MOCKUP · LANDING← all screens
Pretreatment · 40 CFR 403.5

Local limits your regulator can’t send back.

Every limit you place on an industrial discharger has to survive a technical challenge — from the Approval Authority, from a permittee’s consultant, sometimes from a judge. LocalLimitsHQ runs the back-calculation, shows every assumption, and hands you the submittal package.

No spreadsheet macros. No lost formulas. Every number traces to its source.

Copper · back-calculation
Acute aquatic life criterion 0.0048mg/L
× acute dilution factor 15
Allowable final effluent 0.072mg/L
÷ (1 − 0.85 plant removal)
Allowable at headworks 0.480mg/L
× 5.0 MGD × 8.34
Maximum allowable headworks loading 20.02lb/d
− 2.03 domestic − 2.00 safety reserve
Maximum allowable industrial loading 15.98lb/d
÷ 1.0 MGD industrial flow × 8.34
Local limit 1.92mg/L
The incumbent

You are running your pretreatment program on a macro-enabled spreadsheet.

It works, until someone asks why. The workbook that most programs inherited has one column per pollutant, hard-coded criteria that quietly went out of date, and no record of who decided what.

The workbook today

  • Averaging is left to you — the sheet says so in its own instructions.
  • #DIV/0! sits in live cells where sampling data is thin, and gets printed anyway.
  • Criteria are frozen at whatever year the file was published.
  • The binding criterion disappears inside a MIN(). Nothing says why that one won.
  • Every reviewer gets a different copy by email. Nobody knows which is current.

The same study here

  • Non-detects, replicates, and averaging handled once, by a stated convention.
  • Thin data is an explicit insufficient data state — it never renders as a number.
  • Criteria come from a versioned library. Each study pins the version it relied on.
  • The binding pathway is named on every row, with the arithmetic behind it.
  • One study of record, with an audit trail your Approval Authority can follow.
The method

Work backwards from the thing you must not exceed.

A local limit is a derived number. Start from the criterion that protects the receiving water, the biology, the biosolids, or the crew — then trace it back through the plant to the sewer.

1

Describe the plant

Flows, receiving water, dilution factors from your NPDES fact sheet, biosolids pathway, digester.

2

Load the monitoring

Influent, effluent, and biosolids sampling. Removal efficiencies come out of your own data, not a table.

3

Find what binds

Six protection pathways run at once. The most restrictive sets the headworks loading — and says so.

4

Allocate and submit

Divide the industrial loading across your permitted users, then export the package with its full basis.

Regulatory basis

Why this is never finished.

Local limits are not a one-time deliverable. The obligation to develop them is continuous, and the obligation to re-justify them arrives with every permit cycle. That is the work we carry.

40 CFR 403.5(c)

Programs must develop and enforce specific limits on prohibited discharges, and continue to revise them as necessary. Programs without approved pretreatment programs must develop limits where pollutants from non-domestic sources cause interference or pass through that is likely to recur.

40 CFR 122.44(j)(2)(ii)

A written technical evaluation of the need to revise local limits is required following permit issuance or reissuance. Re-evaluation is also warranted when plant performance, influent character, or the applicable criteria change materially.

Pricing

Priced on plant flow, billed annually.

One subscription covers the whole program — unlimited studies, unlimited industrial users, and criteria updates as they are promulgated. Every plan includes the full audit trail.

Small system
≤ 5 MGD · single plant
$3,900 / year
  • Unlimited studies and scenarios
  • Up to 25 permitted industrial users
  • Versioned criteria library
  • Submittal package export
  • 3 seats
Start a study
Most programs
Standard
≤ 25 MGD · up to 3 plants
$9,600 / year
  • Everything in Small system
  • Unlimited industrial users
  • Multi-plant and satellite allocation
  • Scenario comparison for permit renewal
  • Reviewer sign-off workflow
  • 10 seats
Start a study
Authority
Unlimited flow · delegated program
Custom
  • Everything in Standard
  • Contributing jurisdictions and satellites
  • Annual report assembly
  • Criteria set customization
  • Named support engineer
  • Unlimited seats
Talk to us