Ground Water Quality Classifications is a polygon feature-based layer compiled at 1:24,000 scale that includes water quality classification information for groundwaters for all areas of the State of Connecticut. Ground Waters means waters flowing through earth materials beneath the ground surface and the Ground Water Quality Classifications is a designation of the use of the ground waters. The Ground Water Quality Classifications is based primarily on the Adopted Water Quality Classifications Map sheets with information collected and compiled from 1986 to 1997 by major drainage basin. The maps were hand-drawn at 1:50,000-scale in ink on Mylar which had been underprinted with a USGS topographic map base. The digital layer includes ground water water quality classifications. It does not include water quality classifications for ground waters below surface waterbodies. Surface Water Quality Classifications are defined separately in a set of data layers comprised of line and polygon features. The Ground Water Quality Classifications and the Surface Water Quality Classifications are usually presented together as a depiction of water quality classifications in Connecticut. The Ground Water Quality Classes are GA, GAA, GAAs, GB and GC. Classes GAA and GA designate areas of existing or potential drinking water. All ground waters not otherwise classified are considered as Class GA. Class GAAs is for ground water that is tributary to a public water supply reservoir. Class GB is used where ground water is not suitable for drinking water. Class GC is used for assimilation of permitted discharges. Modified classes GA-Impaired, GAA-Impaired, GAA-Well-Impaired, GAA-Well and GA-NY are found in the data layer to categorize special cases of GA or GAA that may not be meeting the goal (impaired), surround public water supply wells (Well) or contribute to a public water supply watershed for another state (NY). There are three elements that make up the Water Quality Standards which is an important element in Connecticut's clean water program. The first of these is the Standards themselves. The Standards set an overall policy for management of water quality in accordance with the directive of Section 22a-426 of the Connecticut General Statutes. In simple terms the policies can be summarized by saying that the Department of Energy and Environmental Protection shall: Protect surface and ground waters from degradation, Segregate waters used for drinking from those that play a role in waste assimilation, Restore surface waters that have been used for waste assimilation to conditions suitable for fishing and swimming, Restore degraded ground water to protect existing and designated uses, Provide a framework for establishing priorities for pollution abatement and State funding for clean up, Adopt standards that promote the State's economy in harmony with the environment. The second element is the Criteria, the descriptive and numerical standards that describe the allowable parameters and goals for the various water quality classifications. The final element is the Classification Maps that show the Class assigned to each surface and groundwater resource throughout the State. These maps also show the goals for the water resources, and in that manner provide a blueprint and set of priorities for Connecticut's efforts to restore water quality. Although federal law requires adoption of Water Quality Standards for surface waters, Water Quality Standards for ground waters are not subject to federal review and approval. Connecticut's Standards recognize that surface and ground waters are interrelated and address the issue of competing use of ground waters for drinking and for waste water assimilation. These Standards specifically identify ground water quality goals, designated uses and those measures necessary for protection of public and private drinking water supplies; the principal use of Connecticut ground waters. These three elements comprise the Water Quality Standards and are adopted using the public participation procedures contained in Section 22a-426 of the Connecticut General Statutes. The Standards, Criteria and Maps are reviewed and revised roughly every three years. Any change is considered a revision requiring public participation. The public participation process consists of public meetings held at various locations around the State, notification of all chief elected officials, notice in the Connecticut Law Journal and a public hearing. The Classification Maps are the subject of separate public hearings which are held for the adoption of the map covering each major drainage basin in the State. The Water Quality Standards and Criteria documents are available on the DEEP website, www.ct.gov/deep. The Ground and Surface Water Quality Classifications do not represent conditions at any one particular point in time. During the conversion from a manually maintained to a digitally maintained statewide data layer the Housatonic River and Southwest Coastal Basins information was updated. The publication date of the digital data reflects the official adoption date of the most recent Water Quality Classifications. Within the data layer the adoption dates are: Housatonic and Southwest Basins - March 1999, Connecticut and South Central Basins - February 1993, Thames and Southeast Basins - December 1986. This data is updated.
