Water Testing

Safety Committee tests the water 3 times a year, in 3 locations.

What we test for

E. Coli and/or fecal coliform: Fecal coliform is a group of several bacteria types that indicate possible, but not definite, contamination from feces in lake water. E. coli is a single type of bacteria found in feces that can cause illness, but most do not. It is an indicator that harmful bacteria and viruses may be present. With water contact such as swimming higher numbers of E. coli increase the chance of contracting illness. E. coli levels under 100 cfu/100 ml (colony forming units per 100 ml of water) are considered safe. At lower levels it is still possible to contract an intestinal illness from lake water, but unlikely. In Illinois a public beach is closed when E. coli exceeds 235 cfu/100ml.
Nitrogen and phosphorus: These are nutrients present in fertilizers that can wash into streams and lakes when it rains. They are also naturally produced when plants and animals die and decompose. Elevated nutrient levels indicate higher runoff volumes into the lake. Such runoff also includes sediment and other pollutants. The result of high nutrient levels is an increase in algae and other aquatic plant growth. A toxic cyanobacteria called “blue green algae” is also more likely to appear in lake coves when nutrient levels are high.

Mercury Containment Advisory for Fish

The Illinois Department of Public Health has placed a statewide mercury contaminant advisory for consumption of predator fish. The advisory recommends that children under 15 and women of childbearing age limit consumption to one meal per week. Dunlap Lake species included in advisory are largemouth bass, walleye, hybrid striped bass and muskie. It does not include bluegill, redear sunfish, crappie, channel catfish or common carp.

What can I do to help?

Work with the DLPOA to improve water quality.
Do not fertilize your lawn, especially the part near the water.
Do not put leaves or grass clippings in the lake.
Reduce soil erosion on your property
Create a rain garden if you have a large runoff area.

Full Reports

August 2024 – Report part 1. Click to see full report.

August 2024 – Report part 2. Click to see full report.

June 2024 – Water tested before 4th of July. Click to see full report.

May 2024 – Water tested before Memorial Day. Click to see full report.

August 2023 – Click to see full report. Phosphorus levels more than doubled from last year. Higher levels increase the chances of aquatic plant life and algae blooms. Nitrogen was similar to previous years. E. coli was analyzed with a test used for drinking water and the levels were very low compared to previous years.

The herbicide 2-4D was tested because it is probably the most common broadleaf herbicide used on lawns. The highest amount was found near the dam at 2.42 micrograms/liter (or parts per billion). The US EPA level for human consumption is <10. This herbicide has reportedly low toxicity to humans but may cause eye irritation at higher levels. Lead was not at detectable levels in any of the samples. The detection level is 0.015 mg/liter, or 15 micrograms per liter.

August 2022 – Dunlap Lake water samples were taken on August 22 to measure E. coli levels prior to Labor Day weekend. E. coli presence indicates contamination from animal or human waste. Some strains of E. coli can infect swimmers and cause illness, however most are harmless to humans. E. coli was not detected near the dam, and at low levels near the center of the lake off of the end of Hollyhock as well as near the south end of the lake off the end of Lotus. E. coli results are measured as the number of colony forming units (cfu) in 100 ml of water. E. coli concentrations were <20 cfu/100ml at the dam, rising to 40 at mid-lake and 60 near the south end. To put this in perspective the Illinois Department of Public Health will close a public beach to swimmers when E. coli is present at 235 cfu/100ml.

Nitrogen and phosphorus were also measured on August 22 to look at nutrients in the water that promote algae and aquatic plant growth. Nutrient levels were slightly lower near the dam than at the other two locations. Nutrient levels as well as E. coli levels were within the typical ranges for Dunlap Lake.

June 2022 – The results are roughly the same as the May sample but the E. coli concentration near the south end was reduced by half. Still, it is higher than the other two sample locations.

May 2022 – Note, since last test, water level had been dropped 10 feet for several months for spillway construction. Dunlap Lake water samples were taken on May 16 to measure E. coli levels prior to Memorial Day weekend. E. coli presence indicates contamination from animal or human waste. Some strains of E. coli can infect swimmers and cause illness, however most are harmless to humans. E. coli was detected at low levels near the dam and near the center of the lake off of the end of Hollyhock, while a moderately high level was present near the south end of the lake off the end of Lotus. E. coli results are measured as the number of colony forming units (cfu) in 100 ml of water. E. coli concentrations were 10 cfu/100ml at the dam and mid-lake locations. The south end sample was 100 cfu/100ml. To put this in perspective the Illinois Department of Public Health will close a public beach to swimmers when E. coli is present at 235 cfu/100ml. Still the level near the south end of the lake is high enough to warrant caution for swimmers.

