4224 RIVERFRONT BLVD 2019-03-14 - Laserfiche WebLink

- �r GEODESIGN Memorandu Page 1 19 To: Jamie Aubrey From: Ryan T. Lawrence, P.E. (Oregon) and Scott V. Mills, P.E. Company: Polygon Northwest Company Date: June 24, 2016 Address: 11624 SE 5`h Street, Suite 100 Bellevue, WA 98005 cc: Nick Abdelnour, Polygon Northwest Company(via email only) GDI Project: Polygon-127-01 RE: Residential Lot 101 Everett Riverfront Simpson Plat Everett, Washington We understand that sewer manhole 31 and associated pipes were to be installed approximately 5 to 10 feet west of Lot 101 in road D/W"J." We observed that the contractor encountered a significant amount of groundwater during their excavation for manhole 31, which resulted in a large excavation that extended beneath the proposed sidewalk on the west side of Lot 101. The contractor was ultimately unable to dewater the manhole excavation, so the sewer line was re-designed to eliminate the need for manhole 31. The contractor backfilled the excavation for manhole 31 with quarry spalls. A layer of geogrid and non-woven geotextile was installed above the spalls approximately 4 feet below finish grade. The contractor then placed and compacted sand, gravel, and crushed rock in lifts above the geogrid and fabric. We observed a proof roll on the completed backfill material and did not observe any deflection or rutting in the excavation area, which extended beneath the proposed sidewalk on the west side of Lot 101. The excavation and backfill for manhole 31 does not have an impact on the stability of Lot 101. RTL:SVM:BAS:rcd WASH/iv V. One copy submitted(via email only) � �,� Document ID: Polygon-127-01-062416-geom-rev.docx tz: y ©2016 GeoDesign, Inc. All rights reserved. fitA 26403,c)ST!~X��r^,� `'61ONAL'O Signed 06/24/2016 15575 SW Sequoia Pkwy,Suite 100 I Portland,OR 97224 1503.968.8787