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20090728073920.pdfOctober 31, 2007 HAATA Project No. 2007-000-21 T063 Davis Construction 14800 West Lake [;Eoodwin Road Stanwood, Washington 98292 Attn: Ren Davis Subject; VLUPsR1JSIDE;tiCE-FoUNDA'i't4NS'f-A ILIZAY'i(. N Location. 8229 138T11 S.,, SW ]EDIVi€ NDS, WA. 98026 Dear Mr. Davis; At your request we visited the above referenced site on October 30, 2007, l ie d.iscit"ed.. the issues witli the contractor and yourscl I'and havo prepared this letter with desigm hiformation for the stabilization of the part of the .foundation that is to be stabilized. Per the contractor's directions, the only issues for this letter are: the stein walls and roof CC]lilE ms at the northeast carne -r of the house, SITLi DESCRIPTION The site= is located in a gently sloping area to the north of 188'x' St. SW in Edmonds Washington (Figure 1). The: site is approximately 100 .[bot wide; along the: road and 136 fest sleep. It alap=s the wwsttrn portion of the site was in cut and the eastern portion was on fill. There appears to have originally been about S Feet of'grade di kmice across the site basical ly filoping from southwest to northeast (Figure 2).. The, noilheast corner of the building would be expected to have the most fill. The house is a single stony rambler built in 1964 on a post and pad foundation. Currently the house is ui idei.goi ii g a major rcauvat ion. The: contractor has flattened the floor which had up (o 2.5 inches of differential settleiiient. The two areas of most collect-li were the fireplace area. and the northeast courier of the house. The fireplace is near the center of the Muse and was suppurtcil On the Mood floor.'. There was no vertical support hear the fireplace and the timbers were sagging, The 1971P x,411, „ t -.,it,- %1V west of the house in that urea was relatively level hence the contractor added Suite act: uw;: STREET FILE R COY D MAR 18 2009 ,)EVEl'a SERVICES C�F Lynnwood, %"'A 9803e.395.7 TO: 18K 425:7744714 ..w+e:►sss.fY,stlsCaens,c .ti[riii October 31, 2007 HWA Project No. 2007-000-21 T063 post and pad supports under the beams in that area and lifted the fireplace to flatten the floor in that area. The northeast corner of the house (Figure 3) was low so the contractor flattened the house in that area with temporary posts and pads under the beams inside the perimeter foundation stem wall. The intent now is to raise the exterior wall foundations (Figures 4 and 5) to meet the current (flattened) elevation of the house. in addition, the roof in that area is supported by four 4x6 columns (Figure 3) on a stem wall which surrounded the deck. Those columns need to be supported also. STRUCTURAL CONSIDERATIONS It is our understanding that the columns need an ultimate support of 17 kips per column and the wall footing needs an ultimate support of 50 kips total over its 28 foot length. The general philosophy is to flatten the floor leaving it perhaps slightly out of level however there is some consideration being given to leveling the floor. GEOLOGY The geologic map referenced at the end of this report indicates that the site is underlain by Vashon Till. Vashon till is a glacially preconsolidated heterogeneous mixture of clay, silt, sand and gravel. It is generally very dense to hard with a very low permeability in its native (undisturbed) state. It is an excellent foundation material. FIELD OBSERVATIONS This investigation was restricted to the northeast corner of the house. There was a porch on the northeast corner of the house that has been removed (Figures 3 and 4). The crawl space is approximately 2 feet high where it could be seen from the northeast corner of the house (Figures 4 and 5). The stern wall supporting the outside house wall is cracked and is no longer level (Figure 6). The area around the northeast corner of the house was explored with several hand holes dug a few inches deep with a shovel and probing with a 6 foot steel probe. The locations and results of the probing are shown on Figure 7. The footings appear to have been placed on the ground surface, which in the northeast corner of the house, was on loose random fill which does not appear to have been compacted. The footings surrounding the deck were placed at one elevation and the footing for the north wall was placed about 12 inches higher, which is about the same elevation as the bottom of the sidewalk and patio slabs. Final repon 2 HWA GEoSCIr;Ncns INC. October 31, 2007 14WA Project No. 2007-000-21 T063 The steel probe was relatively easy to work down into the ground to the point where it stopped on a hard, generally granular, layer. The point where the probe stopped is, in our opinion, then top of the glacial till and the top of the layer that should be used for