HomeMy WebLinkAboutGeoTech Report Review for BLD2002-01644 - BLD Engineering / Geo-tech Reports - 1/14/2003 MASON COUNTY
PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER
Shelton,Washington 98584
DATE: January 141h, 2003
INTER-DEPARTMENTAL COMMUNICATIONS
TO: Scott Longanecker, DCD - Planner
FROM: Alan A. Tahja, P/W - Co. Hydr. Engr. WO# PLG-03
SUBJ: Geo-Tech Report Review NAME: Amendala SFR g Hamma Ridge
BLD2002-01644
Scott,
The original geotechnical assessment, and the addendum prepared for the proposed Barry Tockar
Single Family Residence (SFR) at Hamma Ridge, Mason County has been received and reviewed
by Public Works, raising the following issues;
The following case notes from Permit Plus indicate that a geotechnical report has been requested
for this site;
Due to slopes on site and adjacent to site a Geotechnical Report will be required to
address slope stability, storm water and vegetation management, slope setbacks etc.
Please see the enclosed Landslide Hazard Ordinance section E.S. with regards to
requirements for Geotechnical Reporting. The landslide hazard covenant attached to
the back of the ordinance will also need to be completed and recorded with the Mason
County Auditor prior to permit issuance. Please provide a copy of the recorded
document to the Planning Dept.
Under this ordinance a minimum 50 foot vegetated buffer is required from landslide
hazard areas. It appears that grading may have already occurred in this area. Grading
is allowed in or within 300 feet of landslide hazard areas only under the conditions of
an approved geotechnical report and Mason Environmental Permit, or Land
Modification permit. Further grading is not permitted on site prior to the submittal and
approval of a geotechnical report for the subject property and issuance of a building
permit or other permit as mentioned above.
Your geological engineer will need to address the grading,filling etc. that has already
occurred on site, as well as any additional proposed land modification.
1) A licensed civil engineer should be required to complete portions of the report and stamp
the report as required under Mason County's Resource Ordinance (17.01.100 e.3). The
report contains elements and recommendations which should be required to be certified by
an engineer. Stormwater runoff quantities and retention/detention/treatment facilities need
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to be calculated and designed by a licensed civil engineer.
2) No slope analysis has been provided as required by the County's geotechnical reporting
requirements.
3) The site plan is lacking details needed for a comprehensive review.
With these and other issues in mind,the geotechnical report should not be considered complete.
Please feel free to contact me at County extension 461 if you have any questions regarding these
comments, or if you feel any features need further discussion or attention.
Sin a ely,
lan A. Tahja
File.H:IWPIGEOIReportsL4mendala-Tockar.doc
Bradley-Noble Geotechnical Services
A Division of The Bradley Group, Inc.
PO Box 12267, Olympia WA 98508-2267
Phone 360-357-7883 9 FAX 360-867-9307
10 February 2003
Mr. Greg Amendala
Amendala Brothers construction
8047 Ellison Loop NW
Olympia, Washington 98502
Subject: Addendum to our report of 14 January for
the proposed residential construction
for Mr. Barry Tockar in the Hamma Ridge
development, Mason County Tax Parcel
Number 323047590053, Lot 15.
Dear Mr. Amendala:
In this addendum to our previous report we are
addressing additional site development issues and
presenting additional comments on slope stability in
the project area.
You have indicated that you are considering use of
on-site soils to construct structural fill sections
for the support of footings and slabs on-grade. The
native soils at this site are suitable for
construction of structural fill sections . The soils
do contain plastic fine6 in varying concentrations .
The upper recessional outwash soils are relatively
free of these fines, and we expect that they can be
placed and compacted in all but the most inclement
weather. The underlying till contains higher
percentages of fines and is moisture sensitive.
Compaction can be obtained in these soils if moisture
contents are controlled.
Enclosed with this report is a copy of our Recommended
Grading Specification for your use. Construction of
structural fill sections in conformance with these
specifications will ensure that the structural fill
sections are suitable for support of footings and
slabs on grade. Conformance with these requirements
will also ensure that the work conforms to the
standards of the industry and the minimum requirements
of the Uniform Building Code.
03010402
Page 1 of 3
03010402
Page 2 of 3
The area of recent instability and earth movement
referred to in our report is in excess of 1000
horizontal feet from this property. Based on field
observations, our opinion of the risk to access road
use is considered to be valid as this road crosses the
area of active periodic soil movement.
