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The short version

If you read nothing else, here is the argument in order of what matters most here:

1. Use is large and rising. Herbicide volume nearly quadrupled from 2021 to 2024, driven by replanting after the 2021 Dixie Fire (see Data & Trends).

2. The dominant chemicals here are the water-mobile ones. The most-used are hexazinone and glyphosate, with imazapyr third — and hexazinone and imazapyr are exactly the chemicals that leach and move through soil and water. They are going onto a forested watershed above a rural community on wells and springs.

3. The biggest unknowns are what isn’t tested: the surfactants and ‘inert’ co-formulants (often more toxic than the active ingredient), real-world tank-mix synergy, and the cumulative, year-after-year load on one watershed.

4. The largest ecological effect is probably indirect: removing plants removes the base of the food web — flowers for pollinators, host plants for insects, food for birds and fish.

The contested glyphosate–cancer question (below) is one thread of this story, not the headline — it is the most dose-dependent and the least specific to Plumas. The chemical-by-chemical detail that follows is a reference appendix.

Is the water tested for these herbicides? Not yet.

Point 3 above — the biggest unknowns are what isn’t tested — is not a hunch. We obtained the Central Valley Regional Water Quality Control Board’s post–Dixie Fire water-quality monitoring records for the Greenville watershed by public-records request (July 2026).

What is monitored

Three stations — DF-1 (Setzer Camp Creek / Greenville–Wolf Creek Rd), DF-2 (Spirit Springs Rd / Greenville WWTP) and DF-3 (Stampfli Rd) — sampled roughly monthly. The panel covers the fire-recovery indicators: turbidity and sediment (TSS), nutrients (nitrate, phosphorus, ammonia), bacteria (E. coli, total coliform), major ions, and a full suite of metals (aluminum, arsenic, iron, manganese, mercury, lead and more).

What is not monitored

None of the roughly 20 herbicides applied in these same watersheds — not hexazinone, not imazapyr, not glyphosate, not aminopyralid — appears anywhere in the sampling panel. The Forest Service formally notifies the Water Board of its herbicide operations (e.g. the Wildcat project’s aminopyralid applications, per a 2023 notice in these records), and herbicide & reforestation work is tracked for erosion-control (BMP) compliance — but the water itself is never screened for the compounds being sprayed.

Why isn’t it required?

Public water systems test the state and federal required contaminant list. Of the herbicides used in these watersheds, only glyphosate has an enforceable drinking-water limit (a federal MCL of 700 ppb) — and even then small systems are often granted monitoring waivers. Hexazinone carries only a non-enforceable health advisory (400 ppb) and no MCL; imazapyr, aminopyralid and most of the others are unregulated in drinking water altogether. No required limit means no required test — so the water-mobile compounds applied across these watersheds fall through the gap.

A second county, the same answer

We put the same water-records question to Sierra County — the adjacent county that shares this forest and its watersheds. Through its County Counsel the county responded (August 2026) that it “does not generally have regulatory jurisdiction over watersheds,” and pointed us instead to the State (the Water Board’s Drinking Water Program and GeoTracker) and the Sierra Valley Groundwater Management District. Its only responsive water records are State Small Water System drinking-compliance files — which test the required contaminants (bacteria, nitrate), not the herbicides sprayed in the hills above them. Two counties, the same gap: the water is watched for many things, but never for what is deliberately applied to it.

This is the monitoring gap at the heart of this project: the agency watching this watershed is measuring what a fire leaves behind, not what is being deliberately applied above the community’s wells and springs. Source: California Regional Water Quality Control Board, Central Valley Region (R5) — Nonpoint Source Unit, records provided July 2026 (Dixie Fire water-quality sampling results & monitoring-location records; Plumas National Forest annual monitoring reports 2023–2025).

Where this data comes from — and where it doesn’t

This map combines the public records that exist, and is honest about the gaps.

Private land — full chemical detail

California Pesticide Use Reporting (PUR), filed with the County Agricultural Commissioner and DPR. Covers private timberland, ranches, golf courses and the like — with the actual product, active ingredient, amount, and location. This is the bulk of the map (the warm-colored dots).

Federal land (Plumas National Forest) — activities, not chemicals

USDA Forest Service FACTS activity records (the blue ‘Federal’ layer): treatment activity, NEPA project, acres, year and location — but not the chemical or quantity. The Forest Service has said active-ingredient and amount data require a records request, so those show ‘FOIA pending.’

