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Plans GeoPacific _ h Engineering, Inc. RECD !\ P 14 20 Real -World Geotechnical Solutions Investigation • Design • Construction Support April 9, 2003 �C. ROl3ER. Project No. 03 -8207 RECEIVED Qp Lj Steve Hunt APR 29 2003 STGV- Renaissance Homes, Inc. CITY OF TIGARD ttr:EVISION 1672 Willamette Falls Drive BUILDING DIVISION West Linn, OR 97068 I C.oC k i Fax (503) 656 -1601 �a oda ©Od AP O Z T SUBJECT: INITIAL ROCK WALL EVALUATIONS AP J-! �/ LOTS 2 -4, 6, AND 8 -10 FILE COPY ERICKSON HEIGHTS TIGARD, OREGON This letter presents our initial assessment, findings, and conclusions of the above - referenced rock walls. The main purpose of this initial work phase was to generate cross sections of the wall topography on the lots in question and generate a short letter report grouping the lots based on similarity and complexity of slope geometry. This letter also outlines preliminary conclusions with possible recommendations for either further site investigation for the marginal and complex configurations or immediately assessing the need for reconstruction on the obvious and simple configurations. We understand the tiered rock wall system throughout Lots 1 through 10 was constructed within the last few years. The overall relief is the tiered rockery walls are about 15 to 20 feet over about 20 to 40 feet horizontal. Concerns have been expressed about the stability of the upper rock walls, which were not engineered, but may be surcharging engineered lower rock walls below. Lots 1 and 5 have already been addressed by others and subsequently corrected and therefore are not a part of this report. FIELD WORK Our field geologist generated field sections of the rear yard geometries using a hand tape and slope inclinometer. The locations of the cross section locations are shown on Figure 1. Cross Sections are presented on Figures 2 through 6. Some hand probing of the fill on the slopes was performed. In general, the lower two walls appear to have been founded on engineered fill placed during site development. The grading plan by Harris McMonagle Associates appears not to be accurate for many of the lots, i.e. more fill is present farther back on the lot than is shown; and the fill likely extended to the present grades in the area of the lower two walls. CONCLUSIONS 4 upper two walls on Lot 2 are obviously too close to the second wall to be considered in conformance with standard engineering practices. We recommend removal of the upper two walls on this lot and replacement with one 6 -foot tall wall at the location shown in accordance with the attached design (see Section A -A' and Figure 6). GeoPacific should review the subgrade, retained fill, and new wall during reconstruction. 7312 SW Durham Road Tel (503) 598 -8445 Portland, Oregon 97224 Fax (503) 598 -8705 G.r GEOPACIFIC ENGINEERING, INC. Proposal No. 03 -8207 Erickson Heights Rock Walls Lots 3 and 8 require rather extensive further study, analysis and remediating design. We can provide lot- specific work scopes for these two lots upon request. Much more study and time will be necessary to evaluate these lots. Lots 4, 6, and 9 need minimal further evaluation including hand - excavated test holes, global stability analysis, and more complete evaluation of rockery wall construction. We are providing a proposal for this additional work and estimate two weeks for completions of studies on these lots. In our opinion, Lot 10 needs no further study and the existing walls are adequate as built. The walls on Lot 10 appear to have been mostly constructed during the development stage and where reconstructed, in general accordance with the original wall detail by Carlson Geotechnical. Within the limitations of scope, schedule