A measurement performed at a location at the hydrologic site using a defined instrument producing a value with the units of the specified parameter code. The location at a site where the environmental measurement was performed. The EPA parameter code indicating the parameter and units that were measured. The method code indicating the specific method used to measure the data. The date and time that the measurement was performed. This can be a partial date and time. The value measured. The units are the units of the parameter code. The Code indicating a remark about the value of the measurement.