The Surficial Aquifer Potential Map of Connecticut is a 1:125,000 scale analysis, identifying areas considered to have the greatest potential for ground water yield. This map has been prepared for statewide ground water resource protection, water management, non-point source pollution prevention, and land use planning. The map was compiled from a geospatial analysis of the surficial materials and thickness of glacial sediments digital data layers of the Surficial Materials Map of Connecticut, Stone and others (1992) and Quaternary Geologic Map of Connecticut and The Long Island Sound Basin, Stone and others (1998, 2005). The map identifies areas with greater potential for ground water development based upon the texture and thickness of surficial aquifer deposits. The resulting hydrostratigraphic units define areas of coarse grained deposits, coarse overlying fine grained deposits, fine grained deposits, and areas where fine grained deposits overly coarse grained deposits. Aquifer deposit thickness intervals are 1-50 feet, 50-100 feet, 100-200 feet, 200-300 feet, and 300-400 feet.
Connecticut citizens rely on a readily available water supply, derived from both surface and ground water sources. Ground water occurs in the pore spaces of unconsolidated materials overlying the bedrock, and within bedrock fracture systems. Any geologic formations (sediment or rock) capable of yielding a sufficient quantity of ground water to wells are called aquifers. The amount of ground water available from an aquifer depends on many factors, including: the physical properties of the aquifer (how permeable and well-connected the pore spaces or fractures are), the size and composition of the watershed, climate, connection to surface water bodies, the amount of runoff due to impervious surfaces, and other water uses in the basin. In general, coarse-grained surficial aquifers (unconsolidated sediments overlying bedrock) have more, better connected pore spaces and are more productive than bedrock aquifers. Surface water reservoirs and surficial aquifers serve most of Connecticut's urban areas. Bedrock aquifers have smaller to more moderate yields, but are also an important source of ground water, particularly in the upland areas of Eastern and Western Connecticut, away from urban population centers. The Surficial Aquifer Potential Map delineates areas considered to have the greatest potential for ground water yield. The thicker and coarser-grained deposits have higher potential for water supply development. The most productive surficial aquifers in Connecticut are sand and gravel deposits originating from glacial meltwaters. These deposits are mapped where they occur at the surface and where they occur beneath fine- grained deposits. The map shows total estimated surficial deposit thickness. This includes the combined thickness of fine and coarse-grained portions of the surficial aquifer for units designated as such. Other glacial meltwater deposits are shown on the map to display the full extent of the surficial aquifers, but these fine-grained deposits have significantly lower potential yields. The white areas of the map are areas of till and shallow rock. Till is generally a thin, very poorly sorted glacial deposit with low potential yields. Potential bedrock yields were not included in this compilation. The surficial aquifer potential areas are mapped based upon their geologic features, without regard to possible natural or man-made water quality issues that may exist. For example, coastal and estuarine aquifers may have naturally impaired water quality due to unacceptable levels of salinity. In some urbanized or industrialized areas, chemical contamination may impair ground water quality. Water quality was not considered in constructing this map, but would be critical in determining if the potential aquifer is viable as a water supply. DISCUSSION Coarse-grained glacial deposits have the greatest potential to both store and transmit water. The locations and thickness of these aquifers are of utmost importance for water management. Coarse-grained deposits of thicknesses greater than 50' are considered to have the greatest long term potential ground water yields, particularly where they occur near large rivers and streams. Where coarse-grained deposits have a water saturated thickness of 10' or greater, moderate to very large ground water yields of 50-2000 gallons per minute have been documented. The saturated thickness of these deposits has not been mapped statewide. Therefore, the overall thickness of these deposits may be used as a proxy for saturated thickness in that, given equal recharge, a greater coarse grained deposit thickness would have a higher potential of containing a greater volume of saturated material. Detailed mapping of the surficial materials thickness at 1:24,000 scale is available for only 15% of the State. A wealth of historic hydrogeologic data is available for major watersheds of the State from the USGS Water Resources Bulletins (1968-1975). Generalized thickness estimates for coarse-grained deposits were assigned by geologic region for volume calculations conducted at 1:250,000 scale by DiGiacomo-Cohen and Quarrier (1992). Nevertheless, the most useful statewide compilation of surficial materials thickness became available recently as an element of the Quaternary Geologic Map of Connecticut and Long Island Sound Basin (Stone et al, 1998; 2005). The compilation of surficial aquifer potential presented here is suitable for statewide and regional environmental planning, however there are several mapping enhancements that may be explored. These include evaluation of additional sources of information relative to potential yields and saturated thickness of surficial aquifers. Additional work regarding the nature and impact of bedrock fractures relative to regional ground water flow may reveal a systematic effect on the quantity of available ground water to surficial aquifers. Additional work toward detailed surficial thickness estimates would refine current surficial aquifer potential mapping units. Also, consideration of known water quality threats of both natural and man-made origins would further support assessments of potential surficial aquifer use for water supply.