and budget, GeoPacific attempted to execute our services in accordance with generally accepted professional principles and practices in the fields of geotechnical engineering and engineering geology at the time the report was prepared. Sincerely, GEOPACIFIC ENGINEERING, INC. © PRo ea 4 14743 t �. • OREGON 8 E-7) fc u D. I James D. Imbrie, P.E., C.E.G. Principal Geotechnical Engineer Attachments: Figure 1 - Site Plan Figures 2 through 5 — Cross Sections A through H Figure 6 — Rockery Wall Detail 6 -Foot Rockery wall Design Page 2 • #41' . ; 1N; '� i ! �. i . 'R :�' x � 11y. '� - ' t', ,, t t k { f WW YJail W''s • '"' ' ' '' 1. '." 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Existing Grade 305— X • + 11. • —305 Natural Grade dt Proposed Finished Grad ap 300— (H arris - McMonagle plan —300 dated April 1999) - 295— —295 Property Line 290— 290 Lot 2 Elevation (Feet Above MSL) B Existing Grade B 3 — 310 Pool 305— Proposed Finished Grade • (Harris-McMonagle plan 11111 -305 dated April 1999) - 300 — Natural Grade 411 • —300 • Property Line 295— --I —295 290— —290 285— —285 Lot 3 0 10 I SCALE 1"=10' Date: 03/27/03 Horizontal = Vertical Drawn by: EJL I Project: Erickson Heights Job No: 03-8207 FIGURE 2 Tigard, Oregon o: I r .../Ac ‘... 7312 SW Durham Road Ge ®Pacific Portland, Oregon 97224 CROSS SECTIONS C AND D Enpineernp,Ine. Tel: (503) 598-8445 Elevation (Feet Above MSL) 310— C' —310 Pool 305— -305 300— • Existing Grade —300 295 — Natural Grade —295 Proposed Finished Grade 290— (Harris - McMonagle plan dated April 1999) Property Line - 290 285 285 Lot 3 Elevation (Feet Above MSL) 310 D House D' —310 305— • —305 Existing Grade 300 Proposed Finished Grade • (Harris - McMonagle plan —300 dated April 1999) • 295— Natural Grade dr —295 290— . —290 285 Lot 4 285 0 10 SCALE 1 " =10' Horizontal = Vertical Date: 03/20/03 Drawn by: EJL Project: Erickson Heights Tigard, Oregon Job No: 03 -8207 FIGURE 3 +• ' \ \(\, 7312 SW Durham Road ✓ GeoPacific Portland, Oregon 97224 CROSS SECTIONS E AND F EnWn�nelnc. Tel: (503) 598 -8445 Elevation (Feet Above MSL) 310 E' 310 0 2 305— -305 Existing Grade 300— / —300 Proposed Finished Grade (Hams - McMonagle plan dated April 1999) - 295— dr —295 � Natural Grade •► 290— 1 • —290 Property Line 285— —285 Lot 6 Elevation (Feet Above MSL) 305— -305 Existing Grade House 300 — — 300 Proposed Finished Grade 411111 295— (Harris - McMonagle plan —295 dated April 1999) • 290— Natural Grade —290 285— � —285 Property Line 280 Lot 8 280 0 10 SCALE 1"=10' Horizontal = Vertical Date: 03/27/03 Drawn by: EJL Project: Erickson Heights I Tigard, Oregon Job No: 03 -8207 FIGURE 4 • 4 _el \r; SW Durham Road GeoPafic Portland, Oregon 97224 CROSS SECTIONS G AND H Englnealag.Inc. Tel: (503) 598 -8445 Elevation (Feet Above MSL) 3 G G' 00 —300 Existing Grade 295— 7 -295 Proposed Finished Grade x - 290— (Harris - McMonagle plan ` —290 Natural Grade dated April 1999) . �� 285– - –285 280— • Property Line —280 275— -275 Lot 9 Elevation (Feet Above MSL) 3 H H' 00 —300 295— /' —295 Proposed Finished Grade Existing Grade (Hams - McMonagle plan House dated April 1999) 290– + –290 Itim 41110 Natural Grade 285— I —285 — 111110 OP 280— • o.ertyLine -280 275— --275 Lot 10 0 10 I SCALE 1"=10' Date: 03/27/03 Horizontal = Vertical Drawn by: EJL Project: Erickson Heights I Job No: 03 -8207 FIGURE 5 Tigard, Oregon 7312 SW Durham Road GeoPacific Portland, Oregon 97224 Erickson Heights Lot 2 FIGURE 6 monriamm Tel: (503) 598 -8445 Fax: (503) 598 -8705 Project No. 03 -8207 ROCK SIZE SCHEDULE (See note 4 below) ROCKERY WALL DETAIL D (FT) MIN. WT. (LBS.) TYPICAL SIZE (IN.) MAXIMUM WALL HEIGHT (H) = 6 FEET 1 1,000 24 X 23 X 23 24 X 23 X 23 DRAWING NOT TO SCALE 3 1,800 40 X 28 X 20 D is distance from base 36 X 27 X 27 of boulder to top of wall 5 2,600 48 X 32 X 22 40X29X29 (D = H for toe boulder) 7 4,000 54 X 34 X 24 LEVEL TO 2H:1V MAX. SLOPE 48 X 42 X 42 COMPACTED SILT OR SOIL CLAY 4:ap�u 24 INCHES THICK) L • • D : ° ` ° n ' .CT • ° D (varies) ° D�oo • o .; A 06o' • o p O � • o , Q '.