What settles a dose, and what stops one.
Which instruments settle which question, what gets written down before a vessel moves, what halts a pass, and who else is holding the record while it happens.
The layers
Four sources of truth, and they answer different questions.
The common failure in this category is letting the most impressive layer answer a question it cannot reach.
Earth observation
Sets the search area and the priority order across a zone, days before a shore sample would notice anything. It cannot see under the surface, cannot name a species and cannot set a dose. HABscan is candid about where these products bend.
Moored instruments
Continuity at a fixed point. A buoy string is the only thing that catches the overnight crash nobody was on the water for, and the only record that shows whether a treated volume held its gains a week later.
Profiles at the point of treatment
Dissolved oxygen, temperature, salinity, pH and turbidity through depth, before the pass and after it, at the same depths. This is the layer a dose is actually set from. Nothing above it can substitute.
Samples and assay
Cell counts and toxin assay, sent to a laboratory. Slow, and the only thing that answers what a bloom was carrying. A falling count is a weak proxy and we do not treat it as the verification step.
On the day
A dose is written down before the vessel moves.
The sequence matters less than the order of the paperwork. What gets fixed in advance, and what stays adjustable, is the whole difference between a controlled operation and an improvised one.
Fixed before departure
The oxidant ceiling for that water: maximum concentration, maximum contact time, and the pH and temperature band inside which they hold. Set against a measured background for that site, not against what the plant aboard is capable of producing.
Decided on arrival
Where in the column to deliver, how many passes, transit order across the tasking. All of it from the profile taken on site, because a water column three days old is a guess with a timestamp on it.
Never adjusted at sea
The ceiling. If the water turns out to need more than the ceiling allows, the answer is a new plan agreed ashore with the oversight party, not a crew deciding to push it. An inspector reconstructs this from the log, and the log has to survive that.
The organic background is the part that catches people out. A dose is consumed by whatever is already dissolved in the water long before it reaches the material you were aiming at, and two bays with identical cell counts can need very different plans for that reason alone. It is measured, not assumed.
Stop conditions
Four things halt a pass, and any one voice is enough.
Stop conditions are agreed in writing before a season starts, which is the only time everyone is calm enough to write them properly.
A pass halts when the oxidant ceiling would be breached to achieve the intended result; when dissolved oxygen in the treated volume moves the wrong way; when distressed or dead marine life is observed in or near the treated water; or when two instruments that should agree do not, and nobody can say yet which one is lying.
The treatment operator can stop. So can the master, the duty analyst ashore, and the oversight scientists — individually, without first persuading anybody else. Restarting takes agreement from all of them.
That asymmetry is not politeness. Stopping is cheap and reversible; continuing through an unexplained reading is neither.
Thresholds
The numbers a duty engineer actually needs.
Three of these are routinely quoted at the wrong value in this sector, and each error runs in a direction that would embarrass whoever repeated it. They are worth getting right before they end up in an operating procedure.
The one that would do real damage
A figure of 0.5 to 1.0 mg/L circulates widely as an approximate lethal dissolved-oxygen threshold for fish, and it is traceable to the same Delaware River Basin Commission review quoted above. It is a nineteen-hour result for juvenile White Perch alone, sitting in an appendix table, and the review's actual conclusion is the 4 to 6.4 mg/L band.
An operator who set a night alarm from the appendix figure would be an order of magnitude low, and would find out about it from a fish kill rather than from a report. We name it because it is an easy error to make and a costly one to inherit — pages on this network repeated it until the source was read properly, which is how we came to check.
Routing
Hull-hours are the scarce thing, and routing is how they get spent.
A zone rarely has one problem at one time. It has four, ranked badly.
Every morning the same question comes back: which water, in what order, for how long. The inputs are forecast risk across the zone, the state of anything treated in the last fortnight, tide and wind for the next thirty-six hours, gas remaining, and where the crew is in its rotation.
The output is a tasking, and the discipline is refusing to write it from yesterday's complaint. A patch that has already closed a beach is the loudest item on the list and often the worst use of a hull. The forming patch in the next bay is quieter, cheaper to work, and the one that decides whether next week has an incident in it.
