HomeMy WebLinkAboutReview of Soil Waste Site - GRD Engineering / Geo-Tech Reports - 5/20/1999 MASON COUNTY
PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER
Shelton.Washington 98584
DATE: May 20, 1999
INTER-DEPARTMENTAL COMMUNICATIONS
TO: Randy Neff, Planner - DCD
FROM: Rich Geiger, Engineering Services Manager - PW
SUBJ: REVIEW OF ENGINEER'S REPORT, HAMA HAMA WASTE SITE,
EMERGENCY PERMIT
I have reviewed the engineer's report submitted by Marley Young, P.E., as required by
the limited, emergency grading permit for this site.
I have found the stormwater calculations to be acceptable. I also agree with the
Engineer's opinion that sediment and erosion control requirements are minimal for this
site as no storm water or loose soils can escape this site.
Should imported silts or clays spread on the floor of the bowl which would inhibit
stormwater infiltration, this material should be removed as described by the Engineer in
item 8, page 5. Should sediment and erosion control problems be caused by truck
traffic or spillage between the construction site and the waste site, the contractor should
be required to correct these problems as they occur.
If you have any questions, call me at extension 531.
RICHARD EIGER, P.E.
MARLEY L. YOUNG CONSULTING ENGINEER
P.O. BOX 1343 SHELTON WA 98584 (360)426-7475
Marley L. Young P.E., P.L.S.,
Civil Engineer& Land Surveyor
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Date: May 5, 1999
ENGINEER'S REPORT
TO: Rich Geiger,Engineering Services Manager- Department of Public Works
FROM: Marley L. Young, P.E.,P.L.S.,Consulting Engineer
SUBJ: REVIEW OF SOIL WASTE SITE PROPOSAL,HAMA HAMA COMPANY AND
QUIGG BROS. CONSTRUCTION
The Hama Hama Company located at Eldon, Washington, is working cooperatively with Quigg
Bros.,Inc., a general contractor from Aberdeen, WA, in order to develop an earth disposal site
near Eldon in Mason County.
Last winter rainfalls were at least double that of normal years contributing to several earth slides
near Lilliwaup and Eldon along U.S. 101 in Mason County, which closed the highway to through
traffic.
- - - --- -•- z:-=. The Washington State Department of
xa-
„ H „r _ Transportation is responsible for the
TIDELAND maintenance of U.S. 101. The immediate
Oy"iH.„.WGC►►G CO. concern of the Department is the removal
26 of a sufficient amount of slide material so
ONIM_ that the highway can be opened to through
N TIDELAND ING CM K -
1JAx "'"G GO' traffic. The long range concern of the
Department is to provide permanent
' H '• ;; 0 restoration of the slide areas this summer
TIDE LAND OWNED BY
_ H.H.LOGGING CO, by contracting the removal of the majority
' of the slide material. It has been estimated
" by State representatives that the U.S. 101
, ��,N, , slide at Eldon contains 100,000 to 250,000
1 STATE �A """ ,f' TAX'"`"'""°°""" cubic yards of material that must be
removed.
1
Hama Hama Company-Eldon Disposal Site 2
The Hama Hama Company site appears to be large enough to handle the immediate and the
contractual needs of the Department of Transportation. Topographic information is being
gathered and the preliminary information indicates the site could hold more than a million cubic
yards of material. Quigg Bros., Inc., a general contractor from Aberdeen, WA, is working
closely with the Robbins Family, owners of Hama Hama Company,to investigate the adequacy
of the site and to "permit"this site for earth material disposal.
ENGINEER'S REVIEW OF THE SOILS CONDITIONS AND INFILTRATION
CONDITIONS AT THE DUMP SITE.
This site is perfect for the proposed use.
The dump site is hidden from view from U.S. 101 and the Hood Canal, and is accessed from
U.S. 101 only by a private road owned and maintained by the Hama Hama Company. The
location of this bowl is approximately 500 feet south of the center of section 27 Township 24
North,Range 3 West. W.M. It is twelve miles north of Hoodsport and 15 miles south of Brinnon
on the west side of Hood Canal and south of the Hamma Hamma River. The area was logged in
1970 and 1971 and was reseeded to evergreens. Due to the low productivity of the existing
gravelly sandy soils,the area would not produce merchantable timber until 2051.
The site consists of a long narrow bowl approximately 1200 feet long from west to east and
50+/-feet wide at the bottom and 300+/-feet wide at an elevation 40+/- above the bottom. The
site has more capacity(1,000,000 cu yds)than the estimated immediate needs of the State,
(100,000 to 250,000 cu yds); therefore,the easterly half of the dump site is expected to receive
all the waste material. [Formula for calculating volume: Ellipsoid V=(4/3 x pi x a x b x c)/2]
A convenient unloading area is located at the approximate easterly one third of the bowl. At
present the bowl infiltrates all storm water runoff, and it is expected that even with the disposal
of the State slide material the bowl will continue to function.
The Eldon Slide on U.S. 101 shows a small percentage of clay type(impervious)material to be
removed and a large percentage of gravelly (pervious)material to be removed. It is estimated
that 3/4 of the slide is free-draining sandy gravel, and 1/4 of the slide is brownish silt with some
gravel. There are sufficient quantities of gravelly materials(pervious)to assure that the bowl
will have conduits of free draining material from the top to the bottom of the bowl. The free
draining material being sandy gravel from the slide area will assure that infiltration of
stormwater continues.
A concern has been raised by Mason County that the clay-type (impervious)materials removed
from the State's slide should not be allowed to `seal' the floor of the bowl. I feel that because of
the volume of the bowl and the small percentage of impervious material coming to the site,this
concern is unfounded. It is intended to stabilize the gray clay by mixing it with the sandy gravel.