Publication date of 1:125,000 scale Surficial Materials Map of Connecticut, Stone and others, 1992
Surficial Aquifer Potential Map of Connecticut, 2008, State of Connecticut, Geological and Natural History Survey, Department of Environmental Protection and U.S. Geological Survey, Department of the Interior, Hartford, CT, vector digital data, compilation scale 1:125,000. http://www.ct.gov/deep (Source: State of Connecticut, Geological and Natural History Survey, Department of Environmental Protection and U.S. Geological Survey, Department of the Interior)
Feature geometry. (Source: ESRI)
SRFAQPOT, Surficial Aquifer Potential, field used to delineate areas of coarse-grained glacial meltwater deposits considered to have a favorable potential for ground water yield. (Source: U.S. Geological Survey and State of Connecticut, Geological and Natural History Survey, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Coarse-Grained Deposits | Areas mapped as having coarse-grained glacial meltwater deposits |
| Fines over Coarse-Grained Deposits | Areas mapped as having fine-grained deposits overlying coarse-grained glacial meltwater deposits |
| Other Stratified Drift Deposits | Areas mapped as having glacial meltwater deposits with lower potential ground water yield |
Surficial Aquifer Thickness in Feet (Source: State of Connecticut Geological and Natural History Survey, Department of Environmental Protection, and the U.S. Geological Survey, Department of the Interior, and Long Island Sound Resource Center)
| Value | Definition |
|---|---|
| 0-50 | 0 to 50 FT thickness interval |
| 50-100 | 50 to 100 FT thickness interval |
| 100-200 | 100 to 200 FT thickness interval |
| 200-300 | 200 to 300 FT thickness interval |
| 300-400 | 300 to 400 FT thickness interval |
Thickness Interval - Glacial sediment thickness interval, in feet (Source: Long Island Sound Resource Center compiler, Mary DiGiacomo-Cohen)
| Value | Definition |
|---|---|
| 0-50 | 0 to 50 FT thickness interval |
| 50-100 | 50 to 100 FT thickness interval |
| 100-200 | 100 to 200 FT thickness interval |
| 200-300 | 200 to 300 FT thickness interval |
| 300-400 | 300 to 400 FT thickness interval |
| 400-500 | 400 to 500 FT thickness interval |
| 500-600 | 500 to 600 FT thickness interval |
| > 600 | Greater than 600 FT thick |
Surficial Aquifer Texture - A field used to classify and symbolize surficial material polygon features into categories that describe the texture of surficial aquifers for ground water applications. This attribute condenses the 50 surficial materials map units (SMPOLY_COD values) into 10 textural categories of deposits (artificial fill, beach, coarse, coarse overlying fine, fine, fine overlying coarse, salt marsh, swamp, till and water). (Source: U.S. Geological Survey and State of Connecticut, Geological and Natural History Survey, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Artificial Fill | This category includes SMPOLY_COD value of AF. |
| Beach | This category includes SMPOLY_COD value of B. |
| Coarse | This category includes SMPOLY_COD values of A/S, A/S/SG, A/SG, A/SG/S, G, G/SG, G/SG/S, G/S, S, S/G, S/SG, SG, SG/S, SG/S/SG, SW/S, SW/S/SG, and SW/SG. |
