United States Office of Water EPA 833-F-99-001

Environmental Protection (4203) April 1999

Agency Fact Sheet 1.0

Storm Water Phase II

Proposed Rule

An Overview

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 Phase II of EPA’s Storm Water Program Necessary?

Since the passage of the Clean Water Act (CWA), the quality of our Nation’s waters has improved

dramatically. Despite this progress, however, degraded waterbodies still exist. According to the

1996 National Water Quality Inventory (Inventory), a biennial summary of State surveys of water

quality, approximately 40 percent of surveyed U.S. waterbodies are still impaired by pollution and do

not meet water quality standards. A leading source of this impairment is polluted runoff. In fact,

according to the Inventory, 50 percent of impaired rivers are affected by urban/suburban and

construction sources of storm water runoff.

Phase I of the U.S. Environmental Protection Agency’s (EPA) storm water program was promulgated

in 1990 under the CWA. Phase I relies on National Pollutant Discharge Elimination System

(NPDES) permit coverage to address storm water runoff from: (1) “medium” and “large” municipal

separate storm sewer systems (MS4s) generally serving populations of 100,000 or more people,

(2) construction sites greater than 5 acres, and (3) ten categories of industrial sources.

The Storm Water Phase II Proposed Rule, published on January 9, 1998, is the next step in EPA’s

effort to preserve, protect, and improve the Nation’s water resources from polluted storm water

runoff. The Phase II proposed program would expand the existing Phase I program by requiring

additional owners and operators of MS4s in urbanized areas and construction sites, through the use

of NPDES permits, to implement programs and practices to control polluted storm water runoff. See

Fact Sheets 2.0 and 3.0 for overviews of the proposed Phase II programs for MS4s and construction

activity.

Phase II is intended to further reduce adverse impacts to water quality and aquatic habitat by

instituting the use of controls on the still unregulated sources of storm water discharges that have the

greatest likelihood of causing continued environmental degradation. The environmental problems

associated with discharges from MS4s in urbanized areas and discharges resulting from construction

activity are outlined below.

MS4s in Urbanized Areas

Discharges from MS4s in urbanized areas are a concern because of the high concentration of

pollutants found in these discharges. Concentrated development in urbanized areas results in a

proliferation of surfaces, such as city streets, driveways, parking lots ,and lawns, on which pollutants

from concentrated human activities settle and remain until a storm event washes them into nearby

storm drains. Common pollutants include pesticides, fertilizers, oils, salt, litter and other debris, and

sediment. Another concern is the possible illicit connections of sanitary sewers, which can result in

fecal coliform bacteria entering the storm sewer system. Storm water runoff picks up and transports

these and other harmful pollutants then discharges them – untreated – to waterways via storm sewer

systems. When left uncontrolled, these discharges can result in fish kills, the destruction of spawning

habitats, a loss in aesthetic value, and contamination of drinking water supplies and recreational

waterways that can threaten public health.

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 1.0 – Storm Water Phase II Proposed Rule: An Overview Page 2

Construction Activity

Uncontrolled runoff from construction sites is a water quality

concern because of the devastating effects that sedimentation can

have on local waterbodies, particularly small streams. Numerous

studies have shown that the amount of sediment transported by

storm water runoff from construction sites with no controls is

significantly greater than from sites with controls. In addition to

sediment, construction activities yield pollutants such as

pesticides, petroleum products, construction chemicals, solvents,

asphalts, and acids that can contaminate storm water runoff. 

During storms, construction sites may be the source of sedimentladen runoff, which can overwhelm a small stream channel’s

capacity, resulting in streambed scour, streambank erosion, and

destruction of near-stream vegetative cover. Where left

uncontrolled, sediment-laden runoff has been shown to result in

the loss of in-stream habitats for fish and other aquatic species,

an increased difficulty in filtering drinking water, the loss of

drinking water reservoir storage capacity, and negative impacts on

the navigational capacity of waterways.

What Is the Difference Between the Phase II

Proposed Rule and the Interim Phase II Rule?

The Phase II Proposed Rule, when final, will supersede the

interim Phase II storm water rule published on August 7,

1995 (60 FR 40230), which requires all unregulated (non-Phase I)

storm water dischargers to apply for NPDES permit coverage by

August 7, 2001. The Phase II Proposed Rule would narrow the

universe of covered dischargers and extend their deadline for

NPDES permit coverage to 3 years and 90 days from the

publication of the rule (expected in November 1999). 