This is what the adjacent Deep Strike in the base subscription is for, and it is why proactive protection is priced into the zone rather than sold as a call-out.
Data services
What a programme produces, besides treated water.
A season generates evidence whether anyone plans for it or not. Designing that record in advance is cheaper than assembling it afterwards from memory, and it is the only version that will hold up if the season goes badly.
The pass record
Position, time, gas, concentration, contact time, delivery depth, and the profile either side. One row per pass, written as it happens. This is the artefact a regulator will ask for, so it is built for that reader rather than for a newsletter.
The water-quality series
Continuous telemetry from moored instruments and vessel profiles, through the season, at fixed stations as well as at treatment sites. Untreated control locations included, because a change without a comparison is an anecdote.
The zone risk surface
Forecast conditions across the contracted area for the coming days, assembled from earth observation, in-situ data and meteorology. It drives tasking. It is also handed over, because a client who can see next week is a client who can plan around it.
The season account
What was applied, where, when, and what the water did — set against the parameters agreed before the season began, including the ones that were not met. Written to be checked rather than quoted.
Two copies, and one of them is not ours
Every programme is designed with continuous independent oversight, and the practical form it takes is access rather than assurance. Local scientific institutions engaged for the duration hold the same live water-quality feeds the duty crew steers by — not a curated quarterly digest — and are encouraged to bring instruments of their own.
A season's record that exists only on our servers is a record nobody can examine without asking us first. We insist on the second copy rather than permitting it, because the entire value of the evidence depends on it having been out of our hands the whole time.
What that changes
Nothing, on a good day. On a bad one it changes everything: the pass that missed, the patch that came back overnight, the assay nobody expected. Those are the moments when a single-source record stops being evidence and becomes a matter of trusting the contractor.
If our targets and the health of the water ever pull against each other, this arrangement is how a ministry hears about it from somebody other than us. The evidence page sets out where that sits against everything else on the record.
This section is where /system/data/ used to live. It was a paragraph of intent with nothing underneath it, so it was folded into the page that describes the instruments the data actually comes from.
Limits
What the control system does not do.
Three claims this page could easily have made and will not.
- It does not dose autonomously. Instruments inform a decision that a named person makes and signs. Automation of an oxidant ceiling in open water is not something we would offer, and you should be wary of anyone who does.
- It does not forecast a bloom into existence with any useful precision more than a few days out. Risk surfaces narrow a search and rank a tasking. They do not tell you what August holds in March.
- It does not replace your own monitoring obligations. Whatever a regulator requires of you, you still owe. Our feeds are additional to that record, and available to whoever you are obliged to report to.
Asked by data teams and duty engineers
Four about the instruments
What dissolved-oxygen number should an alarm be set at?
Higher than the number that defines hypoxia. NOAA's 2 mg/L is a classification threshold, not a safe operating level, and treating it as one is how a stocked pen gets lost overnight.
A Delaware River Basin Commission literature review puts lethal-level requirements for sensitive estuarine species at 4 to 6.4 mg/L, with roughly 5 adequate for many species and 6 to 7 protective. Set against that band, then against what your own species and season demand.
Who can stop a pass?
Any of four people, acting alone: the treatment operator, the master, the duty analyst ashore, or an oversight scientist. None of them has to convince the others first.
Restarting requires all of them. Making it easy to stop and difficult to resume is the cheapest safety control available to a programme like this.
Does the oversight body get the raw feeds or a report?
The feeds. Live, as the crew sees them, plus anything they choose to bring and moor themselves.
A summary written by the operator and a telemetry stream are different artefacts, and only one of them can be independently checked. Handing over the second one is the point of the arrangement.
Can a satellite set a dose?
No, and a supplier who implies otherwise is selling imagery.
Earth observation bounds a search area and ranks a tasking, which is genuinely valuable and worth paying for. Everything governing how much oxidant enters water comes from instruments in that water, at depth, on the day.
Where the detail lives
Bring your monitoring people
Ask us what we would measure on your water.
Send the water body, the season and whatever record you already hold. The site read comes back with the stations we would want, the thresholds we would set, and the gaps in the existing data that would have to be filled first.