| Coarse overlying Fine | This category includes SMPOLY_COD values of A/S/F, A/SG/F, A/SG/S/F, G/F, G/S/F, S/F, SG/F, SG/S/F, SM/S/F, and SW/S/F. |
| Fine | This category includes SMPOLY_COD values of A/F, F, SM/F and SW/F. |
| Fine overlying Coarse | This category includes SMPOLY_COD values of A/F/G, A/F/S, A/F/SG, F/G, F/S, F/SG, S/F/SG, SG/F/SG, and SW/F/S. |
| Salt Marsh | This category includes SMPOLY_COD value SM. |
| Swamp | This category includes SMPOLY_COD value SW. |
| Till | This category includes SMPOLY_COD values A, T, TA, TS, and TT. |
| Water | This category includes SMPOLY_COD value W. |
Surficial Aquifer Texture Group - A field used to classify and symbolize surficial material polygon features into broad textural categories of surficial aquifers for ground water applications. This attribute condenses the 50 surficial materials map units (SMPOLY_COD values) into 5 textural categories of deposits (coarse, coarse overlying fine, fine, fine overlying coarse, and not surficial aquifer). (Source: U.S. Geological Survey and State of Connecticut, Geological and Natural History Survey, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Coarse | This category includes SMPOLY_COD values of A/S, A/S/SG, A/SG, A/SG/S, G, G/SG, G/SG/S, G/S, S, S/G, S/SG, SG, SG/S, SG/S/SG, SW/S, SW/S/SG, and SW/SG. |
| Coarse overlying Fine | This category includes SMPOLY_COD values of A/S/F, A/SG/F, A/SG/S/F, G/F, G/S/F, S/F, SG/F, SG/S/F, SM/S/F, and SW/S/F. |
| Fine | This category includes SMPOLY_COD values of A/F, F, SM/F and SW/F. |
| Fine overlying Coarse | This category includes SMPOLY_COD values of A/F/G, A/F/S, A/F/SG, F/G, F/S, F/SG, S/F/SG, SG/F/SG, and SW/F/S. |
| Not Surficial Aquifer | This category includes SMPOLY_COD values of A, AF, B, SM, SW, T, TA, TS, TT, and W. |
Stratified Drift - Classifies surficial material polygon features into fine and course grain stratified drift deposits. This attribute condenses the 50 surficial materials map units (SMPOLY_COD values) into 3 textural categories of deposits (coarse grain stratified drift, fine grain stratified drift, and not stratified drift). (Source: U.S. Geological Survey and State of Connecticut, Geological and Natural History Survey, Department of Environmental Protection)
| Value | Definition |
|---|---|
| Coarse Grain Stratified Drift | This category includes SMPOLY_COD values of A/F/G, A/F/S, A/F/SG, A/S, A/S/SG, A/SG, A/SG/S, F/G, F/S, F/SG, G, G/S, G/SG, G/SG/S, S, S/F/SG, S/G, S/SG, SG, SG/F/SG, SG/S, SG/S/SG, SW/F/S, SW/S, SW/S/SG, and SW/SG |
| Fine Grain Stratified Drift | This category includes SMPOLY_COD values of A/F, A/S/F, A/SG/F, A/SG/S/F, F, G/F, G/S/F, SG/F, SG/S/F, SM/F, SM/S/F, S/F, SW/F, and SW/S/F. |
| Not Stratified Drift | This category includes SMPOLY_COD values of A, AF, B, SW, SM, T, TA, TS, TT, and W. |
SMPOLY_COD (Source: Surficial Materials Polygon Code - A key field used to classify surficial materials units. Attribute values are mostly single characters in length, except for stacked map units that include forward slashes (/) between the different textural types such as A/F, A/F/G, and A/F/SG.)