Additional information on Water Quality Standards and Classification is available on the DEP website at www.ct.gov/dep/wqsc.
publication date
Ground Water Quality Classifications represented as polygon features. Water polygon features such as lakes, ponds and streams were removed from the classifications areas and have no attributes. The polygon attribute field WQCLASSP contains the ground water quality classes GA, GAA, GAAs, GB and GC and the modified classes GA-Impaired, GAA-Impaired, GAA-Well-Impaired, GAA-Well and GA-NY. All the classes are aggregated and symbolized by using the attribute field AV_LEGEND. Class GA is classified in the data layer but is not symbolized on maps by shading or labeling. In the digital data Class GA and GAA polygons that may not be currently meeting the GA or GAA standards are indicated by GA-Impaired, GAA-Impaired, GAA-Well-Impaired. These areas are customarily shaded on maps but not labeled, however, earlier versions of the Water Quality Classifications Maps label them with a current class and a goal (e.g. GB/GA). A Class GAA-Well-Impaired is an impaired area that surrounds a public water supply well. Polygon features classed as GAA-Well and GAA-Well-Impaired are the area of contribution to a public water supply well represented by a 500 ft radius around a well. Well areas are symbolized by creating an overlay after using WEL_LEGEND = 'Well' to select the polygons that represent the area of contribution to wells. A notation of GAA with a state abbreviation (e.g. GAA-NY) indicates a GAA area that contributes to a public water supply watershed for another state. It is symbolized the same as other GAA areas. Generation of annotation for classified polygons is controlled through the use of the polygon attribute field LABEL_FLG. LABEL_FLG contains N (no label) if the word "impaired" is present in the polygon attribute WQCLASSP field, if WQCLASSP is GA, or if the polygon is a part of a larger area that already has a label. To label features use LABEL_FLG = Y to select features for labeling and use the WQCLASSP attributes for the label. (Source: State of Connecticut, Department of Energy and Environmental Protection)
Internal feature number. (Source: ESRI)
Feature geometry. (Source: ESRI)
ArcView Legend. Text field for symbolizing polygon feature types on a map. For a legend, the following substitutions can be used: value GA - label GA; value GAA,GAAs - label GAA, GAAs; value GB - label GB; value GC - label GC; value To GA,GAA - label GA, GAA May be impaired. (Source: State of Connecticut, Department of Energy and Environmental Protection)
| Value | Definition |
|---|---|
| GA |
This category includes WQCLASSP value GA |
| GAA, GAAs |
This category includes WQCLASSP values GAA, GAAs, GAA-Well, GAA-NY |
| GB |
This category includes WQCLASSP value GB |
| GC |
This category includes WQCCLASSP value GC |
| To GA, GAA |
This category includes WQCLASSP value GA-Impaired, GAA-Impaired, GAA-Well-Impaired |
Ground Water Quality Polygon Code. Text values that identify water quality feature types. Certain attributes (GAA-Well, GAA-NY, GA-Impaired, GAA-Impaired and GAA-Well-Impaired) are used only in the digital data for retrieval of features and not as labels (unless LABEL_FLG = "Y"). The Enumerated_ Domain_Value_Definitions come from the Summary of the Water Quality Standards and Classifications found at the http://www.dep.state.ct.us/wtr/wq/wqsinfo.htm website. (Source: State of Connecticut, Department of Energy and Environmental Protection)
| Value | Definition |
|---|---|
| GA |
Designated uses: existing private and potential public or private supplies of water suitable for drinking without treatment; baseflow for hydraulically connected surface water bodies. |
| GAA |
Designated uses: existing or potential public supply of water suitable for drinking without treatment; baseflow for hydraulically connected surface water bodies. |
| GAAs |
Designated uses: existing or potential public supply of water suitable for drinking without treatment; baseflow for hydraulically connected surface water bodies. Ground water that is tributary to a public water supply reservoir. |
| GAA-Well |
Designated uses: Class GAA, an existing or potential public supply of water suitable for drinking without treatment; baseflow for hydraulically connected surface water bodies. The 500 ft radius area that represents an area of contribution to a public water supply well. Modified class designation unique to digital data. |
| GAA-NY |
Designated uses: Class GAA, an existing or potential public supply of water suitable for drinking without treatment; baseflow for hydraulically connected surface water bodies. Area is part of a New York State watershed. Modified class designation unique to digital data. |
| GB |
Designated uses: industrial process water and cooling waters; baseflow for hydraulically connected surface water bodies; presumed not suitable for human consumption without treatment. |
| GC |
Designated uses: assimilation of discharge authorized by the Commissioner pursuant to Section 22a-430 of the General Statutes. As an example a lined landfill for disposal of ash residue from a resource recovery facility. The GC hydrogeology and setting provides the safest back up in case of technological failure. |
| GA-Impaired |
Actual quality of groundwater does not meet the assigned classifications criteria for GA. Modified class designation unique to digital data. |
| GAA-Impaired |
Actual quality of groundwater does not meet the assigned classifications criteria for GAA. Modified class designation unique to digital data. |
| GAA-Well-Impaired |
