United States
Environmental Protection
Agency
Off ice of Water
4606
EPA816-R-98-004
August 1998
P/EPA
Requirements for Locational Data in
the Safe Drinking Water Information
System (SDWIS)
Well Location:
40°5'8"N 75°19'20"W
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Contents
Page
INTRODUCTION 1
USE OF LOCATIONAL DATA 1
REQUIRED LOCATIONAL DATA ELEMENTS 2
SDWIS DATA TRANSFER FORMAT (DTF) ANALYSIS 6
IMPLEMENTATION SCHEDULE 6
SUMMARY 6
APPENDIX A -
Proposed Locational Data Element Definitions and Attributes Mandatory 7
APPENDIX B -
Proposed Locational Data Element Definitions and Attributes Optional 9
SCHEMATICS 11 and 12
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Locational Data Guidance August 1998
INTRODUCTION
EPA, in recognizing the critical need for locational data, established a Locational Data Policy
on May 17, 1990. It mandates the collection of accurate geographic data for all "facilities,
sites, and monitoring and observation points regulated or tracked under federal
environmental programs within the jurisdiction of the EPA." On April 8, 1991 the Deputy
Administrator signed the Agency's Locational Data Policy (LDP), IRM Policy Manual 2100
Chapter 13, requiring geographic coordinates and associated method, accuracy, and
description codes (MAD) for all environmental measurements collected by EPA employees,
contractors and grantees. A key premise of this policy is that secondary use of these data in
geographic information systems (GIS) and statistical mapping programs are significant to the
overall mission of the Agency. To facilitate the integration of data into these systems, coding
of geographic coordinates and associated attributes must be standardized.
In November 1994 EPA released the information coding standards for the method, accuracy
and description codes for the locational data policy (Appendices A and B). These data
standards have been revised during the development of the EPA Envirofacts Warehouse
Locational Reference Tables (LRT), the Environmental Data Registry (EDR) effort, and
related regional work.
An early notice of these locational data requirements was given to state drinking water
administrators and regional coordinators by the Director of the Office of Ground Water and
Drinking Water (OGWDW) in April 1997 (Early Notice on Revised Safe Drinking Water
Information System (SDWIS) Inventory Reporting Requirements, Cynthia Dougherty,
Director, April 11, 1997). That notice was designed to provide information on tentative new
reporting requirements so that states can use this information for planning purposes.
The "Revised Safe Drinking Water Information System (SDWIS) Inventory Reporting
Requirements - Technical Guidance" issued on July 10, 1998 includes the technical guidance
to implement locational data requirements and other revisions, additions and new reporting
requirements for states under the Safe Drinking Water Act. This document was developed in
parallel to this technical guidance and separated from the revised inventory reporting
requirements.
USE OF LOCATIONAL DATA
Locational data in this document are the latitude and longitude (lat/long) coordinates and the
six required and eight recommended/optional method, accuracy, and description codes
required under EPA's Locational Data Policy. There are many uses and needs for these data.
A few of the more significant examples are presented in Exhibit 1.
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Locational Data Guidance
August 1998
The LDP recognizes that latitude and
longitude (lat/long) coordinates and
auxiliary data may not have been
collected retrospectively and
therefore does not require it.
However, it is suggested that data
that have been collected in the past be
submitted if the state has confidence
in its quality. The policy also
recognizes the variance in
technologies available to capture
locational data and thereby establishes
an accuracy goal of 25 meters.
Global Positioning Systems (GPS) is
the recommended technology of use
to achieve this degree of accuracy;
however, where less accurate data
collection methods, such as address
matching, zip code centroid, map
interpolation and photo interpolation
were used, the lat/long data can still
be of use for certain purposes. When
more accurate lat/long data are
collected, the older data should be
replaced with the more accurate data.
These determinations can only be
made by the users of the data.
Therefore, EPA has developed this
guidance to help apply the locational
data policy.
REQUIRED LOCATIONAL
DATA ELEMENTS
There are many uses and needs for lat/long data. A
few of the more significant examples are:
• Latitudes and longitudes of public water supplies
(PWSs) are essential to effectively share data with
other federal, state and local agencies. The
benefits to be realized from this type of data
sharing are generally thought to outweigh the
cost and any other disadvantage of reporting.
• Locational data are needed in conjunction with
monitoring data for analysis of contaminant
occurrence to decide on applicability of
regulating given chemicals and for regulation
development and verification. The need for this
information is critical to successfully implement
the various mandated activities in the 1996
SDWA amendments, including the national
occurrence database, and making the decision on
which chemicals to regulate.