What’s still missing

Federal chemical/quantity data (FOIA to USFS Region 5), the most recent local permits/NOIs (county Ag Commissioner), and additional counties/years are being requested or added. The Streams & water layer is always shown on the map, so you can see treatments relative to waterways.

Coverage of these Plumas map layers: county PUR 2020–2024 (2023–2024 obtained from CDPR by public-records request); federal USFS FACTS 2020 onward, including planned treatments. The statewide database behind the map and Data & Trends is complete 2020–2022, with the five Northern-Sierra counties (Butte, Tehama, Lassen, Plumas, Sierra) extended through 2024. A historical snapshot, not real-time — coverage grows as new public-records / FOIA responses and California’s annual PUR releases arrive. Full source inventory and draft records-requests are in the project repo.

The chemicals actually being sprayed

This started with a concern about glyphosate — and glyphosate is the most-used herbicide here by volume. But the data show a mix of chemicals. By active-ingredient weight it very likely leads as well. The data are a mix, though — and the chemical that stands out for local risk is hexazinone (Velpar), applied as a dry solid and the dominant soil-applied, water-mobile herbicide here, notable for leaching into groundwater. (Liquid gallons and dry pounds measure different things and aren’t added together, so we rank glyphosate first by volume and flag hexazinone as the key water-mover rather than calling either ‘largest by weight’.) The table is built from the EPA registration numbers in the dataset, so the active-ingredient identifications are reliable.

Active ingredientGallonsPoundsApplications
Hexazinone076,204273
Glyphosate26,9120759
Imazapyr7,4080523
Aminopyralid6160185
Oxyfluorfen + penoxsulam41007
Indaziflam364039
2,4-D12905
Sulfometuron/sulfonylurea (verify)9406
Triclopyr2004
Dicamba1605
Clopyralid1304

Figures are formulated product as applied grouped by active ingredient (e.g., Velpar DF is ~75% hexazinone), not pure active-ingredient mass. Liquids (gallons) and solids (pounds) aren't summed. In addition, ~22,600 gallons of adjuvants/surfactants (methylated seed oils, spreaders) were tank-mixed in — these aren't herbicides themselves but matter for toxicity (below). One product flagged "verify" needs its active ingredient confirmed. These detailed chemical figures cover Plumas County 2021–2024 (the county records first obtained and hand-analyzed); the map and Data & Trends now span 2020–2024 for the Northern Sierra as more records arrive.

Hexazinone

The dominant chemical here by weight — a soil-applied forestry herbicide. Brand: Velpar DF.

Applied in Plumas County, 2021–2024: 76,204 lb across 273 applications (formulated product, from county records)

How it works

A triazinone that blocks photosynthesis (photosystem II). Applied to soil; taken up by roots to kill competing brush and broadleaf plants around planted conifers.

Environmental fate — the key local concern

Extremely water-soluble (~33,000 mg/L), poorly held by soil, and only slowly degraded — a combination that makes it highly mobile and prone to leaching into groundwater and running off into surface water. Reported soil half-lives range from about 30 to 180+ days. EPA and state health agencies flag groundwater contamination risk where soils are permeable or the water table is shallow. For a community on wells and springs in a forested watershed, this is the herbicide whose mobility deserves the most attention.

Health science

Low acute toxicity. Long-term animal feeding studies show liver effects (and some kidney/body-weight effects); the chronic reference dose is based on a 1-year dog study. Not classified as a likely carcinogen, but the chronic database is older and thinner than for glyphosate.

Ecological effects

Practically non-toxic to birds and fish acutely and doesn't accumulate in fish, but native woody plants (oak, maple, cherry, willow, hazel) are sensitive, and it can exceed risk thresholds for small mammals at higher rates.

Sources: Drinking-water health advisory (hexazinone) · MN DNR environmental risk assessment · EPA hexazinone problem formulation

Glyphosate

Most-used by volume. Brands here: Accord XRT II, Roundup Pro/Custom, Drexel Duplicator 6, Glystar, Cornerstone Plus.

Applied in Plumas County, 2021–2024: 26,912 gal across 759 applications

How it works

Blocks the EPSP synthase enzyme in the shikimate pathway, which plants (and many microbes) use to make essential amino acids; animals lack this pathway. Non-selective and systemic.

Environmental fate

Binds fairly strongly to soil and is usually broken down by microbes within days to a few months, but it is water-soluble enough to run off into streams. Its main breakdown product, AMPA, is more persistent than glyphosate itself and is widely detected in surface waters.