Actual quality of groundwater does not meet the assigned classifications criteria for GAA for the 500 ft radius area that represents an area of contribution to a public water supply well. Modified class designation unique to digital data. |
The field identifies polygon features that are 500 ft buffer areas around public water supply wells. (Source: State of Connecticut, Department of Energy and Environmental Protection)
| Value | Definition |
|---|---|
| Well |
This area represents a water quality classification area around a well. |
Area of a polygon feature in acres. (Source: State of Connecticut, Department of Energy and Environmental Protection)
The field is used to select those polygon features that should be labele. (Source: State of Connecticut, Department of Energy and Environmental Protection)
| Value | Definition |
|---|---|
| N |
Water Quality Class of this polygon should not be labeled. |
| Y |
Water Quality Class of this polygon may be labeled. |
Includes Ground Water Quality Classifications for ground water areas of Connecticut. Information encoded about these features includes the classification information, standard cartographic symbology classification schemes for features and labels, and guidance for labeling. Use the WQCLASSP to uniquely identify features. WQCLASSP contains actual water quality classifications and modified classifications used for retrieval of features. Use the AV_LEGEND and WEL_LEGEND attributes to symbolize features by classification and type on a map. To label features use the LABEL_FLG attributes to decide whether (LABEL_FLG = "Y") or not to label a feature and use the WQCLASSP attributes for the label.
The 1:50,000-scale Adopted Water Quality Classifications Map Sheets were drafted and maintained by Carol Smith, a cartographer with the State of Connecticut, Department of Energy and Environmental Protection.
79 Elm Street
Ground Water Quality Classification is 1:24,000-scale data. It depicts the location of water quality classifications for ground waters in Connecticut. Use this data layer to show the ground water quality classifications or to spatially query information from other data layers that occurs within the ground water quality classifications areas. Use this data layer with other 1:24,000-scale map data such as Surface Water Quality Classifications, Aquifer Protection Areas, Leachate and Wastewater Discharge Sources, Public Water Supply information, Hydrography and other base map data layers. Not intended for maps printed at map scales greater or more detailed than 1:24,000 scale (1 inch = 2,000 feet.)
This data source provided a visual record of the ground water classification features and the classification applied to each feature.
This data source provided the ground water classification features and the classification applied to each feature for digitizing.
This data source provided the base map and the registration points for digitizing the ground water classification features.
This data source provided the ground water classification features and the classification applied to each feature for the Housatonic, Southwest Coastal and Hudson basins for digitizing.
This data layer provided the point locations of Public Water Supply Wells which were buffered to a radius of 500 feet to create areas representing the areas of contribution.
This data layer provided polygon areas representing the areas of contribution to the public water supply by buffering the point locations of Public Water Supply Wells to a radius of 500 feet.
These data layers provided line features to build the polygons where the Ground Water Quality Classifications features were coincident with the 1:24,000-scale base map. Included are 1:24,000-scale Hydrography, Roads and Trails, Town Boundaries and Railroads.
This data layer provided line features to build the polygons where the Ground Water Quality Classifications features were coincident with the 1:24,000-scale natural drainage basins published by the State of Connecticut, Department of Environmental Protection.
This data source is a point data layer of surface and groundwater discharges that have received a wastewater discharge permit from the state, are active or historic (no longer active) waste disposal sites, salt storage, or are locations of spills, leaks, deposits or discharges of a variety of liquid or solid wastes. This data provided a guide for the delineation and attribution of Water Quality Classifications areas that were updated.
This data source provided additional tabular information about the Leachate and Wastewater Discharge Sources. It is published as booklet to accompany Leachate and Wastewater Discharge Sources maps.
This source provided guidance for the delineation and attribution of Water Quality Classifications areas along the coast. This source is the classifications of shellfishing growing waters for Connecticut shoreline towns. The shellfishing areas are delineated and classified by the Connecticut Department of Agriculture, Bureau of Aquaculture.
This data source provided maps of Water Quality Classifications data, Leachate and Wastewater Discharge Sources data, Base map data and Drainage Basin data covering the Housatonic River and Southwest Coastal Basins for the purpose of in-house reviewing and updating of the Water Quality Classifications by DEP staff.
This source provided town-based maps of the Water Quality Classifications data, Base Map data layers, Drainage Basin data and Leachate and Wastewater Discharge Sources data for the Housatonic River and Southwest Coastal Basins for the purpose of reviewing Water Quality Classifications by town officials.
