Elm Lake IA 02-IOW-657

Assessment Comments

Assessment remains based on information from the IDNR Wildlife Bureau and on watershed modeling by the IDNR Water Quality Bureau.

Basis for Assessment

SUMMARY:  The Class B(LW) aquatic life uses are assessed (evaluated) as "fully supported” based on information from the IDNR Wildlife Bureau.   The fish consumption uses remain "not assessed" due to the lack of water quality information upon which to base an assessment.   Due only to a change in IDNR's assessment/listing methodology, the 2004 assessment of the Class B(LW) aquatic life uses ["fully supporting / threatened" (minor impacts)] is changed to "fully supporting".   Other than this change in methodology, 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:  The aquatic life uses are assessed as "fully supported" based on information from the Iowa DNR Wildlife Bureau.   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.   The 2004 assessment is included below:

2004 ASSESSMENT:  EXPLANATION:  The aquatic life uses are assessed as "fully supporting / threatened."  The upgrade in support of the aquatic life uses from "partially supporting" (see assessments for the 1998 and 2000 reports above) to "fully supported / threatened" is based on the following information from the Iowa DNR Water Quality Bureau.   Watershed modeling on this wetland indicates that sediment delivery to the wetland is estimated at 1.6 tons/2" rainfall event from the entire watershed.   This is a very low sediment delivery rate and would be difficult to reduce further.   Based on this information, the previous identification of "siltation" as impairing the aquatic life uses of this wetland was probably in error.   Thus, the level of support of the aquatic life uses is upgraded from "partially supported" to "fully supporting / threatened."  The assessment category for this wetland is "evaluated."  In terms of Section 305(b) reporting, "monitored assessments" are based primarily on recent, site-specific ambient monitoring data and thus have relatively high confidence.   "Evaluated assessments" are those based on data older than five years or other than site-specific ambient monitoring data (e.g., desktop models or questionnaire surveys of fish and game biologists [=best professional judgement]) and thus have relatively lower confidence.  

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring.   In general, Iowa wetlands are not managed for recreational fisheries; thus, fish contaminant monitoring is not typically conducted at these waterbodies.