Review of the geologic information and our field
observations did not indicate active earth movements
in the area of: proposed construction. This is
consistent with the mapped geology of the area. We
find a thin layer of recessional outwash soils over
highly overconsolidated soils . Failure of highly
overconsolidated material at slope angles present in
the general area is considered unlikely. Slope angles
are less than the angle of internal friction of the
highly overconsolidated soils . When slope angles are
less than the angle of internal friction, slope
stability is inferred. There is no active erosion in
the toe area to oversteepen the slope.
Topography of the area was presented on the
topographic and geologic maps . At the scale and
contour of these maps, determining actual slope angles
in the project area are not reliable. You have
provided us a survey that you conducted between the
road and top of slope to the northeast of the proposed
building area. This map indicates a fall of 60 feet
in 510 feet, or about 7 degrees or 12 percent slope.
You also provided a contour map that was indicated as
being prepared as part of the subdivision. The scale
of this map appears to be 1 inch representing 200 feet
with a contour interval of five feet. Measuring from
center of northeast property line to center of south
property line, we have a horizontal distance of about
660 feet and a vertical relief of 140 feet or about 11
degrees or 21 percent slope.
Based on our field observations, research, and
evaluation of topographic information recently
provided to us, it is our opinion that a residence may
be constructed at the location indicated on this lot
with no risk of slope failure or erosion of the slope
face affecting the foundation support. We do not
consider the preparation of a geotechnical report
appropriate for this site. The recommendations
presented in this report and previous report must be
03010402
Page 3 of 3
incorporated in the site development work. As
discussed, the slope must be protected from
concentrated flows of storm water as these
uncontrolled flows can cause localized destabilization
and accelerated erosion.
If you have any additional questions, or if we may be
of additional service to you or your client on this
project, please contact us at our Olympia office.
C� Wash .
Cordially, e ��9 \
f
BRADLEY-NOBLE GEO`PECHNICAL SERVICES
Sed Ge o
David C. Stro g, L.E.G
DAVID C. STRONG
Enclosure: Recommended Grading Specification
Bradley-Noble Geotechnical Services
A Division of The Bradley Group, Inc.
PO Box 12267, Olympia WA 98508-2267
Phone 360-357-7883 • FAX 360-867-9307
RECOMMENDED GRADING SPECIFICATIONS
In areas under structures, paving sections, and
sidewalks, strip all topsoil and organic material .
For structural fill in areas under footings and slabs
on grade, we recommend that all soils be compacted to
a minimum density of 95% of ASTM D-1557 . This
includes proof-rolling native soils exposed in the
bottom of the excavation prior to placement of fill .
Materials under the paving section should also be
compacted to the minimum density by proof-rolling
prior to placement of the paving section. This
includes proof-rolling in-place soils , soils that have
been disturbed during construction, and all structural
fill materials .
For imported structural fill we recommend that a
clean, six-inch minus, well graded gravel or gravelly
sand (classifying as GW or SW as determined by
ANSI/ASTM test method D-2487 ) be used. On site
material proposed for use to construct structural fill
sections will require the approval by the soils
engineer or engineering geologist prior to placement.
We also recommend that no more than 7% by weight pass
the #200 screen as tested by ANSI/ASTM D-1140 test
procedure. Other material may be substituted with
prior written approval for use by the soils engineer
or engineering geologist.
Backfill for walls restraining earth should conform to
WSDOT 9-03 . 12 (2 ) gravel backfill for wall to ensure
drainage.
All fill should be placed in uniform horizontal lifts
of six to eight inches loose thickness, conditioned to
the optimum moisture content, and compacted to the
specified minimum density before placing the next
lift . It is the contractor's responsibility to ensure
that sufficient density tests or field verification of
the fill has been performed to ensure that the
required minimum density has been uniformly achieved
prior to placement of additional structural fill
material . We further recommend that all utility
trench backfill be compacted as specified above.
Earthwork should be performed by an approved testing
laboratory under the supervision of Bradley-Noble to
ensure compliance with the compaction requirements .
Recommended Grading Specifications
Page 1 of 2
Recommended Grading Specifications
Page 2 of 2
Placement of fill sections on slopes greater than 4 : 1
(horizontal to vertical) will be benched as directed
into native soils . Height and width of the bench will
be determined in the field by the soils engineer or
engineering geologist.
Unrestricted slopes shall not exceed 2 : 1 (horizontal
to vertical) for fill embankments and cuts that expose
native soils without written approval by Bradley-Noble
Geotechnical Services . All fill slopes will be
rolled. The project's civil engineer is responsible
for the protection of the constructed fill slopes from
uncollected runoff . All fill slopes will be compacted
by track rolling or other approved methods to densify
the surface of the fill slope. We recommend that all
cut-and-fill slopes be seeded as soon as possible
after construction to allow the establishment of
vegetation to protect the slope from sheet washing.
