The Spec Sheet Quoted a Regulation That Had Been Dead for Ten Years. It Was Also Stricter Than the Live One.

A client sent us two documents for the same building and asked us to confirm the chamber sizes before he poured his partitions. One was a photograph of a specification table he had been given. The other was a sheet out of the master plumber's drawing set, titled STP Details, carrying the full performance specification for the plant. I read them side by side, which is what we always do with somebody else's paperwork, and they did not agree with each other.

That by itself is ordinary. Two documents on one job usually disagree somewhere. What was not ordinary is how they disagreed. The drawing set was asking for an effluent standard taken from a regulation that had been superseded about ten years earlier, and in two places that dead regulation was stricter than the rule that actually applies today, while in three places it asked for nothing at all. Those three places are the ones that decide most of the plant.

We have written before about reading a finished drawing somebody sent us and pricing it honestly, and about reading somebody else's quotation line by line. This is a third kind of document reading, and the one I had not written down yet: reading a specification and finding a regulation inside it that no longer exists.

What the sheet actually asked for

The STP Details sheet gave flows, an influent design basis, an effluent table, a process flow and a sludge requirement. The flows were marked assumed value only, to be confirmed, which is honest, and worth respecting: what you eventually declare is what you are held to. The influent was BOD around 400, COD 600, suspended solids 400, oil and grease 100. The effluent table was headed with the name of the old regulation.

The owner's photographed table, from a different source entirely, gave a much stronger influent — BOD 700, oil and grease 150, ammonia 50, nitrate 30, phosphate 30 — and its effluent column was, line for line, the current Class C set under the regulation in force.

So the current regulation was in the room. It was simply in the wrong document. The one bound into the construction drawings, the one a contractor would actually build to, was the old one.

Stricter in two places, which is why nobody questions it

This is the part that makes an old specification so hard to spot. The superseded sheet asked for BOD 30 and suspended solids 50. The current Class C standard the building will actually be judged against is BOD 50 and suspended solids 100.

Read quickly, that looks like a tight specification. A consultant has asked for better water than the law requires, and nobody argues with a specification that errs on the safe side. An owner reading it feels looked after. A contractor reading it prices a slightly larger plant and moves on.

And in those two rows, the sheet is genuinely safe. A plant that holds BOD 30 holds BOD 50 comfortably. The trouble is entirely in the rows that are not there.

Silent in three places, and those three decide the design

The old sheet carried colour, surfactants, coliform, residual chlorine, a temperature rise limit and a sludge dryness requirement. It carried no ammonia limit, no nitrate limit and no phosphate limit at all. The regulation it was quoting predates them.

Those three parameters are not trim. They are most of the plant:

A contractor who builds exactly what that sheet asks for can hand over a plant that passes its own specification on every row and still fails the standard the building is actually held to. Those three limits are the ones that fail in practice, and we see them fail on plants that were built properly to the wrong brief.

Over-strict in two rows and silent in three is the signature of a template

I want to be careful here, because it would be easy to turn this into a story about a careless consultant, and that is not what I think happened. A specification that is tighter than the law in two places and absent in three is not the shape a person produces when they are thinking about a particular building. It is the shape a document takes when it has been carried forward from job to job for years, and the law moved underneath it.

We have done the same kind of thing ourselves. I found a line sitting in our own quotation template asking the client to confirm his own receiving water classification — work that is ours, not his — and it had been there long enough that nobody read it any more. Templates rot quietly. That is the whole lesson. Nobody spots it because the document still looks like a specification.

The wider version of this is a thing we see often enough to have written about separately: nothing changes at a plant and everything changes around it. A document is just an earlier version of the same problem. And when a standard did move, it is worth knowing exactly what it moved and what it did not rather than assuming the whole table shifted.

The note at the bottom of the sheet

There was a note on that drawing, in small type, saying in effect that the sizing and the tank and equipment dimensions would be provided by the STP contractor and that the drawing was for the contractor's reference only.

