I I I -
PERFORATED PIPE WITH
PERFORATIONS TO THE
SIDE OR IN A DOWNWARD
DIRECTION.
TRENCH
BACKFILL TO BE
1Y2"-3"
WASHED ROCK
LAYER OF
FILTER
FABRIC OR
SUITABLE
ALTERNATIVE AROUND
TRENCH
NOTE:
PERFORATED CONCRETE UNDERDRAIN PIPE MEETING W.S.D.O.T.
SPECIFICATIONS CHAPTER 9-05.2 (2) MAY BE USED WITH THE
ADDITIONAL CONDITIONS: THE PERFORATIONS SHALL BE
CIRCULAR AND A MINIMUM OF Y2" DIAMETER. THEY SHALL BE
CLEANLY CUT AND BE SMOOTH AND UNIFORM WITH NO EXCESS
CONCRETE LEFT FROM THE HOLE PERFORATIONS PROCESS.
THERE SHALL BE A MINIMUM OF 7 SETS OF PERFORATIONS WITH
2 HOLES PER SET OF PERFORATIONS FOR EACH 3Y2' OF PIPE
LENGTH. RUBBER GASKETS OR GROUTING OF JOINTS FOR
PERFORATED PIPE RUNS WILL NOT BE REQUIRED. INSPECTION OF
THE PERFORATED CONCRETE PIPE SHALL BE MADE BY THE
MUNICIPALITY BEFORE INSTALLATION OF THE PIPE IN THE
GROUND.
STORMWATER INFILTRATION TRENCH SECTION
N.T.S.
RESUBMITTED
M-10-2-A.DWG JAN 1 8 2007 TRONCH SECTIONRMWATER INFILTRATION
APPROVED: REI CITY OF FEDERAL WAY
DRAWN: DJD IRE BUILDING DEPT. APPENDIX: A DETAIL:10.2