Placement of fill will be suspended during periods of
unfavorable weather. No fill is to be placed while
the fill is :frozen or thawing. When work is stopped
by rain, the placement of fill will not resume until
the soils engineer or engineering geologist determines
that the moisture content is suitable for compactive
effort and that the previously placed fill has not
been loosened. The contractor will take appropriate
measures during unfavorable weather to protect the
fill already :in place. Measures that may be required
include the limiting of wheeled traffic and grading to
provide temporary drainage of the fill . At the
direction of the soils engineer or engineering
geologist, the contractor will be responsible for the
removal or reworking of fill that has softened to less
than the required compaction.
I
04/21/2003 09:01 3608660475 HORIZON AMENDALA WAGE el
30
04/17/03 09:o9 FAX 1 360 867 931D7 Bradie7 Group 1A01
Bradley-Noble Geotechnical Services
A Qivlsian of The Brodicy Group, Inc-
PO Box 12267, Olympia WA 98508-2267
Phone 350-357-7BB3 • FAX 360-867-9307
17 April 2003
Mr. Crag Amendala
Awndala Bmthere ConStruction
6047 Blli.aon Loop RW
Olympia, Washington 98502
subjects Relocation of the drain field at the
Bar Toakar pro jQct in tbg Hammy. Ridge
Devel.op>Qent, mason County, xau3ningtozx.
Dear Mr. Amandala!
From our talephoTLe di.scuanion, Wo underetaad that thQ
drain field for this residence is now proponed to bw
construG#�od about 50 fAQt to the nQrtheast of tha
residence. This ins still in an areas of modarat8 slope
and upelope from the break in elope whQ" the slave
angle increases darn to the nortberaat On this
property. On Our orIg"al Visit to this site, thia
area had outwassh s;anda and gravels exposed ;Ln the zest
pits that wore open at this time. ThPas soils are
r_mmable and po:rOUB. We did observe till. in a nym, of
the restrictive` la r•
the test pits at 4i?pth which is a reetrict� y$
Ixrat%l.lati0n of a gravity Ayet®m is in our opinion a
better solution than relying o>1 a F-OW mystmn' with
pumps you need power, and they are prow to failure
and require mii.ntonarwo. From discussion vi-Lh septic
e s we undarctand that much of the effluent
design ors,� irad
water i,r� thought to be
ei.tbar evaporated or transp
by planta . The actual volumes of water bai g
introduced into the drain field when d1stributed by
the lateral systez is not expected to be high on a per
square LOOM DQSI.D. we der xx,ot a ez �1as� �k,is wntcar
when distributed over the area of the drainfi®ld would
have any adverse effect on the aoile of the slope or
elope stability.
If you have any qu�eozl.o ia, or if •ro may be of turthe£
assistance to YOU, please Contact us at our Olympia
office.
dk W ashl
Cordially,
BRADLEY-NORT.R [ 9MIEMMICAL SERVICES
1129
David C. trong�_ E.G. ensued a O
v
MASON COUNTY
PUBLIC WORKS DIRECTORICOUNTY ROAD ENGINEER
Shelton,Washington 98584
DATE: January 24t', 2003
INTER-DEPARTMENTAL COMMUNICATIONS
TO: Scott Longanecker, DCD -Planner
FROM: Alan A. Tahja, P/W- Co. Hydr. Engr. Work Order# PLG-03
SUBJ: Geo-Tech Assessment Review NAME: Tockar SFR g Hamma Ridge
BLD2002-01644
Scott,
The geotechnical assessment prepared for the proposed Barry Tockar SFR in the Hamma Ridge
Development area,has been received and reviewed by Public Works. Case notes appear to
indicate that a geotechnical report was required to be prepared for the proposed residential
development. The assessment submitted lacks many of the details required in a geotechnical
report conforming to County critical resource ordinance requirements.
Though the report preparer indicates he has no objections to the proposed development,he has
not provided the required information needed for Public Works to be able to express an opinion
that geological concerns have been adequately and conclusively addressed.
The applicant should be contacted and directed to have his agent/geologist provide the required
information.
Please feel free to contact me at County extension 461 if you have any questions regarding these
comments, or if you feel any features need further discussion or attention.
Sin ely,
I
h �
Alan A. Tahja
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Bradley-Noble Geotechnical Services
A Division of The Bradley Group, Inc.