| Value | Definition |
|---|---|
| A | Floodplain Alluvium - Sand, gravel, silt, and some organic material, on the floodplains of modern streams. The texture of alluvium commonly varies over short distances both laterally and vertically, and is often similar to the texture of adjacent glacial deposits. Along smaller streams, alluvium is commonly less than 5 ft thick. The most extensive deposit of alluvium on the map is along the Connecticut River where the texture is predominantly fine to very fine sand and silt; here and along other larger rivers, it may be as much as 25 ft thick. Alluvium typically overlies thicker glacial stratified deposits, the general texture of which is indicated by the stacked unit. |
| A/F | Alluvium overlying Fines |
| A/F/G | Alluvium overlying Fines overlying Gravel |
| A/F/S | Alluvium overlying Fines overlying Sand |
| A/F/SG | Alluvium overlying undifferentiated Fine deposits overlying coarse deposits (Sand and Gravel) |
| A/S | Alluvium overlying Sand |
| A/S/F | Alluvium overlying Sand overlying Fines |
| A/S/SG | Alluvium overlying Sand overlying Sand and Gravel |
| A/SG | Alluvium overlying undifferentiated coarse deposits (Sand and Gravel) |
| A/SG/F | Alluvium overlying undifferentiated coarse deposits (Sand and Gravel) overlying Fine deposits |
| A/SG/S | Alluvium overlying Sand and Gravel overlying Sand |
| A/SG/S/F | Alluvium overlying Sand and Gravel overlying Sand overlying Fines |
| AF | Artificial Fill - Earth materials and manmade materials that have been artificially emplaced. Artificial fill is common throughout the map area but has been shown on this map only where extensive areas of 'made land' occur, principally along the coast. |
| B | Beach deposits - Sand and and gravel deposited along the shoreline by waves and currents and by wind action. The texture of beach deposits varies over short distances and is generally controlled by the texture of nearby glacial materials exposed to wave action. Beach deposits are generally well sorted and rarely more than a few feet thick. Many sand beaches along the Connecticut coast have been 'restored'; these have not been distinguished from natural beaches on this map; however, extensive beaches that consist totally of 'made-land' are mapped as artificial fill. |
| F | Fines (very fine sand, silt, and clay) - Composed of well-sorted, thin layers of alternating silt and clay, or thicker layers of very fine sand and silt. Very fine sand commonly occurs at the surface and grades downward into rhythmically bedded silt and clay varves (lake-bottom deposits) |
| F/G | Fines overlying Gravel |
| F/S | Fines overlying Sand-- Fines of variable thickness, commonly in thinly bedded layers overlie sand of variable thickness (distal lake-bottom deposits overlying slightly older more delta-proximal lacustrine sediment) |
| F/SG | Fines overlying Sand and Gravel - Fines of variable thickness, commonly in thinly bedded layers overlie sand and gravel of ariable thickness (lake-bottom deposits overlying slightly older collapsed proximal fluvial or deltaic deposits); in a few places sand or sand and gravel, generally less than 25 ft thick occurs on top of the F/SG unit and is indicated as S/F/SG and SG/F/SG on the map, respectively |
| G | Gravel - Composed mainly of gravel-sized particles; cobbles and boulders predominate; minor amounts of sand within gravel beds, and sand comprises few separate layers. Gravel layers generally are poorly sorted and bedding commonly is distorted and faulted due to postdepositional collapse related to melting of ice. Gravel deposits are shown only where observed in the field; additional gravel deposits may be expected, principally in areas mapped as unit SG (proximal fluvial deposits or delta-topset beds) |
| G/F | Gravel overlying Fines - Gravel is generally less than 20 ft thick, horizontally bedded and overlies thicker thinly bedded fines (proximal fluvial deposits overlying lake-bottom sediments) |
| G/S | Gravel overlying Sand-- Gravel is generally less than 20 ft thick, horizontally bedded, and overlies thicker, inclined layers of sand (proximal deltaic deposits) |
| G/S/F | Gravel overlying Sand overlying Fines - Gravel is generally less than 20 ft thick, horizontally bedded and overlies thicker inclined beds of sand which in turn overlie fines of variable thickness (proximal deltaic deposits overlying lake-bottom sediments) |
