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Report (755) d rlson Geotechnical Main Office S al e t Office ' B end Office eC P.O. Box 23814 4060 Hudson Ave., NE P.O. Box 7918 A Division of Carlson Testing, Inc. Tigard, Oregon 97281 Salem, OR 97301 Bend, OR 97708 Geotechnical Consulting Phone (503) 684 -3460 Phone (503) 589 -1252 Phone (541) 330 -9155 Construction Inspection and Related Tests FAX (503) 670 -9147 FAX (503) 589 -1309 FAX (541) 330 -9163 Geotechnical Engineering Services Lowe's H.I.W. — Generator Pad and Rockery Wall Tigard, Oregon CGT Project: G0001561.B Prepared for Mr. Jim Bryan Sconzo Hallstrom Architects 919 124 Avenue, N.E., Suite 101 Bellevue, WA 98005 March 15, 2001 • Salem Carlson Geotechnical P.0 3814 4060 Hudson A Ave., NE o s Office A Division of Carlson Testing, Inc. Tigard, Oregon 97281 Salem, OR 97301 Bend, OR 97708 Geotechnical Consulting Phone (503) 684 -3460 Phone (503) 589 -1252 Phone (541) 330 -9155 Construction Inspection and Related Tests FAX (503) 670 -9147 FAX (503) 589 -1309 FAX (541) 330 -9163 March 15, 2001 Mr. Jim Bryan Sconzo Hallstrom Architects 919124' Avenue N.E., Suite 101 Bellevue, WA 98005 Geotechnical Engineering Services Lowe's H.I.W. — Generator Pad and Rockery Wall Tigard, Oregon CGT Project G0001561.B INTRODUCTION Carlson Geotechnical is pleased to present the results of our geotechnical engineering recommendations for the generator pad and rockery wall at the above project. The location of the site is shown on Figure 1. Our scope of work was as follows: • Visit the site to observe the proposed location of the generator pad and current site conditions. • Provide geotechnical engineering recommendations for support of the generator. • Provide geotechnical engineering recommendations for rockery walls behind the generator. PROJECT INFORMATION AND SUBSURFACE CONDITIONS Project Information The project consists of installing a generator on the north side of the existing building as shown on the attached site plan, Figure 1. The proposed location of the generator is in a landscaped area. An approximately 4 -foot tall rockery wall is located at the east side of the proposed location of the generator. According to the plans and specifications there will be a cut of approximately 7 feet in the landscaped area and a rockery wall is to be constructed behind and around the generator. Carlson Geotechnical has previously performed a geotechnical investigation and construction observations for the entire Lowes site. We used information from our report dated June 9, 1997 for the current work at the site. Lowes H.l. W. — Generator Pad and Rockery Wall Tigard, Oregon March 15, 2001 CONCLUSIONS Based on the results of our previous subsurface explorations, we conclude that the generator pad and rockery walls can be built in the proposed area provided that the recommendations of this report are incorporated into the design and construction of the project. The following sections provide specific recommendations for construction of the generator pad and rockery walls. RECOMMENDATIONS Site Preparation The existing landscaped area should be stripped and removed from the proposed generator and wall locations. Based on the site plans that you provided and our observations, we anticipate that approximately 8 feet of cut will be required. Stripped and /or excavated material should be transported off site for disposal. Silt fences, hay bales, or other measures should be used, as required, to reduce sediment transport during construction to acceptable levels. , Measures to reduce erosion should be implemented in accordance with Oregon Administrative Rules 340-41 -006 and 340 - 41-455 and Washington County regulations regarding erosion control. After site stripping and grading, a representative from Carlson