Human-health science — and the controversy

This is the genuinely contested one. In 2015 the WHO's cancer agency (IARC) classified glyphosate as a probable human carcinogen (Group 2A), citing limited human evidence for non-Hodgkin lymphoma plus animal and genotoxicity data. The U.S. EPA instead concluded it is 'not likely' carcinogenic — but in June 2022 a federal appeals court (9th Circuit) vacated EPA's human-health finding, ruling EPA used inconsistent reasoning and ignored evidence; EPA withdrew that interim decision and is still re-evaluating, and now expects to issue its final glyphosate registration decision in 2026. One nuance often lost in this fight: IARC assesses hazard (whether a chemical can cause cancer at some dose), while EPA assesses risk (whether it does at real-world exposures) — part of why two serious bodies can land in different places. EPA and IARC reached opposite conclusions largely because EPA leaned on industry-submitted, unpublished studies while IARC weighted independent published literature. Recent reviews also report associations with endocrine effects, liver changes and gut-microbiome disruption.

Ecological effects

Toxicity to aquatic life depends heavily on the formulation's surfactant (see 'What isn't well studied'). Kills non-target vegetation on contact/drift.

Sources: EPA – Glyphosate · 9th Circuit vacated EPA finding (2022) · EPA vs IARC genotoxicity review

Imazapyr

Second-largest by volume. Brands here: Alligare Rotary 2SL, Polaris SP, Nufarm Polaris SP, Cavalier 2L.

Applied in Plumas County, 2021–2024: 7,408 gal across 523 applications

How it works

An imidazolinone that inhibits the ALS enzyme (acetolactate synthase), blocking branched-chain amino-acid synthesis. Animals lack this enzyme, so direct animal toxicity is low; it is broadly lethal to plants.

Environmental fate

Highly water-soluble and weakly bound to soil. It breaks down quickly in water by sunlight (half-life a few days) but is persistent in soil — months to as long as ~1–2 years. Sources differ on leaching: its chemistry suggests high groundwater-leaching potential, though some field studies found limited downward movement. It can move off-site via runoff and eroded soil.

Non-target plant effects

Damages non-target vegetation at very low residue levels — as little as ~1/50 of a normal application rate — so drift, runoff and soil persistence can harm desirable and rare plants well beyond the treated area, and can disrupt soil nutrient cycling.

Health science

Low mammalian toxicity by the standard endpoints; the main residue concern is plant damage rather than acute animal harm.

Sources: NPIC / NCAP imazapyr factsheet · Massachusetts imazapyr review

Aminopyralid

Brand here: Milestone. A small volume, but with an outsized off-site footprint.

Applied in Plumas County, 2021–2024: 616 gal across 185 applications

How it works

A pyridine-carboxylic-acid 'auxin mimic' that causes uncontrolled growth in broadleaf plants. Grasses tolerate it.

Environmental fate — persistence beyond the field

Field soil half-life is roughly 20–70 days, but it is famous for carryover: it survives passage through animals and the composting process and can remain active in hay, manure and compost for months to years. It damages sensitive broadleaf crops (tomatoes, beans, etc.) at concentrations as low as ~1 part per billion, and aquatic half-lives can exceed a year.

Health & ecology

Low acute toxicity to mammals, birds, fish and bees; chronic reference dose 0.5 mg/kg/day. The dominant real-world risk is unintended damage to non-target broadleaf plants via persistence and movement.

Sources: OSU – aminopyralid in compost · EPA aminopyralid fact sheet

Indaziflam

Brand here: Esplanade F. A newer, long-residual pre-emergent.

Applied in Plumas County, 2021–2024: 364 gal across 39 applications

How it works

Inhibits cellulose biosynthesis, preventing seeds/seedlings from establishing. Long-lasting in soil — residual control can persist up to ~3 years.

Health science

Marketed as low acute toxicity, but the nervous system is the main target in mammal studies (reduced motor activity, neuropathology in rats and dogs). Studies also report effects on thyroid (possible endocrine disruption), liver, kidney and reproductive organs, plus developmental effects; emerging research raises genotoxicity (DNA-damage) concerns. It was used for about a decade under an incomplete ('conditional') registration.

Ecological effects

Highly toxic to aquatic and terrestrial plants and long-lived in soil, so impacts ripple through the base of the food web; some reviews also raise soil-microbe concerns that warrant further study.