This source provided the updated Water Quality Classifications data on town-based maps for the Housatonic River and Southwest Coastal Basins for use during the Public Hearing phase of the Water Quality Classifications Maps adoption process.
This data source refers to all surface and ground water classification features combined in one statewide data layer. Since initial publication in 1995, subsequent publications or editions of the data layer were generated by the State of Connecticut in order to change data format, convert from NAD 27 to NAD 83, or add and modify features. Consequently, over the period of many years, different copies of this data layer were produced, representing various steps in the data layer development and maintenance process (metadata lineage). Changes made to the entire data layer are reflected in metadata process steps where this particular data source is cited as both the Source Used and the Source Produced. The Water Quality Classifications is in ArcInfo Coverage format.
This data source refers to all ground water quality classifications features separated from the statewide water quality classifications data layer and with the hydrography polygon features removed (erased). Since initial publication in 2000, subsequent publications or editions of the data layer were generated by the State of Connecticut in order to add and modify features. Consequently, over a period of years, different copies of this data layer were produced. Changes made to the entire data layer are reflected in metadata process steps where this particular data source is cited as both the Source Used and the Source Produced. The Ground Water Quality Classifications is in ArcInfo Coverage format.
This data source refers to all surface water quality classifications features separated from the statewide water quality classifications data layer and with additional hydrography line and polygon features added. The Surface Water Quality Classifications is in ArcInfo Coverage format.
Includes all polygon features from the Ground Water Quality Classifications where the AV_LEGEND attribute was not blank (AV_LEGEND <> " "). This criterion only includes true ground water classifications features and excludes secondary polygon features from the ArcInfo coverage that represent areas where surface water features exist and the ground water is not classified. Ground_Water_Quality_Classifications_Polygon.shp is in Shapefile format.
Statewide geodatabase format ground water classification datalayer. Includes all ground water classifications polygon features except public water supply well buffered areas or final aquifer protection areas. Includes temporary (and potentially inaccurate) ground water classifications under surface waters. This layer forms the base for the derived WaterQualityClass_Ground datalayer.
Statewide geodatabase format surface water quality classifications for all waterbody area features such as lakes, ponds, bays, harbors, sounds and rivers and streams large enough to be represented as polygons at 1:24,000 scale.
Statewide geodatabase format surface water quality classifications for all waterbody line features such as rivers and streams represented as lines at 1:24,000 scale.
Statewide geodatabase format datalayer of 500 foot buffer areas around Public Water Supply Wells. These buffers are ground water classification areas and are added to the WaterQualityClass_Ground_Master datalayer during creation of the final WaterQualityClass_Ground datalayer. These buffered areas are kept separate for easier maintenance of the ground water classifications data.
Statewide geodatabase format of ground water quality classification as polygon features. It includes the 500 ft buffered areas around public water supply wells and final aquifer protection areas (as this data is adopted). It excludes ground water classifications under surface waterbodies.
Statewide shapefile format of ground water quality classification as polygon features. It includes the 500 ft buffered areas around public water supply wells and final aquifer protection areas (as this data is adopted). It excludes ground water classifications under surface waterbodies.
Statewide shapefile format of surface water quality classification as polygon features.
Statewide shapefile format of surface water quality classification as line features.
Provides the State of Connecticut and State waters as a single polygon
The ground water quality class GA assigned to the State of Connecticut and state waters as a single polygon. Provides this class during the creation of the Source 23 - WaterQualityClass_Ground.
Provides a recognizable regularly-sized, systematically-organized set of polygons.
Process Overview - The original Water Quality Classifications mapping (e.g. Source 1 Adopted Water Quality Classifications Map Sheets) contain both Surface Water and Ground Water Classifications. Both surface water and ground water features were processed as this information was recreated in a digital form as the Source 15 Water Quality Classifications data layer. The Water Quality Classifications data layer was maintain with both surface and ground water features until 2000 when the data model was changed to separate Surface Water Quality Classifications and Ground Water Quality Classifications. Process steps up to this time refer to both the surface and ground water features.
