AAC R18-9-A902: Industrial Stormwater

ADEQ's page sets the scope: "The MSGP identifies 29 different sectors that are subject to permitting for industrial stormwater discharges to protected surface waters." Your business type (its SIC code) decides the sector. Warehousing and trucking are Sector P, which covers motor freight transportation and warehousing (SIC 4212 to 4231), local and highway passenger transportation, the Postal Service, railroads and petroleum bulk stations.

The biggest limit is stated right on the same page: "If industrial stormwater will not discharge to protected surface waters, either directly or by way of a conveyance (such as a street, ditch, etc.), stormwater permit coverage is not required." Much of the Valley retains stormwater on site, so this matters.

The parts:

• Plan first. "Before submitting an NOI, you must complete a Stormwater Pollution Prevention Plan (SWPPP)."
• Apply in myDEQ. The Notice of Intent "must be submitted electronically using ADEQ's on-line permitting portal myDEQ."
• Timing for new sites. File "at least 30 calendar days before discharge is anticipated."
• Coverage starts once a complete NOI and the fee are received in myDEQ.
• Term. Coverage under this permit expires "at midnight, January 15, 2030."
• Fees. Based on acreage and billed every year in the NOI anniversary month. ADEQ's fee page lists $527.93 for up to 1 acre, $755.40 for over 1 to 40 acres and $1,509.75 for over 40 acres, and says fees "are subject to annual adjustment."

• Stormwater associated with industrial activity. Rain or runoff that touches industrial materials, equipment or operations, defined in A.A.C. R18-9-A902 by reference to federal rule 40 CFR 122.26.
• Protected surface water. A water on ADEQ's protected surface water list: rivers, washes, lakes and the like. Street gutters and ditches count as conveyances if they lead there.
• SWPPP. The site's written plan: where runoff goes, what could pollute it, and the controls and inspections that keep it clean.
• No Exposure Certification. An exemption for sites with no industrial materials or activities exposed to rain.
• No Discharge Certification. An option in myDEQ for sites whose industrial stormwater doesn't leave the property.

Operators of facilities in the 29 sectors whose industrial stormwater reaches a protected surface water. The facility operator, often the tenant running the warehouse, files. A property manager should know whether each tenant has coverage.

This does not apply if:

• Nothing is exposed. The permit says facilities "are exempt from the requirement to obtain a permit coverage if there is no exposure of industrial materials or activities from precipitation or runoff." That determination is site-wide, not outfall by outfall.
• The business isn't in a listed sector. A retail store or office building isn't covered.
• Runoff stays on site in retention basins and drywells and never reaches protected water. Drywells bring their own ADEQ inventory rule.

A Tolleson freight terminal. Trucks fuel and get serviced in an open yard that drains to the street and on to a wash. The operator writes a SWPPP, files the NOI in myDEQ and pays the annual fee.

A Phoenix e-commerce warehouse. Every dock is under cover, forklifts charge indoors, and nothing is stored outside. The operator looks at the No Exposure Certification instead of full coverage.

A Mesa site with full retention. The answer flips again: every drop of yard runoff goes to a retention basin with drywells. With no discharge to protected water, MSGP coverage isn't required, but the drywells still need ADEQ's Class V inventory.

1. 1Find your SIC code and match it to a sector in Appendix C of the MSGP.
2. 2Trace where your runoff goes: to a basin, a street, a storm drain or a wash.
3. 3Decide the path: full coverage, No Exposure Certification, or No Discharge Certification.
4. 4Write the SWPPP before filing, if you need coverage.
5. 5File in myDEQ at least 30 days before a new discharge, and pay the acreage fee.
6. 6Keep up the inspections and records the SWPPP calls for, and re-file before January 15, 2030.

• "Every warehouse needs a stormwater permit." Only if it's in a listed sector and its runoff reaches a protected surface water.
• "Our 2019 permit still covers us." ADEQ says 2019 coverage not renewed by the deadline "will be automatically terminated."
• "Washing trucks is fine if the soap is biodegradable." Sector P coverage doesn't authorize washwater discharge at all.
• "The landlord holds the permit." The operator of the industrial activity files.
• "A roof over the docks settles it." No Exposure is judged site-wide. One uncovered fuel island or outdoor pallet of drums breaks it.

A site that needs coverage and discharges without it is discharging without an AZPDES permit. The practical fix is the same either way: sort out coverage, and keep oily yard runoff and washwater out of storm drains and drywells.

For the drywell side of the same site, see AAC R18-9-I652: Drywell Inventory Rules. For floor and dock drains that back up, see floor drain backing up.

Read ADEQ's MSGP page, the 2024 MSGP permit (PDF), ADEQ's general permit fee page and R18-9-A902 on the Cornell LII mirror. This page explains the permit; the official text governs.