That note is the most important sentence on the sheet and almost no owner notices it. It means the consultant has explicitly handed the sizing to whoever builds the plant. The chamber schedule the owner is looking at, and in this case was about to pour partitions to, is not a design. It is a reference layout, and the person who signed it has said so in writing.

I do not think that is wrong of the consultant. A plumbing set is not the place to design a biological process, and saying so plainly is better than pretending otherwise. But it does change who is carrying the design. The owner thought he had a designed plant and a contractor to build it. What he actually had was a reference drawing and a sizing job that nobody had started. That is a reasonable arrangement only if the owner knows it is the arrangement, which is why we point at the note rather than at the regulation first when we explain this to somebody.

What we did with the two documents

We did not write a paper proving the sheet wrong. There is a way of handling a contradiction in a client's paperwork that wins the paragraph and loses the week, and pointing triumphantly at a dead regulation is it.

What we did was make one decision and state it on the first page of our design basis: we design to the current regulation, and to the stronger of the two influent sets.

The current regulation, because that is the only standard that will ever be sampled. The stronger influent, because the two sheets disagreed about strength as well and one of them had to be chosen — and in this case the building was not yet occupied, so there was nothing to sample and never will have been. When the choice is between two assumed numbers, take the one that costs you volume rather than the one that costs you compliance. We said in the document that it was an assumption and showed what the plant looks like at each strength, which is how we present every design now.

The other thing we did was deliberately not use the contradiction as leverage. Finding an error in a client's consultant's work is not a selling position. It is a survey question: which of these two sets would you like your building judged against, and has anyone established where the water actually goes? Where the water goes, and what class it is, decides more of the cost than the technology does, and establishing it is our job, not the owner's.

What an owner can check on his own set

If you are holding a drawing set for a building you are about to build, there are four things on it worth half an hour. They sit alongside the questions I would ask before signing for a plant at all:

  1. Which regulation does the effluent table name, and is that regulation still live? A name and a year is enough to check. If the table names nothing at all, that is the same problem wearing different clothes.
  2. Does the table have rows for ammonia, nitrate and phosphate? If it does not, the plant behind it was not sized for them, whatever else the drawing shows.
  3. Does the sheet say who is responsible for the sizing? Read the notes, not the schedule. If it says the contractor, then the schedule is a sketch and the real design has not happened yet.
  4. Is there one influent basis or two? If two documents give different strengths, somebody has to choose, and the choice belongs on paper with a reason beside it.

None of that needs an engineer. It needs somebody to read the sheet as a document rather than as a picture. If you want to see what the arithmetic does with those answers, our design generator and the price estimator will both take a flow and a strength and show you the shape of the answer, and the parameters by industry page is where I would start if you are not sure which limits your building will be read against. If you already know your flow and want a plant quoted properly rather than referenced, that starts here. For the three parameters the old sheet was silent on, we keep separate notes on ammonia, nitrate and phosphate.

Where this does not transfer

Every site differs, and I would not want this read as a rule that old specifications are always wrong and new ones always right.

On a small job a thin specification is often appropriate and the right answer is a short document, not a longer one. On a plant discharging to a sewer rather than to a water body, some of these parameters genuinely do not apply, and a sheet that leaves them out may be correct. Industrial effluent is judged by a different table again, and a domestic standard copied onto a process stream is a worse error than a stale date. And a specification can name the current regulation perfectly and still be unbuildable, which is a different review entirely — the design is where the cost is decided, not the cover sheet.

What does transfer, I think, is the habit. Read the paperwork as paperwork. Check the date on the rule it names. Count the rows. Read the notes at the bottom before the schedule in the middle. We are a wastewater design and build company and we do this on every job we take on, including our own documents. Most of that work is in Cebu, and the contractor side of it is the same reading habit applied to a build, because we have had our own templates go stale on us. If you would rather not do it alone, book a free 15-minute consultation and bring the sheet.

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