Inside a Wastewater Discharge Permit Application: What POTWs Require
If your facility sends process wastewater to the sanitary sewer, your local POTW (the Publicly Owned Treatment Works, usually a city sanitation department or sanitation district) needs to know what’s in it before it accepts the discharge. The vehicle for that conversation is an industrial wastewater discharge permit application.
If your facility sends process wastewater to the sanitary sewer, your local POTW (the Publicly Owned Treatment Works, usually a city sanitation department or sanitation district) needs to know what’s in it before it accepts the discharge. The vehicle for that conversation is an industrial wastewater discharge permit application.
The application is not a one-page form. Most California POTWs build their packages off the federal pretreatment program in 40 CFR 403, then layer on local requirements. The end result is a package that asks for company information, a detailed picture of every process that produces water, flow data, drawings, pretreatment information, and signed certifications. Below is what we see across the applications we prepare, what you’ll need to provide, and what trips facilities up.
For the broader picture of where this permit fits, see our industrial wastewater discharge permit in California guide.
Who Asks for It and Why It Varies
In California, the regulatory chain sits under the State Water Resources Control Board (SWRCB) and the nine Regional Water Quality Control Boards, backed by the federal Clean Water Act and the National Pretreatment Standards. Day to day, the agency you talk to is your local POTW. San José-Santa Clara, the LA County Sanitation Districts, OCSD, EBMUD, Union Sanitary District, and Livermore each maintain their own application package and their own quirks.
The core questions are the same across districts: what does your facility do, what goes into the sewer, how much, and how do you control it. The format, the level of detail, and the supporting documents vary. That’s why we look up the specific district’s current application form before we scope any work. The version you downloaded two years ago may not match what they want today.
What’s Actually in a Permit Application
Most California POTW applications collect the same categories of information. The depth varies by district and by facility complexity.
Company and process identification. Legal business name, site address, SIC or NAICS code (the industry classification that identifies your type of operation), ownership structure, the person responsible for compliance, and a description of every industrial process that produces wastewater. This is where job shops, metal finishers, food processors, semiconductor fabs, and surface-treatment operations end up describing their work in plain language for the POTW reviewer.
A 12-month water balance. This is the technical core of the application and the part facilities most often get wrong. The balance accounts for every drop of water entering and leaving the site: incoming municipal supply, well water, process water used in production, evaporative losses, water shipped off site, water reused on site, and water discharged to the sewer. Inputs and outputs have to reconcile, typically within about 10%. When the math doesn’t close, the POTW asks for a corrected balance before it issues anything.
Pollutant source identification. A list of the chemicals and constituents that could end up in the discharge, tied to the processes that use them. Plating lines, parts washers, cooling towers, lab drains, floor wash water, and rinse stages all get itemized. If your facility uses cyanide, hexavalent chromium, solvents, oils, or any of the listed pretreatment categorical pollutants, the source is identified here.
Drawings: plot plan, process flow, pretreatment, spill containment. A site plan showing the building footprint, sewer connections, floor drains, storm drains, chemical storage, and waste accumulation areas. Process flow diagrams tracing each waste stream from generation to discharge. Drawings of any pretreatment equipment (pH adjustment, oil-water separators, clarifiers, filters, evaporators) and spill containment around tanks and chemical storage.
Pretreatment description. A written explanation of how each pretreatment unit works, what it removes, who operates it, and how it’s maintained. If your facility relies on closed-loop systems, batch treatment, or pH adjustment before discharge, the application is where you document it. How industrial wastewater pretreatment works covers the technical side in more depth.
Sampling and lab results. Many districts require influent or effluent sampling and a certified lab analysis attached to the application. The list of analytes is set by the district, usually keyed to the pretreatment standards that apply to your industrial category.
Slug discharge control plan. A separate written plan covering spill prevention, containment, tank schedules, and the notification chain when something goes wrong. Most California POTWs require it as a condition of the permit, not as a separate filing. See slug discharge control plans for what’s actually in the document.
Signatory certification. Under 40 CFR 403.12, the application has to be signed by a responsible corporate officer (president, vice president, general partner, sole proprietor, or a duly authorized representative whose written authorization has been submitted to the Control Authority). A consultant cannot sign in their place. CDMS prepares the package; your authorized officer certifies.