Feature digitizing and attribution (using tablet digitizing and feature selection methods) - Source 2 Water Quality Classifications Mylar Quadrangles and Source 4 Draft Water Quality Classifications Quadrangles depict both surface water and ground water quality classifications. From these two sources line features (polygons began as outlines) for all classifications were captured and attributed as work progressed quadrangle by quadrangle in the creation of Source 15 Water Quality Classifications. Using ESRI ArcInfo software, features were tablet digitized by registering the source map to the digitizing tablet and using the crosshairs of the digitizer's mouse to manually capture the geometry (location) of features drafted on the map. The source map was registered to the digitizing tablet by first digitizing (entering) the locations of four corner registration points shown on the USGS 7.5 minute topographic quadrangle maps. ArcInfo software compared the values of the digitized coordinates with the actual (true) values for the quadrangle corner (tic) features. The Root Mean Square (RMS) error generated by the ArcInfo software indicated the amount of error involved in transforming coordinates from the registered map to the digital layer. RMS errors higher than 0.004 were not acceptable and required re-registering the source map by digitizing the tic locations again. The source maps were positioned on top of the USGS Topographic Quadrangles for a best fit. After correct registration, individual features that were not coincident with existing 1:24,000-scale Base Map data layers (hydrography, roads and trails, railroads, town boundaries) or 1:24,000-scale Drainage Basins were manually digitized off Source 2 or Source 4 and assigned WQCLASSA values for line features, including outlines of ground water quality classifications. Lines were not digitized for ground water quality Class GA. Where necessary, additional minor edits to feature geometry were manually digitized on the screen (heads-up digitizing) at display scales greater than 1:24,000. Using ESRI ArcInfo software, features appearing in and coincident with the existing 1:24,000-scale Base Map Data Layers (hydrography, roads and trails, railroads, town boundaries) or 1:24,000-scale Drainage Basins were manually selected, copied and used as the basis for features in the Water Quality Classifications. Hydrography features were used for surface water quality classifications features. Only features classified other than A or SA were taken from Hydrography, except for Class A waters emanating from GAA (public water supply watershed) areas. Feature geometry (location) required partial editing and adjustment to match information on Source 1 Adopted Water Quality Classifications Mylar Maps, Source 2 and Source 4. Using ESRI ArcInfo software, the Water Quality Classifications was built as both line features and polygon features. The polygons were checked and edited to follow the topology rules. Label points were automatically added. Polygon features were assigned WQCLASSP attribute values based on information in Source 1, Source 2 and Source 4. Ground water quality Class GA was not designated since no polygon features for it were digitized directly in the Water Quality Classifications. Any ground water areas not otherwise classified are assumed to be Class GA. Most surface water quality Class A and SA were not designated since only certain instances of these features were created directly in the Water Quality Classifications. Most surface water quality Class A and SA features were represented by those features in the 1:24,000-scale Hydrography that were not incorporated in the Water Quality Classifications. Feature location and attribute accuracy was visually checked and inspected by symbolizing and labeling features according to attribute value on the computer screen and on hard copy paper maps, and comparing this information to the orginal source data. These check plot maps were printed at the same scale as the Water Quality Classifications Mylar Quadrangles in order to visually inspect digitizing quality and the assignment of attribute values.
Feature creation and attribution - Using ESRI ArcInfo software, the Public Water Supply Wells were buffered to a radius of 500 feet to create areas that represent areas of contribution. Features were assigned WQCLASSP attribute values based on information in the Adopted Water Quality Classifications Mylar Map Sheets.
Combining of data layers - Using ESRI ArcInfo software, the Public Water Supply Well Buffers features were added to the Water Quality Classifications using the Update method. Feature location and attribute accuracy was visually checked and inspected by symbolizing and labeling features according to attribute value both on the computer screen and on hard copy paper maps, and comparing this information to the orginal source data.
Update of water quality in two major basins - In 1995, the DEP revised Water Quality Classifications in the Housatonic River and Southwest Coastal Basins. The source information for Water Quality Classifications for these two basins was in draft form and was compiled prior to 1986. A set of quadrangle-based maps showing the Water Quality Classifications, Leachate and Wastewater Discharge Sources, Base map data layers and Drainage Basins was prepared for review by DEP staff. The results of the staff review were compiled into a list of changes. A set of town-based maps with the Water Quality Classifications, Leachate and Wastewater Discharge Sources, Base map data layers and Drainage Basins was prepared and mailed to each town for review by town officials. The results of the town review were compiled into a list of changes. State of Connecticut, Department of Environmental Protection staff Randy May and Fred Banach conducted a review of the Water Quality Classifications based on the staff review, the town review, the Shellfish Area Classifications and their own extensive knowledge and experience of the area and the conditions. During the review notes for updates were placed on copies of the same maps that DEP staff reviewed. Features and attributes of the Water Quality Classifications data were revised to reflect the decisions of May and Banach. 1:24,000-scale Base Map data layers and 1:24,000-scale Drainage Basin data provided the source for coincident features and other feature changes were digitized on screen. Surface water and ground water were revised. The Surface Water Quality Classifications are required by statute to be adopted through a public process. The Water Quality Classifications were printed on town-based maps and made available at the DEP and at a location in each town for a period of public review and comment. The maps were available at the Public Hearings held at several locations in these two major basins. Comments from the public review process were incorporated into the Water Quality Classifications data where acceptable by the DEP. After the revisions were finalized the adopted date for the Water Quality Classifications features within Housatonic River and Southwest Coastal Basins became 1997
Federal review - The Environmental Protection Agency (EPA) conducted a review of the updated Water Quality Classifications maps for the Housatonic River and Southwest Coastal Basins in 1997. The surface water quality classifications are subject to federal review and adoption. Edits were made to the digital data for changes to the water quality maps agreed to by the EPA and the DEP. The most significant changes were made to the marine water quality classifications along the coastline of the Southwest Coastal Basin.
