United States Office of Water EPA 833-F-99-015

Environmental Protection (4203) April 1999

Agency Fact Sheet 4.0

Storm Water Phase II

Proposed Rule

Conditional No Exposure

Exemption for Industrial Activity

This fact sheet is based on the Storm Water Phase II Proposed Rule. Therefore, the information provided herein is subject to

change upon publication of the final Phase II rule in November 1999. A revised series of fact sheets will be provided at that

time. A comprehensive list of the current fact sheets is in the text box at left.

Why Is the Phase I No Exposure Exemption Addressed in the Phase II Proposed

Rule?

The 1990 storm water regulations for Phase I of the federal storm water program identify eleven

categories of industrial activities that must obtain a National Pollutant Discharge Elimination

System (NPDES ) permit. Operators of certain facilities within category eleven (xi), commonly

referred to as “light industry,” were exempted from the definition of “storm water discharge

associated with industrial activity,” and the subsequent requirement to obtain an NPDES permit,

provided their industrial materials or activities were not “exposed” to storm water. This Phase I

exemption from permitting was limited to those facilities identified in category (xi), and did not

require category (xi) facility operators to submit any information supporting their no exposure claim.

In 1992, the Ninth Circuit court remanded to EPA for further rulemaking the no exposure exemption

for light industry after making a determination that the exemption was arbitrary and capricious for two

reasons. First, the court found that EPA had not established a record to support its assumption that

light industrial activity that is not exposed to storm water (as opposed to all other regulated industrial

activity not exposed) is not a “storm water discharge associated with industrial activity.” Second, the

court concluded that the exemption impermissibly relied on the unsubstantiated judgment of the light

industrial facility operator to determine the applicability of the exemption.

This fact sheet describes the conditional no exposure exemption as presented in the Phase II Proposed

Rule. EPA relied heavily upon the conditional no exposure exemption concept and rule language

developed by the Urban Wet Weather Flows Federal Advisory Committee. The Committee included a

balanced mix of representatives from State and local government, industry, construction, and

environmental groups.

Who Would Be Eligible to Claim No Exposure?

As revised in the Phase II Proposed Rule, the conditional no exposure exemption applies to ALL

industrial categories listed in the 1990 storm water regulations, regardless of the type of industry,

except for construction activities disturbing more than 5 acres (category ten (x)) and those facilities

individually designated by the NPDES permitting authority.

What Would Be Required Under the No Exposure Provision?

The Phase II proposal represents a significant expansion in the scope of the original no exposure

provision in terms of eligibility (as noted above) and responsibilities for facilities claiming the

exemption. Under the original no exposure provision, a light industry owner/operator was expected to

make an independent determination of whether there was “exposure” of industrial materials and

activities to storm water and, if not, simply not submit a permit application. Under the proposed

conditional no exposure exemption, however, an owner/operator seeking an exemption, including

Storm Water Phase II

Proposed Rule

Fact Sheet Series

Overview

1.0 – Storm Water Phase II

Proposed Rule Overview

Small MS4 Program

2.0 – Small MS4 Storm Water

Program Overview

2.1 – Who’s Covered? Designation

and Waivers of Regulated Small

MS4s

2.2 – Urbanized Areas: Definition

and Description

Minimum Control Measures

2.3 – Public Education and

Outreach Minimum Control

Measure

2.4 – Public Participation/

Involvement Minimum Control

Measure

2.5 – Illicit Discharge Detection and

Elimination Minimum Control

Measure

2.6 – Construction Site Runoff

Control Minimum Control Measure

2.7 – Post-Construction Runoff

Control Minimum Control Measure

2.8 – Pollution Prevention/Good

Housekeeping Minimum Control

Measure

2.9 – Permitting and Reporting:

The Process and Requirements

2.10 – Federal and State-Owned

MS4s: Program Implementation

Construction Program

3.0 – Construction Program

Overview

Industrial “No Exposure”

4.0 – Conditional No Exposure

Exemption for Industrial Activity
Fact Sheet 4.0 – Conditional No Exposure Exemption for Industrial Activity Page 2

As proposed, no exposure means all industrial

materials or activities are protected by a stormresistant shelter so that they are not exposed to rain,

snow, snowmelt, or runoff. Industrial materials or

activities include, but are not limited to, material

handling equipment or activities, industrial

machinery, raw materials, intermediate products,

byproducts, or waste products, however packaged.

existing light industry owners/operators (i.e., category (xi)

facilities) claiming no exposure, would need to:

 Submit written certification that the facility meets the

definition of “no exposure” to the NPDES permitting

authority once every 5 years.