Hama Hama Company-Eldon Disposal Site 3
Even if part of the bowl were sealed,there is adequate bowl capacity to provide the infiltration
function.
The naturally occurring gravelly sandy material at the dump site is free draining. Infiltration
tests conducted on May 3, 1999, showed that the gravelly sandy soils were so porous that the
infiltration rates were faster than one inch per minute. The gravelly sandy material surrounding
the dump sight was free draining. el
It is recommended that any overburden,topsoil, humus and organic material removed from the
bowl should be stockpiled and later returned to the site as site reclamation. It is intended that
the completed portions of the site will be seeded back to evergreens.
The Robbins have contour maps of their property. Using this information,I estimate that the
bowl is at the bottom of a sixty-two-acre drainage basin. Forest Land Surveys is gathering
additional information of topography and contours of the bottom of the bowl including the
winter water elevation. Using this information to calculate area and volume of the winter pond,
we estimate that the pond maximum volume was 95,400 cubic feet, and a maximum of five feet
deep. Using the WaterWorks Software for Hydrology from Engenious Systems,Inc., and the
Washington State Department of Ecology's Stormwater Management Manual for the Puget
Sound Basin:
STORM EVENT DESIGN ASSUMPTIONS
Based on DOE s Stormwater Management Manual.
■ STORM EVENT
■ Rain Precipitation(in.)
■ Six-month, 24-hour Storm Event 3.00"
■ Two-year, 24-hour Storm Event 4.70
■ Ten-year,24-hour Storm Event 6.50
■ Hundred-year, 24-hour Storm Event 9.00
■ Rainfall choice IA
■ Hydrograph SBUH**
** Santa Barbara Urban Hydrograph method
■ DRAINAGE BASIN
■ (Hg)Hoodsport Gravelly Sandy Loam 3045%
■ Hydrologic Soil Group A
■ Infiltration Rate 4 min/inch
■ Preexisting Conditions Young Second Growth 62 acres at CN# 55
0 Developed Conditions Young Second Growth 62 acres at CN# 55
Hama Hama Company-Eldon Disposal Site 4
DESIGN RESULTS- STORMWATER CONTROL
Pre Flow and Post Flow will be retained on site.
Storm Event 6-month Two-year Ten-year Hundred-year
► Pre Flow -cfs L 109 3.679 9.728 24.558
► Pre Volume ac-ft 1.006 4.312 9.369 18.022
► Post Flow -cfs 1.109 3.679 9.728 24.558
► Post Volume ac-ft 1.006 4.312 9.369 18.022 r
Assuming the area of the Dump site will not change the 62-acre drainage pattern.
Assumed a Trapezoidal Basin as the Existing Pond Conditionss(Pond Floor at 85+/
► Floor Length: -ft 70 Side Slopes 54:1 and 24:1
► Floor Width: -ft 18 Side Slopes 3:1 and 3:1
► Min. Depth: -ft 5.13 at 100 Year Storm Event
► Infiltration Rate -min/inch 4.0
► Infiltration Trench-No Discharge as the Existing Pond Conditions:
► Storm Event 6-month Two-year Ten-year 100-year
► Post-Flow -cfs 0.00 0.00 0.00 0.00
► Post-Volume -cf 0000 0000 0.00 0.00
► Post-Depths -ft 0.33 1.40 2.96 5.13
► Pond-Volume -cf 721 7600 32241 100691
There is adequate room in the westerly end of the bowl to provide infiltration. As the following
calculations show,the Pond will be moved to the west and the Pond Floor Elevation will be 95.0
Assumed a Trapezoidal Basin as the Existing Pond Conditions:
► Floor Length: -ft 130 Side Slopes 4:1 and 24:1
► Floor Width: -ft 70 Side Slopes 8:1 and 8:1
► Min. Depth: -ft 4.60 at 100 Year Storm Event
► Infiltration Rate -min/inch 4.0
► Infiltration Trench-No Discharge as the Existing Pond Conditions:
► Storm Event 6-month Two-year Ten-year 100-year
► Post-Flow -cfs 0.00 0.00 0.00 0.00
► Post-Volume -cf 0000 0000 0000 0000
► Post-Depths -ft 0.05 0.16 2.14 4.60
► Pond-Volume -cf 461 1500 31786 106898
Hama Hama Company-Eldon Disposal Site 5
CONCLUSIONS OF SITE CONDITIONS:
1. The site is isolated.
2. The site is self contained.
3. The materials making up the sides of the bowl are free-draining gravelly sand, which
indicates stability. No lenses of glacial till have been encountered.
4. Some of the silt buildup in the bottom of the bowl will be removed to augment infiltration.
5. The dump site activity will not materially increase the stormwater runoff from the sixty-two-
acre basin.
6. The impact to the bowl as an existing infiltration pond will not change; therefore,the impact
to the surroundingarea will not change.
7. The wasted soils will drain and compact, and the surrounding soils will absorb the
stormwater.
8. The sandy gravel from the slide areas can be placed along the sides of the bowl and the face
of the fill slope to produce free draining conduits from bottom of bowl to top of finished
fill. In the bottom of the bowl approximately every 50 feet a strip of silt material should
be removed to expose the free draining gravels underneath in order to augment the
existing infiltrations.
9. The majority of the slide material is sandy gravel. This material, even in a saturated state, is
stable at a 3:1 slope. Type 3 compaction is cat-track compaction and readily achieves
90% compaction. Ninety percent compaction should be acceptable because the site will
be reforested rather than used for any kind of building or structure foundations. Also,
over time this material will naturally settle to 95%or better compaction.
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