PO Box 12267, Olympia WA 98508-2267
Phone 360-357-7883 • FAX 360-867-9307
14 January 2002
Mr. Greg Amendala
Amendala Brothers Construction
8047 Ellison Loop NW
Olympia, Washington 98502
Subject: Evaluation of soil bearing capacity and
other geotechnical considerations for
your proposed residential construction
project for Mr. Barry Tockar in the
F[amma Ridge development, Mason County
Tax Parcel Number 323047590053 .
Dear Mr. Amendala:
As requested, we have visited the above site in order
to develop an opinion on the suitability of the site
soils to safely support the proposed single-family
residence. At the time of our site visit, the access
road had been rough cleared, the building and
drainfield areas had also been stripped of vegetation
and native soils exposed. Excavation had exposed soil
profiles in the building site. This letter will
present our opinion and observations of site soil
conditions .
The project site is located in an upland area to the
south of Jurst:ed Creek and to the west of Highway
101 . The area of proposed construction is on a nearly
level area with a northeast-facing slope. The slope
is gentle in the area of proposed construction and
steepens to the northeast. The area of proposed
construction is above and west of the toe of the slope
where sliding and slumping has been active along
Highway 101, especially during winters of heavy
rains . Work by the Department of Transportation has
stabilized much of the toe area along Highway 101 at
the access to this development. We also noted that in
driving up to the site, the first 400 to 600 feet of
the access road from Highway 101 in the Mile 322 area
was showing distress from soil movement associated
03010401
Page 1 of 3
03010401
Page 2 of 3
with previous mass wasting events . Access to the
building site may be temporally lost until the road
can be reconstructed.
We found slopes moderate in the general area and less
than 2 : 1 horizontal to vertical) in the building
area. From our discussion, we understand that the
clearing was conducted to allow construction of the
residence, decks, garage, and drainfield. From the
stakes indicating building corners, we do not consider
the clearing to have been excessive.
Site geology in this area consists of glacial
deposition associated with the Vashon lobe of the
Frazier continental glaciation. Cropping out are
fluvially deposited sands and gravels associated with
Vashon recessional outwash. Below the outwash
deposits, we found in some of the open test pits, the
very dense and highly overconsolidated subglacial
till . Clasts contained in the soils are associated
with continental glaciation rather than alpine
glaciation from the Olympic mountains .
To verify our interpretation of the site geology, we
have referred to the Geologic Map of the Brothers
Quadrangle, Jefferson, Mason, and Kitsap Counties,
Washington by W. M. Cady, M. L. Sorensen, and N. S .
Macleod, 1972 , GQ 969 , published by the Department of
the Interior, U.S . Geological Survey. The general
area of this site is mapped as Qc, continental glacial
deposits . The project site is outside of mapped areas
of geologic hazards from erosion or landslide hazard.
The site soils offer good support for standard spread
footings . All footings must be founded on the dense
native soils . We also recommend that the footings be
founded a minimum of 1 . 5 feet below adjacent finish
grade for frost protection and confinement. Safe
bearing capacity of these soils exceeds 3000 pounds
per square foot. For footings founded on the dense
native soils, we do not expect that significant
long-term total or differential settlement is likely.
Attention to collection and disposal of storm water
from impervious surfaces will be required. We
recommend that a continuous perimeter footing drain
system be installed around the structure to protect
03010401
Page 3 of 3
the crawl space or daylight basements from surface
flow of water. The subglacial till is for all
practical purposes impermeable and flows of water will
develop on its surface during periods of heavy or
prolonged rainfall. The water from roof rain leaders
should be collected into a separate tightline system
isolated from the footing drains . The roof rain
leader system and footing drains may be connected into
a common discharge line at an elevation such that
backup into the footing zone cannot occur.
Collected water should be carried below the drainfield
area for disposal . Point discharge is to be avoided.
Point discharge can create areas of localized
saturation and induce slope instability or accelerated
erosion. We recommend that the water be infiltrated
using either swales or perforated pipes following the
contour. This will allow the water to be infiltrated
over a wide area and avoid concentrated flow.
After completion of the construction, we recommend
that all areas of exposed mineral soil be reseeded to
control surface erosional processes by sheet flow of
water. The Mason county agricultural agent can
provide you with recommend species. We also recommend
that the property owner review the DNR recommendations
for creating a defensible area around the residence in
event of fire.
Based on our site inspection and review of available
geologic information we have no objections based on
geotechnical considerations to the proposed
development if the general recommendations of this
report are included in the site work.
Cordially,
BRADLEY-NOBLE GEOTECHNICAL SERVICES
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David C. Strong, L.E.G. 'R`
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