Sources: USFS indaziflam health & ecological risk assessment · PEER indaziflam fact sheet

Oxyfluorfen + penoxsulam

Brand here: Cleantraxx — a deliberate two-chemical mix.

Applied in Plumas County, 2021–2024: 410 gal across 7 applications

How it works

Oxyfluorfen inhibits the PPO enzyme (Group 14); penoxsulam is an ALS inhibitor (Group 2). The two are combined for a synergistic, broader-spectrum, residual pre-emergent.

Environmental fate & effects

Oxyfluorfen is poorly water-soluble, binds strongly to soil and sediment, is persistent, and is labeled toxic to aquatic organisms; penoxsulam is more mobile. Because this is a fixed mixture, its combined and synergistic effects are exactly the kind of thing single-chemical testing doesn't fully capture (see below).

Note

Confirm the current EPA carcinogenicity/toxicology classification for oxyfluorfen against the EPA label/assessment before citing specifics publicly.

Sources: EPA Cleantraxx label (62719-702)

Triclopyr, 2,4-D, dicamba, clopyralid

Smaller-volume 'growth-regulator' (auxin-type) herbicides used for brush.

Applied in Plumas County, 2021–2024: 28 gal across 5 applications

Triclopyr

Auxin-mimic. Slightly toxic to mammals acutely; animal studies show moderate reproductive/developmental toxicity (fetal loss and skeletal changes in rabbits at higher doses) and a couple of unpublished studies suggested mammary tumors. The ester (BEE) form is more runoff-prone than the amine salt; inert ingredients such as kerosene and triethylamine in some products add their own hazards; it is an emerging aquatic contaminant.

2,4-D, dicamba, clopyralid

Older auxin-type herbicides used in small amounts here. 2,4-D has its own long-running cancer-hazard debate (IARC 'possible carcinogen', Group 2B). Dicamba is prone to drift/volatilization and off-target damage. Clopyralid, like aminopyralid, is a persistent compost/manure-carryover chemical.

Sources: NPIC triclopyr general fact sheet · Triclopyr toxicological profile

Impacts on insects, pollinators & wildlife

Most of these herbicides are rated "practically non-toxic" to bees, fish and birds in the acute lethality tests regulators rely on. That is exactly why the real ecological story is mostly about two things those tests miss: sublethal effects and indirect, food-web effects.

Pollinators (bees)

Glyphosate doesn't kill bees outright, but at field-realistic doses it disrupts their gut microbiome (reducing beneficial bacteria like Snodgrassella and Lactobacillus), impairs navigation and learning, weakens immunity, and raises susceptibility to pathogens such as Nosema and Deformed Wing Virus — lowering survival. Glyphosate has been detected in pollen, nectar, honey and larvae. Standard pollinator testing measures acute death of adult honey bees and largely misses these effects, and honey bees may not represent native/solitary bees.

Soil life

Glyphosate-based formulations have been shown to reduce earthworm activity and reproduction and to shift soil nutrient cycling. Indaziflam (Esplanade) has been reported to harm soil amoebae — microbial predators that help drive nutrient cycling. Imazapyr can disrupt the soil enzymes that break down plant material. These are the organisms that keep forest soils alive.

Aquatic invertebrates & amphibians

The aquatic risk often comes from the surfactant, not the named herbicide: the POEA surfactant in many glyphosate products is far more toxic to amphibian larvae and aquatic invertebrates than glyphosate itself. Oxyfluorfen (in Cleantraxx) is labeled toxic to aquatic organisms. Given hexazinone's and imazapyr's tendency to reach water, aquatic food webs in treated catchments warrant monitoring.

The food web — the biggest indirect effect

Herbicides work by removing plants — so fewer plants means fewer flowers for pollinators, fewer host plants for caterpillars, and fewer insects overall, which means less food for birds, amphibians and fish. Conservation scientists link herbicide-driven loss of milkweed and nectar plants to monarch-butterfly decline (documented largely in farmland, but the mechanism — simplifying habitat and removing forage — applies to sprayed forest understory too). This habitat and forage loss is probably the single largest ecological impact of broadcast herbicide use, and it is poorly captured by chemical-by-chemical toxicity testing.

The insecticide in the mix

Alongside the herbicides, a small number of applications (about 6) used Tombstone Helios, whose active ingredient is the pyrethroid insecticide bifenthrin. Unlike the herbicides, bifenthrin is designed to kill insects and is highly toxic to bees and extremely toxic to fish and aquatic invertebrates; it is a restricted-use, persistent compound. Even small volumes near water or flowering plants carry outsized risk to insects.