support. CONCLUSIONS The house should have been placed on the Glacial till or on a controlled fill placed on the glacial till. This was probably done over most of the house. The house has been there for over 40 years with relatively minor settlement. It is likely that there would not be any new settlement of existing foundations unless more load is placed on them. When any portion of the house is raised, that changes the load distribution on the remaining footings which should lower the loads on the footings that were not used for lifting and therefore no more settlement would be expected on them. However if any footing is used for lifting and future support of the house, that footing would be expected to settle further over time. Every building support where lifting is done ,should be supported on the glacial till. RECOMMENDATIONS The recommendations are limited to the Northeast corner of the house and are limited to the used of pin piles with lifting brackets used to lift the entire foundation. Deck area It is our understanding the entire area around the deck is to be, lifted to at least flatten the inside floor if not to level it. Every point used for foundation support should be supported in the glacial till. We recommend the use of an ultimate bearing capacity of 8.5 kips per pile with 2 -inch double extra strong galvanized pin piles driven to refusal with a 140 lb jack hammer. Refusal should be defrned as a penetration rate of '/2- inch per minute. This will require two pin piles under each roof truss column support and a minimum of 6 piles across the house stem walla The house stem wall is badly cracked in two locations leaving three distinct areas of relatively intact stem wall. The pin piles should be spread out along the wall such that there is good support under each section of foundation wall. The locations should be chosen by a structural engineer and may require more than 6 pin piles to get the coverage needed. North wall It is our understanding that if the house is leveled (rather than flattened) it will require lifting the northeast corner of the house. This will require lifting the eastern portion of Final report 3 H WA GEoSCIENCES INC. October 31, 2007 HWA Project No. 2007-000-21 T063 the north stem wall. We do not have loading for this walla It is probably relatively light but the stem wall is not very high, It is likely that the spacing of the pin piles would be controlled by the span that the footing and stem wall would support rather than the load bearing capacity of the pin piles. CONDITIONS AND LIMITATIONS We have prepared this geologic and geotechnical assessment report based only on visual inspection, Geologic maps, shallow test holes, and probing. The report and any other applicable geotechnical data should be viewed in its entirety; conclusions and interpretations should not be construed as a warranty of the subsurface conditions. Experience has shown that subsurface soil and ground water conditions can vary significantly over small distances and over time, hence we may not have seen every condition and even those we saw can change with time. The scope of work did not include subsurface soil investigation, environmental assessments or evaluations regarding the presence or absence of wetlands or hazardous substances in the soil, surface water, or ground water at this site. This film does not practice or consult in the field of safety engineering. We do not direct the contractor's operations and we cannot be responsible for the safety of personnel other than our own on the site; the safety of others is the responsibility of the contractor. The contractor should notify the owner if any of the recommended actions presented herein are considered unsafe. O.O Final repos 4 HWA GEOSciEmcEs INC. 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I O33 0 SO2® $ t co ® y \� / z22 i m -11 m O k & 0 \ I ¥ 17 October 31, 2007 HWA Project No. 2007-000-21 T063 We appreciate the opportunity to be of service. if you have any questions or concerns, please do not hesitate to contact us. Sincerely, HWA GlsoSCti✓Nms INC. p�S C. 4k �fl�� oru�►s�l� ,th_134�� ExikII 9/3/ O491 Thomas C. Kinney, Ph.D., P.E. Vice President Attachments: Figure 1 Vicinity Map Figure 2 Photograph of House From South Figure 3 Photograph of Northeast Corner of House Figure 4 Photograph of Deck Area Figure 5 Photograph of Cracks in East Wall Figure 6 Photograph of Cracks in North Wali Figure 7 Probe Locations and Depths REFERENCES Machey Smith, Preliminary Surficial Geologic Map of the Edmonds East and Edmonds West Quadrangles, Snohomish and King Counties, Washington, Geologic Map GM -14, State of Washington Department of Natural Resources, Division of Geology and Earth Resources. Final report 5 HWA GEQSCIENCES INC.