40 · Irvine
Irvine sits on the core of the Irvine Ranch, Rancho San Joaquin (≈50,000 ac, acquired 1864) plus Rancho Lomas de Santiago (≈47,000 ac, 1866), one of the largest livestock operations in California, with a named southern cattle headquarters at Bommer Canyon that worked from the 1870s to about 1970. Irvine has the strongest cattle-operations profile of the coastal study areas, yet no located record names a dip vat anywhere on the ranch, and where arsenic does appear in Irvine soils it co-occurs with orchard pesticides, not grazing. The prime candidate ground, the preserved, undeveloped Bommer Canyon camp, is precisely the parcel that never triggered a modern subsurface investigation. No contamination is asserted.
History
- The ranch: Rancho San Joaquin + Rancho Lomas de Santiago assembled by James Irvine from 1864; large sheep flocks from 1868, then decades of cattle. [B1/B2]
- Bommer Canyon Cattle Camp was the ranch's southern cattle headquarters (~1870s-1970): spring roundups, "processing," corrals, loading ramps, holding pens; buildings and equipment survive. [B1, Irvine Ranch Conservancy]
- Orange County was a heavily infested quarantine county under the compulsory 1907 arsenical-dip law (USDA Circular 174 tiering). [A1/B1]
- The definitive ranch history is silent. Cleland, The Irvine Ranch of Orange County (1952), contains no "dipping / vat / quarantine / scab / tick fever", a meaningful absence in the one source most likely to mention it; USDA BAI annual reports 1905-1911 (full-OCR grep) never mention Irvine. [B1 / A1]
Dipping evidence tier
HIGHLY PROBABLE (inference). Huge cattle operation + heavy quarantine county + compulsory arsenical dipping → the practice almost certainly occurred somewhere on the ranch. No vat is located, and central Irvine sat on (possibly outside) the NW edge of the last-held March 1912 quarantine district, the exact 1912 road alignment is not georeferenced. The tier ranks the probability of the practice only.
Figures
| Figure | Path |
|---|---|
| 1931 Irvine Ranch aerial, ranch building complex (identity unconfirmed) |  |
| research/irvine/imagery/bommer_1931_equalized.jpg | |
| 1931 structures zoom |  |
| research/irvine/imagery/bommer_1931_structures_zoom.jpg | |
| The 1931 complex over 2022, now under homes + golf |  |
| research/irvine/imagery/bommer_hq_overlay.jpg | |
| 1938 systematic sweep of the southern ranch core (3×2 grid) |  |
| research/irvine/imagery/irvine_1938_sweep_montage.jpg | |
| NE farmstead (orchard/crop node), 1938 zoom |  |
| research/irvine/imagery/irvine_1938_pondcluster_zoom.jpg | |
| NE farmstead then/now |  |
| research/irvine/imagery/pondcluster_beforeafter_overlay.jpg | |
| 1938 drainage traced under the modern city |  |
| research/irvine/imagery/pondcluster_water_highlight.jpg | |
| The whole ~4-mi ranch core, 1938 vs 2022 |  |
| research/irvine/imagery/irvine_core_overlay.jpg |
Imagery discipline: no dip vat is identifiable in any frame, a ~30-60 ft trough is at or below resolution. The 1931 complex first labeled "Bommer HQ" is a developed ranch node of unconfirmed identity ~0.7 mi NW of the preserved camp; its name remains open pending ranch maps (Sherman/UCI).
Environmental review
| Field | Finding |
|---|---|
| What review exists | 66 EnviroStor + 379 GeoTracker records in Irvine; DTSC school-site investigations across former ranch land; CEQA reviews with a 1938 aerial floor (e.g., Gateway Village EIR cultural review: aerials 1938→; topos 1935→). A statewide EnviroStor search for "DIP VAT"/"DIPPING" returns 0, the only animal-dip comparator anywhere is the Presidio "Former Horse Dip Area," proving DTSC registers such sites when documented. [A1, live REST] |
| Sampled soil? | Yes, on former orchard/row-crop parcels (DTSC school investigations: Woodbridge HS, Woodbury, Orchard Hills, others). No, at the undeveloped Bommer Canyon camp, which never triggered a Phase I or drilling. [A1] |
| Analytes tested | Orchard parcels: organochlorine pesticides (DDT/chlordane) + arsenic + lead per DTSC ag guidance. Grazing-only parcels (Turtle Ridge; comparators Laguna Niguel Elem., San Juan Hills HS): clean / methane only. [A1] |
| Arsenic tested? | YES, but only in the orchard context (former farmed parcels). |
| Which arsenic signature | Lead-arsenate (As WITH Pb + OCP suite), the orchard signature. The dip signature (high localized As with little/no Pb) has never been targeted; aggregate databases cannot resolve it. |
| Verdict | Tested-for-the-wrong-source on farmed land; never-tested at the prime cattle-handling candidate (Bommer Canyon). |
Honest limits & counter-evidence
- The strongest counter-evidence in the project: in south OC, arsenic tracks with orchards and row crops, not with grazing, pure former-grazing parcels repeatedly test clean (including Oso Grande in Ladera Ranch: livestock past-use, "No Contaminants found"). [A1]
- Two caveats keep the question open: (a) a dip vat's fingerprint is distinguishable from orchard residue but the databases don't resolve it; (b) the very place a vat would most plausibly stand, the preserved cattle camp, has had the least investigation. Absence of record ≠ absence of fact.
- No dipping record names Irvine anywhere: not CDNC (exhaustive), not USDA BAI reports, not Cleland 1952. The named 1908 OC dipping is all eastern/southern county. [B2/A1/B1]
- The cattle camp operated to ~1970, so a durable corral/vat complex would appear on 1927-1970 aerials; the targeted aerial screen found ranch complexes but nothing dip-diagnostic. Confirmation requires higher-resolution frames + ranch maps + records work.
This platform is an independent research and data-organization project. It does not provide medical advice and does not establish that any pesticide, property, organization, employer, school, water provider, government agency, or other party caused any illness. Publicly reported health events may not have been independently medically verified. Geographic and temporal overlap does not establish exposure or causation. Formal conclusions require authorized epidemiological analysis, verified medical information, exposure assessment, toxicological review, and independent scientific evaluation.