Sources: Xerces Society · Glyphosate & bee gut microbiota (PNAS) · NPIC bifenthrin · Bifenthrin toxicity to bees

What isn't well studied

The strongest scientific argument is often not "chemical X definitely causes Y," but how much remains unexamined:

1. The "inert" ingredients and surfactants

Regulatory testing focuses on the active ingredient, yet the co-formulants — surfactants, solvents, "other ingredients" — are frequently more toxic than the active ingredient itself and are largely undisclosed. The classic example: the POEA surfactant in older glyphosate formulations is far more toxic to amphibians and aquatic life than glyphosate alone. Roughly 22,600 gallons of surfactants/oils were tank-mixed into these applications.

2. Mixtures and synergy

Chemicals here are sprayed in combinations (herbicide + oil + sometimes multiple herbicides). One product, Cleantraxx, is itself a deliberate two-herbicide synergy. Regulators test single active ingredients one at a time; the combined and synergistic toxicity of real-world tank mixes is largely unstudied.

3. Chronic, low-dose and endocrine effects

Registration leans on acute and high-dose animal studies. Low-dose, long-term, endocrine-disruption, gut-microbiome and neurodevelopmental effects — signals that have appeared for glyphosate and indaziflam — are emerging areas not central to the approval framework.

4. Cumulative, repeated watershed exposure

These forests are treated year after year, and use here is rising. The combined load on a single watershed over time — plus breakdown products like AMPA (glyphosate), hexazinone's degradates, and imazapyr's metabolites — and real-world exposure for rural residents on wells and springs, are not well captured by single-application risk models.

5. Formulation vs. pure chemical, and incomplete registrations

Genotoxicity testing of formulated products often differs from tests on the pure active ingredient, and some chemicals (e.g., indaziflam) were used for years under conditional registrations with data still outstanding.

Sources: Surfactants in GBHs (Mesnage/Benbrook) · POEA toxicity to amphibians · Co-formulant cytotoxicity

References & further reading

Every claim on this page traces to the sources below — regulatory assessments (EPA, IARC, USDA Forest Service, state agencies) and peer-reviewed studies. Open links to verify; classifications can change over time.

Cancer hazard & glyphosate

  1. Guyton KZ, Loomis D, Grosse Y, et al. (2015). "Carcinogenicity of tetrachlorvinphos, parathion, malathion, diazinon, and glyphosate." The Lancet Oncology 16(5):490–491. doi:10.1016/S1470-2045(15)70134-8. https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(15)70134-8/fulltext
  2. IARC (2015). Monographs Vol. 112: Some Organophosphate Insecticides and Herbicides (glyphosate classified Group 2A). https://www.iarc.who.int/featured-news/media-centre-iarc-news-glyphosate/
  3. Benbrook CM (2019). "How did the US EPA and IARC reach diametrically opposed conclusions on the genotoxicity of glyphosate?" Environmental Sciences Europe 31:2. https://link.springer.com/article/10.1186/s12302-018-0184-7
  4. U.S. Court of Appeals, 9th Circuit (2022) vacated EPA’s human-health glyphosate finding; EPA subsequently withdrew its interim decision. https://www.epa.gov/pesticides/epa-withdraws-glyphosate-interim-decision
  5. U.S. EPA. "Glyphosate" (agency assessment & status). https://www.epa.gov/ingredients-used-pesticide-products/glyphosate

Insects, pollinators, soil & food web

  1. Motta EVS, Raymann K, Moran NA (2018). "Glyphosate perturbs the gut microbiota of honey bees." PNAS 115(41):10305–10310. doi:10.1073/pnas.1803880115. https://www.pnas.org/doi/10.1073/pnas.1803880115
  2. Balbuena MS, et al. (2015). "Effects of sublethal doses of glyphosate on honeybee navigation." J. Experimental Biology 218:2799–2805.
  3. Gaupp-Berghausen M, Hofer M, Rewald B, Zaller JG (2015). "Glyphosate-based herbicides reduce the activity and reproduction of earthworms and lead to increased soil nutrient concentrations." Scientific Reports 5:12886. doi:10.1038/srep12886.
  4. Xerces Society. "Understanding Pesticides & Their Risks" (herbicide indirect/habitat effects; monarch & milkweed). https://xerces.org/pesticides/understanding-pesticides

