River segments, lakes, and estuaries designated under Section 303(d) of the Clean Water Act. Each State will establish Total Maximum Daily Loads (TMDLs) for these waters. 1998 303(d) Waterbodies coded onto route.rch (Transport and Coastline Reach) feature of NHD to create Point Events. Point events are attached to a reach in NHD to represent a TMDL for many reasons: to represent an estuary, to represent a shellfish area (if state prefered to represent the TMDL in this manner) - refer to NOAA's shellfish areas for a more accurate representation (<http://www.esdim.noaa.gov/noaaserver-bin/NSdescription.pl?db=NOS&docid=0%206619%20%2fNS_metadata%2fNOAA_metadata%2fNOS%2fORCA%2fSEA%2f1_SEA_94-02.fgd&bytes=6619&type=FGDC&startdate=&enddate=&sbndgcoord=70.0&wbndgcoord=-50.0&nbndgcoord=10.0&ebndgcoord=-180.0&simple=shellfish&convert=HTML>), represent a point source discharger, or if there is no reach in NHD to represent the TMDL.
Procedures Used: State Water Quality Agencies supplied EPA's Office of Water lists of waters reported under §303(d). These lists contained text which identified the locations of individual waters on their list. Many states also submitted GIS coverages and/or maps that outlined the spatial extent of their listed waters. These base materials were used by EPA to code the spatial extent onto the route.rch (Transport and Coastline Reach) feature of NHD to create NHD - Point Events. Using the EPA NHD Reach Indexing Tool (NHD-RIT), event tables were created by conflating the state's data to NHD reaches and the reaches were attributed with the §303(d) identifiers supplied by the states. Some reaches are also displayed offset from the original reach - this is done to display each TMDL on a state's list as a separate entity. So if 2 TMDLs on a state's list are actually in the same spatial location, one is shown offset from the actual reach. Revisions: The event tables were sent to each state for review and comment. The format of the reviewed data was state dependent. Formats consisted of hardcopy maps, shapefiles or coverages with events. In some cases, modifications were noted by the State and then corrections were made by RTI. Related_Spatial_and_Tabular_Data_Sets: The EPA 1998 TMDL Tracking System contains relevant data that links to this shapefile. The ENTITY_ID field in the event table can be linked to the LIST_ID in the EPA's TMDL tracking system.
1998
Internal feature number.(Source:
ESRI)
Feature geometry.(Source:
ESRI)
| Range of values | |
|---|---|
| Minimum: | 2000010100000100001 |
| Maximum: | 999912312400009999 |
Specifies the location of the point along a route.(Source:
EPA's NHD Reach Indexing Tool)
| Range of values | |
|---|---|
| Minimum: | 0 |
| Maximum: | 200 |
Offset distance of event from associated NHD route reach location.(Source:
User input)
| Range of values | |
|---|---|
| Minimum: | 0 |
| Maximum: | 999999 |
Unique identifier of the digital update unit in the NHD database.(Source:
NHD)
| Range of values | |
|---|---|
| Minimum: | 0000000001 |
| Maximum: | 9999999999 |
Numeric code that uniquely identifies a reach in NHD, consisting of two parts: the first eight digits are the hydrologic unit code of the cataloging unit in which the reach is located; the last six digits are a sequentially, arbitrarily-assigned number.(Source:
NHD)
| Formal codeset | |
|---|---|
| Codeset name: | NHD Reach codes |
| Codeset source: | FIPS/NHD |
Date that the reach code (Rch_code) was assigned, displayed as YYYYMMDD.(Source:
NHD)
| Range of values | |
|---|---|
| Minimum: | 19970101 |
| Maximum: | 99991231 |
Indicates the attribute type or program being indexed.(Source:
UNKNOWN)
| Formal codeset | |
|---|---|
| Codeset name: | Alphanumeric |
| Codeset source: | ASCII |
Value associated with the attribute program in the field Attr_prg.(Source:
UNKNOWN)
| Formal codeset | |
|---|---|
| Codeset name: | Alphanumeric |
| Codeset source: | ASCII |
Identifier used to aggregate reaches into homogenous units. It is also used to link the event table to external data sources.(Source:
UNKNOWN)
| Formal codeset | |
|---|---|
| Codeset name: | Alphanumeric |
| Codeset source: | ASCII |
State abbreviation according to the FIPS standard.(Source:
User input)
| Formal codeset | |
|---|---|
| Codeset name: | Federal Information Processing Standard |
| Codeset source: | Two digit FIPS state code (character). |
Link to the metadata table(Source:
Unknown)
| Formal codeset | |
|---|---|
| Codeset name: | Alphanumeric |
| Codeset source: | ASCII |
Feature geometry.(Source:
ESRI)
Point event themes georeferences to the National Hydrography Dataset (NHD).
The Reach Indexing Tool for the National Hydrography Dataset (NHD-RIT) User Guide- Draft, June 2000.
EPA Headquarters Ariel Rios Building 1200 Pennsylvania Avenue, NW
To be used to identify the spatial extent of waters listed under §303(d). These waters can be linked to the 1998 §303(d) information stored in the EPA TMDL Tracking System for query and display. The ENTITY_ID field in the event table can be linked to the LIST_ID in the EPA's TMDL tracking system.
Each state sent RTI a marked-up map or existing GIS coverage denoting the location and extent of each waterbody. Using the EPA's NHD Reach Indexing Tool (NHD-RIT), event tables were created by conflating the state's data to NHD. Event identifiers were populated with the §303(d) codes supplied by each states' list.
Dataset copied.
Dataset Copied. Points lying completely within a set of southern and eastern states were selected, and converted into a shapefile. This was reprojected into GCS_WGS_84 and loaded into an ArcSDE/Oracle database.
Statements of horizontal positional accuracy are based on accuracy statements made for USGS topographic quadrangle maps. These maps were compiled to meet National Map Accuracy Standards. For horizontal accuracy, this standard is met if at least 90 percent of points tested are within 0.02 inch (at map scale) of their true positions. Additional offsets to positions may have been introduced where there are many features to improve the legibility of map symbols. In addition, the digitizing of maps is estimated to contain a horizontal positional error of less than or equal to 0.003-inch standard error (at map scale) in the two component directions relative to the source maps. Visual comparison between the map graphic (including digital scans of the graphic) and plots or digital displays of points, lines, and areas is used to assess the positional accuracy of digital data. Linear features of the same type along the adjoining edges of data sets are aligned if they are within a 0.02-inch tolerance (at map scale). To align the features, the midpoint between the end of the corresponding features is computed, and the ends of features are moved to this point. Features outside the tolerance are not moved; instead, a feature of the type connector was added to join the features. For more information, see the National Hydrography Dataset Concepts and Contents document (February 2000) available at <http://nhd.usgs.gov/chapter1/index.html#_Toc474479787>
Statements of vertical positional accuracy for elevation of water surfaces are based on accuracy statements made for USGS topographic quadrangle maps. These maps were compiled to meet National Map Accuracy Standards. For vertical accuracy, this standard is met if at least 90 percent of well-defined points tested are within one-half contour interval of the correct value. Elevations of water surface printed on the published map meet this standard; the contour intervals of the maps vary. These elevations were transcribed into the digital data; the accuracy of this transcription was checked by visual comparison between the data and the map. For more information, see the National Hydrography Dataset Concepts and Contents document (February 2000) available at <http://nhd.usgs.gov/chapter1/index.html#_Toc474479787>.
State review underway
Chain-node topology present
Unknown
Data format: |
Size: 0.856 |
|---|
4503F U.S. EPA Headquarters Ariel Rios Building 1200 Pennsylvania Avenue, NW