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MadronaK-8_Final_Geotechnical Observation Summary.pdfSHANNON 6WILSON, INC. - GEOTECHNICAL AND ENVIRONMENTAL CONSULTANTS December 21, 2018 Edmonds School District No. 15 20420 68th Avenue West Lynnwood, WA 98036 Attn: Ms. Taine Wilton ALASKA CALIFORNIA COLORADO FLORIDA MISSOURI OREGON WASHINGTON WASHINGTON DC METRO WISCONSIN RE: FINAL REPORT FOR GEOTECHNICAL CONSTRUCTION OBSERVATION SERVICES, MADRONA K-8 SCHOOL REPLACEMENT PROJECT, 9300 236TH STREET SW, EDMONDS, WASHINGTON This letter presents our final report for geotechnical construction observation activities for the Madrona K-8 School Replacement Project in Edmonds, Washington. The scope of services was based on our proposal for geotechnical construction observation services dated April 28, 2017. We observed the following geotechnical items listed in the scope of services: • Site excavations, clearing, and grading. • Stockpiling soils for reuse as backfill. • Preparation of footing subgrades and soil bearing verification. • Preparation of utility trench subgrades and structural backfill. • Preparation of retaining walls foundation subgrades. • Installation of permanent subsurface drainage. • Backfill of retaining walls. • Evaluation of asphalt and concrete pavement and base course materials. • Observation and flow testing of UIC well construction. • Geoblock pavement installation • Erosion and Sediment Control • Bioretention Cells The following paragraphs summarize our construction observations for each of these services. A preconstruction meeting was held on site and attended by a Shannon & Wilson representative. A Shannon & Wilson representative made a total of 94 daily site visits between June 22, 2017 and December 7, 2018. We prepared and submitted daily Field Activity Reports (FARs), numbered FAR 1 to FAR 94, to Edmonds School District 415, Mahlum, KPFF, CPL, and FORMA. 400 NORTH 34TH STREET, SUITE 10C P.O. BOX 300303 SEATTLE, WASHINGTON 98103-8636 206-632-8020 FAX: 206-695-6777 www.shannonwilson.com 21-1-22082-010 Taine Wilton Edmonds School District 915 December 21, 2018 Page 2 of 4 Site Excavations, Clearing, and Grading SHANNON 6WILSON, INC. We observed site excavations, clearing, and grading operations throughout the construction phase with our first visit dated June 22, 2017. We observed site grubbing and grading operations prior to subgrade preparation and utility line work. We observed FORMA and LMH export material off site, as well as stockpiling native material. Stockpiling Soils for Reuse as Backfill FORMA and LMH stockpiled native soils on site for reuse as backfill. We performed laboratory testing on native soil to determine the Modified Proctor values used for compaction testing. We observed the use of imported granular backfill when conditions were unsuitable to compact on - site soil. In our opinion, the stockpiled soils used for backfill were in accordance with project plans and specifications. Preparation of Footing Subgrades and Soil Bearing Verification Footing subgrade was probed for density using a 0.5-inch-diameter steel T-bar probe. Bearing soils encountered for footings were glacially overridden and exhibited very dense, stiff, and unyielding condition. In our opinion, subgrade soils were prepared in accordance with project plans and specifications. Preparation of Utility Trench Subgrades and Structural Backfill We observed utility work completed by LMH and Ramsett for storm drain, water, mechanical and electrical trench lines. Backfill used for trench lines consisted of native on -site material and imported granular fill. Backfill compaction was verified with a Nuclear Density Gauge and steel T-bar probe. In our opinion, the trench subgrade was suitable and backfill was placed and compacted in accordance with project plans and specifications. Preparation of Retaining Walls Foundation Subgrades Retaining wall foundation subgrades were probed for density using a steel T-bar probe. Bearing soils for retaining walls were generally consistent with footing subgrade soils and demonstrated very dense and unyielding conditions. In our opinion, subgrade soil was prepared in accordance with project plans and specifications. 21-1-22082-010 Taine Wilton Edmonds School District 915 December 21, 2018 Page 3 of 4 Installation of Permanent Subsurface Drainage SHANNON 6WILSON, INC. We observed the installation of subsurface drainage system, which included under -slab capillary break and footing foundation drains. Foundation drains included a perforated polyvinyl chloride pipe and gravel backfill. We also observed the installation of storm drain cleanouts and down drains located around the school and courtyard areas. In our opinion, the subsurface drainage was installed in general accordance with project plans and specifications. Backfill of Retaining Walls Backfill used for retaining walls consisted of native on -site material and imported granular fill. Compaction of backfill was achieved with a variety of equipment including a plate compactor, jumping jack, and excavator mounted hoe -pack. Backfill compaction was evaluated and verified with a T-bar probe. In our opinion, retaining wall backfill was placed and compacted in accordance with project plans and specifications. Evaluation of Asphalt and Concrete Pavement Subgrade and Base Course Materials We evaluated subgrade and base course for asphalt and concrete pavement using a T-bar probe. Subgrade was verified for bearing capacity with soils encountered generally probing dense and unyielding. Base course materials were evaluated for compaction using a T-bar probe. We made site visits and submitted field activity reports on October 4, 2018, October 23, 2018 and November 2, 2018, prior to asphalt paving installation. Based on our observations, the subgrade and base course materials were in accordance with project plans and specifications. Observation of UIC Well Construction and Flow Testing We observed the installation of UIC wells and performed flow testing on each of the wells. A separate final letter report will be prepared and submitted for our hydrogeology scope of services. Geoblock Pavement Installation We observed the partial installation of geoblock pavement used in landscaping areas within the school courtyard area. Based on our conversations with Morgan Salcido (FORMA), geoblock pavement installation will be completed in mid -January of 2019. In our opinion, the geoblock pavers completed to -date were installed in accordance with project plans and specifications. We will issue a supplemental final letter after this work is completed in 2019. 21-1-22082-010 Taine Wilton Edmonds School District #15 December 21, 2018 Page 4 of 4 Erosion and Sediment Control SHANNON 6WILSON, INC. We observed implementation and maintenance of the temporary erosion and sediment control measures outlined in the project plans and specifications. In our opinion, the erosion and sediment control measures used on site were suitable and maintained during the project. Some silt fencing and catch basin protection (silt socks) are in place and will remain until the final site landscaping is completed. Bioretention Cells We observed the installation of bioretention cells located within the parking lot and school courtyard areas. The bioretention cells consisted of a perforated drain pipe backfilled with gravel and a layer of bioretention top soil. PACE Engineers Inc. verified the elevations of the bioretention cells on site. In our opinion, the bioretention cells were installed in accordance with project plans and specifications. CLOSING A review of the project FARs and related recommendations pertaining to our scope of services indicates that no outstanding items require correction. In our opinion, geotechnical construction activities, evaluated and observed by Shannon & Wilson and included in our FARs, have been accomplished in a satisfactory manner and in accordance with our recommendations. To the best of our knowledge, the work was completed in conformance with the Madrona K-8 School Replacement project approved plans, specifications, and recommendations provided during construction. If you have any questions regarding this letter, please contact me at (206) 695-6975 or Martin Page at (206) 695-6875. LEA Sincerely, SHANNON & WILSON, INC.. James Wil ' son GeotechnicaI Staff Martin Page, PE, LEG Vice President Geotechnical Engineer 21-1-22082-010