| G/SG | Gravel overlying Sand and Gravel - Gravel is generally less than 20 ft thick, horizontally bedded, and overlies thicker, inclined layers of sand and gravel (proximal deltaic deposits) |
| G/SG/S | Gravel overlying Sand and Gravel overlying Sand |
| S | Sand - Composed mainly of very coarse to fine sand, commonly in well-sorted layers. Coarser layers may contain up to 25 percent gravel particles, generally granules and pebbles; finer layers may contain some very fine sand, silt, and clay (delta-foreset beds, very distal fluvial deposits, or windblown sediment) |
| S/F | Sand overlying Fines - Sand is of variable thickness, commonly in inclined foreset beds and overlies thinly bedded fines of variable thickness (distal deltaic deposits overlying lake-bottom sediment) |
| S/F/SG | Sand overlying Fines overlying Sand and Gravel |
| S/G | Sand overlying Gravel - Sand of variable thickness overlies gravel of variable thickness (younger distal deltaic or fluvial sediments overlying older, more proximal fluvial or deltaic sediments) |
| S/SG | Sand overlying Sand and Gravel - Sand of variable thickness overlies sand and gravel of variable thickness (distal deltaic or fluvial sediments overlying slightly older proximal fluvial or deltaic sediments) |
| SG | Sand and gravel - Composed of mixtures of gravel and sand within individual layers and as alternating layers. Sand and gravel layers generally range from 25 to 50 percent gravel particles and from 50 to 75 percent sand particles. Layers are well to poorly sorted; bedding may be distorted and faulted due to postdepositional collapse. It is likely that some deposits within this map unit actually are gravel or sand and gravel overlying sand. It is less likely that some of these deposits are sand (fluvial deposits or delta-topset beds) |
| SG/F | Sand and Gravel overlying Fines - Sand and gravel is generally less than 20 ft thick, horizontally bedded and overlies thicker thinly bedded fines (fluvial meltwater terrace deposits overlying lake-bottom sediment) |
| SG/F/SG | Sand and Gravel overlying Fines overlying Sand and Gravel |
| SG/S | Sand and Gravel overlying Sand - Sand and gravel is generally less that 20 ft thick, horizontally bedded, and overlies thicker, inclined layers of sand (deltaic deposits) |
| SG/S/F | Sand and Gravel overlying Sand overlying Fines - Sand and gravel is generally less than 20 ft thick, horizontally bedded and overlies thicker inclined beds of sand which in turn overlie thinly bedded fines of variable thickness (deltaic deposits overlying lake-bottom sediment) |
| SG/S/SG | Sand and Gravel overlying Sand overlying Sand and Gravel - Sand and gravel is generally less than 20 ft thick, horizontally bedded, and overlies thicker inclined layers of sand; thickness of sand and gravel at the base of the section is variable (deltaic deposits overlying slightly older, more proximal deposits) |
| SM | Salt-marsh and tidal-marsh deposits - Peat and muck interbedded with sand and silt, deposited in environments of low wave energy along the coast and in river estuaries. Marsh deposits are dominantly peat and muck, generally a few feet to 35 ft thick. In the major estuaries marsh deposits may overlie estuarine deposits which are sand and silt with minor organic material as much as 40 - 90 ft thick. These deposits are generally underlain by the glacial material shown adjacent on the map; either till or sand and gravel. Where they are known or inferred to be underlain by sand or fines, they are shown on the map by stacked units. |
| SM/F | Salt-marsh and tidal-marsh deposits overlying Fines |
| SM/S/F | Salt-marsh and tidal-marsh deposits overlying Sand overlying Fines |
| SW | Swamp deposits - Muck and peat that contain minor amounts of sand, silt, and clay, accumulated in poorly drained areas. Most swamp deposits are less than about 10 ft thick. Swamp deposits are underlain by glacial deposits or bedrock. They are often underlain by glacial till even where they occur within glacial meltwater deposits. Where swamp deposits are known or inferred to be underlain by sand and/or fines, they are shown on the map by the stacked unit. |
| SW/F | Swamp deposits overlying Fines |
| SW/F/S | Swamp deposits overlying Fines overlying Sand |
| SW/S | Swamp deposits overlying Sand |