Geotechnical should observe the generator and rockery wall footing subgrades to identify areas of excessive yielding. If areas of soft soil or excessive yielding are identified, the material should be excavated and replaced with compacted materials as recommended for structural fill. Generator Pad Construction We recommend that the generator pad be founded on native medium stiff silt soils or on structural fill as recommended below. A coefficient of friction of 0.32 may be used for sliding resistance along the bottom of the concrete slab. A subgrade modulus of 175 pounds per cubic inch (pci) may be used for design of the slab. Since we previously evaluated the potential settlement due to liquefaction in these areas, differential settlement is anticipated to be approximately 2 inches. The concrete slab foundation should be founded on a minimum 6- inch -thick layer of free draining, well graded crushed gravel founded on the medium stiff silt. Between the gravel and the medium stiff silt, an approved geotextile should be placed on the firm undisturbed ground surface. The crushed gravel should then be placed on the fabric so as not to damage the fabric or subgrade. The crushed gravel should have a maximum particle size of 1 inches and contain not more than Carlson Geotechnical Page 2 of 5 Lowes H.I. W. — Generator Pad and Rockery Wall Tigard, Oregon March 15, 2001 5% passing the No. 200 sieve (based on a wet sieve analysis) and should be compacted to a dry density of at least 95% of the maximum dry density as determined by ASTM D -1557. Prior to placing the crushed gravel, the subgrade should be evaluated by CGT to ensure that the on -site soils will provide consistent support across the bottom of the concrete slab. If soft or loose zones are encountered, they should be removed, replaced with crushed gravel and compacted as described above. The generator design including all cables, hoses, etc., should be flexible enough that could accommodate 2 inches of differential settlement due to liquefaction on the soils at the site. Rockery Wall Construction We have included general design criteria for construction of the new rockery wall on Figure 2. These criteria are based on our experience and on soil conditions at the site and generally accepted practice for the construction of rockery walls. Rockery walls are typically used for cosmetic or erosion control purposes and are assumed incapable of withstanding significant lateral earth pressures. Our recommendations are based on the assumption that the slope is stable and the wall is not subjected to any significant lateral earth pressure. The Geotechnical Engineer should observe the condition of the cut slope prior to rockery wall construction to evaluate slope angle for temporary cut. We recommend that backfill within 3 feet of the back of the wall be compacted using hand - operated tamping equipment and be compacted to between 85 and 90 percent of the maximum dry density of the backfill, as determined by ASTM D -1557. Drainage Considerations We recommend that subsurface wall drains be connected to a tightline leading to the storm drain. Subgrade surfaces should be sloped such that the water collected by the wall drain is collected and routed to suitable discharge points. Structural Fill We recommend the use of imported granular material for structural fill used in excavations for the foundation subgrade for the rockery walls. Imported granular material should consist of angular pit or quarry run rock, crushed rock, or crushed gravel and sand that is fairly well - graded between coarse and fine particle sizes. The fill should contain no organic matter or other deleterious materials, have a maximum particle size of 3 inches, and have Tess than 5 percent passing the U.S. No. 200 Sieve. The percentage