Co-formulants, surfactants & mixtures

  1. Mesnage R, Benbrook C, Antoniou MN (2019). "Insight into the confusion over surfactant co-formulants in glyphosate-based herbicides." Food and Chemical Toxicology 128:137–145. https://www.sciencedirect.com/science/article/pii/S0278691519301814
  2. Mikó Z, Hettyey A (2023). "Toxicity of POEA-containing glyphosate-based herbicides to amphibians is mainly due to the surfactant, not to the active ingredient." Ecotoxicology. doi:10.1007/s10646-023-02626-x. https://link.springer.com/article/10.1007/s10646-023-02626-x

Hexazinone

  1. Montana DEQ / U.S. EPA Office of Water. Hexazinone Drinking-Water Health Advisory & water-quality standard (toxicity, mobility, groundwater). https://deq.mt.gov/files/Water/WQPB/Standards/Hexazinone.pdf
  2. Minnesota DNR. Environmental Risk Assessment: Hexazinone (forestry use, mobility, non-target plants). https://files.dnr.state.mn.us/forestry/certification/pesticides/dnr-esra-hexazinone.pdf
  3. U.S. EPA. Problem Formulation / Registration Review docket for hexazinone (environmental fate & degradates). https://downloads.regulations.gov/EPA-HQ-OPP-2009-0755-0007/content.pdf

Imazapyr, aminopyralid, indaziflam, triclopyr, oxyfluorfen

  1. Massachusetts Dept. of Conservation & Recreation. Imazapyr review (environmental fate, non-target plants). https://www.mass.gov/doc/imazapyr/download
  2. Oregon State University Extension. "Aminopyralid Residues in Compost" (carryover/persistence). https://smallfarms.oregonstate.edu/smallfarms/aminopyralid-residues-compost
  3. U.S. EPA. Aminopyralid Pesticide Fact Sheet (2005). https://www3.epa.gov/pesticides/chem_search/reg_actions/registration/fs_PC-005100_10-Aug-05.pdf
  4. USDA Forest Service / SERA (2020). Indaziflam Human Health and Ecological Risk Assessment. https://www.fs.usda.gov/foresthealth/pesticide/pdfs/Indaziflam-Report.pdf
  5. National Pesticide Information Center (Oregon State Univ). Triclopyr General Fact Sheet. http://npic.orst.edu/factsheets/triclogen.pdf
  6. U.S. EPA. Cleantraxx pesticide product label, EPA Reg. 62719-702 (penoxsulam + oxyfluorfen). https://www3.epa.gov/pesticides/chem_search/ppls/062719-00702-20160224.pdf

The insecticide (bifenthrin)

  1. National Pesticide Information Center. Bifenthrin General Fact Sheet (toxicity to bees, fish, aquatic invertebrates). https://npic.orst.edu/factsheets/bifgen.html
  2. Center for Biological Diversity (2022). Press release on emergency approvals of bifenthrin (high toxicity to bees). https://biologicaldiversity.org/w/news/press-releases/emergency-loophole-used-to-ok-highly-toxic-pesticide-for-10th-straight-year-2022-08-05/

This summary is a starting point for further reading, compiled from regulatory and peer-reviewed sources; it is not legal or medical advice. Active ingredients were identified from EPA registration numbers in the dataset. Before using any specific claim in public materials, follow the linked sources and confirm the current EPA/IARC status, which can change.

Program focus: Plumas & Northern Sierra. This is a case for industry to evaluate — not a mandate. Timber, land, and business decisions stay with owners, mills, and land managers. Chemical evidence lives on the Map / Data / Science tabs; the harvest-volume case is unproven until local numbers fill the worksheet (see tests below).

Plumas Working Forests

Harvest the wood. Keep the forest. Skip the spray — if the data support it.

What this is. A voluntary silvicultural and economic framework from the Plumas Grassroots Collective: commercial logging that thins and re-enters, keeps continuous forest character, and does not rely on clearcut plantations plus broadcast glyphosate / hexazinone / imazapyr free-to-grow programs.

What this is not. A ban on logging. A takeover of private land. A promise that multi-entry forestry always matches today’s board-foot totals. If volume, mill sorts, or owner economics fail the tests below, we will say so.

The short version

1. Logging stays. Mills, loggers, truckers, and private timberland are part of any serious solution here.

2. The spray is tied to a silvicultural system — open the canopy hard, plant conifers, kill competing plants until free-to-grow. That system is optional, not a law of nature. spraymapca documents the chemical half; this page describes a substitute harvest system.

