Dale Maffitt Reservoir IA 04-RAC-1119

Polk County S31T78NR25W at SW edge of Des Moines.

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 2020 - 2022
Stream/River Water Quality Data	CY 2020 - 2022
Lake Water Quality Data	CY 2018 - 2022
Biological Sampling Data	CY 2018 - 2022*
Fish Kill Data	CY 2018 - 2022
Fish Tissue Sampling Data	CY 2018 - 2022
Continuous Dissolved Oxygen Sampling Data	CY 2018 - 2022
*Biological sites sampled in both 2017 and 2021 were also assessed.

Open Segment Map
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Cycle: 2024
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: Mesotrophic
Trend: Stable
Created: 11/1/2023 8:13:07 AM
Updated: 2/5/2024 8:42:07 AM

Use Support

Class A1

Recreation - Primary contact

Fully Supported

Class BLW

Aquatic Life - Lakes and wetlands

Fully Supported

Class C

Drinking Water -

Fully Supported

Class HH

Human Health -

Not Assessed

Impairment Delistings

No delistings for this assessment cycle.

Documentation

Assessment Summary

The Class A1 use was assessed (monitored) as “fully supported.” The Class BLW use was assessed as “fully supported.” The Class C use was assessed as “fully supported” based on water quality monitoring data and drinking water compliance monitoring required by the DNR. In terms of nutrient condition and water transparency, this lake continues to demonstrate exceptional water quality. All other designated uses were “not assessed.”

Assessment Explanation

Data Sources:

Data Source	Data Source ID	Data Type	Data Age	Site ID	Site Name	Site Description
PWS	27	WQ	CY 2018-2022	99990173	Dale Maffitt Reservoir	Des Moines Water Works Raw water intake
Iowa DNR	6	WQ	CY 2018-2022	22250002	Dale Maffitt Reservoir

Class A1 - Indicator Bacteria:

Site ID

Data Source ID

# Samples per Year (2020/ 2021/2022)

2020 Geometric Mean

2021 Geometric Mean

2022 Geometric Mean

Violates Annual Geometric Mean?

# 2020 SSM violations / SSM Violations needed for impairment

# 2021 SSM violations / SSM Violations needed for impairment

# 2022 SSM violations / SSM Violations needed for impairment

Violates Annual SSM Significantly >10% Rule?

Assessment Type

Support Level

99990173

34/36/35

3 / 7

0 / 7

2 / 7

Mon

Full

Class A1 - pH:

Site ID	Data Source ID	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
22250002	6	12 / 4	8.2	8.7	8.4	0	4	NO	Mon	Full
99990173	27	207 / 5	7.83	8.98	8.45	0	27	NO	Mon	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
22250002	6	Chlorophyll a TSI	15 / 5	15	59	36	NO	Mon	Full
22250002	6	Secchi TSI	15 / 5	38	50	44	NO	Mon	Full
22250002	6	Total Phosphorus TSI	15 / 5	24	48	37	NA	NA	NA
99990173	27	Total Phosphorus TSI	208 / 5	61	73	61	NA	NA	NA
22250002	6	Inorganic suspended solids	15 / 5	0.6	4	1.7	NA	NA	NA

Class BLW - Binomial Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	# Violations	# Acute / Chronic Violations	Violations needed for impairment	Violates Significantly >10% Rule?	Assessment Type	Support Level
99990173	27	Chloride	208 / 5	1.7	16.5	14.1	NA	0 / 0	27	NO	Mon	Full
22250002	6	Dissolved Oxygen	15 / 5	7.3	10.1	8.3	0	NA / NA	4	NO	Mon	Full
22250002	6	pH	12 / 4	8.2	8.7	8.4	0	NA / NA	4	NO	Mon	Full
99990173	27	pH	207 / 5	7.83	8.98	8.45	0	NA / NA	27	NO	Mon	Full
99990173	27	Sulfate	208 / 5	1.7	21.1	17.6	0	NA / NA	27	NO	Mon	Full
22250002	6	Temperature	15 / 5	19.9	28.9	25.4	0	NA / NA	4	NO	Mon	Full

Class BLW - Toxic Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Maximum Value	Mean Value	Median Value	# Acute / Chronic Violations	>1 Acute / Chronic Violation	Assessment Type	Support Level
22250002	6	Ammonia	12 / 4	0.019	0.01	0.01	0 / 0	NO	Mon	Full

Class C - Binomial Parameters:

Site ID	Data Source ID	Parameter Name	# Samples / # Years	Minimum Value	Maximum Value	Mean Value	Median Value	# Violations	Violates Significantly >10% Rule?	Assessment Type	Support Level
99990173	27	Chloride	208 / 5	1.7	16.5	14.1	14.4	0	NO	Mon	Full
99990173	27	Fluoride	208 / 5	25	340	249	250	0	NO	Mon	Full
22250002	6	Inorganic nitrogen (nitrate and nitrite)	14 / 5	0.02	0.4	0.1	0.045	0	NO	Mon	Full
99990173	27	Nitrate	208 / 5	0.02	1.09	0.06	0.02	0	NO	Mon	Full
99990173	27	Nitrite	208 / 5	0.05	0.05	0.05	0.05	0	NO	Mon	Full
22250002	6	pH	12 / 4	8.2	8.7	8.4	8.4	0	NO	Mon	Full
99990173	27	pH	207 / 5	7.83	8.98	8.45	8.44	0	NO	Mon	Full

Class C - Iowa Drinking Water Compliance Report:

Compliance monitoring required by the Iowa DNR Water Supply Operations and Engineering Sections did not show violations of finished water caused by source water at the Des Moines Water Works facility during the 2020-22 monitoring period. The results of compliance monitoring as reported in annual compliance reports are available at the following location at the Iowa DNR’s home page: https://www.iowadnr.gov/Environmental-Protection/Water-Quality/Water-Supply-Engineering/Annual-Compliance-Report

Class HH - No Data

Monitoring and Methods

Assessment Key Dates

3/5/2018

Monitoring Start

12/12/2022

Monitoring End

Methods

200

Physical/Chemical Monitoring

275

Drinking water compliance reports

860

Other Agencies/Organizations provided monitoring data