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Geo Report - Storm Water Runoff from Pool & Patio Area.pdfGary A. Flowers, PLLC Geological and Geotechnical Consulting June 14, 2018 Project No. 14-045 Mr. Lloyd White 8545 Talbot Road Edmonds, WA 98026 Subject: Control of Storm Water from Pool Patio Area 8545 Talbot Road Edmonds, Washington Dear Mr. White: As per our letter dated June 12, 2018 regarding adding additional drainage to collect water runoff from the pool deck at your new residence, this letter is to confirm that the drain was installed on June 13/14 and the work has been completed as recommended. Thank you for the opportunity to be of service. Should you have any questions please do not hesitate to contact our office. Respectfully submitted, eot wash 10 4�y used Geo�o Gary A. Flowers Gary A. Flowers, P.G., P.E.G. Engineering Geologist of wnSy� 0 16Y71 0 2 L 0- pclslt �SS/ONM- Robert M. Pride, P.E. Geotechnical Engineer Phone: 206-819-4304 5205 231d Ave W, Everett, WA 98203 email: gflowersO1 @comcast.net Gary A. Flowers, PLLC Geological & Geotechnical Consulting 5205 23" Avenue West Everett, WA 98203 June 12, 2018 Project No. 14-045 Mr. Lloyd White 8545 Talbot Road Edmonds, WA 98026 Subject: Control of Storm Water from Pool Patio Area 8545 Talbot Road Edmonds, Washington Dear Mr. White: As required by City of Edmonds we visited the subject site on June 11, 2018 to evaluate potential storm water impacts to the steep bank area north of the swimming pool and pool patio/deck area at the north end of the residence. The concern is that uncontrolled storm water runoff from the large patio/deck could have an adverse impact on the nearby slope. The north end of the pool deck/retaining wall is located approximately 30 feet from the top of the nearby steep slope. The slope leads down to the railroad embankment at the toe of the slope. The area between the pool deck and top of slope is covered with lawn grass. As noted in previous reports to you, and observed in the basement excavation, the core of the slope is comprised of very dense glacial drift soils. As with all slopes the outer 2 to 3 feet is comprised of colluvial sediments that have been loosened over time by the effects of weathering. While on site we tested the slope of the pool deck by running water from a garden hose onto the deck area. The majority of the water on the east deck area flows over the wall at the east end of the deck where the slope gradient is back to the south and away from the slope. Virtually all the water from the west end of the deck area flows to the west side at the NW corner of the deck. We also saturated the ground on the north side (closest to the slope) of the deck and observed that water flow into the storm water vault at the NE corner of the property increased which means at least some of the water is being picked up by an existing drain line. Given the water flow pattern from the deck area it is our opinion that the only water which concentrates and could be a potential issue is the water at the NW corner of the deck. We recommend that a catch basin be installed at the NW corner where the water exits the deck. The box should be set flush with the deck such that all water runoff enters the catch basin. The catch basin should then be plumbed into the drain line that is located along the west side of the house. Gary A. Flowers, PLLC. 5205 23' Avenue West Everett, Washington 98203 206-819-4304 Lloyd White Residence Geotechnical Assessment Report 8545 Talbot Road, Edmonds, Washington The flow off the east end of the deck can either be allowed to cascade down the wall and flow subsurface to the south, away from the steep slope, or it can be controlled either with a gutter or an interceptor trench, and either discharged to the existing storm water vault or to the nearby driveway drain which is also connected to the existing storm water vault. Given the very limited amount of water observed to flow over the north side of the deck area and the fact that at least a portion of this water is picked up by existing drain lines, a full drainage trench along the north side is not in our professional opinion, needed for your property. Our findings and recommendations provided in this report were prepared in accordance with generally accepted principles of engineering geology and geotechnical engineering as practiced in the Puget Sound area at the time this report was submitted. We make no other warranty, either express or implied. Sincerely, �eotwasbl� Z M. y �f used Ge o,- 1SIE� Gary A. Flowers �SStONAI- Gary A. Flowers, P.G., P.E.G. Robert M. Pride, P.E. Engineering Geologist Geotechnical Engineer Gary A. Flowers, PLLC. 5205 23`d Avenue West Everett, Washington 98203 206-819-4304