3. Implementation is industry’s call. It is their timber, their business, and their land (or their federal contract). We publish a standard and a volume test; they adopt, adapt, or reject.

4. Data decides. Decade-scale board feet, mill offtake, logger rates, and owner NPV must be checked with local inputs. Toy models are labeled illustrative. INSUFFICIENT DATA for a Plumas-validated volume claim today.

Two pathways

Status quo plantation path

  • Large regeneration harvest / clearcut units
  • Plant even-aged conifers
  • Broadcast site-prep & release herbicides (glyphosate, hexazinone, imazapyr — see Herbicides & Science)
  • High MBF per acre at one entry; long wait; chemical dependency

Working forest path

  • Variable-density commercial thin (matrix)
  • Small group openings (prefer 0.25–1 ac, cap ~2 ac) + skips
  • Natural regen preferred; plant where fire/failure requires
  • Mechanical/manual release first; no broadcast free-to-grow chemistry under the Standard
  • Re-enter ~15–30 years for steady wood flow

Full prescription text is in the project repo under program/PRESCRIPTION_STANDARD.md.

Volume thesis — and how it fails

Matching “current harvest levels” is a landscape and decade question, not a single clearcut unit question.

Thesis: Lower MBF per acre per entry can still match total MBF if you treat more acres and/or return more often — especially where California already has a fuels/restoration thinning backlog that needs commercial offtake to scale.

Fail conditions (we report these):

  • Local MBF worksheet parity ratio < 1.0 and cannot be fixed with real acres/markets
  • Mills will not buy the sort mix (stranded wood)
  • Logging cost permanently exceeds what owners/mills will pay, with no real offtake or cost-share
  • Owner NPV rejects multi-entry cash flow — their land, their hurdle rate

T1 VOLUME: NOT YET VALIDATED FOR PLUMAS — needs CalTREES / USFS cut-sold / mill inputs. Chemical use intensity is already documented on this site; board-foot parity is not.

What each player needs

PlayerMust getHow the case tries to deliver
LoggersBillable days, safe partial-cut workMore commercial thin acres/year
MillsSteady MBF + usable sortsMulti-entry flow; mix of small & larger wood
Biomass / chipsReliable small woodThin material as co-product
Private ownersNPV they acceptEarlier partial cash flows; optional public cost-share for public benefits
USFSTimber + fuels targetsCommercial thin as forest end-state, not sprayed plantation
CommunityForest character, less watershed chemistryNo broadcast free-to-grow under the Standard

If any row fails in a real pilot, industrial scale-up fails for that context — even if the residual stand looks good.

Pass / fail tests (program rules)

TestPass ifStatus now
T1 Volume10-year landscape MBF (working) ≥ baseline system on same land baseDATA GAP
T2 MillSorts actually purchasedDATA GAP
T3 LoggerAcres/days at rates crews takeDATA GAP
T4 Owner NPVOwner accepts multi-entry economicsTHEIR CALL
T5 ChemicalBroadcast free-to-grow ≈ 0 under StandardBY DESIGN

Public language when T1 fails: “Under current assumptions, Working Forests do not match baseline harvest.” No spinning.

Private land vs public land

Private: Fee-simple owners and their RPFs choose THP silviculture and whether to spray. This program offers a Standard and a measurement design. spraymapca will keep mapping reported pesticide use either way.

Public (e.g. Plumas National Forest): Prescriptions are set through USFS planning and contracts. Communities can request no-broadcast free-to-grow alternatives; agencies decide under law.

Planting after fire: Allowed. The objection is to broadcast chemical plantation free-to-grow as the default on sites that can be managed as working forest — not to all reforestation.

Geometry pilot: how Plumas NF harvest is laid out

USFS FACTS timber-harvest polygons — pre-2020 focus. Live from data/pwf_geometry_pilot.json.

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Further optimization: progressive layout (no jumping)

Silviculture can keep the forest and keep crews moving in a continuous front.

The ops problem. Multi-entry thinning without a layout plan means loggers leapfrog across the ownership — repeated move-in, cold equipment, long empty trucking. That burns money even when the residual stand looks good.

