Chapter 8 — Key Takeaways

A one-page reference card. Self-contained: you should be able to re-ground yourself from this alone.

Key Takeaways

• Read the boring logs, not the recommendations. The recommendations are a generalized interpretation written for the structural engineer. The logs are the evidence. At Northgate, log B-9 disclosed N-values of 4, 5, and 6 at footing elevation, and nobody read it — a $59,200 direct cost plus three calendar days.
• The geotechnical report is information, usually not a warranty. Whether you may rely on it, and how much independent investigation you were deemed to perform, is a contract question that varies by form, owner, and jurisdiction. Find the differing-site-conditions clause and its notice period before you need them.
• Every earthwork number is bank, loose, or compacted — and almost none of them say which. LCY = BCY × (1 + swell). CCY = BCY × (1 − shrinkage). Hauling bank yards instead of loose yards under-prices a haul by roughly the swell factor: 25% on Northgate, about $75,000.
• Earthmoving is a matched-fleet problem. Trucks required = cycle time ÷ load time. Running short-handed does not save money — hauling is a cost per yard-mile — it just stretches the duration and keeps the excavator, the crew, and the site on the clock.
• The testing laboratory controls your schedule more than you expect. You cannot place the next lift until the last one passes. Compute how many tests your specification actually requires, and book technicians by the week off your look-ahead.
• The water-cement ratio is the strongest single predictor of concrete strength and durability. Excess water leaves capillary voids behind when it goes. Get workability from a superplasticizer, not from a hose. Read, sign, and keep the batch ticket.
• On a concrete-frame building, the form cycle sets the schedule — not the concrete. A cycle planned at 5 days and run at 8 adds 3 days per floor. Twelve floors is 36 work days, roughly 50 calendar days, and every following trade inherits it.
• On a steel-frame building, the submittal is the long pole. Lead-time chains do not add — they snap. Six days of slip in your own office landed on a fixed mill rolling slot and became 23 calendar days, or $244,950 at Northgate's $10,650 per calendar day.
• Every system has a submittal lead time, a weather window, an inspection hold point, and a following trade waiting on it. Those four attributes are what a construction manager actually manages. The soil mechanics and the connection design belong to somebody with a stamp.
• Excavation and steel erection are two of the highest-exposure activities on any job. Cave-in and falls are both OSHA Focus Four hazards, and both have dedicated subparts of 29 CFR 1926. Schedule pressure is a hazard exactly like an unshored wall — and it is the hazard your job creates.

Action Items — this week, on your job

1. Find the geotechnical report and read the boring logs. Overlay the boring location plan on the foundation plan at matching scale. Build a one-page watch list of footings near low N-values. Half a day.
2. Open your contract to the differing-site-conditions article. Write down the notice period and who it goes to, and put that on a card in your truck.
3. Recompute your truck fleet if the haul distance has changed since the estimate. Cycle time ÷ load time. If the answer is different from the trucks on site, you are losing money right now.
4. Count the density tests your specification requires for the fill remaining. Divide by the technicians the lab will actually send. That number is your real production rate — put it on the look-ahead.
5. Back-schedule your longest-lead structural submittal from the fabricator's fixed slot, not forward from today. Ask the fabricator for the slot date in writing.
6. Pick your next concrete cycle and decompose it into stations, with a crew and an hour count per station. Compare required labor-hours to available labor-hours. Fifteen minutes.
7. Confirm the notice requirement for every inspection hold point in the next four weeks — special inspector, testing lab, building department, geotechnical engineer — and put the notices on the schedule as activities.

Common Mistakes and the Fix

Decision Framework

Before you dig

1. Have I read the boring logs at bottom-of-footing elevation, or only the recommendations?
2. Which footings are nearest the lowest N-values, and which sit in a transition zone between a good boring and a bad one?
3. What does my contract's differing-site-conditions clause say, and what is the notice period?
4. Will the on-site material pass as structural fill, and what is the full-import case worth if it does not?
5. Are the locates current, and have I hand-dug or vacuum-excavated inside the tolerance zone?
6. Who is the competent person, and is the daily inspection actually happening and being recorded?

Before you commit to a structural system

Ask five questions, in this order:

1. What is the actual constraint — design, procurement, site space, labor, weather, or money? Never solve a procurement constraint with a system whose advantage is field speed.
2. What is the longest lead item, and what fixed slot does it depend on — a mill rolling slot, a casting bed, a barge, a crane mobilization window?
3. What is the weather window, and does it fall inside my schedule or outside it? Concrete, masonry, steel erection, and mass timber each have a different one.
4. What are the inspection hold points, and who controls the notice?
5. Which following trade cannot start until this is done, and what does one day of delay cost? On Northgate: $10,650 per calendar day — $5,150 extended general conditions plus $5,500 liquidated damages.

The arithmetic to carry in your head

Deeper references: Appendix A for the math, Appendix C for unit costs, productivity, and waste factors, and Appendix F for Focus Four and competent-person duties.