• The Phase II Proposed Rule includes a draft threepage Checklist for No Exposure Certification that

uses a series of yes/no questions to aid facility

owners/operators in determining whether they have a

condition of no exposure. The Checklist serves as the

necessary certification of no exposure if the owner/

operator is able to answer all the questions in the

negative.

• A copy of the draft Checklist can be obtained from

the U.S. EPA Office of Wastewater Management

(OWM) web site, the Storm Water Phase II Proposed

Rule published in the Federal Register, or by

contacting OWM.

 Submit a copy, upon request, of the Checklist to the

municipality in which the facility is located.

 Allow the NPDES permitting authority or, if discharging

into a municipal separate storm sewer system, the owner/

operator of the system, to (1) inspect the facility and (2)

make such inspection reports publicly available upon

request.

A regulated industrial owner/operator would need to either apply

for a permit or submit a no exposure certification in order to be in

compliance with the NPDES storm water regulations. It is

important to note that any permit held before submitting a

certification would become null and void.

Even when an industrial owner/operator certifies to no exposure,

the NPDES permitting authority would still retain the authority to

require the owner/operator to apply for an individual or general

permit if the NPDES permitting authority has determined that the

discharge is contributing to the violation of, or interfering with

the attainment or maintenance of, water quality standards,

including designated uses.

What Is The Proposed Regulatory Definition of

“No Exposure”?

The intent of the no exposure provision is to provide facilities

with industrial materials and activities that are entirely

sheltered from storm water a simplified way of complying with

the storm water permitting provisions of the Clean Water Act

(CWA). This includes facilities that are located within a larger

office building, or facilities at which the only items permanently

exposed to precipitation are roofs, parking lots, vegetated areas,

and other non-industrial areas or activities. The Phase II

proposed regulatory definition of “no exposure” follows.

The term “storm-resistant shelter,” as used in the proposed no

exposure definition, would include completely roofed and walled

buildings or structures, as well as structures with only a top cover

but no side coverings, provided materials under the structure are

not otherwise subject to any run-on and subsequent runoff of

storm water. While the intent of the proposed no exposure

provision is to promote a condition of permanent no exposure, it

would allow certain machinery, such as trucks, to pass between

buildings and, during passage, be exposed to rain and snow. 

Adequately maintained mobile equipment (e.g., trucks,

automobiles, trailers, or other such general purpose vehicles

found at the industrial site that are not industrial machinery or

material handling equipment and that are not leaking

contaminants or are not otherwise a source of industrial

pollutants) also could be exposed to precipitation or runoff. Such

activities alone would not prevent a facility from certifying no

exposure under the proposed provision. Similarly, trucks or other

vehicles awaiting maintenance at vehicle maintenance facilities

that are not leaking contaminants or are not otherwise a source of

industrial pollutants, would not be considered exposed.

In addition, EPA recognizes in the proposed rule that other

instances could occur in which permanent no exposure of

industrial activities or materials is not possible and, therefore,

under such conditions, materials and activities could be covered

with temporary covers (e.g., tarps) between periods of permanent

enclosure. The proposed rule does not specify every such

situation, but NPDES permitting authorities could address this

issue on a case-by-case basis.

