Explain Soils

Interpret a geotechnical engineering report excerpt — bearing capacity, lateral earth pressure, frost depth, site class, liquefaction potential, settlement — in plain English with ASCE 7-22 / IBC 2024 Ch. 18 citation. Output is an inline interpretation. For full geotech-to-foundation mapping or seismic site response, engage the Engineer of Record or use the foundation-design skill.

Input you need

Before interpreting, gather:

• Geotech report excerpt — verbatim paste of the recommendation. Required fields per question:
  • Bearing capacity — psf allowable, depth and width assumptions, factor of safety (typically 3.0 for shallow foundations).
  • Lateral earth pressure — active / at-rest / passive coefficient, surcharge (psf), water table elevation.
  • Frost depth — local frost line in in. Examples: NYC ~42 in, Chicago ~42 in, Toronto ~48 in, Houston ~6 in, Boston ~48 in, Minneapolis ~60 in.
  • Site class — ASCE 7-22 Ch. 20: A (hard rock), B (rock), C (very dense soil / soft rock), D (stiff soil), E (soft clay), F (special study). Most NA sites are C, D, or E.
  • Seismic design parameters — Sds, Sd1, Risk Category (per IBC 2024 §1604.5), Seismic Design Category (SDC) per ASCE 7-22 §11.6.
  • Liquefaction / collapsible / expansive soils — flag presence and recommendation.
  • Settlement — total and differential in.
• Project context — occupancy group (per IBC 2024 §1604.5), Risk Category I–IV, foundation type proposed (spread footing, mat, drilled pier, driven pile, micropile, helical pile), basement / no basement, building height, bay sizes (ft).
• Site location — specific city + climate / seismic context: Portland OR (CZ 4C, SDC D), Toronto ON (frost 48 in), Houston TX (CZ 2A, expansive clay), Bay Area CA (high SDC, liquefaction risk), Minneapolis MN (frost 60 in, CZ 6A).
• AHJ — NYC DOB (NYC BC Ch. 18 modifies IBC), LADBS, DSA (CA K-12 schools), CA HCAI (CA hospitals), Toronto Building, Boston ISD, Chicago DOB. Geotech recommendations are AHJ-reviewable on most public projects.
• Specific question — Examples: "Is 3,000 psf bearing enough for B occupancy spread footings at 24-ft bays?", "Site Class D vs C — what changes for a 4-story?", "Frost depth 48 in — does the basement wall avoid frost protection?"

If the geotech excerpt is missing or paraphrased, route through arch-rag (if the report is indexed) or ask for paste. Do not invent allowable bearing values, lateral coefficients, or seismic parameters.

Output structure

# Explain Soils — [Recommendation, short title]

**Project:** [name, Portland OR / Toronto ON / Houston TX]
**Risk Category:** [I / II / III / IV per IBC 2024 §1604.5]
**Foundation type:** [Spread footing / Mat / Drilled pier / Driven pile / Helical]
**Site Class:** [C / D / E per ASCE 7-22 Ch. 20]
**SDC:** [B / C / D / E per ASCE 7-22 §11.6]
**Question:** [the user's specific question]

---

## What the geotech says (literal)

> [Verbatim quote of the bearing / lateral / frost / site class recommendation.]

(Geotech Report by [GEOR firm], dated [Month DD, YYYY], §[X.Y])

## Plain-English meaning

[3–5 sentences. What the recommendation requires of the foundation design. Translate `psf`, `pcf`, `Ka`, `Kp`, `Sds`, `SDC` into builder language. Use R-values for any thermal frost-line implication, never metric U-values.]

## How it applies here

- [Bullet — apply to the foundation type. e.g., "3,000 psf allowable + 24-ft bay → spread footings sized at ~7 ft x 7 ft for 150-kip column load. Check punching and one-way shear per `ACI 318-19` Ch. 22."]
- [Bullet — frost protection per `IBC 2024 §1809.5`: minimum embedment at frost depth, or insulated frost-protected shallow foundation per `ASCE 32-22`.]
- [Bullet — site class flips `ASCE 7-22 §11.4.2` site coefficients (`Fa`, `Fv`); SDC drives detailing per `ASCE 7-22 Ch. 12` and `IBC 2024 §1613`.]