Would Municipally Owned or Operated Sources

Exempted by the Intermodal Surface

Transportation Efficiency Act (ISTEA) of 1991 Be

Affected by the Proposed Rule?

Provisions within ISTEA temporarily exempted Phase I

industrial activities owned or operated by municipalities with

populations less than 100,000 people (with the exception of

power plants, airports, and uncontrolled sanitary landfills) from

the need to apply for or obtain a storm water discharge permit. 

Congress extended the permitting moratorium for these facilities

to allow small municipalities additional time to comply with

NPDES requirements. The interim Phase II rule set a deadline of

August 7, 2001, for these facilities to submit a permit application,

thereby ending this temporary exemption. The Phase II Proposed

Rule would maintain this deadline for all ISTEA-exempted

municipally owned or operated industrial activities (e.g.,

treatment works treating domestic sewage with a design flow of

1.0 mgd or more, or those required to have an approved

pretreatment program) to be covered under an NPDES storm

water permit.

How Was the Phase II Proposed Rule Developed?

EPA developed the Phase II Proposed Rule during extensive

consultations with a cross-section of interested stakeholders

brought together on a subcommittee chartered under the Federal

Advisory Committee Act, and with representatives of small

entities participating in an advisory process mandated under the

Small Business Regulatory Enforcement Fairness Act. EPA

considered and attempted to address the primary concerns of

the participating State, Tribal, municipal, industrial, and

environmental representatives in the proposed preamble and rule

language.

Why Does Part of the Phase II Proposed Rule Use a

Question and Answer Format?

The provisions pertaining to owners or operators of small

MS4s were written in a “readable regulation” form that uses

the “plain language” method. Questions and answers are used to

create more reader-friendly and understandable regulations. The

plain language method uses “must” instead of “shall” to indicate a

requirement and words like “should,” “could,” or “encourage” to

indicate a recommendation or guidance. Also, the readable

regulation format allows guidance to be included with rule

requirements. Such guidance is enclosed in parentheses and

directly follows the requirements it explains. 

Who Would Be Covered by the Phase II Proposed

Rule?

The proposal would automatically cover two classes of storm

water dischargers on a nationwide basis:

(1) Owners or operators of small MS4s located in

“urbanized areas” as defined by the Bureau of the

Census. A “small” MS4 is any MS4 not already

covered by Phase I of the NPDES storm water program. 

See Fact Sheets 2.1 and 2.2 for more information on

small MS4 coverage.

(2) Owners or operators of construction activities that

disturb equal to or greater than 1 (one) and less than

5 (five) acres of land. See Fact Sheet 3.0 for more

information on construction activity coverage.

Waivers

Phase II dischargers designated on a nationwide basis would be

eligible to certify for a waiver from the Phase II program

requirements if they meet the necessary criteria. See Fact Sheets

2.1 (small MS4 waiver) and 3.0 (construction waivers) for details.
Fact Sheet 1.0 – Storm Water Phase II Proposed Rule: An Overview Page 3

Additional Designations by the Permitting Authority

Small MS4s located outside of urbanized areas and construction

activity disturbing less than 1 acre, as well as any non-Phase I

industrial sources, could be designated for coverage by the

NPDES permitting authority on a case-by-case basis where

watershed plans, total maximum daily loads (TMDLs) analyses,

or other local water quality assessments identify a need to control

these sources of storm water runoff. See Fact Sheet 2.1 for more

information on the proposal to require evaluation, and potential

designation, of certain small MS4s located outside of urbanized

areas.

What Would Be Required by the Phase II Proposed

Rule?

Owners or operators of Phase II-designated small MS4s and

construction activity would be required to apply for NPDES

permit coverage, most likely under a general rather than

individual permit, and to implement storm water discharge

management controls, commonly referred to as best management

practices (BMPs). Specific requirements proposed for each type

of discharge are listed below.

 A regulated small MS4 owner or operator would need to

develop and implement a storm water management

program designed to reduce the discharge of pollutants

from their MS4 to the “maximum extent practicable” and

to protect water quality. The proposal assumes the use

of narrative, rather than numeric, effluent limitations in

the form of measurable goals.

