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Report 04/30/03 WED 16:32 FAX 503 843 1905 KLEINFELDER Iaj013 ,/ CfoLs7 /3 Filee s w 1e r,r KLEI NFELDER TECHNICAL MEMORANDUM ` ^ Materials Testing b Environmental Science & Engineering Water Resources Earthquake Engineering Air Quality Date: April 30, 2003 To: MR. GEORGE MARSHALL HEIGHTS CONSTRUCTION _ P.O. BOx 91249 Portland, Oregon 97297 -0249 = - 44 '.� . • Fax: 503.291.6917 r From: Robert L. Stephens, P.E. miaow Senior Geotechnical Engineer NZ*: , e r g e tb �► t.. sue'" Project No.: C60- 8634 -01 ex, .1-349.44 Subject: ROCKERY WALL DESIGN AND CONSTRUCTION RECOMMENDATIONS DAFFODIL HILL SUBDIVISION TIGARD, OREGON The attached Kleinfelder report: "Rockery Wall Design and Construction Recommendations, Daffodil Hill Subdivision, 13735 SW Bull Mountain Road, Tigard, Oregon," dated January 21, 2002 may be used for construction of the proposed rockery walls located at Lots 7 through 10 at the subject Subdivision. We understand that the existing walls at these lots may be raised from their current heights to heights not exceeding the maximum exposed wall height listed in our January 21, 2002 report. Kleinfelder will perform examination of the existing walls at Lots 7 through 10 to verify that previous construction was in compliance with the recommendations of our January 21, 2002 report. Please reference our letter to you dated April 23, 2003. New construction of these walls will also require observation by an Oregon - licensed engineer familiar with rockery wall design and construction. -o0o- Thank you for the opportunity to provide our services on this project. Please contact the undersigned at your convenience with any comments or questions regarding the recommendations provided. L• 120031prolectS10608634011POR3L081 .doc 15050 SW Ko1I Parkway Copyright 2003 Kleinfelder, Inc. Suite L Beaverton. OR 97006 -6028 Tel. 503 - 644 -9447 F. 503 -643 -1905 04/30/03 WED 16:26 FAX 503 643 1905 KLEINFELDER @1002 KLEINFELDER Geotechnlcal Engineering TECHNICAL MEMORANDUM Materials Testing &Inspection Environmental Silence & Engineering Water Resources Earthquake Engineering Air Qualfty Date: January 21, 2002 1... L. h To: MR. GEORGE MARSHAL P.O. Box 91249 f i ' j Portland, Oregon 97291 CITY MR. LANCE LUDWICK BUILDING; DIV Harris - McMonagle Associates, Inc. 12555 SW Hall Boulevard Tigard, OR 97223 Fax (503) 639 -1232 From: Travis T. Nguyen, P.B. Geotechnical Engineer Robert L. Stephens, P.E. Geotechnical Group Leader Project No.: 60- 8634 -01 Subject: ROCKERY WALL DESIGN AND CONSTRUCTION RECOMMENDATIONS DAFFODIL HILL SUBDIVISION 13735 SW BULL MOUNTAIN ROAD TIGARD, OREGON INTRAni trTIAN Per your authorization, we have prepared this Technical Memorandum addressing the proposed rockery wall along the south side of the above referenced project site. This memorandum summarizes our understanding of the proposed wall and provides our recommendations for construction. In preparing these recommendations, we reviewed the Site Grading Plan provided by Harris - McMonagle Associates, Inc. and the Geotechnical Investigation report prepared for the project site by Geotechnical Resources, Inc. (GRI) dated July 24, 2001. A Kleinfclder engineer also made a brief site visit on January 21, 2002 to observe the existing conditions. L•\ 20021projects \6086340116022R016.doc Page 1 of 5 15050 SW KoII Parkway Copyright 2002 beintelder. Inc. Suite L Beaverton, OR 97008 -8028 Tel. 503 -644 -8447 — - Fax. -503 -943 -1905 04/30/03 WED 16:29 FAX 503 643 1905 KLEINFELDER lI003 • KLEI NFELDER Kleinfelder has conducted no subsurface explorations and has not conducted an overall geotechnical evaluation of the site. Our services have been provided in accordance with the Engineering Services Agreement between Hams - McMonagle Associates, Inc. and Kleinfelder, Inc. for the above referenced project. The remainder of this Technical Memorandum includes the following: description of the proposed wall.; assumptions used to develop the rockery wall design recommendations; and, general rockery wall construction recommendations and specifications. A Rockery Wall Typical Construction Detail is attached as Figure 1. Rockery Calculation Illustration (Figure 2) and the calculations