Datum conversion - Using ESRI ArcInfo software, the Water Quality Classifications was converted from the Connecticut State Plane Coordinate System of 1927 (NAD27) to the Connecticut State Plane Coordinate System of 1983 (NAD83). The NADCON (North American Datum CONversion) data transformation was used.
Data model change, data layer separation - The Water Quality Classifications was separated into two data layers, one for Ground Water Quality Classifications and one for Surface Water Quality Classifications. The reasons for this change are several: the user will have the choice of displaying one or both of the classifications data layers without manipulating the data, Surface Water Quality Classifications and Ground Water Quality Classifications potentially have different user communities, Surface Water Quality Classifications has oversight by the Environmental Protection Agency, Ground Water Quality Classifications are subject to changes in classification through an application process and may change twice yearly. The separation was accomplished using ESRI ArcInfo software by eliminating the Ground Water features from a copy of the Water Quality Classifications and by eliminating the Surface Water features from a copy of the Water Quality Classifications. The Public Water Supply Wells Buffers were added to the Ground Water Quality Classifications again using the ArcInfo Update command. Each new data layer was inspected on-screen and errors in topology, pseudonodes and label errors were corrected. Printed maps at 1:24,000 scale were inspected and the data was corrected for coding errors.
Data model change, integration with hydrography - After the Water Quality Classifications data layer was separated into Ground Water Quality Classifications and Surface Water Quality Classifications, the Surface Water Quality Classifications needed to be fully integrated with the Hydrography. The reasons for this change are that the user can get a complete picture of water quality classifications without displaying the Hydrography and the data can be queried in a web or other GIS application. Previously, the user had to assume that water features not found in the Water Quality Classifications were Class A and that areas not found in Ground Water Quality Classifications were Class GA. Using ESRI ArcInfo software and several processing iterations, the attributes of the Surface Water Quality Classifications were transferred to a copy of the Hydrography data. The line feature attributes and the polygon feature attributes were processed separately. Line features were split to allow the correct placement of line attributes. Polygon features were split where necessary by on-screen digitizing of closure lines to allow the correct placement of polygon attributes. The Ground Water Quality Classifications contained areas that were beneath surface waters where DEP does not classify ground water. Using ESRI ArcInfo software, the water features were isolated from the Hydrography and used with the ArcInfo Erase command to eliminate (knock out) polygon areas where water features exist in Hydrography. Both new data layers were inspected on-screen for errors in topology. Printed maps at 1:24,000 scale were inspected and the data was corrected for coding errors.
Attribute enhancements - WQCLASSP and WEL_LEGEND attributes were changed from storing abbreviated values in upper case to full length values in both upper and lower case.
Export to Shapefile Format - Converted data from ArcInfo Coverage to Shapefile format and named the shapefile Ground_Water_Quality_Classifications_Polygon.shp. Excluded the AREA, PERIMETER, WQGCLASS#, WQGCLASS-ID attributes from the Shapefile because their values are only maintained by ArcInfo software with data that is in ArcInfo Coverage format. Includes all polygon features from the Ground Water Quality Classifications where the AV_LEGEND attribute was not blank (AV_LEGEND <> " "). This criterion only includes ground water classifictations areas and excludes polygon features from the ArcInfo coverage that represent areas where surface water features exist and ground water is not classified.