The further method. Keep Working Forest rules (thin + small gaps + no broadcast free-to-grow spray), but harvest as a progressive wave:

  • Parallel strips or compartments worked in order (side-to-side / contour-aligned), not random polygons
  • Designated skid/skyline corridors reused every entry (fixed extraction skeleton)
  • CTL / boom-corridor thinning on dense young stands — harvester marches corridor-by-corridor
  • One active front per road-shed per year so mills get steady wood without scatter

Satellite check (honest). Landsat/Hansen tree-cover loss can show where canopy dropped, not silvicultural method. In Plumas, 2021–2025 loss is dominated by wildfire (Dixie era), not orderly commercial patterns — so recent GFW maps are a poor guide to “how loggers moved.” Pre-2020 loss + USFS FACTS harvest polygons + CalTREES footprints are the stack needed to measure clearcut blocks vs diffuse thin vs progressive fronts. Until that overlay is built, progressive layout is a design standard, not a satellite-proven Plumas map product.

Full write-up: repo program/PROGRESSIVE_LAYOUT.md. Optional conformance tags P1–P3 on the Prescription Standard.

Targeted grazing: brush & fuel control without the spray

Sheep and goats are a working-forest substitute for broadcast “free-to-grow” herbicide — a biological way to knock back competing brush and fine fuels.

What it is. Prescribed (targeted) grazing puts a managed herd, a herder, temporary electric fencing, water and livestock-guardian dogs on a unit for a set number of animal-days against a written plan. Goats browse woody plants — manzanita, ceanothus, tanoak and brush resprouts, Himalayan blackberry, scotch broom, even poison oak. Sheep graze grasses and forbs — cheatgrass, medusahead and the herbaceous competition around seedlings.

Where it fits in a working forest

  • Fuel reduction & shaded fuel breaks — the same job CAL FIRE, utilities and water districts already hire grazers for.
  • Conifer “release” without herbicide — setting back competing brush around planted or naturally regenerating trees: the direct, pesticide-free alternative to broadcast hexazinone / glyphosate / imazapyr free-to-grow.
  • Post-fire site prep & invasive control before and between plantings.
  • Understory maintenance on the multi-entry, thin-and-re-enter path this page describes.

The honest trade-offs

Grazing is a tool, not a silver bullet. It needs water, herding, fencing and predator protection, works best in repeat passes over a few seasons, and is limited by terrain, access and scale. Timing and species matter: goats will browse conifer seedlings too, so grazing is aimed before planting or with the herd managed to hit the brush, not the crop trees. Per-acre cost is site-specific and competitive with mechanical or manual release once the co-benefits are counted — no chemical load on a watershed of wells and springs, plus nutrient cycling and community acceptance.

An aligned local effort you can back. A community goat fuel-reduction pilot in Genesee Valley — roughly 100 acres grazed by Brush Busters as an alternative to herbicides and heavy equipment (about $75,000, ~$750/acre) — is exactly the pesticide-free work this page describes. We’re not running the pilot; we’re amplifying an aligned local voice and helping raise for it. Support it at the fundraiser Saturday, August 8 at the Rich Bar Taproom in Quincy, or through our Donate button (choose “Goat grazing”).

Voluntary pilots

A pilot runs only if an owner or agency wants one. Metrics: deck-scale MBF, residual structure, regen at years 3–5, actual costs, herbicide = no broadcast, mill acceptance. Failed pilots, documented, are useful — they stop false claims.

Details: repo program/PILOT_SPEC.md.

Costs & losses — absolute data so far

Machine file: data/working_forests_costs.json. Confidence: A official CA / harvest series · B regional study range · D gap (we show the hole).

This is the path to a full method comparison: every dollar we can source, every loss pathway we can name, and nulls where industry or public data are not public yet. Net owner profit by method is still a gap — filling it is what makes the industrial case real or not.

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Get involved / correct our numbers

Mill capacity, logging costs, CalTREES harvest-by-method, or owner corrections make this real. Material errors will be fixed in public.

Email spraymapca@gmail.com · Full program package in the open GitHub repo under program/ · Chemical map: use the Map tab.

Repo docs: README, PLUMAS_WORKING_FORESTS, PRESCRIPTION_STANDARD, ECONOMICS, STAKEHOLDER_MAP, PILOT_SPEC, POLICY_ASKS, SOURCES; tool: program/tools/volume_sketch.py.

Source data — record sample. A reviewable sample of the largest reported applications (top 80 per county by amount) for the area chosen in the selector above, drawn live from the project database. The complete dataset is 12M+ records. For the five Northern Sierra counties (Butte, Tehama, Lassen, Plumas, Sierra) the data now runs through 2024, obtained directly from CDPR by public-records request; the rest of California is the statewide Pesticide Use Reports (2020–2022); coverage is updated as new public-records / FOIA responses arrive. For full county records use the records-request templates in the repo.

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