for determining the minimum rock sizes are included behind the Rockery Wall Typical Construction Detail. The rockery wall design recommendations have been developed on the assumption that the exposed height of the rockery wall will not exceed 9 feet. PROPOSED ROCKERY WALL: Retaining wall is shown at one location on the Site Grading Plan. Wall location, maximum wall height (as shown on the Plan), and slope condition above and below the wall are summarized below. It is our understanding that the maximum wall exposed height as shown on the Plan do not exceed approximately 7 feet. If the owner desires to reduce the proposed slope height above the wall, the wall maximum exposed height may be increased to approximately 9 feet. South Wall The proposed I- shaped rockery wall extends for a linear distance of approximately 373 feet on the south side of the site. The proposed wall is oriented east -west. The wall will support an existing cut. The proposed slope behind the wall extends up to an undeveloped and vegetated area at inclinations varying up to approximately 4H:1V (Horizontal:Vertical). The maximum existing vertical cut slope on the site is on the order of 7 feet in height at the central portion of the wall and tapers to about 5 feet at both ends. As mentioned above, the wall height as shown on the Plan do not exceed approximately 7 feet. However, if the owner desires to reduce the proposed slope height above the wall, the wall maximum exposed height may be increased to approximately 9 feet. ASSUMPTIONS USED IN ROCKERY WALL DESIGN Retained Soil: Ba on the GR1 geotechnical report, the native soil consists of medium stiff to stiff silt. We have assumed that the rockery walls will retain the undisturbed native silty soils. For the purpose of this design, we are assuming the lateral earth pressure on the rockery walls from on -site native soils will be no greater than the earth pressures the walls would be subjected to from a cut in the native soils. In our stability calculations we assumed the following strength parameters: c = 0 and 4)--29°. We have assumed a unit weight for the saturated soil the rockeries will support of y =120 pounds per cubic foot (pet). The friction angle- and-soil-unit L: 120021projects16086340116022R018 .doe Page 2 of 5 15050 SW Koll Parkway Copyright 2002 Kleinfelder, Inc. Suite L Beaverton. OR 97006 - 6028 Tel. 503.644 - 9447 Fax. 503 -643 -1905 04/30/03 WED 18:29 FAX 503 843 1905 KLEINFELDER Z004 KLEINFELDER weight values used correspond equivalent fluid pressure of 49 pef for a non- restained wall with 4H: l V backslope. Wall Configuration: Our design assumes that the rockery wall will have a maximum exposed height of 9 feet and wall will be battered at an inclination of no steeper than 1H:4V with a 4H:1V backslope. We have assumed that building foundations will extend below the IH:IV restricted zone shown on the attached Rockery Wall Typical Construction Detail, Figure 1. Our Rockery Wall Typical Construction Detail is attached as Figure 1. It includes minimum required rock size details. Rockery Calculation Illustration is attached as Figure 2. Calculations are provided behind Figure 2. GENERAL CONSTRUCTION RECOMMENDATIONS AND SPECIFICATIONS Rock wall construction is a craft, and the stability of rock walls depends in large part on the skill and experience of the builder. Kleinfelder should he notified at the time of wall construction to visit the site and observe the progress of the work. It will be necessary for walls in the designated areas to be built using the appropriate base rock and embedment parameters shown on the Rockery Wall Typical Construction Detail. If base rocks for 9 feet exposed height wall are not available, Kleinfelder should be contacted to revise the design. Note that we have specified a minimum rock size of 250 pounds on the Rockery Wall Typical Detail. On short wall and near the top of higher wall, smaller rocks would be suitable from an analytical standpoint; however, smaller rocks can be more easily dislodged by children or pets. If it is desired to use smaller rocks, we recommend that the top layer of rocks be mortared into place. Even with 250 pound rocks, it is possible that the rocks can become dislodged by