AZIZ Engineering Company SERVING THE NORTHWEST & ALASKA SINCE 1984 half-century power of ideas engineers geotechnical geostructures civil | surveying October 14, 2020 Project No. 881801

Leo Suver President Steve Burnstead Construction LLC 11980 NE 24th Street, Ste 200 Bellevue, WA 98005

Geotechnical Special Inspections Completion Statement Mallard Pointe Structural Earth Walls (Permit No BLD19-00017) Issaquah, Washington

The above captioned project geotechnical and geostructural construction elements are now complete. The last geotechnical special inspections report through 13 December 2019 listed the project status as ready for the casting of south wall and storm vault concrete facing. Rain and freezing weather conditions delayed this for more than a month due to spalling of the vault north wall. To prevent this and for recovery, the entire vault excavation was covered with a temporary wood-frame and plastic roof and partial segmental-block walls were built around the soil nailing under my directions – all consistent with the permit plans. Consequently, the plan shotcrete base wall facing became impractical due to full height excavation walls and scheduling of a shotcrete contractor; therefore, all vault walls were form cast in coordination with the structural engineer of record who directed minor structural plan revisions, on record with our office. The storm vault and south wall were substantially complete last early March. A summary of our daily site observations since last mid-December is attached to complete our weekly inspections reporting. See page 2 for our statement of project completion. The permit special inspections and monitoring were addressed as follows:

1. Soil Bearing and Stability Verification. We closely monitored the wall and vault excavation and verified the soils conditions while directing erosion control and stabilization, daily during the foul weather conditions last December and January. 2. Monitoring of Soil Nailing. We monitored all placement and nail penetration rates for consistency with the wall stability analysis report – all spiralnails significantly exceeded the minimum bond load capacities. 3. Verify Nailhead and Wall Assembly. We verified quality, driving of spiralnails, wiretruss wall and nailhead assembly for consistency with the plan specifications – all found to meet the specifications and plan dimensions . 4. Observe and Monitor Excavation. We observed all excavation embankments while open, more specifically the excavation for the storm vault construction which remained stable and easily recoverable after some spalling due to capillary water migration in dense silt during freeze-thaw events. 5. Subsurface Drainage Installation. We closely monitored and tested the correct installation of perimeter foundation drainage, and the storm vault sump including all temporary pump operations – all verified as correctly installed and operational when needed. 6. Monitor Slope Stability – We observed all temporary and permanent excavation walls and embankments throughout the construction – all remaining stable without shoring. 7. Erosion Control, Temporary and Permanent. The landscape features and ground surface protections are substantially complete. For temporary erosion control, see #1 and #4 above.

7740 196th Avenue NE (Historic Red Brick Road) • P.O. Box 2758 • Redmond, WA 98073-2758 (Street 98053-4710) 425/ 898-1007 • fax 425/ 898-9699 • [email protected] • www.aziznw.com Geotechnical Special Inspections Completion Statement Mallard Pointe Structural Earth Walls (Permit No BLD19-00017) Issaquah, Washington October 14, 2020 Page 2

In accordance with our observations throughout the construction, and follow up post construction observations to date, the spiralnail wall systems and drainage, and the storm water vault as constructed are consistent with our recommendations and the permit plans. We expect the Mallard Pointe structural earth walls to perform satisfactorily with minimal risk of settlement, deep or shallow slope instability – and with minimal risk of slope failure affecting this project or the adjacent lands. The subject wall systems as well as the site slopes and grounds require regular fall and spring annual maintenance that should never be ignored.

I am pleased with the successful conclusion of this project under difficult circumstances.

Sincerely, f Was o h i e ng AZIZ Engineering Company t t a o t n S

Enayat S. Aziz, L.E.G, P.E. L Engineering Geologist i t c s Geotechnical Engineer and e 2502 i

n o g

s Engineering Geologist ed G eol 10/16/2020 Enayat S. Aziz

Attachment: Geotechnical Special Inspections Summary – Dec 2019 through May 2020 Mallard Pointe Structural Earth Walls (Permit No BLD19-00017) dated October 14, 2020