Convert to GeoDatabase Feature Class format - Water Quality Classifications datalayers were converted to geodatabase format feature classes according to the following steps: defined new Feature Class, imported the spatial reference, defined or imported the attribute definitions, loaded features from coverage, imported metadata from shapefile, edited metadata. The unpublished parent to Source 16 - Ground Water Quality Classification was converted to polygon feature class Source 19 - WaterQualityClass_Ground_Master. Source 16 - Ground Water Quality Classification was not converted from coverage format. The equivalent datalayer, Source 20 - WaterQualityClass_Ground, is generated through overlay techniques from Source 19 - WaterQualityClass_Ground_Master, Source 23 - Public Water Supply Well Buffers 500 Ft and Source 21 - WaterQualityClass_Surface_Poly polygon feature classes. Source 17 - Surface Water Quality Classification was converted to polygon feature class Source 21 - WaterQualityClass_Surface_Poly and to line feature class Source 22 - WaterQualityClass_Surface_Line. Source 6 - Public Water Supply Well Buffers was converted to polygon feature class Source 23 - Public Water Supply Well Buffers 500 Ft. Spatial Reference Properties used for Feature Classes: Coordinate System: NAD_1983_StatePlane_Connecticut_FIPS_0600_Feet XY Domain MinX: 100000; MaxX: 2247483.645 XY Domain MinY: 200000; MaxY: 2347483.645 Precision: 1000 WaterQualityClass_Ground_Master feature class was reworked to eliminate the empty areas originally introduced by erasing the ground water quality layer with the surface water quality layer. The original purpose of the erasure was to eliminate ground water classifications occuring under surface waterbodies. This erasure step now occurs live during creation of the WaterQualityClass_Ground feature class derived from the WaterQualityClass_Ground_Master. To create the new WaterQualityClass_Ground_Master feature class the tools and processes available in ESRI ArcGIS 9.1 were employed. Automated and manual methods were used iteratively to eliminate "doughnut holes" and replace empty areas with appropriately attributed polygons. Where ground water polygons changed classification across waterbodies, centerlines following the waterbodies were manually digitized to form the boundary between classifications. Source 19 - WaterQualityClass_Ground_Master contains continuous Ground Water Quality polygon features, including temporary features that are fully or partially replaced during the generation of the final ground water datalayer, Source 20 - WaterQualityClass_Ground. The steps used to create Source 20 - WaterQualityClass_Ground are 1) used the ESRI ArcMap 9.1 Update tool to replace ares of Source 19 - WaterQUalityClass_Ground_Master with Source 23 - Public Water Supply Well Buffers 500 Ft 2) used the ESRI ArcMap 9.1 Erase tool to eliminate areas contained in Source 21 - WaterQualityClass_Surface_Poly from the output datalayer resulting from step 1. This method of maintaining the Ground Water Quality CLassifications datalayer simplifies the process and reduces errors. Changes can be made to any of the participating datalayers or another datalayer can be introduced and a new Source 20 - WaterQualityClass_Ground can be generated.The attribute field HY_LEGEND was retained for WaterQualityClass_Surface_Line, for maintenance purposes, but dropped from WaterQualityClass_Surface_Poly. During the conversion from coverage to geodatabase format certain attribute fields were dropped from the surface water quality. The attribute fields HYARC_COD, HYPOLY_COD, STREAM_NO, STREAM, STREAM_NO2, LAKE_NO, LAKE, LAKE_NO2, BAY_NO, BAY_NO2, HARBOR_NO, HARBOR_NO2, SOUND_NO and SOUND_NO2 were dropped from WaterQualityClass_Surface_Line and WaterQualityClass_Surface_Poly.
Export to Shapefile Format - Converted data from Geodatabase to Shapefile format and named the shapefiles after the geodatabase version. Excluded the SHAPE_Area and SHAPE_Length fields because their values are not maintained by the shapefile format. Excluded HY_LEGEND attribute field from WaterQualityClass_Surface_Line.shp.WaterQualityClass_Ground.shp includes all polygon features from WaterQualityClass_Ground. WaterQualityClass_Surface_Poly.shp includes all polygon features from WaterQualityClass_Surface_Poly. WaterQualityClass_Surface_Line.shp includes all line features from WaterQualityClass_Surface_Line except for those line features classified in AV_LEGEND as "No Show". Earlier designations of "SHARED" or of "Change of Class" are subsets of "No Show" and are eliminated also.
Create an independent ground water quality Class GA datalayer - Using ESRI ArcMap software, selected and deleted Class GA polygons from Source 19 - WaterQualityClass_Ground_Master. This makes it easier to update the areas that are subject to Class GB reclassification. The Source 27 - Connecticut State Polygon was copied, given the same attribute fields as Source 19 - WaterQualityClass_Ground_Master and assigned Class GA to form Source 28 - WaterQualityClass_Ground_Master_GA. This single polygon layer is used to reintroduce Class GA whenever Source 23 - WaterQualityClass_Ground is recreated.
