Comment submitted by James Schmidt, Wisconsin Department of Natural Resources (WIDNR)

I've got two comments on the proposed criteria, one is fairly simple and the other is a bit more complicated. 1) I think there's a typographical error in the tabe on page 43, namely the acute criteria for mussels absent at temperature 18C. Earlier on page 35, the document states the criteria for mussels absent increases with decreasing temperature until it reaches a maximum at 16.6C. However, in the table on page 43, the criteria are the same at 16C and 18C; if the criteria increase until 16.6C then the results at 18C should be different than (and more stringent than) those at 16C. The difference isn't great (I checked some examples), but it's still a diffeence that should be corrected. I didn't check the other temperatures, but this is just one that jumped out because there should have been a difference. Second, and more significant, I question the document retaining the assumed relationships between pH and temperature and ammonia toxicity from the equations in the 1999 document. I realize the impact on the equations isn't great, but given that there are over twice as many acute toxicity study results in the new draft than there were in 1999, I find it hard to believe that there's no change in the assumed relationship. Given the impact these criteria have on wastewater discharges, I feel it's responsible of you to have all the statistical considerations current. The 1999 document had 37 results from invertebrate tests and 255 for fish, this draft has 148 results for invertebrates and 479 for fish and amphibians and given that many of those species have three or more results, it's almost certain that the pH and temperature relationships would change. I didn't check what the changes are, but Wisconsin used similar logic to adjust the hardness/toxicity relationships for metals in recent criteria changes and we would expect the same would be done here especially given the larger database size. - James Schmidt WI DNR 6082677658 jamesw.schmidt@wisconsin.gov