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Home My WebLink AboutBLD1988-00412 Geo Tech � � • ; � • • / ;' General Testing Laboratories, Inc. 18970 3rd Avenue NE, P.O. Box 1586, Poukho, Washington 98370 The HART Company October 28, 1987 Project B-7188 Mr. & Mrs. L. E. Scott 2651 Circle Drive Newport Beach, Ca. 92663 Re: Slope Evaluation Lot 11, Port Ludlow #5 Port Ludlow, Washington Dear Mr. & Mrs. Scott; At the request of Ms. Pat Thompson, your realtor with Bayview Properties, Inc. , Mr. Allen Hart, an engineering geologist with our firm, visited the referenced site on October 27, 1987 to evaluate the steep slope area along the east side of the site and recommend appropriate set-back requirements. In addition to visiting the site, we have reviewed information in our files from previous work in the area. Mr. Hart's observations, conclusions and recommendations are as follows: The site is located on the east side of Montgomery Court , North of Montgomery Lane and overlooks Hood Canal to the East from atop a 50± foot high bluff. Soils exposed in the bluff area consist of fine sands which overlie inter- bedded clay and silt in the upper bluff area. The lower portion of the bluff is made up of interbedded sand and sand and gravel. All of the undisturbed soils are in a firm to dense condition. OBSERVATIONS: 1. The portion of the site back of the bluff has been roughly cleared and graded. 2. There is a well developed drainage/runoff path in the county easement North of the property. This drainage/runoff path leads to a deep depression near the northeast property corner where collected water appears to stand until A. It overflows through a "tunnel" into the natural drainage channel to the north, or B. It seeps into the ground to follow natural flow paths to the bluff face and/or to the natural drainage channel. 3. Ground water seepage/flows were observed in the bluff area and drainage channel north of the site and near the toe of the bluff in the south half ± of the site. There is evidence of seasonal ground water seepage/flow across the entire bluff face. Quality Assurance for Northwest Construction POULSRO(206)779-9196 TACOMA(206)272-6880 BREMERTON(206) 377.2013 • I • III Mr. & Mrs. L. E. Scott Slope Evaluation Page Two 4. A piped outfall extends from a manhole to the beach near the southeast property corner. There is no erosion protection at the beach, however, erosion caused by water flow from the pipe appears minor at this time. 5. Bluff slope angles range from 60° to 70° at the north end while at the south end slopes are on the order of 50° . Flatter slopes are found in both areas on talus slopes (ranging from 32° Co 35°) and in areas of instability where slopes are as flat as 25° to 28°. 6. Evidence of soil creep and sloughing is present all along the bluff face. A "recently" active slide is present near the piped outfall line in the south portion of the site. It appears that some of the materials involved in this movement may have originated from over-bank disposal of excess soil during installation of the manhole and associated piping. 7. We understand that the water line serving the area, from Montgomery Court, is periodically drained and the water allowed to free-flow across the site. This may be a contributory factor in the instability noted in item 6 and would be rectified by development of the site. 8. There has been fairly heavy tree fall along the beach, which, in con- junction with the build-up of drift piles, has aided in stabilization of the beach and protection of the bluff toe area. CONCLUSIONS AND RECOMMENDATIONS: Based on our visual observation only, the long-termed stability of the slope cannot be fully evaluated. However, the site area appears to be generally of good to fair stability with no signs of ongoing or recent major catastrophic type slope failures. With adequate design and grading consideration, we foresee no reason that the site cannot be developed generally as planned. The following recommendations should be incorporated with the site development and planning considerations. GENERAL STATEMENT The slopes on site appear to have been stable, except for localized creep or sloughing, for some S to 15 years or more. The length of time a slope area is stable is highly dependent upon the intensity of winter storms, modifications to the slope (undercutting of the slope, removal of vegetation, loading, etc.) , and on the efficiency of measures taken to protect the slope toe and to divert surface water runoff from flowing toward and over the top or across the slope. The past history of slope recession in similar areas indicates these longevity estimates are reasonable. However, no guarantee can be, or is made in this regard. Mr. & Mrs. L. E. Scott Slope Evaluation Page Three As a general rule, we strongly recommend that efforts be made to protect all slope areas by planting deep-rooted, fast-growing trees, shrubs and other types of vegetation, and controlling water runoff. In addition, there is substantial evidence to indicate that certain actions will accelerate the deterioration of the slope. Any cutting of the existing deep-rooted vegetation, trees or brush which tend to anchor the soil, or any action which tends to retain or accumulate moisture or loading at the top of the slope would adversely affect the slope. Finally, although the Puget Sound region is not noted as being overly active seismically, some quaking does occur and could cause a large soils movement if other conditions are favorable. RECOMMENDATIONS: 1. We recommend that all structures be designed to be a minimum of 50 feet in back of the top of the slope, as determined in the field. 2. Structures sited forward of the 50 foot set-back line, noted above, should be designed such that all foundation loads bear a minimum of three feet below a 35° plane sloping downward toward the east and originating at the set-back line. 3. All runoff from roofs, driveways, patios and paved areas should be inter- cepted, collected and tight-lined into the storm drainage system or tight-lined to the beach. Downslope discharge of collected water should not be allowed where the waters will hazard soils, slopes, structures or property down slope. The use of dry wells for water disposal is not recommended. 4. The removal of trees and/or brush from the slope should be avoided. Trees should only be felled for safety reasons. Topping, where possible, would be preferable to felling. Stumps from felled trees should not be removed. 5. Brush, limbs or other debris should not be disposed of over any slope. 6. No soil should be disposed of over the slope or bluff area. 7. No filling should take place on the site area between the set-back line and top of slope, other than what is needed to level the area or fill stump holes and then minimized. 8. Protection of the toe area of the bluff should be encouraged. The build-up of drift piles and other protective measures is encouraged. It may be desirable, at some later time, to reconstruct the drainage way presently in existence adjacent to the north property line. This could include piping of the collected water to the beach and removal of the "tunnel" section. If no corrective measures are undertaken then periodic maintenance of the "tunnel" depression and adjacent bluff section should be planned. 411 Mr. & Mrs. L. E. Scott Slope Evaluation Page Four REPORT LIMITATIONS: The conclusions and recommendations contained in this report are based on our interpretation of the site conditions as they presently exist and anticipated future construction activities. This report has been prepared for the exclusive use of Mr. & Mrs. L. E. Scott for specific application to the referenced development. Within the limitations of scope, schedule, and budget for our work, we warrant that our work has been done in accordance with generally accepted practices followed in this area at the time this report was made. No other warranty, expressed or implied, is made. Should you have any questions with regard to this report please call our office. Respectfully Submitted, GENERAL TESTING L ORATORIES, INC. 011/2 J. R. art, resident Report prepared by: Allen L. Hart, Engineering Geolog'. JRH:ALH:111 cc: Bayview Properties, Inc. Attn: Mr. Pat Thompson 7470 Oak Bay Road - Suite 102 Port Ludlow, Wa. 98365