Revision 4.0 by Tara Scharaga on March 30, 2023. To review the changes that were made, see “VersionHistory.txt” in the attached files section. In May 2017, the data authors discovered that a small subset of the silicate measurements made between January 2011 and February 2014 have questionable reliability. The authors removed these data in the revised file: "SanFranciscoBayWaterQualityData1969-2015v3.csv". On 27 December 2016, the data authors discovered that the data file associated with this data release had an error. The original data file had inconsistencies in the format of dates. The author corrected that error in the attached data file "SanFranciscoBayWaterQualityData1969-2015v2.csv".