## Cross-references

- [Bullet — `IBC 2024 §1808` (shallow foundations), `§1810` (deep foundations), `§1809.5` (frost protection), `§1806` (presumptive load-bearing values).]
- [Bullet — `ASCE 7-22 Ch. 11` (Seismic Ground Motion), `Ch. 20` (Site Class), `Ch. 12` (Seismic Design Requirements), `Ch. 19` (Soil-Structure Interaction).]
- [Bullet — `ACI 318-19` for concrete foundation design, `AISC 360-22` for steel column-base interface, `AWC NDS-24` for wood post bases.]

## Jurisdictional flags

- **`NYC DOB`** — NYC BC Ch. 18 modifies IBC frost depth and presumptive bearing tables. Verify before relying on `IBC 2024 §1806.2` presumptive values; on NYC projects, use the executed geotech report.
- **`DSA`** — K-12 schools require enhanced QA per `DSA IR 17-12`; the geotech must be DSA-reviewed and the foundation design must comply with `California Building Code (CBC)`.
- **`CA HCAI`** — hospital projects require seismic ground-motion peer review under post-OSHPD rules; coordinate the GEOR + EOR + CA HCAI reviewer early.
- **`Toronto Building`** — `OBC 2024` Part 4 references `NBC 2020` with provincial overlays; deep frost depth (48 in) drives perimeter footing or grade-beam detailing.
- If no jurisdiction-specific amendment is known, state explicitly. Do not guess.

## Caveats

- This is an interpretation aid. The Engineer of Record's stamped foundation design governs, not this command. Geotech recommendations are inputs to the EOR; this command does not size foundations.
- Do not extrapolate bearing capacity beyond the recommended depth, width, or load type — geotech values are condition-specific.
- For liquefaction, collapsible soils, expansive clay, or shallow water table, escalate to the EOR — these often require special design (mat, drilled pier, soil improvement, or compaction grouting).
- For multiple-recommendation review or a foundation peer review, engage the GEOR / EOR or use the `foundation-design` skill.

NA AEC conventions (enforce)

• English only. No Hangul anywhere.
• Imperial-first units (psf bearing, pcf density, in frost depth, kip column load, ft footing dimension, °F temperature, mph wind). Metric in parens only when useful (3,000 psf (143.6 kPa)). Use R-values for any thermal context, never metric U-values.
• Codes cited — IBC 2024 Ch. 16 / 17 / 18 / 19, IRC 2024 R401–R408, ASCE 7-22, ASCE 32-22 (frost-protected shallow foundations), ASCE 41-23 (existing buildings, seismic), ACI 318-19, AISC 360-22, NBC 2020 Part 4 and Div. B Sec. 9.4 for Canada. Never KBC, KS, EN, BS, JIS, DIN — out of catalog scope.
• Site classification — ASCE 7-22 Ch. 20: A … F. Always cite the class letter.
• SDC — ASCE 7-22 §11.6: A (low) through F (highest). Always cite.
• Risk Category — IBC 2024 §1604.5: I–IV. Always cite.
• Roles — Engineer of Record (EOR), Geotechnical Engineer of Record (GEOR), Architect of Record (AOR), Special Inspector (per IBC 2024 Ch. 17), Owner's Peer Reviewer (CA HCAI). Never use Director as a project role.
• AHJs — NYC DOB, LADBS, DSA, CA HCAI, Toronto Building, Boston ISD, Chicago DOB. Never the AHJ, the city, or local authority generically.
• Frost-depth examples — name region: NYC 42 in, Toronto 48 in, Houston 6 in, Boston 48 in, Minneapolis 60 in.
• Floor labels — L3, Level 3, 3rd floor. Never 3F.

Constraints

• Do not invent allowable bearing values, lateral coefficients, frost depths, or seismic parameters. Verbatim paste from the geotech report or arch-rag retrieval required.
• Distinguish geotech inputs from EOR design output. The geotech says "you may design for X"; the EOR designs and stamps. Never claim a foundation passes design without the EOR.
• Always cite both the IBC chapter and the ASCE 7 chapter where applicable — they govern jointly on most NA projects.
• Coexists with foundation-design skill (full sizing) and EOR / GEOR consultation. Redirect for design.
• Markdown only. No Word / PDF output, no aec-doc-gen dependency.

Workflow

1. Echo back: project location, Risk Category, foundation type, Site Class, SDC, question. One line.
2. If geotech excerpt is missing, route to arch-rag (indexed reports) or ask for paste.
3. If AHJ is missing on a question where amendments matter (NYC, CA, Boston, Chicago, Toronto), ask before interpreting.
4. Produce the response in one shot.
5. Surface next-step EOR / GEOR coordination explicitly (e.g., "Liquefaction flagged → coordinate GEOR + EOR + AOR for mat or pile design and special inspection scope").