Geotechnical Report Addendum

Addendum Transmittal
Page 1
To:
Fred Gast
Company:
Polygon Northwest Company
Address:
109 East 13 Street
From:
Shawn Dimke
Date:
March 10, 2015
th
Vancouver, WA 98660
cc:
Jim Lange, Pacific Community Design (via email only)
GDI Project:
Polygon-113-01
RE:
Roshak Ridge
Date
Original File Name
Polygon-113-01-012813-
1/28/13
Document Title
Report of Geotechnical Engineering Services;
Roshak Ridge; SW Bull Mountain Road and SW Roy
geor
Rogers Road; Tigard, Oregon
Addendum
Number
Date
1
3/10/15
Description
Tract DD Stormwater Pond (attached)
kt
Attachment
One copy submitted (via email only)
Document ID: Polygon-113-01-031015-geoat-1.docx
© 2015 GeoDesign, Inc. All rights reserved.
15575 SW Sequoia Pkwy, Suite 100 l Portland, OR 97224 l 503.968.8787
Memorandum
Page 1
To:
Fred Gast
From:
Shawn M. Dimke, P.E., G.E.
Scott V. Mills, P.E., G.E.
Company:
Polygon Northwest Company
Address:
109 East 13 Street
Date:
March 10, 2015
th
Vancouver, WA 98660
cc:
Jim Lange, Pacific Community Design (via email only)
GDI Project:
Polygon-113-01
RE:
Addendum 1
Tract DD Stormwater Pond
Roshak Ridge
GeoDesign, Inc. is pleased to submit this addendum for the proposed Roshak Ridge residential
development located northeast of the intersection of SW Roy Rogers Road and SW Bull Mountain
Road in Tigard, Oregon. Our geotechnical report1 for the site is dated January 28, 2013. We
reviewed the attached preliminary grading plan provided by Jim Lange dated March 5, 2015. Based
on the grading plan, cuts for the Tract DD stormwater pond at the northwest corner of the site will
vary up to approximately 9 feet deep below the existing ground surface. Wall designs will be
required for the retaining walls planned on the east and west sides of the pond. A hand auger
exploration (HA-4) completed for our prior report near the northern edge of the planned pond
encountered medium stiff to stiff silt to the depth explored of 9.5 feet below ground surface.
Accordingly, we expect the excavation for the pond can be completed with conventional earthwork
equipment.
At the time of our explorations in January 2013, seepage was encountered in the hand auger;
therefore, it is possible dewatering may be needed for the excavation. A sump located within the
excavation likely will be sufficient to remove accumulated water. Flow rates for dewatering are likely
to vary depending on location, soil type, and the season during which the excavation occurs. If
needed, dewatering systems should be capable of adapting to variable flows.
1
GeoDesign, Inc. Report of Geotechnical Engineering Services; Roshak Ridge; SW Bull Mountain Road and SW Roy Rogers Road;
Tigard, Oregon, dated January 28, 2013. GeoDesign Project: Polygon-113-01
15575 SW Sequoia Pkwy, Suite 100 l Portland, OR 97224 l 503.968.8787
Memorandum
Page 2
The proposed pond can be excavated and constructed as shown on the preliminary grading plan,
and other than the associated retaining walls that need to be designed, we have no further
geotechnical recommendations or requirements for the pond.
SMD:SVM:kt
Attachment
One copy submitted (via email only)
Document ID: Polygon-113-01-031015-geoa-1.docx
© 2015 GeoDesign, Inc. All rights reserved.
15575 SW Sequoia Pkwy, Suite 100 l Portland, OR 97224 l 503.968.8787
ATTACHMENT
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EXISTING FENCE
GRADING SECTIONS
SEE SHEETS 7.2 - 7.4
POLYGON NW COMPANY
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N:\proj\395-010\09 Drawings\03 Planning\Sheets\395010.(7.1-7.4).PGRADE.dwg - SHEET: (7.1) GRADE Mar 06, 2015 - 1:44pm erik
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