people climbing or walking on the finished wall, or by intentional acts. If it is not possible to prevent this occurrence, larger stones or mortar should be used. Other comments pertaining to wall construction: • No permanent excavations should be made below the toe of the rock walls. Temporary cuts should conform to OSHA requirements, and in no event should an excavation extend below a 1H:1V slope projected downward from the toe of a wall. If groundwater is encountered, or if excavations are left open for an extended period of time, shoring or other slope support measures may be necessary. • The first course of rock must be placed on a 6 -inch layer of crushed rock (bedding layer) overlying firm unyielding soil or well compacted granular fill. There should be full contact between the rock and gravel layer. We have indicated a bedding layer of crushed rock below the wall on the Rockery Wall Typical Construction Detail. L: 120021projecta 6088340116022R018.doc Page 3 of 5 15050 SW Koll Parkway Copyright 2002 Kleinfetder, Inc. Suite L Beaverton, OR 97006 -6025 Tel. 503. 644 -9447 — — Fax. - 503=843 -1905 - - • • 04/30/03 WED 16:29 FAX 503 643 1905 KLEINFELDER lit 005 1111 KLEINFELDER • Our design is based on the use of quarry stones that contain significant flat areas and that can be placed in a manner that provides significant bearing between rock courses. Rocks that are rounded, or that do not match the spaces that are made available by the lower course should not be placed. • Rocks should be staggered so that there are no continuous vertical joints in the wall; each rock must bear on at least two rocks below it. • The long dimension of all rocks should extend back towards the excavation to provide maximum stability. • If gravel backfill is used, voids between rocks must be small enough that the gravel cannot be washed through the face. Larger voids must be chinked with spalls or smaller stones (or geotextile fabric placed between the backfill and face rocks). . • A drainage layer is shown behind the wall to prevent the buildup of hydrostatic pressure from underground water sources. This layer is not intended to collect surface water. Surface water must be intercepted above the wall and routed to a positive discharge on either end of the wall. A perforated drain pipe is included at the base of the wall to facilitate drainage of any water that collects behind the wall. The drain pipe should be sloped to drain to positive outlet(s). • Any changes to the design can potentially make the wall unstable and should be reviewed by Kleinfelder. Such changes include, but are not limited to: temporary excavations of ditches or trenches within five feet of the wall; surface or subsurface water allowed to flow over or behind the wall in any quantity; any other changes to the geometry and conditions depicted on the attached figures. Kleinfelder is available to provide intermittent observations of materials and procedures used during wall construction to evaluate compliance with our recommendations. These services will be provided on an as requested basis. FENCE RECOMMENDATIONS: If a fence is installed along the top of the wall, post supports should be embedded at least 4 feet into the retained soil behind the drain rock. The supports should not be placed within the rockery wall zone. L: 12002 1proJects160863401%022R01B .doe Page 4 of 5 15050 SW Koll Parkway Copyright 2002 Kleinfelder, Inc. Suite L Beaverton. OR 97006.6028 Tel. 503 -644 -9447 Fax. 503. 643 -1905 04/30/03 WED 16:30 FAX 503 643 1905 KLEINFELDER Zoos • KLEINFELDER Thank you for the opportunity to provide our services on this project. Please contact either of the undersigned at your convenience with any comments or questions regarding the recommendations provided. Sincerely, KLE1NFELDER, INC. . ., .. NPL v OQp b a -a- Travis T. Nguyen, P.E. Robert L. Stephens, P.E. Geotechnical Engineer Geotechnical Group Leader Attachments: Figure 1 - Rockery Wall Typical Construction Detail Figure 1 - Rockery Calculation Illustration Supporting Calculations • L t.20021projects6088340116022R018 .dot Page 5 of 5 15050 SW Koll Parkway Copyright 2002 Kklntelder, Inc. Suite L Beaverton. OR 97008 -6028 Tel. 503 -644 -9447 Fax. 503. 843 -1905