of fines can be increased to 12 percent of the material passing the U.S. No. 200 Sieve, if placed during dry weather and provided the fill material is moisture - conditioned, as necessary, for proper compaction. The material should be placed in lifts with a maximum uncompacted thickness of 8 inches and be Carlson Geotechnical Page 3 of 5 Lowes H.I. W. — Generator Pad and Rockery Wall Tigard, Oregon March 15, 2001 compacted to not less than 92 percent of the maximum dry density, as determined by ASTM D -, 1557, using hand - tamping equipment. During the wet season or when wet subgrade conditions exist, the initial lift thickness should be increased to 24 inches to prevent subgrade disturbance. LIMITATIONS AND GENERAL NOTES We have prepared this report for use by the owner and other members of the design and construction team for the proposed generator pad and rockery wall. The opinions and recommendations contained within this report are not intended to be, nor should they be construed as a warranty of subsurface conditions, but are forwarded to assist in the planning and design process. We have made observations based on our previous explorations that indicate the soil conditions at only those specific locations and only to the depths penetrated. These observations do not necessarily reflect soil types, strata thickness, or water level variations that may exist between explorations. If subsurface conditions vary from those encountered in our site exploration, CGT should be alerted to the change in conditions so that we may provide additional geotechnical recommendations, if necessary. Observation by experienced geotechnical personnel should be considered an integral part of the construction process. The owner is responsible for insuring that the project designers and contractors implement our recommendations. When the design has been finalized, we recommend that the design and specifications be reviewed by our firm to see that our recommendations have been interpreted and implemented as intended. If design changes are made, we request that we be retained to review our conclusions and recommendations and to provide a written modification or verification. The scope of our services does not include services related to construction safety precautions, and our recommendations are not intended to direct the contractor's methods, techniques, sequences, or procedures, except as specifically described in our report for consideration in design. Within the limitations of scope, schedule, and budget, our services have been executed in accordance with the generally accepted practices in this area at the time this report was prepared. No warranty or other conditions express or implied, should be understood. Information contained herein is not to be reproduced, except in full, without prior authorization from this office. We would be pleased to provide additional input, if requested. Carlson Geotechnical Page 4 of 5 9 Lowes H.l. W. — Generator Pad and Rockery Wall Tigard, Oregon March 15, 2001 We appreciate the opportunity to serve as your geotechnical consultant on this project. Should you have any questions regarding this report, please let us know. Sincerely, CARLSON GEOTECHNICAL Wi ' ton San o Sta Engineer t - -� 4 #15648 17. _ E NE M. tO Jea e M. iem= , P.E. I EXPIRES: Princi�►al G; .technical Engineer I2 �� Attachments: Figures 1 and 2 Doc. ID: P: \GEOTECH\Projects (Engrec)\2000 Projects\Lowes H.I.W. - Generator Pad\1561B.DOC Carlson Geotechnical Page 5 of 5 1 i ? I4 75 NORTH _� • • ,c' J - -- - -.-b 11 } L. - -` `�'• attt�t♦ _ --- �t —to! - - - - —700 • • 6hDC 3C�•0n. • / .- c.QR:CnC? - • - A. LWDRA \ `701.0 WC: CnCFAiC•i UO[lf BRbEWAY .., • A - A • NE'. • �R �i 10 TION r._ • =w 1 7 ,...---.. DCESSS 30hC s �,...