| SW/S/F | Swamp deposits overlying Sand overlying Fines |
| SW/S/SG | Swamp deposits overlying Sand overlying undifferentiated coarse deposits (Sand and Gravel) |
| SW/SG | Swamp deposits overlying undifferentiated coarse deposits (Sand and Gravel) |
| T | Thin Till - areas where till is generally less than 10-15 ft thick and including areas of bedrock outcrop where till is absent. Predominantly upper till; loose to moderately compact, generally sandy, commonly stony. Two facies are present in some places; a looser, coarser-grained ablation facies, melted out from supraglacial position; and a more compact finer-grained lodgement facies deposited subglacially. In general, both facies of upper till derived from the red Mesozoic sedimentary rocks of the central lowland of Connecticut are finer-grained, more compact, less stony and have fewer surface boulders than upper till derived from crystalline rocks of the eastern and western highlands. |
| TA | Talus - Loose, angular blocks (mostly boulders) accumulated by rockfall at the bases of steep bedrock cliffs. Talus forms steep unstable slopes and is generally less than 10 ft thick. It occurs most extensively along the linear basalt and diabase ridges within the central lowland. |
| TS | Sandy Till, Sand and Gravel, some areas of dense surface bolders (End moraine deposits) - Composed predominantly of ablation facies sandy upper till; lenses of stratified sand and gravel occur locally within the till. Surface boulders on end moraine deposits are generally more numerous than on adjacent till surfaces; dense concentrations of boulders are present in some places. Deposits occur as free-standing hummocky landforms, commonly in elongate ridges that trend NNE - SSW, and range in thickness from 10 to 60 ft. |
| TT | Thick Till - areas where till is greater than 10-15 ft thick and including drumlins in which till thickness commonly exceeds 100 ft (maximum recorded thickness is about 200 ft). Although upper till is the surface deposit, the lower till constitutes the bulk of the material in these areas. Lower till is moderately to very compact, and is commonly finer-grained and less stony than upper till. An oxidized zone, the lower part of a soil profile formed during a period of interglacial weathering, is generally present in the upper part of the lower till. This zone commonly shows closely-spaced joints that are stained with iron and manganese oxides. |
| W | Water - Defined as streams, lakes, ponds, bays, and estuaries greater than 5 acres in size. Surficial Material water polygon features are outlined by Surficial Material line features with a SMARC_COD attribute value of 2 (for Hydrography Shoreline). |
Surficial Materials - The SURFM_POLY attribute includes longer text values for the mostly single-character values stored in the SMPOLY_COD field. SURFM_POLY is the English language equivalent of (decodes) the SMPOLY_COD field. For example, SMPOLY_COD and SURFM_POLY attribute values for the same polygon feature are G and Gravel, respectively. SURFM_POLY attribute values for stacked map units include forward slashes (/) between the different textural types such as Aluv/Fines, Aluv/Fines/Gravel, and Alluv/Fines/Sand+Gravel. (Source: U.S. Geological Survey and State of Connecticut, Department of Environmental Protection)
Internal feature number. (Source: ESRI)
Surficial Materials Description - Based on the SMPOLY_COD attribute, a longer decoded description of the map unit than that provided by the SURFM_POLY attribute. For example, SMPOLY_COD, SURFM_POLY, and DESCRIP attribute values for the same polygon feature are A/S, Aluv/Sand, and Aluvium overlying Sand, respectively. (Source: U.S. Geological Survey and State of Connecticut, Department of Environmental Protection)
Feature geometry. (Source: ESRI)
Dataset shows the distribution and thickness of coarse-grained glacial sediment deposits in Connecticut. Mapping units include areas of glacial meltwater deposits, with particular value to ground water resources. Coarse-grained deposits are delineated in intervals of 0-50 ft thick; 50-100 ft thick; 100-200 ft thick; 200-300 ft thick; 300-400 ft thick. Fine-grained deposits overlying coarse-grained deposits include areas 0-50 ft thick; 50-100 ft thick; 100-200 ft thick; 200-300 ft thick. Other glacial meltwater deposits with lower potential ground water yield are also delineated.
