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Miles Residence Pool Everett Washington Limited Geologic Hazard Reconnaissance the walls. Thus, the compaction level is critical and must be tested by our firm during placement. The recommended compaction of 92 percent of ASTM D-1557 applies to any structural fill placed behind the wall within a distance equal to the wall height and up to the elevation of the top of the wall. Structural fill used to construct slopes behind retaining walls should be compacted to at least 95 percent of ASTM D-1557 if the fill is placed above the elevation of the top of the wall. Surcharges from adjacent footings, heavy construction equipment, or sloping ground must be added to the above -recommended lateral pressures. Wall Drainage It is imperative that proper drainage be provided so that hydrostatic pressures do not develop against the walls. This would involve installation of a minimum 1-foot-wide blanket drain for the full wall height (excluding the uppermost 1 foot of backfill) using imported washed gravel against the walls. The wall drain material must be hydraulically connected to a footing drainpipe constructed with sufficient gradient to allow gravity discharge away from the structure to an approved discharge location. Drains must not discharge on or above the steep slope area. Passive Resistance and Friction Factor Lateral loads can be resisted by friction between the foundation and the natural, medium dense to dense, glacial sediments or supporting structural fill soils, or by passive earth pressure acting on the buried portions of the foundations. The foundations must be backfilled with compacted structural fill to achieve the passive resistance provided below. We recommend the following allowable design parameters: • Passive equivalent fluid = 250 pcf • Coefficient of friction = 0.35 Pool Operation/Maintenance We anticipate and recommend that the pool be maintained on a regular basis. Part of the recorded maintenance records should include necessary filling to maintain pool water levels. If a trend of excessive make-up water usage develops, the pool shell and plumbing elements should be inspected for leaks and promptly repaired if necessary. CLOSURE This letter has been prepared for, and limited to, the evaluation of the proposed swimming pool. Our conclusions and recommendations have been prepared in accordance with generally accepted professional engineering and geologic principles and practices. We make no other warranty, either express or implied. Our conclusions are based on the results of our interpretation of surface conditions. If subsurface conditions are encountered that appear to be different than those described in this letter report, we should be notified so that we may review and verify or modify our recommendations. November 15, 2022 ASSOCIATED EARTH SCIENCES, INC. JPL/jh - 20220343EO01-003 Page 4