v>EPA
United States
Environmental Protection
Agency
Office of Water EPA 833-F-00-004
(4203) December 1999 (revised December 2005)
Fact Sheet 2.2
Storm Water Phase II
Final Rule
Storm Water Phase II
Final Rule
Fact Sheet Series
Overview
1.0-Storm Water Phase 11 Final
Rule: An 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
2.4 - Public Participation/
Involvement
2.5 - Illicit Discharge Detection
and Elimination
2.6 - Construction Site Runoff
Control
2.7 - Post-Construction Runoff
Control
2.8 - Pollution Prevention/Good
Housekeeping
2.9 - Permitting and Reporting:
The Process and Requirements
2.10 - Federal and State-Operated
MS4s: Program Implementation
Construction Program
3.0 - Construction Program
Overview
3.1 - Construction Rainfall
Erosivity Waiver
Industrial "No Exposure"
4.0 - Conditional No Exposure
Exclusion for Industrial Activity
Urbanized Areas:
Definition and Description
As discussed in Fact Sheet 2.1, Who's Covered? Designation and Waivers of Regulated
Small MS4s, the Phase II Final Rule covers all small municipal separate storm sewer
systems (MS4s) located within an "urbanized area" (UA). Based on the 2000 Census, there
are 464 UAs in the United States that cover approximately 2 percent of total U.S. land area
and contain nearly 70 percent of the Nation's population. These numbers include Puerto Rico
and the Commonwealth of the Northern Mariana Islands — the two U.S. Territories with
UAs.
UAs constitute the largest and most dense areas of settlement. UA calculations delineate
boundaries around these dense areas of settlement and, in doing so, identify the areas of
concentrated development. UA designations are used for several purposes in both the public
and private sectors. For example, the Federal Government has used UAs to calculate
allocations for transportation funding, and some planning agencies and development firms
use UA boundaries to help ascertain current, and predict future, growth areas.
What Is an Urbanized Area (UA)?
'"The Bureau of the Census determines UAs by applying a detailed set of published UA
-*- criteria (see 55 FR 42592, October 22, 1990) to the latest decennial census data.
Although the full UA definition is complex, the Bureau of the Census' general definition of a
UA, based on population and population density, is provided below.
An urbanized area is a land area comprising one or more places —
central place(s) — and the adjacent densely settled surrounding area —
urban fringe — that together have a residential population of at least
50,000 and an overall population density of at least 1,000 people per
square mile.
The basic unit for delineating the UA boundary is the census block. Census blocks are based
on visible physical boundaries, such as the city block, when possible, or on invisible political
boundaries, when not. An urbanized area can comprise places, counties, Federal Indian
Reservations, and minor civil divisions (MCDs - towns and townships).
How Can Status as a Regulated Small MS4 Be Determined?
The drawing below (see Figure 1) is a simplified UA illustration that demonstrates the
concept of UAs in relation to the Phase II Final Rule. The "urbanized area" includes
within its boundaries incorporated places, a portion of a Federal Indian reservation, an entire
MCD, a portion of another MCD, and portions of two counties. Any and all operators of small
MS4s located within the boundaries of the UA are covered under the Phase II Final Rule,
regardless of political boundaries. Operators of small MS4s located outside of the UA are
subject to potential designation into the Phase IIMS4 program by the NPDES permitting
authority.
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Fact Sheet 2.2 — Urbanized Areas: Definition and Description
Page 2
Figure 1
Central Place
f j Incorporated Place
/ \ Federal Indian Reservation (FIR)
Unincorporated "Urbanized
Area" Portion of a Town
(MCD) or County
... Urbanized Area
Town or Township as a
functioning Minor Civil Division
(MCD). An MCD is the primary
subdivision of a County.
County
Operators of small MS4s can determine if they are located
within a UA, and therefore covered by the Phase II storm
water program, by contacting one or more of the institutions
listed below for more detailed information on the location of
the UA boundary. At this time, the States and EPA have
compiled a list of municipalities to be covered under the
Phase II Rule, but the urbanized area boundaries are important
in some cases for determining the specific area within a
municipality's boundaries that is covered (e.g., a county
included in Phase II might only be required to implement their
program for the urbanized area of the county).