•� STABLE TEMPORARY CUT .... o e o °.` (SLOPE ANGLE VARIES) e • °, ° •aa H ° °• Q a 4 - a 11-4 _ 4 " -0 CRUSHED AGGREGATE -*co. • LIGHTLY COMPACTED IN 12 °: • INCH LIFTS , .CI OO o PER SECTION A -A' v ° - • _ TOE BOULDER °'° 4 " -0 OR 1 1/2 " -0 CRUSHED MIN. WIDTH = 4 FT ; �� AGGREGATE WITH NO MORE THAN 7% 12 IN. MIN. FINES PASSING THE NO. 200 SIEVE, • s LIGHTLY TAMPED 12 IN. MIN e b " 3 or 4 INCH DIAM. PERFORATED PLASTIC PIPE ADS HIGHWAY GRADE OR EQUIVALENT MIN. KEYWAY WIDTH = 5 FT CONSTRUCTION NOTES: 1. For walls supporting engineered fill, the fill should be overbuilt as a temporary 1H:1V slope starting at a minimum distance of H/3 from the base of the wall. The slope should then be trimmed back such that the wall is constructed against a stable excavated face of compacted fill. 2. Keyway subgrade and embedment should be verified by GeoPacific Engineering, Inc. 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 be placed to the top of the wall. Rocks should be no smaller than 1,000 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 crushed aggregate with no more than 7% fines passing the U.S. Standard No. 200 sieve. Backfill should be placed in 12 inch lifts and lightly compacted to an unyielding state as each course of rocks is placed. All values per foot of wall All Values per foot of wall. Weight of Rock 134 pcf Heel Bearing = 960.7 psf < 2500 psf OK Coefficient of friction 0.5 Toe Bearing = 125.7 psf > 0 psf OK Passive Pressure 375 pcf E.F.P. 50 pcf Area = 6.0 ft Surcharge 1 ft e = 0.769 ft < B/ 6 Allowable Bearing 2500 psf F.S. Overturning 1.5 F.S. Overturning = 1.61 > 1.5 OK F.S. Sliding 1.5 F.S. Sliding = 1.51 > 1.5 OK Batter 4 :1 H1 6 ft H2 1 ft I lid L1 4 ft C2 d1 1 ft 4 Y 1.87 ft I •!i5° d 2.02 ft "'•, = d2 1.75 ft _ 4 , A . Batter Angle 14.04 degrees H1 a -. %I All values per foot of wall _ ° ,bA ° • Overturning Moment 4083.3 lb -ft -. Sliding Force 1575.0 pounds Y 1, c ,, 4 M : Yh T? 4 d Vertical Weight 3259.5 pounds _ rm e, •/ • Resisting Moment 6588.3 lb -ft °1_ _ r to b Resisting Passive 750.0 pounds I � - -- • I Ll Resisting Sliding 1629.7 pounds Total Sliding Resistance 2379.7 pounds All Calculations are per foot of wall Overturning Moment = 50pcf * (6ft. + 1ft.) ^2 / 2 + ((50pcf * 0.5ft. * (6ft. + 1ft.)* (6ft. + 1ft.) / 2)= 4083.3 lb. - ft. Sliding Force = 50pcf " (6ft. + 1ft.) " ^2 / 2 + 50pcf * 0.5ft. " (6ft. + 1ft.)= 1575.0pounds Vertical Weight = 134 pcf * (4 ft " ( 6ft + 1ft) - ( 6ft + 1 ft)* (tan 4.29) • (6 ft + 1 ft))= 3259.5 pounds Resisting Moment = 3259.5 lb * 20 ft. = 6588.3 lb -ft. Resisting Sliding = 0.5 * 3259.5 lb = 1629.7 pounds Passive Resistance = 375pcf * (1ft. + 1ft.) ^2 / 2 = 750.0 pounds Total Sliding Resistance = 750.0 lb + 1629.7 lb = 2379.7 pounds Batter Angle = arctan (1 / 4 ) " 180 / PI = 14.04 degrees F.S. Overturning = 6588.3 lb -ft. / 4083.3 t. = 1.61 F.S. Sliding = 3259.3 lb / 1629.7 lb = 1.51 , / / i 1 )09 1 i i / / / / „ , i / I I i / ior* /cu 1 I / / / . / I AV i / 1 I / j I i I f 1 ..--- --a- ----------- / / l b / / / / / / / / // .......„.,,,,... 7 Z/ / / i / ,..-/ V / / , ,, 2 / / , , , , , ------ / ''' . i / 7 ; ------ / r / I I / / i i / / / / ,- / / / / \ \ \ \ \ / , i I 1 7 / / \ , , 1 ‘ \ \ ,/ / 7 / / I / / / i i ' 7 / / , r / , , ------ , / / / / I J \ \ 1 ‘ ' / ,..--" -- ___,----- ...---- \ / / 1 ' I , % / ---• / , , I 1 \ 1 ,/ „--/ 1 \ ' k (-- / , „,-- / , / / / j , „..-- 1 x / 7 „-- 1 • / •-• ..--•-----7, V 7 ! 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