2004, 11-17 Geotechnical Design EvalZ�����E
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Materials Testing • Geotechnical Engineering
LETTER OF TRANSMITTAL
ATTENTION: Mr. Tom Loasdon
COMPANY:
PROJECT NAME: 1307 South Center
DATE: November 17, 2004
PROJECT LOCATION: Spokane Valley, WA PROJECT #: 204-073
FROM: Paul Nelson (cw)
# COPIES
DATE,
DESCRIPTION
2
11/17/04
Geotechnical Design Evaluation
COMMENTS: Thank you for allowing us an opportunity to be of service to you.
CC:
1010 N. Lake Road Spokane, WA 99212 (509)534-4411 Fax (509)534-9326
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Materials Testing • Geotechnical Engineering
November 17, 2004
Mr. Tom Logsdon:'
10511 East 8th Avenue
Spokane Valley, WA 99206
Re: Geotechnical Design Evaluation
Proposed Boulder Retaining Wall and Slope
1307 South Center Drive
Spokane Valley, Washington
Dear Mr. Logsdon,
As you requested, we have completed the geotechnical evaluation of the boulder
retaining wall and slope at the above -referenced site in Spokane Valley, Washington.
The purpose of our services was to evaluate the stability of the as -constructed slope
and wall and to evaluate the proposed design for the north portion of the wall. This
letter presents the results of our site observations, evaluations, and conclusions.
SITE OBSERVATIONS
A geotechnical engineer visited the site on November 16, 2004. The existing wall
(boulder rockery) extends from the east side of the property west along Beverly Drive
and turns to the; north along Center Drive. The boulders along Beverly Drive range in
size from approximately 4 to 8 feet in diameter. The rockery has an estimated batter
of 2:1 (horizontal to vertical) along this section.
The portion of the rockery beginning approximately 15 feet north of the southwest
corner of the rockery was constructed steeper (approximately 1.5:1) and the boulder
diameters were much smaller, most of which were smaller than approximately 2 feet
in diameter. In addition, an open ditch is present along the roadway extending along
the toe of the slope from the culvert outlet on the south side of the driveway to the
intersection of Beverly and Center Drives. The driveway is present above this
portion of the slope. The natural soils and fill soils consisted of coarse, clean, free -
draining sands and gravels. These soil types are typical of this area and are
reflected on the soil maps from the Soil Survey of Spokane County.
1010 N. Lake Road • Spokane, Washington 99212 • (509) 534-4411 • Fax (509) 534-9326
Geotechnical Evaluation
Proposed Boulder Retaining Wall
204-073
Page 2
CONCLUSIONS AND RECOMMENDATIONS
Based on our site observations, it is our opinion that the portion of the rockery along
the south side of the site to approximately 15 feet north of the southwest corner has
been adequately constructed and will provide suitable long-term performance.
Regarding the remainder of the rockery, Mr. McCrea indicated that they propose to
extend the culvert from the south side of the driveway south along Center Drive past
the end of the rockery and bury the pipe. He also indicated that he would remove
the boulders from the north portion of the rockery and reuse them to reconstruct the
slope. He proposes to move the bottom of the rockery closer to the roadway, lower
the driveway grade approximately 1 to 2 feet, reconstruct the slope at a 2:1
(horizontal to vertical) angle, place larger boulders on the slope face, and plant
evergreens between the boulders.
Based on Mr. McCrea's description and our observations of the site, it is our opinion
that the proposed changes to this portion of the rockery will be suitable. By
extending the culvert, the potential for water to saturate the toe of the slope will be
reduced. Based on the soil types at the site, it is our opinion that a 2:1 slope will be
stable. The boulders and vegetation will aid in reducing the potential for erosion.
REPORT LIMITATIONS
This report has been prepared to assist the planning and design of reconstruction of
the rockery at 1307 South Center Drive in Spokane Valley, Washington. Our services
consist of professional opinions and conclusions made in accordance with generally
accepted geotechnical engineering principles and,practices. This acknowledgement is
in lieu of all warranties either expressed or implied.
It has been a pleasure being of service to you on this project. If you have any
questions or need additional information, please do not hesitate to. call us at your
convenience.
Sincerely,
AIIWest Tes 'ng & Engineering, LLC
W�
Paul T. Nelson, P.E. —
oeu-u // �r =177Senior Geotechnical Engineer
EST
Materials Testing • Geotechnical Engineering
04/16/2004 15:56 FAX 5094777655
SPOKANE COUNTY ENGINEERS
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