73 
cruise AND there is a record for at least one fixed station not located particularly 
close to the boundary of the targeted segment. 
20. The seasonal averages for each interpolator cell should then be inserted into a 
spreadsheet designated for the assessment. 
STEP 5. DESIGNING THE ASSESSMENT SPREADSHEET 
21. Set up the spreadsheet where the assessment will be done. It should have 
columns corresponding to the interpolator cells (or centroids) — either as a 
unique ID the analyst has created or as the UTMx and UTMy coordinates 
assigned to those centroids. A field containing segment identification (e.g., 
“TF1” or “PH") should also be created. The sequence of the centroids should 
match exactly with the sequence from the “.esf’ file, to allow for easy copying 
and pasting. 
22. Because only the James River main stem requires assessment, certain centroids 
need to be excluded from the analysis. It is recommended that the analyst keep 
these centroids on the spreadsheet, but that instead of being assigned a segment 
ID (e.g., “CHKOH”), they should be marked with a null character, such as a 
period or an asterisk. Along with the centroids within Appomattox and Chicka- 
hominy segments, individual JMS centroids falling in small embayments and 
non-CPB tributaries (like the Pagan River) should be restricted from the assess¬ 
ment. GIS can be used to identify these centroids. 
23. Create a field called “chlorophyll”. This is where the Interpolator estimates will 
be inserted. 
24. The next field will contain the assessment binary (“pass” or “fail”) for each 
centroid. Because each segment has a different criterion, an “IF” statement 
similar to the following should be created: 
=IF(chlorophyll=“IF(chIorophyll>criteria,“fail”,“pass”)) 
where chlorophyll = chlorophyll value for centroid 
= null value (if centroid has missing data) 
criteria = chlorophyll value the centroid is being assessed against 
fail = exceeds the criteria 
pass = less or equal to the criteria 
The statement, reduced to layman’s terms, says: “If the chlorophyll value for this 
cell is missing, insert a null value. If it’s greater than this specified value, insert 
a ‘fail’. If it’s less than or equal to this specified value, insert a ‘pass’.” 
In Virginia, refer to the table on page 35 of the Water Quality Assessment Guid¬ 
ance Manual for Y2008 for the criteria for each segment and season. 
25. A table should be created that tallies up the number of “fails” for each segment 
and calculates a percentage of “fails” from the total number of cells in a 
segment. This percentage will be used to calculate the CFD. In addition, the 
analyst should also calculate the percent of area interpolated for each segment 
by tallying up the number of null characters in the assessment field. 
appendix g • Chlorophyll a Assessment Protocol 