• Latitude and longitude data are essential to utilize
geographic information systems (GIS). The
development of GIS capabilities has continued to
expand and the number of real-world practical
applications now available makes investing in
this technology more worthwhile.
• Locational data can be used to target areas for
enforcement/compliance assistance based on
multiple environmental concerns. The data also
can be used for siting facilities in watersheds for
the purpose of conducting source water
assessments and other watershed assessment
activities.
Exhibit 1: The Need for Latitude/Longitude Data.
The latitude and longitude coordinates and the six method, accuracy and description (MAD)
codes under the 1994 Information Coding Standards (ICS) are to be reported for all active
sources of water for all community and nontransient, noncommunity water systems (See
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Locational Data Guidance August 1998
Exhibit 2).1 This translates most commonly into all active water supply wells (wellhead) and
surface water intakes.
In addition, the EPA Facility Identification Initiative (FII) _, ,. „ . „,„_ .
' J ^ ' The following WSF types are
Interim Data Standard (EPA Order 2180.3) requires and
the locational data policy suggests that the physical
location (1 at/long coordinates or address) of the water
treatment plant(s) also be obtained. Therefore either the
latitude/longitude of the treatment plants, OR the physical
address needs to be reported as part of the Core Data Set
in SDWIS/FED.2
WL (Well)
Under the FII, EPA has developed a multi-relational
considered to be sources of water:
• CC (Consecutive Connection)
IN (Intake)
RC (Roof Catchment)
SP (Spring)
IG (Infiltration Gallery)
NP (Non-Piped)
RS (Reservoir)
entity "facility" concept to accommodate complex Exhibit 2: Various WSF Types
facilities such as PWSs that may or may not be Considered to be Sources of Water
geographically contiguous and may require multiple
environmental permits. EPA, through Envirofacts, will assign a facility identifier to all
PWSs. When a PWS owns treatment facilities, which are not geographically contiguous with
the PWS, an additional FII number will be assigned to each treatment facility. Since the
number will be assigned and maintained by EPA, the states are not required to submit this
information to SDWIS/FED under any of the time frames found in this document. The FII
requirements as they pertain to the drinking water program have not been finalized, so this
guidance document attempts to establish reporting requirements that will satisfy the general
initiative while at the same time not adding significantly to the SDWIS/FED reporting
requirements. States will be notified of this requirement at a later time. The FII information
contained in this document is for information only at this time.
The required locational data fields and their definitions are the following:
1. Latitude - The measure in decimal degrees of the angular distance on a meridian
north or south of the equator.
JWater System Facility (WSF) data includes such entities as sources of water (wells and
intakes), treatment plants, entry points and storage tanks.
2For more information the reader is directed to Section 4 of the full Reporting Guidance
issued on July 10, 1998. To meet the minimum reporting requirements of the Core Data Set, the
following WSF information must be reported: all active sources of water for all PWSs; the
treatment data associated to these sources; and the locational coordinates of these sources.
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Locational Data Guidance August 1998
2. Longitude - The measure in decimal degrees of the angular distance on a meridian
east or west of the prime meridian.
3. Method of Collection - The text or code that describes or identifies the method used
to determine the latitude and longitude coordinates for a point on the earth [address
matching; GPS, map interpolation].
4. Accuracy Value & Unit - The measure of accuracy (in meters) of the latitude and
longitude. Given in a range of+/- meter units.
5. Description Category - The text or code that identifies or represents the place for
which the geographic coordinates were established [plant entrance; well; intake;
center of facility].
6. Horizontal Datum - The name or code that describes or represents the reference
datum used in determining latitude and longitude coordinates [NAD27; NAD83;
Unknown].
7. Source Scale - The number that represents the proportional distance on the ground
for one unit of measure on the map or photo [1:24,000; 1:250,000; etc.].
8. Point-Line-Area - The name or code that identifies or represents the geometric
entity represented by one point or sequence of latitude and longitude points.
The information coding standards (ICS) for these elements area found in Appendix A. It
should be noted that if the locational feature is a polygon (e.g. treatment plant or well field)
or linear (a series of intakes in close proximity) under required element number (8) above,
then the optional element Data-Point-Sequence is required.