What You Provide vs. What We Handle
Some facilities want CDMS to prepare the entire application from a blank page. Others have a draft ready and want a second set of eyes before they sign and submit. We do both. Here’s how the work typically splits.
| Category | You Provide | CDMS Handles |
|---|---|---|
| Company information | Legal name, ownership, signatory officer, contact roles | Formatting into district-specific application sections |
| Processes and chemicals | A walkthrough of operations, chemical inventory, SDS list | Process descriptions written for the POTW reviewer, pollutant source tables |
| Water use data | Meter readings, production records, evaporative estimates | The 12-month water balance, reconciliation to within district tolerance |
| Drawings | Existing plot plans, facility CAD if available | Process flow diagrams, sewer/drain overlay, pretreatment and spill-containment drawings |
| Pretreatment equipment | Equipment make/model, operating logs | Written pretreatment description, maintenance and monitoring narrative |
| Sampling | Site access; collection by client or by CDMS field staff | Lab coordination, analytical comparison to district limits |
| Slug plan / TOMP | Tank schedule, chemical list, emergency contacts | Drafted plan, notification chain per local POTW requirements (federal rules require immediate notification; local permits typically add specific deadlines) |
| Signature | Responsible corporate officer signature per 40 CFR 403.12 | Signature blocks, certification language, submittal package |
| Agency follow-up | Decisions on any district requests | Response to district comments, revisions, resubmittal |
For review-only engagements, we look at the package you’ve prepared, mark up gaps, check the water balance and the math, verify the drawings against the site, and tell you what the POTW reviewer is likely to come back on.
Where Facilities Get Stuck
The water balance is the single most common deficiency. Facilities track municipal water purchases, but most don’t track evaporative losses, on-site reuse, or non-discharging streams accurately. When we walk a new facility, the first thing we ask for is twelve months of water bills, twelve months of production records, and any sub-meter readings. Most of the time the numbers don’t close on the first pass and we have to estimate evaporation from cooling towers, plating tanks, or wash stages to make the balance work.
The second most common problem is drawing accuracy. The site plan on file shows where the floor drains were ten years ago. The actual drains were moved during a remodel, or the storm drain was tied into the sanitary line during a tenant build-out that nobody documented. We walk every drain before we draw it.
The third is process-flow completeness. Facilities describe their main production line and forget the parts washer, the lab sink, the cooling tower blowdown, or the floor-scrubber recycle that occasionally gets dumped. Inspectors notice. So do POTW reviewers.
What Happens After You Submit
The POTW reviews the application, sometimes asks follow-up questions, and issues the permit. The permit sets your contaminant limits, monitoring frequency, and reporting schedule. From that point, the recurring obligations begin.
Self-monitoring reports. Most permits require periodic sampling and reporting, sometimes monthly, often quarterly, sometimes every six months. The frequency is set in your permit conditions. See self-monitoring and baseline monitoring reports for wastewater permits for what these contain.
Baseline monitoring reports and TTO certifications. Categorical industrial users (metal finishers, electroplaters, and others covered by federal pretreatment standards) owe a baseline monitoring report after permit issuance and, in many cases, ongoing total toxic organics certifications.
Renewal. Permits expire. Some districts require renewal applications 180 days before expiration; new operations may need to file six months before they begin discharging. Renewal is a recompete of the same documentation, updated to reflect any process changes.
A Note on California-Specific Quirks
Federal pretreatment standards in 40 CFR 403 set the floor. California POTWs almost always go beyond it. Local limits for metals, cyanide, oil and grease, and pH are typically stricter than the federal categorical standards. Surcharge programs at large districts (LA County, others) layer additional reporting on top of the permit itself for high-volume or high-strength discharges. None of this shows up on the federal forms. It shows up in your specific district’s local sewer use ordinance, and it’s why scoping the work starts with looking up your jurisdiction, not assuming a national template.
Not sure the permit applies to you yet? Do you need a wastewater discharge permit? Cooling, wash, and lab drains →
Not sure a permit even applies to your drains? See whether you need a wastewater discharge permit →
Already permitted and facing expiration? See how to renew your wastewater discharge permit →
Trusted throughout California
BSY started working with CDMS last year after our in-house EHS person departed the company. CDMS reviewed our existing operational permits as well as any additional Federal, State and Local regulations that could apply and helped us to create a comprehensive compliance calendar to track regulatory deadlines and submittal due dates. The CDMS team does an excellent job of tracking everything and can be relied upon to complete the forms accurately and assist with submittals, allowing me to focus on our business.
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