For purposes of the proposed exemption, particulate matter

emissions from roof stacks/vents that are regulated by, and in

compliance with, other environmental protection programs

(i.e., air quality control programs) and that do not cause storm

water contamination would be considered not exposed. Visible

deposits of residuals (e.g., particulate matter) near roof or side

vents would be considered “exposed.” Likewise, visible “track

out” (i.e., pollutants carried on the tires of vehicles) or windblown

raw materials would be considered “exposed.” Leaking pipes

containing contaminants exposed to storm water would be

deemed “exposed,” as would past sources of storm water
Fact Sheet 4.0 – Conditional No Exposure Exemption for Industrial Activity Page 3

contamination that remain onsite. General refuse and trash, not of

an industrial nature, would not be considered exposed industrial

materials; however, industrial refuse and trash that is left

uncovered would be deemed “exposed.”

Would There Be Any Concerns Related to Water

Quality Standards?

Yes. The proposed rule specifies that actions taken to qualify

for no exposure must not interfere with the attainment or

maintenance of water quality standards, including designated

uses. Designated uses can include use as a drinking water supply

or for recreational purposes.

Many efforts to achieve no exposure would employ simple good

housekeeping and contaminant cleanup activities such as moving

materials and activities indoors into existing buildings or

structures. In limited cases, however, industrial owners/operators

may make major changes at a site to achieve no exposure. These

efforts could include constructing a new building or cover to

eliminate exposure or constructing structures to prevent run-on

and storm water contact with industrial materials and activities. 

Major changes undertaken to achieve no exposure, however,

could increase the impervious area of the site, such as when a

building with a smooth roof is placed in a formerly vegetated

area. Increased impervious area can lead to an increase in the

volume and velocity of storm water runoff, which, in turn, can

result in a higher concentration of pollutants in the discharge,

since fewer pollutants are naturally filtered out.

The concern of increased impervious area is addressed in the last

question on the draft Checklist, which asks, “Have you paved or

roofed over a large, formerly exposed, pervious area in order to

qualify for no-exposure? Please indicate approximately how

much area was paved or roofed over from the choices below.” 

The single purpose of this question is to aid the NPDES

permitting authority in assessing the likelihood of such actions

interfering with water quality standards. Completing this question

would not influence the ability to qualify for the conditional no

exposure exemption and would be used for informational

purposes only.

What Would Happen if the Condition of No

Exposure Is Not Maintained?

Under the proposal, the no exposure exemption would be

conditional and not an outright exemption. Therefore, in

cases in which there is a change in circumstances that causes

exposure of industrial activities or materials to storm water, the

owner/operator would be required to comply immediately with all

the requirements of the NPDES Storm Water Program, including

applying for and obtaining a permit.

Failure to maintain the condition of no exposure or obtain

coverage under an NPDES permit would result in the

unauthorized discharge of pollutants to waters of the United

States, which could result in penalties under the CWA. Where a

facility operator determines that exposure would occur in the

future due to some anticipated change at the facility, the operator

would need to submit an application and acquire storm water

permit coverage prior to the exposed discharge to avoid such

penalties.

Having the proposed no exposure exemption be conditional and

requiring submission of a written certification is EPA’s response

to the court’s second basis for the remand, which criticized

allowing the facility owners/operators to determine for themselves

that there was no exposure and then simply not apply for a permit

without any further action. The draft Checklist provides a greater

assurance of actual no exposure as defined by EPA, while the

conditional nature of the exemption removes the chance of

potentially harmful discharges being legally unpermitted.

For Additional Information

Contacts

 U.S. EPA Office of Wastewater Management

• Phone : 202 260-5816

• E-mail: SW2@epa.gov 

• Internet: www.epa.gov/owm/sw2.htm

 Your NPDES Permitting Authority. (A list of names

and phone numbers for each U.S. EPA Region is

included in Fact Sheet 2.9. Additional contact names,

addresses, and numbers for each State can be

obtained from the U.S. EPA Office of Wastewater

Management) 

Reference Documents

 Storm Water Phase II Proposed Rule Fact Sheet

Series.

 • Contact the U.S. EPA Water Resource Center at

202 260-7786 or at waterpubs@epa.gov 

 • Internet: www.epa.gov/owm/sw2.htm

 Storm Water Phase II Proposed Rule, published on

Jan. 9, 1998 in the Federal Register (63 FR 1536).

• Internet: www.epa.gov/owm/sw2.htm