The recommended/optional data elements and their definitions are the following:
1. Date of Collection - The calendar date when data were collected.
2. Source - The name or code of the party responsible for providing the latitude and
longitude coordinates [state FIPS code; region; contractor, etc.].
3. Description Comments - The text that provides additional information about the
geographic coordinates [150-length character field to give more detail on the facility
described; the data collection; or post-processing].
4. Vertical Measure - The measure of elevation (i.e. altitude) in meters above or below
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Locational Data Guidance August 1998
a reference datum [e.g. measuring point of a well; intake point; ground surface at
sampling point].
5. Vertical Measure Method of Collection - The text or code that describes or
represents the method used to collect the vertical measure of a reference point
[several types of GPS measurements; trigonometric leveling; surveying techniques].
6. Vertical Measure Accuracy - The measure of accuracy (in meters) of the vertical
measure of a reference point. Given in a range of +/- meter units.
7. Vertical Datum - The name or code of the reference datum used to determine the
vertical measure [NAVD88; MSL; Unknown].
8. Verification - The text or code that describes or represents the process used to verify
the latitude and longitude coordinates [point in polygon(county); ground truth
conducted; verified relative to map features].
The information coding standards (ICS) for these elements are found in Appendix B.
The ICS are still undergoing some revisions, so even though these "standards" are proposed,
this guidance establishes the requirements under the 1991 policy and the 1994 release of the
method, accuracy and description codes. Some additional revisions are anticipated during
future development of the EPA Envirofacts Warehouse Locational Reference Tables (LRT),
the Environmental Data Registry (EDR) effort, and related regional work. Other agency
programs like the Reinventing Environmental Information (REI) are designed to improve
data quality and integration and may result in further changes to the data standards at a later
time.
A water treatment plant can generally be considered the facility(s) at which a variety of
treatment processes take place to remove contaminants from source water. Individual
treatment processes may be used in a "treatment train" to remove unwanted contaminants or
decrease the contaminant concentration. The most commonly used processes include
filtration, coagulation and flocculation, sedimentation, and disinfection. Some small treatment
systems may not contain any of these processes or may have only disinfection before
distribution.
Examples of the required assignment of latitude and longitude coordinates to facilities of
PWSs are given in the two attached schematics.
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Locational Data Guidance August 1998
SDWIS DATA TRANSFER FORMAT (DTF) ANALYSIS
A technical appendix is available to provide the technical detail for reporting locational
information in data transfer format to SDWIS/FED. This appendix is an analysis of SDWIS
for modifying the DTF to fully support the reporting of the latitude and longitude coordinates
and the MAD codes. This Appendix outlines the descriptions, formats, and permitted values
for each of the above locational data elements and provides examples as to the data element
values. The DTF supports the reporting of latitude and longitude data in either the
traditional degrees/minutes/seconds format or the decimal degrees format. SDWIS/FED will
store in its database the latitude and longitude data in the format in which it is reported as
well as convert the input into the other format.
IMPLEMENTATION SCHEDULE
The following implementation schedule dates apply to the reporting requirements for
locational data.
* Community Water Systems January 1,2000
(CWS)
* Nontransient, noncommunity water systems 20% of the data are due by
(NTNCWS) January 1, 2001 and 20% more
per year until January 1, 2005
* Transient, noncommunity water systems Currently a Data Sharing Goal
(TNCWS)
States are encouraged to submit data for transient systems even though this is a goal at this
time. States are also encouraged to submit locational data before the scheduled due dates
above.
SUMMARY
The use of geographic data is critical to many of the activities in the OGWDW and the
interrelationship among many of EPA's media programs. The geo-referencing of data is
necessary for cooperation among federal and state environmental programs and critical for
effectively linking and sharing data across all programs and information management systems.
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Locational Data Guidance
August 1998
Appendix A
Proposed Locational Data Elements Definitions and Attributes
June
1998
MAD Codes
EDR Data
Elements
Proposed Definitions
Length
Code
Set
Mandatory
Latitude
Longitude
Method of
collection
Accuracy Value
and Unit
Description
Category
Horizontal Datum
Latitude Measure
(DE 5518:1)
Longitude
Measure (DE
5520:1)
Horizontal
Collection Method
Text (DE 573 1:1)
The measure of the angular distance
on a meridian north or south of the
equator.
The measure of the angular distance
on a meridian east or west of the
prime meridian.
The test that describes the method
used to determine the latitude and
longitude coordinates for a point on
the earth.