Q The State or NPDES Permitting Authority
(may be the State or the U.S. EPA Region)
Storm Water Coordinators: The NPDES permitting
authority may be the State or the U.S. EPA Region.
The Storm Water Coordinators for each U.S. EPA
Region are listed in the For Additional Information
section in Fact Sheet 2.9. These regional contacts can
assist with UA information and provide the names of
State storm water contacts. Regional and State contact
information can also be obtained from OWM.
State Data Centers. Each State's Data Center receives
listings of all entities that are located in UAs, as well as
detailed maps and electronic files of UA boundaries.
The Bureau of the Census web site includes a list of
contact names and phone numbers for the data in each
State at www.census.gov/sdc/www.
State Planning/Economic/Transportation Agencies:
These agencies typically use UAs to assess current
development and forecast future growth trends and,
therefore, should have detailed UA information readily
available to help determine the UA boundaries in any
given area.
Q County or Regional Planning Commissions/
Boards
As with State agencies, these entities are likely to have
detailed UA data and maps to help determine UA
boundaries.
Q U.S. EPA
NPDES Web Site. EPA has developed a set of digitized
maps for each urbanized area as defined by the 2000
U.S. Census. These maps are organized by state and
are available at
http://www.epa.gov/npdes/stormwater/urbanmaps.
Enviromapper Web Site. EPA modified a Web-based
geographic program called Enviromapper. This allows
MS4 operators to enter a location and see a detailed
map of the UA boundary (called "city boundaries").
Enviromapper can be accessed at
http://www.epa.gov/enviro/html/em/index.html.
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Fact Sheet 2.2 — Urbanized Areas: Definition and Description
Page 3
Q The Bureau of the Census
Urbanized Areas Staff: 301-457-1099
Web Site: The site allows users to obtain free UA
cartographic boundary files (Arc/Info export format) for
Geographical Information System (GIS) use at
http://www.census.gov/geo/www/ua/uaucbndv.html.
Also, detailed UA maps are available to download in
PDF for printing in large format. Each map is intended
to be printed on a 36- by 33-inch sheet. For a listing of
UAs for download, visit
http ://www. census, gov/geo/www/ maps/ua2kmaps. htm.
How Will Subsequent Censuses Affect the
Determination of Status as a Regulated Small
MS4?
Any additional automatic designations of small MS4s based
on subsequent census years is governed by the Bureau of the
Census' definition of a UA in effect for that year and the UA
boundaries determined as a result of the definition.
Once a small MS4 is designated into the Phase II storm water
program based on the UA boundaries, it can not be waived
from the program if in a subsequent UA calculation the small
MS4 is no longer within the UA boundaries. An
automatically designated small MS4 will remain regulated
unless, or until, it meets the criteria for a waiver (see Fact
Sheet 2.1 for more information on the regulated small MS4
waiver option).
For Additional Information
Contacts
"^ U.S. EPA Office of Wastewater Management
http://www.epa.gov/npdes/stormwater
Phone: 202-564-9545
"^ Your NPDES Permitting Authority. Most States and
Territories are authorized to administer the NPDES
Program, except the following, for which EPA is the
permitting authority:
Alaska
District of Columbia
Idaho
Massachusetts
New Hampshire
New Mexico
American Samoa
Guam
Johnston Atoll
Midway and Wake Islands
Northern Mariana Islands
Puerto Rico
Trust Territories
"^ A list of names and telephone numbers for each EPA
Region and State is located at http ://www. epa. gov/
npdes/stormwater (click on "Contacts").
Reference Documents
"^ EPA's Stormwater Web Site
http://www.epa.gov/npdes/stormwater
• Stormwater Phase II Final Rule Fact Sheet Series
• Stormwater Phase II Final Rule (64 FR 68722)
• National Menu of Best Management Practices
for Stormwater Phase II
• Measurable Goals Guidance for Phase II Small
MS4s
• Stormwater Case Studies
• EPA Urbanized Area Maps: http://www.epa.gov/
npdes/stormwater/urbanmaps
"^ Census 2000 Urbanized Area Information
• General Information: http://www.census.gov/
geo/www/ua/uaucbndv.html
• Maps: http://www.census.gov/geo/www/maps/
ua2kmaps.htm
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