Allen Green Refuge Marsh IA 02-ICM-620

Assessment Comments

Assessment remains based on information from the IDNR Wildlife Bureau.

Basis for Assessment

SUMMARY:  Continued to assess (evaluate) support of the Class B(LW) aquatic life uses as "partially supported" due to de-watering from an adjacent drainage ditch.   This type of impairment is appropriate for Category 4c of Iowa's Integrated Report (I.e.,  impairment due to a non-pollutant stressor).   Fish consumption uses remain "not assessed."  This is the same assessment as used for the 2002 and 2004 assessment/listing cycles.

EXPLANATION:  According to the DNR Wildlife Biologist (Ohde), the nutrient impact identified for this wetland in previous Section 305(b) assessments no longer exists:  the cattle feedlot virtually on the banks of the wetland has now been abandoned for several years.   The impacts from hydrological modification caused by the adjacent drainage ditch, however remain.   This ditch has completely altered the natural hydrology of the wetland.   The ditch is lower than the bottom of the wetland basin and tends to speed drying of the basin such that the wetland has been altered from a mostly open semi-permanent wetland to a seasonal wetland dominated by perrenial emergent vegetation.   Water is pumped into the wetland in the fall for use by migratory waterfowl, but the rate of water loss to the drainage ditch makes year-round pumping to restore wetland function (1) impossible given current pumping capabilities and (2) cost prohibitive.   The assessment category for this wetland of "evaluated" indicates that the assessment is based entirely on "best professional judgement."  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.   IDNR considers waterbodies identified as "impaired" based on "monitored assessments" as candidates for the state's Section 303(d) list.   "Evaluated assessments" are those based on data older than five years or other than site-specific ambient monitoring data (e.g., questionnaire surveys of fish and game biologists [=best professional judgement]) and thus have relatively low confidence.   IDNR does not consider waterbodies identified as "impaired" based on "evaluated assessments" as candidates for the state's Section 303(d) list.  

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