10
11
40
No
No
Yes
Textual Data or Code Data for this Element
Horizontal
Collection Method
Code (DE 5238:1)
Horizontal
Accuracy Measure
(DE 5264:1)
Reference Point
Text (DE 5288:1)
The code that represents the method
used to determine the latitude and
longitude coordinates for a point on
the earth.
The measure of the accuracy (in
meters) of the latitude and longitude
coordinates.
The text that identifies the place for
which geographic coordinates were
established.
3
6
50
Yes
No
Yes
Textual Data or Code Data for this Element
Reference Point
Code (DE 5608:1)
Horizontal
Reference Datum
Name (DE
5292:1)
The code that represents the place
for which geographic coordinates
were established.
The name that describes the
reference datum used in
determining latitude and longitude
coordinates
3
7
Yes
Yes
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Locational Data Guidance
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MAD Codes
Source Scale
Point-Line-Area
EDR Data
Elements
Proposed Definitions
Length
Code
Set
Textual Data or_Code Data for this Element
Horizontal
Reference Datum
Code (DE 5308:1)
Source Map Scale
Number (DE
5318:1)
Geometric Type
Name (DE
5761:1)
The code that represents the
reference datum used in
determining latitude and longitude
coordinates.
The number that represents the
proportional distance on the ground
for one unit of measure on the map
or photo.
The name that identifies the
geometric entity represented by one
point or a sequence of latitude and
longitude points.
3
19
6
Yes
No
Yes
Textual Data or Code Data for this Element
Geometric Type
Code (DE 5614:1)
The code that represents the
geometric entity represented by one
point or a sequence of latitude and
longitude points.
3
Yes
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Locational Data Guidance
August 1998
Appendix B
Proposed Locational Data Elements Definitions and Attributes
June
1998
MAD Codes
EDR Data
Elements
Proposed Definitions
Length
Code
Set
Optional
Date of Collection
Source
Description
Comments
Vertical Measure
Vertical Measure
Method of
Collection
Vertical Measure
Accuracy
Data Collection
Date (DE 5296:1)
Coordinate Data
Source Name (DE
5322:1)
The calendar date when data were
collected.
The name of the party responsible
for providing the latitude and
longitude coordinates.
8
35
No
Yes
Textual Data or Code Data for this Element
Coordinate Data
Source Code (DE
5310:1)
Location
Comments (DE
5616:1)
Vertical Measure
(DE 5612:1)
Vertical Collection
Method Text (DE
5326:1)
The code that represents the party
responsible for providing the
latitude and longitude coordinates.
The text that provides additional
information about the geographic
coordinates.
The measure of elevation (i.e., the
altitude), in meters, above or below
a reference datum.
The text that describes the method
used to collect the vertical measure
(i.e., the altitude) of a reference
point.
3
150
10
41
Yes
No
No
Yes
Textual Data or Code Data for this Element
Vertical Collection
Method Code (DE
5314:1)
Vertical Measure
Accuracy (DE
5312:1)
The code that represents the method
used to collect the vertical measure
(i.e., the altitude) of a reference
point.
The measure of the accuracy (in
meters) of the vertical measure (i.e.,
the altitude) of a reference point.
2
8
Yes
No
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Locational Data Guidance
August 1998
MAD Codes
Vertical Datum
Verification
EDR Data
Elements
Vertical Reference
Datum Name (DE
5324:1)
Proposed Definitions
The name of the reference datum
used to determine the vertical
measure (i.e., the altitude).
Length
17
Code
Set
Yes
Textual Data or Code Data for this Element
Vertical Reference
Datum Code (DE
5306:1)
Verification
Method Text (DE
5737:1)
The code that represents the
reference datum used to determine
the vertical measure (i.e., the
altitude).
The text that describes the process
used to verify the latitude and
longitude coordinates.
2
40
Yes
Yes
Textual Data or Code Data for this Element
Verification
Method Code (DE
5268:1)
The code that represents the process
used to verify the latitude and
longitude coordinates.
2
Yes
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Locational Data Guidance
August 1998
Your Town
USA
PopuMioa;
s: 6
a residents
Lagind
Coifdinitis
B -
Ciordinatis
C - &. treatment
Well
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Locational Data Guidance
August 1998
Your Town
USA
43
ConnBctiont; 15
1
2 Tresttntrf
1 Tar* - 1 .5
3
1
R. U. A. Trailer Court
(consecutive connection]
Legend
A-CWS
B-NTNOnS
C - TNCWS1
Wei
Well
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