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Home My WebLink AboutGEO-Tech Review for BLD2000-01503, 01504 - BLD Engineering / Geo-tech Reports - 1/11/2001 MASON COUNTY PUBLIC WORKS DIRECTOR/COUNTY ROAD ENGINEER Shelton,Washington 98584 DATE: Jan. 11 tn, 2001 INTER-DEPARTMENTAL COMMUNICATIONS TO: Shandra O'Haleck, DCD-Planner FROM: Alan A. Tahja,P/W-Co. Hydr. Engr. DCD/Planning WO# 0 1-0112 SUBJ: Geo-Tech Assessment Review NAME: Knobloch(a,Union BLD2000-01503 & 01504 Shandra, A geotechnical assessment prepared for the proposed Knobloch residence and garage in Union have been received and reviewed by Public Works. The report conforms to standards of sound engineering principles and practices and conforms to the requirement of DCD for geotechnical assessment reporting. The owners and their agents need to be aware that erosion and sediment control measures need to be implemented during construction,of a nature adequate to ensure their activities will not adversely impact neighboring properties or public roadways. Please feel free to contact me at County extension 461 if you have any questions regarding these comments, or if you feel any features need further discussion or attention. Si cerely, ?r1M T Alan A. Tahja File: H:\WP\GEO\ASESMNTS\Knobloch.doc WORK ORDER - PUBLIC WORKS DEPT. (N Date: I - 1CJ-0 1 (p Work Order PERMIT#: fiUpgOCC)-6it�02 gr\ob ocV� Number. Requested by: Authorized by: Date: Type of Work: CHARGE TO: NAME AGENCY/COMPANY BILLING ADDRESS PHONE x 5- B Pub. Works Person In Charge: (C) Project Time Line: (from-to dates) F TO Projed SSW date: Estimated FhIsh Date: ApproxhWe hours: ESTIMATED TOTAL$'S: COST ESTIMATE (D) Employee LRALO H2u-M Subtotal Fringe% TOTAL$ Ag EAM TOTAL$*S EQUIPMENT USED: MATERIAL USED: (F) Actual Cost $ BARS: PROD 0: DATE Employee WORKED Narne Hours Subtotal Frince% TOTAL$ EQUIPMENT USED: to unit Rate TOTAL MATERIAL USED: TOTAL ALL (G) BILLED DATE INV 0 PAID DATE REC.0 CK# p 1,02-00 0 - 0 K-O S Bradley-Noble Geotechnical Services A Division of The Bradley Group, Inc. PO Box 12267, Olympia WA 98508-2267 Phone 360-357-7883 • FAX 360-754-4240 or 867-9307 e-mail: bradleynoble@juno.com 3 December 2001 Mr. Rob McGuire Dogwood Construction East 90 Tower Lane Union, Washington 98592 Subject: Geotechnical assessment of the site soil conditions and slope stability at the new residence for Terry and Sharon Knobloch, Mason County Tax Parcel Number 32232-75-90011:Tract 1 of sp no. 2688, Union, Washington. Dear Mr. McGuire: As requested, we visited the above site to evaluate slope stability issues for the planned, single-family residence to be constructed on this lot. At the time of our visit, the area had been cleared and you had indicated the approximate corners for the new residence. The indicated location of the structure is set back from existing slopes to the north which in areas to the north can be steep as the slope goes down toward the town of Union and the Hood Canal. The immediate area of this lot is of low relief and gentle slopes . Exposed in road cuts in the general area, we observed two soil units . The upper soils are Vashon recessional outwash soils of sands and gravels . These soils are deposited on the very dense and highly overconsolidated Vashon subglacial till. Subglacial till has many engineering properties similar to those of lean concrete because of the grain size distribution and as a result of loading by the Vashon continental ice sheet, thought to have been about one-half to one mile thick in this area. We have reviewed the soil logs from the septic design. These logs indicate that in this area the recessional outwash soils are at least five to six feet thick. No cemented soils were indicated on the soil logs . 01010301 Page 1 of 3 lam" 01010301 Page 2 of 3 To verify our interpretation of the area geology, we have reviewed Plate 1 of the Water-Supply Bulletin 29, Geology of Southeastern Mason County, Washington prepared by John Noble and Dee Molenaar. We have also reviewed the Relative Slope Stability of the Southern Hood Canal area, Washington by Mackey Smith and R. J. Carson. We believe that the project area is in a Class 1 area, which is believed to be stable. We expect that only minimal additional site grading will be required for construction of the proposed residence. Excavation should encounter sandy gravels which are suitable for use as backfill against foundations or for site grading and leveling around the structure. Based on soil logs, we do not expect that excavation or footings will extend to the subglacial till. During periods of heavy or prolonged rainfall, subsurface flows of ground water will develop on the surface of the subglacial till as it is for all practical purposes impermeable. Short-term soil saturation may develop to within a few feet of the surface. The flow of ground water on the surface of the subglacial till is the cause of seeps and springs in the lower area of the slope to the north of the site. These flows are not expected to have an adverse effect on this project. Water from impervious surfaces and footing drains may be collected into a common tightline drainage system. The footing drain should be connected at a depth such that backup into the footing zone cannot occur. The collected water can be infiltrated using shallow trenches or swales along the north property line into the pervious sands and gravels . We do not recommend that the water be discharged as a point flow, as it may accelerated downslope erosion. Based on our site inspection and review of the area geology, and our understanding of the proposed construction, we do not expect that adverse soil conditions will be encountered. We do not expect that slope stability concerns would have any effect on this lot. Attention to the control of surface storm water must be included in your site plans to ensure dry crawl spaces . We have no objection based on geologic 01010301 Page 3 of 3 factors to construction of the proposed new residence at this site. If you have any questions, or if we may be of additional service to you, please contact us at our Olympia office. Cordially, BRADLEY-NOBLE GEOTECHNICAL SERVICES /-avi D Strong Engineering Geologist December 12, 2000 Terry and Sharon Knobloch 15717 97th Avenue Court East Puyallup, WA 98375 RE: Resource and Critical Areas Review for Parcel Number 32232-75-90011; Tract 1 of sp#2688 Union. Dear Mr. and Ms Knobloch: Due to the degree of the slope on your property and that it is mapped on Mason County's Landslide Hazard Areas a geo-assessment of your site will be required prior to permit approval. I have included the main points that should be included below: • A discussion of geological conditions in the immediate vicinity of the project, and a discussion of specific soil types at the project site. Terminology should be consistent with U.S. Geological maps of Mason County. • A discussion of ground water conditions at the site, including depth to water and quantity of surface seepage. • The approximate depth to hard or dense component soil, e.g. glacial till or outwash sand. • A discussion of landslide activity in the area(from "Relative Slope Stability of the Southern Hood Canal Area, Washington" by Smith and Carson, 1977 or from records on file with Mason County Community Development). • An opinion on potential for landslide activity in light of the proposed development. Enclosed please find the applicable chapter of Mason County's Resource Ordinance that addresses landslide hazard areas. If you have any questions, please contact me at (360)427-9670, ext. 295. Sincerely, Shandra O'Haleck, Senior Planner Mason County Planning Department