Comparison of DEP’s sonde data and Rettew’s sonde data collected downstream of Fisherman’s Paradise. DEP sonde was SC04, later the naming changed to 09SC. Rettew sonde was CIM-04. Sondes were similiarly placed upstream of USGS 01546500 station and Spring Creek Road bridge. Only data where both DEP and Rettew had approved/corrected values are included in this comparison.

WATER TEMP

Specific Conductivity

pH

Dissolved Oxygen mg/L

Comment

Rettew didn’t take the same approach as DEP did when correcting data. Rettew calculated a calibration error very similar to the DEP calibration error calculation. They did not calculate a fouling error, or a discrete/undocumented error that DEP also applies to the correction of CIM data.These additional corrections have potential to move data(if applied) with more accuracy. DEP also calculates total errors and applies grades to this total error. Some data can have such large errors, that the data is deleted. Rettew’s approach doesn’t appear to do this.

Even though R^2 numbers are good for this particular station, the data values are different. As can be seen with the DO and pH data comparison plots, Rettew’s data generally have higher daily max’s, and higher daily mins.

A brief look at their data also found an error in their spreadsheet for CIM-04 Maintenance Check #1 (2021-08-04 to 2021-09-16), as shown in the two screen shots below. The count value should be 1613, but the error was calculated using 1353.