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Westside Apartments Soil-Nail Shoring Wall
Soil-nail shoring · 32 ft cut
Why bid: Soils, geometry, and cut depth are textbook for our soil-nail crew. Project location is within our standard service area and the GC has a prior relationship from the Bonneville Heights job we won in 2025.
Five-story podium apartment building requires a 32-foot temporary shoring wall along the north and east property lines to support 6-story neighboring structures and an active city sidewalk during basement excavation. Geotechnical investigation describes medium-dense silty sand grading to dense gravelly sand below 15 ft — favorable for hollow-bar soil nails. Two-tier installation with 8 ft horizontal and 5 ft vertical spacing meets the 1.5 FOS global stability requirement. Critical to confirm groundwater elevation; the September boring logs show dry conditions but the project is being bid for a March excavation start when seasonal high groundwater could reach the lower nail elevation.
Medium-dense silty sand to dense gravelly sand. Self-drilling hollow-bar nails (R32-280) installed in single pass; conventional grouted nails would also work but at lower production.
0.002H lateral deflection criterion at top of wall to protect neighboring structural integrity. Drives tighter horizontal nail spacing (8 ft vs typical 10 ft) in the upper tier.
Bid window targets March excavation start, but boring logs are from September. Historical wells in the area show ~4 ft seasonal rise. Lower-tier nails may install through saturated soil.
Two-tier hollow-bar soil-nail wall with shotcrete facing
Seasonal groundwater higher than September boring conditions
HIGHMitigation: Carry contingency for grout-loss premium below el. 4,232. Request supplemental boring with March observation well before NTP.
Neighboring building monitoring required — instrumentation unclear
MEDIUMMitigation: Spec calls for inclinometers and crack gauges but assigns no party. Confirm responsibility before bid; $25K swing.
Right-of-way encroachment requires city approval
MEDIUMMitigation: Nail tail length extends ~6 ft into the public sidewalk subsurface. Standard SLC encroachment permit available but 4-week review.
Who provides and reads the inclinometers and crack gauges?
HIGH prioritySpec assigns instrumentation install to 'shoring contractor' but reading and reporting to 'owner-rep'. Unclear who funds the data tracker.
Confirm temporary wall life — 18 months or 24?
MEDIUM priorityBid form says 18, spec section 02500 says 24. Affects corrosion protection requirement for hollow bars.
- Hollow-bar nail material — 186 nails × ~22 LF avg
- Shotcrete labor and pumping
- Encroachment permit review window
- Optional dewatering allowance if spring boring confirms wet conditions
This is one of three sample analyses.
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