Nitrogen and phosphorus were also measured on May 16 to look at nutrients in the water that promote algae and aquatic plant growth. Like E. coli levels, the nutrient levels were higher in near the south end of the lake. Both nutrient and E. coli inputs from the upper Mooney Creek watershed are the likely reason for elevated levels at the south end of Dunlap Lake.

2021 August – Dunlap Lake water samples were taken on August 17 to measure E. coli levels prior to the Labor Day weekend. E. coli presence indicates contamination from animal or human waste. Some strains of E. coli can infect swimmers and cause illness, however most are harmless to humans. E. coli was below measurable levels levels near the dam. It was present but at the lowest detectable concentration (10 colony forming units/100ml water) near the center of the lake off of the end of Hollyhock and in the south end off of Lotus. Swimmers will have minimal risk from E coli.

Nitrogen and phosphorus were also measured on August 17. Again, nitrogen and phosphorus are trending higher than last year. These nutrients are found in fertilizers and lead to increased plant and algae growth in the lake.

2021 June – Dunlap Lake water samples were taken on June 14 to measure E. coli levels prior to the 4th of July weekend. E. coli presence indicates contamination from animal or human waste. Some strains of E. coli can infect swimmers and cause illness, however most are harmless to humans. E. coli was below measurable levels levels near the dam, and near the center of the lake off of the end of Hollyhock. The sample near the south end of the lake off of the end of Lotus was inconclusive. Because E coli was higher than normal there in May and rainfall is forecast this week, we advise swimmers to use caution near the south end of the lake this holiday weekend. We believe that runoff from the Mooney Creek watershed after heavy rains may introduce higher levels of E coli in that portion of the lake.

Nitrogen and phosphorus were also measured June 14. Nitrogen levels were up by 30% from this time last year. Phosphorus levels were slightly higher than last June. These nutrients are found in fertilizers and lead to increased plant and algae growth in the lake.

2021 May – Dunlap Lake water samples were taken on May 18 to measure E. coli levels prior to Memorial Day weekend. E. coli presence indicates contamination from animal or human waste. Some strains of E. coli can infect swimmers and cause illness, however most are harmless to humans. E. coli was detected at low levels near the dam and near the center of the lake off of the end of Hollyhock, while a moderately high level was present near the south end of the lake off the end of Lotus. E. coli results are measured as the number of colony forming units (cfu) in 100 ml of water. E. coli concentrations were 10 cfu/100ml while the mid-lake contained 30 cfu/100/ml. The south end sample was 100 cfu/100ml. To put this in perspective the Illinois Department of Public Health will close a public beach to swimmers when E. coli is present at 235 cfu/100ml. Still the level near the south end of the lake is high enough to warrant caution for swimmers.

Nitrogen and phosphorus were also measured on May 18 to look at nutrients in the water that promote algae and aquatic plant growth. The dam and mid-lake samples were similar to previous years but the south end were slightly lower than in the past.

2020 August – Swimming should be safe, at least by lake standards. Nitrogen and phosphorus were up compared to the previous samples this year but similar to August samples in previous years. The water has been green due to algae blooms the past couple of months but fortunately there has not been an abundance of filamentous algae that gums up boat motors and fishing lures. From my observations the cyanobacteria or blue green algae blooms have not been as prevalent in recent weeks as they were earlier in the summer.

2020 June – The results did not show any reason for concern about nutrient levels or E coli concentrations. The lowest detectable E coli level is 10 colony forming units/100ml water and none of the samples exceeded that. I am not sure why exact figures for phosphorus were not given on two of the samples, but still they were in the normal range for Dunlap Lake.

2020 May – The results did not show any reason for concern about nutrient levels or E coli concentrations. The lowest detectable E coli level is 10 colony forming units/100ml water. That was the count near the south end. There was no detectable E coli near the dam. The highest E coli level was in the central lake sample at 20 cfu/100ml.