 The small MS4storm water management program would

need to include the following six minimum control

measures: public education and outreach; public

participation/ involvement; illicit discharge detection and

elimination; construction site runoff control; postconstruction runoff control; and pollution

prevention/good housekeeping. See Fact Sheets 2.3

through 2.8 for more information on each measure,

including BMPs and measurable goals.

 A regulated small MS4 owner or operator would need to

include their selection of BMPs and measurable goals

for each minimum measure in their permit application. 

The evaluation and assessment of those chosen BMPs

and measurable goals would then need to be included in

periodic reports to the NPDES permitting authority. See

Fact Sheet 2.9 for more information on permitting and

reporting.

 The specific requirements for storm water controls on

Phase II construction activity would be defined by the

NPDES permitting authority on a State-by-State basis.

 It is anticipated that NPDES permitting authorities would

use their existing Phase I general permits for construction

activity as a guide for their Phase II permits. If this

occurs, a storm water pollution prevention plan would

likely need to be developed for each construction site. 

See Fact Sheet 3.0 for more information on potential

program requirements and appropriate BMPs for Phase II

construction activity.

What Is the Proposed Phase II Program Approach?

The proposed Phase II program, based on the use of federally

enforceable NPDES permits:

 Encourages the use of general permits;

 Provides flexibility for regulated owners and operators

to determine the most appropriate storm water controls;

 Allows for the recognition and inclusion of existing

NPDES and non-NPDES storm water programs in 

Phase II permits;

 Includes public education and participation efforts as

primary elements of the small MS4 program;

 Attempts to facilitate and promote watershed planning

and to implement the storm water program on a

watershed basis; and

 Works toward a unified and comprehensive storm water

program with the existing NPDES Storm Water Phase I

program.

How Would the Phase II Proposed Rule Address

the Phase I Industrial “No Exposure” Provision?

I

n addition to the designation of two classes of new sources,

Phase II addresses the “no exposure” provision originally

included in the 1990 regulations for Phase I of the NPDES storm

water program (see 40 CFR 122.26(b)(14)). This provision was

remanded to EPA for further rulemaking and, subsequently,

included in its revised form in the Phase II proposal.

Small MS4s

Construction Activity 
Fact Sheet 1.0 – Storm Water Phase II Proposed Rule: An Overview Page 4

Under the proposal, a conditional no exposure exemption would

be made available to owners or operators of all categories

of Phase I regulated industrial activity (except category (x)

construction activity and facilities individually designated by the

NPDES permitting authority) who can certify that industrial

materials, material handling operations, and industrial processes

are not exposed to storm water. The proposal includes a No

Exposure Certification Checklist that is intended to be submitted

to the NPDES permitting authority for approval. See Fact Sheet

4.0 for more information on the no exposure exemption.

What Is the Proposed Phase II Program

Implementation “Tool Box?”

EPA is committed to providing tools to facilitate

implementation of the final Phase II storm water program in

an effective and cost-efficient manner. The “tool box” is

expected to include the following components:

 Fact Sheets;

 Guidance Documents;

 Information Clearinghouse/Web Site;

 Training and Outreach Efforts;

 Technical Research; and

 Support for Demonstration Projects.

EPA plans to have a preliminary working toolbox in place by the

time the final Phase II rule is published. Three years after

publication of the final rule, when the general permits are issued,

a fully operational tool box is scheduled to be available.

In addition to these tools, the American Public Works Association

(APWA) currently is conducting introductory workshops on the

Storm Water Phase II Proposed Rule. For more information on

workshop dates, locations, and registration, call APWA at 202

393-2792, or visit: www.apwa.net/education/edu-3202.htm. 

What Is the Proposed Phase II Schedule?

 The final Phase II rule is scheduled for publication in the

Federal Register in November 1999.

 The Conditional No Exposure Exemption option would be

available immediately upon publication of the final rule.

 The NPDES permitting authority would issue general

permits for Phase II-designated small MS4s and

construction activity within 3 years from the date of

publication of the final rule.

 Owners or operators of Phase II-designated small MS4s

and construction activity would obtain permit coverage

within 3 years and 90 days of publication of the final rule.

 The regulated small MS4s would fully implement their

storm water management programs by the end of the first

permit term, typically a 5-year period.

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 telephone numbers for each U.S. EPA Region is

included in Fact Sheet 2.9. This list, including State

storm water contacts, can be obtained by contacting

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