Loch Ayr IA 05-GRA-1381

Ringgold County S30T69NR29W 2 miles N of Mt. Ayr.

Open Data Collection Period Modal

For purposes of developing stream/river water quality assessments for integrated reporting, three years of water quality data are typically used for both conventional pollutant parameters (e.g., indicator bacteria) and the less frequently monitored toxic parameters (e.g., toxic metals). Since the 2004 IR cycle, DNR has used a three-year data gathering period for streams, rivers, and beaches. For most assessments, the use of three years of data increases the number of samples upon which the decision on use support is based and helps address the problem of weather-related year-to-year fluctuations in water quality.

Due to the lower sampling frequency in Iowa’s ambient lake, biological, fish kill, and fish tissue monitoring programs, five years of data are used for developing IR assessments and for identifying Section 303(d) listings.

Data Type	Data Timeframe
Beach Sampling Data	CY 2014 - 2016
Stream/River Water Quality Data	CY 2014 - 2016
Lake Water Quality Data	CY 2012 - 2016
Biological Sampling Data	CY 2012 - 2016*
Fish Kill Data	CY 2012 - 2016
Fish Tissue Sampling Data	CY 2012 - 2016
Continuous Dissolved Oxygen Sampling Data	CY 2012 - 2016
*Biological sites sampled in both 2011 and 2015 were also assessed.

Open Segment Map
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Cycle: 2018
Release Status: Final
Overall IR: 2 - Some of the designated uses are met but there is insufficient data to determine if remaining designated uses are met.
Trophic: Unknown
Trend: Unknown
Created: 6/11/2019 1:19:28 PM
Updated: 8/27/2019 10:36:44 AM

Use Support

Class A1

Recreation - Primary contact

Not Assessed

Class BLW

Aquatic Life - Lakes and wetlands

Not Assessed

Class C

Drinking Water -

Fully Supported

Class HH

Human Health -

Not Assessed

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 (primary contact recreation) uses and the Class B(LW) aquatic life uses remain "not assessed" (IR 3a) due to the lack of water quality information upon which to base an assessment. The assessment of the Class C (drinking water) uses remains “fully supported” (IR Category 2a) based on results of atrazine monitoring from 2010-12. Fish consumption uses remain "not assessed" (IR 3a) due to the lack of fish contaminant monitoring at this lake. The source of data for this assessment remains the results of atrazine monitoring from October 2010 to October 2012 as part of Syngenta’s voluntary monitoring program. This monitoring was conducted through a cooperative sampling arrangement between Syngenta and Iowa DNR.

Assessment Explanation

The Class A1 and Class B(WW) uses remain "not assessed" due to the lack of water quality information for this lake upon which to base an assessment.

The assessment of support of the Class C (drinking water) uses remains “fully supporting” (IR Category 2a) based on results of atrazine monitoring conducted as part of Syngenta’s voluntary monitoring program through a cooperative arrangement with Iowa DNR. The long-standing impairment of drinking water uses at this former water supply reservoir was based on the results of Syngenta-sponsored atrazine monitoring in 2000 and 2001. These data showed that while average levels of atrazine were below the MCL, data from monitoring in 2001 suggested an increasing (worsening) trend such that full support of the Class C uses was “threatened” (see assessment narratives for previous assessments for the details of this assessment). According to DNR's Section 305(b) assessment methodology, if the average contaminant levels in source water are less than the MCL, but average levels appear to be trending upward, the Class C (drinking water) uses of the source water should be assessed as "fully supported/threatened". Thus, this impairment was added to Iowa’s 2002 Section 303(d) list.

No additional data for atrazine have been generated from Loch Ayr from 2002 through 2009, and this former water supply reservoir has remained assessed as Section 303(d) impaired during this time. Syngenta-sponsored monitoring began again in 2010 through a cooperative arrangement with Iowa DNR. Twenty-five monthly samples were collected from October 2010 through October 2012. None of the 25 samples collected exceeded the atrazine MCL of 3 ppb (maximum = 0.92 ppb). All of the 14 moving annual averages were well below the MCL (maximum = 0.35 ppb). According to Iowa DNR’s assessment/listing methodology, the Class C (drinking water) uses should be assessed as “fully supporting” if all moving annual average levels of atrazine are less than the maximum contaminant level (MCL) of 3 ug/l. Thus, the drinking waters uses for Loch Ayr were assessed as “fully supporting” for the previous IR cycle and remain assessed as "fully supporting" for the current IR cycle.

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring at this lake.

Monitoring and Methods

Assessment Key Dates

1/10/2000

Fixed Monitoring Start Date

12/10/2001

Fixed Monitoring End Date

10/5/2010

Fixed Monitoring Start Date

10/2/2012

Fixed Monitoring End Date

Methods

270

PWS chemical monitoring (ambient water)