Grannis Creek IA 01-VOL-322

Assessment Comments

Assessment is based on a 2006 summary of trout reproduction in Iowa streams prepared by the IDNR Fisheries Bureau.

Basis for Assessment

SUMMARY:  The Class B(CW) coldwater aquatic life uses are assessed (monitored) as "fully supported" based on the May 2006 summary of trout reproduction in Iowa streams as prepared by the IDNR Fisheries Bureau.   Fish consumption uses remain "not assessed."  Due only to a change in IDNR's assessment/listing methodology, the 2004 assessment of the Class B(CW) aquatic life uses ["fully supporting / threatened" (minor impacts)] is changed to "fully supporting".   This new (2006) assessment is the same as that developed for the previous (2004) assessment/listing cycle (not impaired) and does not reflect any known change in water quality.

EXPLANATION:  Based on an updated summary of trout reproduction in Iowa streams prepared by the DNR Fisheries Bureau in May 2006, the Class B(CW) uses are assessed as "fully supported".   According to the updated summary, Grannis Creek is in the group of Iowa coldwater streams that supports natural reproduction of trout.   Based on results of surveys by the IDNR Fisheries Bureau, this stream is placed in the category of Iowa trout streams that exhibit recent, but inconsistent reproductive success and that are generally not capable of maintaining a viable population for the resident trout species at this time.   This assessment is consistent with previous assessments of the ability of this stream to support natural reproduction of trout.   At the recommendation of U.S.  EPA Region 7, IDNR's 2006 assessment/listing methodology was changed to eliminate use of the "fully supported/threatened" (not impaired) category.   Thus, previous assessments identified as "fully supported/threatened" (not impaired) were changed to "fully supported" for the 2006 assessment/listing cycle.   This change does not alter the 2004 assessment:  this waterbody remains in IR Category 2a.

Fish consumption uses remain "not assessed" due to lack of fish tissue monitoring in this stream reach.