Mormon Trail Lake IA 05-NOD-1404

Adair County S17T76NR31W 1.5 mi SE of Bridgewater.

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 2016 - 2018
Stream/River Water Quality Data	CY 2016 - 2018
Lake Water Quality Data	CY 2014 - 2018
Biological Sampling Data	CY 2014 - 2018*
Fish Kill Data	CY 2014 - 2018
Fish Tissue Sampling Data	CY 2014 - 2018
Continuous Dissolved Oxygen Sampling Data	CY 2014 - 2018
*Biological sites sampled in both 2013 and 2017 were also assessed.

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Cycle: 2020
Release Status: Final
Overall IR: 5 - Water is impaired or threatened and a TMDL is needed.
Trophic: Eutrophic
Trend: Stable
Created: 8/25/2020 3:02:11 PM
Updated: 10/15/2020 7:44:18 AM

Use Support

Class A1

Recreation - Primary contact

Fully Supported

Class BLW

Aquatic Life - Lakes and wetlands

Fully Supported

Class HH

Human Health -

Partially Supported

Fish Consumption Advisory: Mercury

Support Level

Partially Supported

Impairment Code

5a - Pollutant-caused impairment. TMDL needed.

Cause Magnitude

High

Status

Continuing

Source

Unknown: Source Unknown

Source Confidence

High

Cycle Added

2008

Impairment Rationale

Fish consumption advisory in effect: no more than 1 meal/week

Data Source

Fish contaminant monitoring: Iowa DNR

TMDL Priority

Tier IV

General Use

General Use water -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 uses are assessed (monitored) as “fully supported.” The Class BLW uses are assessed (monitored) as “fully supported." Class HH uses remain assessed (monitored) as “partially supported” due to the issuance of a fish consumption advisory at this lake.

Assessment Explanation

Sources of Data:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
Iowa DNR	6	WQ	CY 2014-2018	22010004	Mormon Trail Lake	Lake Deep Point
Iowa DNR		FT	See Below	73	Mormon Trail Lake

Class A1 - Indicator Bacteria: No Data

Class A1 - pH:

Site ID	Data Source ID	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Violations	% Violations	Significantly >10% Violations	Assessment Type	Support Level
22010004	6	14 / 5	8.7	8.5	8.6	0	0%	NO	Monitored	Full

Class A1 - Lake TSI's

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Median Value	Median TSI Violation	Assessment Type	Support Level
22010004	6	Chlorophyll a TSI	15 / 5	36	67	57	NO	Monitored	Full
22010004	6	Secchi TSI	15 / 5	53	67	57	NO	Monitored	Full
22010004	6	Total Phosphorus TSI	15 / 5	48	65	57	NA	NA	NA
22010004	6	Inorganic suspended solids	15 / 5	0.4	64	2.1	NA	NA	NA

Class BLW - Conventional Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	% Acute/ Chronic Violations	Significantly >10% Violations	Assessment Type	Support Level
22010004	6	Ammonia	14 / 5	0.1224	0.02	0.01	0 / 0	0% / 0%	NO	Monitored	Full
22010004	6	Dissolved oxygen	15 / 5	11.11	8.44	8.4	NA / 0	NA / 0%	NO	Monitored	Full
22010004	6	pH	14 / 5	8.7	8.5	8.6	0 / NA	0% / NA	NO	Monitored	Full
22010004	6	Temperature	15 / 5	29.2	24.54	24.4	0 / 0	0% / 0%	NO	Monitored	Full

Class BLW - Lake Planktonic Cyanobacteria:

Site ID	Data Source ID	# Samples	Maximum Cyanobacteria Wet Mass	Maximum Cyanobacteria % Composition	Median Cyanobacteria Wet Mass	Median Cyanobacteria % Composition	Median Cyanobacteria Wet Mass = 75th Percentile	Assessment Type	Support Level
22010004	6	11	45.827	95 %	10.696	87.5 %	NO	Evaluated	NA

Class HH - Fish Tissue Sampling:

Site ID

Date

Species Name

Biopart

# in sample

chlordane result

chlordane violation?

PCBs result

PCBs violation?

Hg result

Hg violation?

Assessment Type

Support Level

7/28/15

largemouth bass

plug

0.274

Monitored

Full

8/11/09

largemouth bass

fillet

0.341

Yes

Evaluated

Partial

9/23/09

walleye

fillet

0.245

Evaluated

Full

8/11/09

snapping turtle

shoulder

<0.03

<0.09

0.138

Evaluated

Full

The level of mercury in a sample of largemouth bass was below the advisory level, however, according to Iowa DNR’s assessment listing methodology, if two consecutive samplings show that contaminant levels are below the consumption advisory threshold, the impairment of the Human Health designated use can be removed. Therefore, the fish consumption advisory remained at Mormon Trail Lake, and the fish consumption uses for this lake have remained assessed as "partially supported."

Monitoring and Methods

Assessment Key Dates

6/16/2014

Fixed Monitoring Start Date

8/26/2018

Fixed Monitoring End Date

8/11/2009

Fish Tissue Monitoring

9/23/2009

Fish Tissue Monitoring

7/28/2015

Fish Tissue Monitoring

Methods

120

Surveys of fish and game biologists/other professionals

222

Non-fixed-station monitoring (conventional during key seasons and flows)

260

Fish tissue analysis

340

Primary producer surveys (phytoplankton/periphyton/macrophyton)

420

Indicator bacteria monitoring