Chemical Data From 40 Years of Monitoring a Treated-Wastewater Groundwater Plume in a Sand and Gravel Aquifer, Cape Cod, Massachusetts, 1978-2018

This U.S. Geological Survey data release provides a comprehensive dataset of water-quality data and sampling-site characteristics collected in 1978-2018 during a study of the effects of land disposal of treated wastewater on groundwater quality in an unconsolidated sand and gravel aquifer on Cape Cod, Massachusetts. Treated sewage-derived wastewater was discharged to rapid-infiltration beds at Joint Base Cape Cod for nearly 60 years before the disposal was moved to a different location in December 1995. The discharge formed a plume of contaminated groundwater that partly discharges to a glacial kettle lake about 1,600 feet from the beds and extends about 4.5 miles toward coastal saltwater bodies at Vineyard Sound. Water-quality samples were collected from monitoring wells, multilevel samplers (MLSs), continuous multichannel tubing samplers (CMTs), AMS gas-vapor sampling points (AMS, Inc., American Falls, Idaho), piezometers, temporary borings drilled by direct-push methods, and surface-water bodies to characterize the nature and extent of the contaminated groundwater and to observe the water-quality changes before and after wastewater disposal ended in 1995. Data are presented here for 604 wells (at 188 well-cluster locations), 1,155 MLS ports (at 61 locations), 42 CMT ports (at 6 locations), 13 gas-vapor points (at 1 location), 17 piezometers (at 5 locations), 536 depth intervals in direct-push profile borings (at 68 locations), 1 glacial kettle lake, and 1 wastewater-disposal discharge in and near the treated-wastewater plume. About 20,740 visits were made to individual sampling points between 1978 to 2018. This data release presents field water-quality measurements (specific conductance, pH, dissolved oxygen, turbidity and temperature; iron, MBAS and phosphate concentrations; and alkalinity); absorbance of ultraviolet/visible light; and concentrations of selected gases (including nitrous oxide, methane, dissolved inorganic carbon), dissolved organic carbon, selected nitrogen species (including nitrate, nitrite, ammonium, and total dissolved nitrogen), and selected inorganic solutes (including cations, anions, and minor elements). Information on sample collection and processing can be found in the Federal Geographic Data Committee (FGDC) metadata and "TableDefs CapeCodToxicsDatabase.xlsx." The data are presented in two formats: Microsoft (MS) Access database (.accdb) and comma-delimited text (.csv) files. The MS Access version of the database ("DataRelease_CapeCodToxicsDatabase.accdb") contains 15 data tables linked by established relationships and 4 queries that repackage the data for the convenience of the user. Versions of the 4 queries and 15 tables exported from the MS Access database as comma-delimited text files have been zipped together by type ("tables" and "queries," respectively). The text files are comma delimited, contain headings, and use double quotation marks to denote text fields. Numeric fields enclosed in double quotation marks are treated as text to preserve number formatting. Users not familiar with MS Access may prefer the text files to the MS Access database. The database can be reconstructed in Access or another relational data management platform from text-file tables in conjunction with the physical data model, the definitions of the table and field descriptions, and the Structured Query Language (SQL) commands described in a readme file zipped with the query text files. The table descriptions, field definitions, and significant figures for this database are documented by "TableDefs CapeCodToxicsDatabase.xlsx" and the FGDC metadata. The physical data model for this database is documented by "Relationships for CapeCodToxicsDatabase.jpg." The relationships expressed in the .jpg file are further explained by an MS Word document titled "Relationships for CapeCodToxicsDatabase.docx." Three types of data are included in the data tables: site and sample characteristics, water-quality data, and water-quality analysis codes: (1) Site and sample-characteristic tables describe the location coordinates, altitude, and type of each sample site, and the date, time, and sampling technique for each water-quality sample ("SiteNetworkInfo," "ProfileDepthInfo," "SamplingEventCodes," and "WellWaterLevelData"). (2) Water-quality data tables describe the results from field and laboratory water-quality analyses of physical properties and chemical constituents such as dissolved oxygen, pH, specific conductance, and alkalinity ("FieldData"); nitrogen species and selected anions ("AnionAndNitrogenData"); carbon species ("CarbonData"); inorganic solutes, such as major cations, selected anions, and trace metals ("ICPAESCation" and "ICPAESChelex"); and dissolved gases, such as methane and nitrous oxide ("DissolvedGasData"). (3) Water-quality analysis code tables describe the detection limits, instruments, and methods of analysis for the laboratory water-quality results described previously ("AnionAndNitrogenAnalysisCodes," "CarbonInorgAnalysisCodes," "CarbonOrgAnalysisCodes," "ICPAESAnalysisCodes," and "DissolvedGasAnalysisCodes"). Analysis codes are not included for the field data, as they are documented in many previous publications. The reader is directed to those publications in the metadata. Four queries repackage the data for the convenience of the user: (1) A summary of the sampling events, including their duration ("QRY_SummarySamplingEvents"). (2) Location coordinates, land-surface and screen altitudes, and results from selected field and laboratory water-quality analyses for all environmental sample records ("QRY_QWSamplesFormatted"). (3) Results for selected water-quality analytes for laboratory blanks and equipment rinseate sample records ("QRY_QAQCSamplesFormatted"). (4) Average water-level depths and land-surface altitudes at monitoring wells from measurements made between 1978 and 2018 ("QRY_AverageWellWaterLevel"). 'RelevantReferences.csv' is a comma-delimited text file that lists reports relevant to historical data collection in and near the treated-wastewater plume. The references are divided into four types: (1) Interpretative reports about the natural restoration of water quality in the sand and gravel aquifer after removal of the treated-wastewater source, along with summaries of the water quality in the treated-wastewater plume. (2) Previously released data related to water-quality monitoring in and near the treated-wastewater plume that are re-released in this data release. (3) Reports that discuss the analytical and sampling methods used in the collection of these data. (4) Reports that contain additional data relevant to the water-quality characteristics and natural restoration of the sand and gravel aquifer that are not included in this data release. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.