Surficial Aquifer Potential Map of Connecticut, 2008, State of Connecticut, Geological and Natural History Survey, Department of Environmental Protection and U.S. Geological Survey, Department of the Interior, Hartford, CT, vector digital data, compilation scale 1:125,000. http://www.ct.gov/deep
Margaret Thomas of the Connecticut Geological and Natural History Survey, Department of Environmental Protection in consultation with Janet Stone, U.S. Geological Survey for Surficial Aquifer Textures and Textural Groups used in the development of this map. Corinne Fitting, of CT DEP Aquifer Protection Program, provided comments on the map. This project was supported by the DEP Nonpoint Source Management Program, through the Federal Clean Water Act Section 319 administered by the U.S. Environmental Protection Agency.
79 Elm Street
The Surficial Aquifer Potential Map was prepared by the Connecticut Geological Survey at the request of the Water Protection and Land Reuse Bureau of the Department of Environmental Protection. A statewide view of surficial aquifer resources is necessary to facilitate proactive aquifer protection and water supply planning. Previous statewide groundwater availability (Meade 1978) and ground water yields mapping (Mazzaferro 1986) provided excellent planning documents at the time of publication. The compilation presented here incorporates geologic mapping and interpretations of Stone et al (1992; 1998; 2005) unavailable in the earlier treatments. Notably, the Surficial Materials Map of Connecticut (Stone et al 1992), used in this compilation, provides detailed 1:24,000 scale mapping which delineates larger and more numerous areas of coarse-grained deposits than previously known.
Surficial Aquifer Texture based on a reclassification and generalization of the 1:24,000 scale compilation Surficial Materials Map of Connecticut by Stone and others, 1992. Surficial_Aquifer_Texture_Data is in GeoDatabase data table format. The TEXTURE_GRP attribute values were combined with thickness of unconsolidated materials data, THICK_UNCONSOL_MAT to produce Connecticut Surficial Aquifer Potential.
Thickness of Unconsolidated Materials, THICK_UNCONSOL_MAT, 1:125,000 scale compilation, Thickness of Glacial Sediments in Connecticut and Long Island Sound Basin Polygon Glacial_Sediment_Thickness_poly is in Geodatabase Feature Class format. The THICKI_FT attribute values were combined with Surficial Aquifer Texture data SURF_AQUIF_TEXT to produce the Connecticut Surficial Aquifer Potential Map.