� • _ X 746 _ _ r• -- • • . N. 704 - cux eCLd.O -i- • � Ue.iGCN:Y n. LconaG 70].1) (EC) • - .. , � GCNEt D R 00.1f uRYEtCAY J , . - • /�' 8 -13 GENERATQR LOCATION S�GTION ... - .. . • • . GPI sCALE: I . TO 0 } • 1 � 1 • ' LOWES' - GENERATOR PAD (Nor PART CF . , . TOTAL 911E1 . 1 " r L r l. \ . u.; oo G � • - . � r�. c F �,q SITE PLAN • mr U ©.a1 7- `a��a coi, SR F tel i s : � .. . _ �,�� 03/13/01 FIGURE 1 lib' , , G' . V ; t oc; ..r. o o c • , ,�r., � CGT JOB NUMBER o4 cal': 1 v e • °o ° v ° ° v • ° _ I L N �� o fi - ca ,/0.1 ,/ f , �y�: , o o o ±�� w G0001561 b LOT 28�' -r , ,, ,�? 91, "6� ' c v V 0 c 4 �d R %ilk:, i 12 4 4 . - 1,9,rom ,. - .141; 7Z V .,..,--,-.-4,17, • -. W LEGEND . , N61 / ,,...:, — _,..? . ail triQ• ' °`-'1■"`"-% '6Cti ) • - r t1 `� L ' i . ��7cT �� V i• . J; b (y • _ !� scl�r: fC - ?_ ``;• .ij� ,� . N T o S ca l e V �a,�- : e°90 - ROCKERY WALL !�_ O -.L.-- 09.L.9.. : o - • _- - NEW GENERATOR 4 ON -GRADE • = = RECEIVING_ . - ► .•.:1;!'-ii, 1 r�_r ,,, 1 All locations are approximate. io TRUCK WELL 1 1 m ' � . J - Drawing provided byHallstrom Architechs, P.S.C. The drawing has been reproduced and modified by CGTistaff. CARLSON GEOTECHNICAL I ,.- ,- .a:_._.. -_r -_II r,.,.,... .... ..... .......,.,...,..1 -. A DIVISION OF CARLSON TESTING INC. ' A • ROCK SIZE SCHEDULE (Eqn. = 250D + 250) LBS. ROCKERY WALL DESIGN H (FT) MIN. WT. (LBS.) TYPICAL SIZE (IN.) MAXIMUM WALL HEIGHT (H) = 9 FEET 9 2,500 29 X36 X 29 29 X 29 X 29 DRAWING NOT TO SCALE 7 2,000 36 X 30 X 20 28X28X28 5 1,500 34 X 26 X 18 25X25X25 LEVEL TO 2H :1 V MAX. SLOPE 3 1,000 28 X25 X 16 22X22X22 22 X 19 X 14 COMPACTED SILT 1 500 18 X 18 X 18 OR CLAY SOIL :, ( to 24 INCHES .O� THICK) oQ -Qo o Q Q A -OQ A oO: - .7 0 0, 5 !4: 1 - �Qa D °�0°�0 �oi° o o;5 ° STABLE TEMPORARY CUT a,0 la,0e' (SLOPE ANGLE VARIES) 4t1 MIN. WT. � „.., H . 250D +250 o t;p °,4.� . Oo � '0� aw ° =4 °° °”` 4 "-0 CRUSHED AGGREGATE, ___ r _ °,O�a ,°' COMPACTED IN 12 INCH LIFTS .r o 0. , 0 L F ill -li 0.35H o al� A , 1 1/2 "-0 CRUSHED AGGREGATE Oo WITH NO MORE THAN 7% FINES / Vi — °O PASSING THE No. 200 SIEVE, 12 IN. MIN. = • LIGHTLY TAMPED a , % 6 IN. 4 IN. DIAM. MIN. PERFORATED PLASTIC PIPE '`s SCHEDULE 40 or ADS HIGHWAY GRADE KEYWAY 0.4H MIN. FOR OSHA STABLE ROCK, 0.5H MIN. FOR OSHA "TYPE A" SOILS, AND CONSTRUCTION NOTES 0.6H MIN.. FOR OSHA "TYPE B" SOILS 1. For walls supporting engineered fill, the fill should be overbuilt and the wall constructed against an excavation into already compacted fill. 2. Keyway subgrade and embedment depth should be verified by CARLSON GEOTECHNICAL. 3. Rocks should have a cubical, tabular, or semi- rectangular shape that roughly matches the space created by the previous rock course. Rocks should be laid flat with the long dimension oriented perpendicular to the wall and extending towards the excavation face. Rocks should be staggered such that each rock bears on at least two rocks below and vertical joints are discontinuous. Rock placement and wall integrity should be checked (by builder) by lightly hammering on the top of each rock with excavator bucket. 4. Minimum rock sizes should be determined using the ROCK SIZE SCHEDULE above, where D is the distance from the base of the rock to the top of the wall. Rocks should be no smaller than 500 lbs. 5. Voids greater than 6 inches wide where there is no contact between adjacent rocks should be chinked with a small rock. 6. Backfill behind the rocks should consist of an average 12 -inch -wide sheet of 4 "-0 well graded crushed aggregate with no more than 7% fines passing the U.S. Standard No. 200 sieve. Backfill should be placed in lightly compacted to an unyielding state in 12 inch lifts has each course of rocks is placed. a r q y Carlson Testing, Inc. Figure 2 P.O. Box 23814 LOWE'S - GENERATOR PAD Tigard, Oregon 97281 CGT Job No. G0001561 B .