Split WaterQualityClass_Ground_Master_GA polygon into smaller sections - Using ESRI ArcMap software, intersected Source 29 - USGS Quadrangle Index and Source 27 - Connecticut State Polygon to form Source 28 - WaterQualityClass_Ground_Master_GA. This creates a statewide polygon datalayer that is subdivided into multiple polygons equivalent to the size and shape of the USGS Quadrangle Index polygons that cover the State of Connecticut. When added back to the Source 19 - WaterQualityClass_Ground_Master to form the Source 23 - WaterQualityClass_Ground it is obvious that the Class GA areas have been deliberately split into smaller polygons. Smaller Class GA polygons improve performance when drawing or identifying the ground water quality datalayer.
The Ground Water Quality Classifications retains the feature types and information identified by the State of Connecticut, Department of Energy and Environmental Protection and obtained from the 1:50,000 scale Adopted Water Quality Classification Mylar Map Sheets. All attributes have valid values. Values are within defined domains. The accuracy test for the WQCLASSP attribute values was conducted by comparing the Ground Water Quality Classifications information presented in the source data with 1:24,000-scale check plots or interactive displays of the data on a computer graphic system. These check plot maps and computer displays depicted and labeled the Ground Water Quality Classifications features in different colors based on WQCLASSP values for comparison with the original data source. AV_LEGEND is a broad classification of Ground Water Quality Classifications features. AV_LEGEND was not manually entered. This additional field was populated by joining to a lookup data table with WQGCLASSP as the relate key field. Lookup data tables contain records that account for the unique occurrences of WQGCLASSP and AV_LEGEND values in the Ground Water Quality Classifications. Ground Water Quality Classifications features were manually selected and populated with WQGCLASSP, WEL_LEGEND, and LABEL_FLG attributes values to identify and describe individual features. See Process Step 12 - Convert to GeoDatabase Feature Class format for changes to attribute fields.
The horizontal positional accuracy of this data is no better than the United States National Map Accuracy Standards for 1:24,000 scale maps. According to this standard, not more than 10 percent of the locations tested are to be in error by more than 1/50 inch (40 feet) measured on the publication scale of a USGS 7.5 minute topographic quadrangle map. Feature locations were created by using features from hydrography, roads and trails, railroads and town boundaries data layers based on USGS 7.5 minute topographic quadrangle DLG data and from drainage basin boundaries and from screen-digitized lines interpreted from features depicted on USGS 7.5 minute topographic quadrangle maps.
The completeness of the data reflects the feature content of the data sources which include the Adopted Water Quality Classifications Mylar Map sheets. The Ground Water Quality Classifications is complete in the sense that it accurately reflects the contents of the Water Quality Classifications information available at the time the State of Connecticut, Department of Energy and Environmental Protection created the data layer. This data is updated.
Polygon features conform to the following topological rules. Polygons are single part. There are no duplicate polygons. Polygons do not self overlap. Polygons do not overlap other polygons. The tests of logical consistency were performed by the State of Connecticut using ESRI ArcInfo software to maintain feature topology in ArcInfo coverage format. The data is topologically clean. The ArcInfo Clean function was repeatedly used following edits to verify topology and enforce a minimum distance between vertices of 4 feet (fuzzy tolerance) and a minimum allowed overshoot length of 10 feet (dangle length). Polygon features in the Geodatabase format conform to a 2 foot cluster tolerance.
No restrictions or legal prerequisites for using the data. The data is suitable for use at appropriate scale, and is not intended for maps printed at scales greater or more detailed than 1:24,000 scale (1 inch = 2,000 feet). Although this data set has been used by the State of Connecticut, Department of Energy and Environmental Protection, no warranty, expressed or implied, is made by the State of Connecticut, Department of Energy and Environmental Protection as to the accuracy of the data and or related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the State of Connecticut, Department of Energy and Environmental Protection in the use of these data or related materials. The user assumes the entire risk related to the use of these data. Once the data is distributed to the user, modifications made to the data by the user should be noted in the metadata. When printing this data on a map or using it in a software application, analysis, or report, please acknowledge the State of Connecticut, Department of Energy and Environmental Protection as the source for this information.
79 Elm Street
| Data format: |
in format Shapefile, Feature Class (version ArcGIS)
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| Network links: | http://www.ct.gov/deep |
The data distributor does not provide custom GIS analysis or mapping services. Data is available in a standard format and may be converted to other formats, projections, coordinate systems, or selected for specific geographic regions by the party receiving the data.
79 Elm Street