Surficial Aquifer Texture, SURF_AQUIF_TEXT, data TEXTURE_GRP attribute vales were combined with thickness of unconsolidated materials data, THICK_UNCONSOL_MAT data SRFAQTHKFT attribute values to produce hydrostratigraphic mapping units. These hydrostratigraphic units define areas with similar potential for ground water flow. Resulting units included areas of coarse-grained deposits, coarse-grained deposits overlying fine-grained deposits, fine-grained deposits, and areas where fine-grained deposits overlie coarse grained deposits, each with thickness intervals of 0-50 ft., 50-100 ft., 100-200 ft., 200-300 ft., 300-400 ft., 400-500 ft., 500-600 ft., and greater than 600 ft. Areas of coarse-grained deposits, and fine-grained deposits overlying coarse-grained deposits (attribute SRFAQPOT) with corresponding thicknesses were saved for inclusion in the final map. Other areas of glacial meltwater deposits considered to have lower potential ground water yield were aggregated into a single map unit.
79 Elm Street, 6th floor
The Connecticut Surficial Aquifer Texture data retains the underlying surficial material polygon feature and attribute information of the 1:24,000-scale Connecticut Surficial Materials layer, which retains the feature types and information identified on the 1:24,000-scale compilation sheets for the Surficial Materials Map of Connecticut, Stone and others, 1992. All attributes have valid values. Values are within defined domains. The accuracy test for the SMPOLY_COD attribute values was conducted by comparing the geologic map unit information presented on the source mylar overlays with 1:24,000-scale check plots or interactive displays of the digital data on a computer graphic system. These check plot maps and computer displays depicted and labeled the surficial material polygon features in different colors and line-fill patterns based on SMPOLY_COD attribute values for comparison with the original data source. SURFM_POLY and DESCRIP represent both brief and full text English language equivalents of (decodes) the SMPOLY_COD attribute, respectively. The TEXTURE, TEXTURE_GRP and STRAT_DRIFT that classify the SMPOLY_COD values into various texture categories and were populated by joining the Surficial_Aquifer_Texture_Data lookup data table to the polygon features using SMPOLY_COD as the relate key field instead of manually entering these values for each polygon feature. The Surficial_Aquifer_Texture_Data lookup table accounts for all 50 values of SMPOLY_COD, assigning each value a corresponding TEXTURE, TEXTURE_GRP and STRAT_DRIFT value.
The horizontal positional accuracy of this data complies with 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 interpolated from the transporation features, surface water features, elevation contours, buildings, built-up areas, and other natural features and landforms depicted on USGS 7.5 minute topographic quadrangle maps.
The data reflects the content of the data sources: the Surficial Aquifer Texture data layer, a derivitive product of the Surficial Materials datalayer, and the thickness of glacial sediments datalayer of the Quaternary Geologic Map of Connecticut and The Long Island Sound Basin. The Surficial Materials datalayer was digitized 1:24,000-scale mylar compilation sheets.The materials texture was taken from a set of 1:24,000 scale mylar sheets used to compile and publish the Surficial Material Map of Connecticut, Stone and others, 1992 (U.S. Geological Survey in cooperation with the Connecticut Geological and Natural History Survey, DEP, 2 sheets, 1:125,000 publication scale). The thickness of glacial sediments..............................
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. Lines are single part. Line features conform to the following topological rules. There are no duplicate lines. Lines do not self overlap. Lines do not overlap other lines. Lines intersect only at nodes, and nodes anchor the ends of all lines. Lines do not overshoot or undershoot other lines they are supposed to meet and intersect. In general, there are no duplicate features, unresolved intersections, overshooting lines, open polygons, sliver polygons, or unlabeled (unattributed) 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 0 feet (dangle length).
The Surficial Aquifer Potential Map of Connecticut is suitable for regional and statewide water resource planning at 1:125,000 scale, and may be a useful tool for water resource classification relative to potential ground water availability. A surficial aquifer texture map was prepared as an intermediate product of the surficial aquifer potential map compilation. As a reclassification of the original mapping of Stone and others (1992), the aquifer texture map is suitable for use at the original data compilation scale of 1:24,000.
| Data format: | vector digital data Shapefile, Feature Class Size: 16M |
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| Network links: | http://www.ct.gov/deep |
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