We are very fortunate in Lake County to have a group of scientists who carefully monitor the environmental health of our area. The Lakes Management Unit periodically surveys lakes in the county and issues reports on them. They have issued two reports on Gray's Lake to date. Attached below is the 2002 report. A link to their web site is located on the Links page in this web site.
The first report was issued in March 1989; it is important to keep this fact in mind when considering the following conclusions issued at the time.
1. 83% of water clarity measurements failed to achieve a depth of four feet and averaged 3.3 feet.
2. Storm water flowing into the lake from the storm drains in the north and south end of the lake contribute to lake degradation. Lead and mercury levels in the channel were at 50% and 80% of their standards respectively. Fecal coliform bacteria were high in the storm water but satisfactory in the lake and in the beach water.
3. "Aquatic plants in the lake display a remarkable amount of diversity...". The quantity of aquatic plants indicates excessive levels or nitrogen and phosphorous (from fertilizer) in the water.
4. High levels of cadmium were found in the lake's sediments exceeding state standards. However, a public health hazard does not yet exist since the lake is not used for drinking water and elevated cadmium levels were not found in the fish. The sediments "probably" also have high levels of nitrogen and phosphorous nutrients.
5. Sediment in the southeast end of the lake also contain 8 organic compound derivatives of coal/tar. The source of these compounds is not explained. However, this end of the lake is adjacent to Route 120 and at the time was near a gas station and within proximity of the Skokie Valley Asphalt plant.
6. Ammonia-nitrogen levels were elevated in the northwest channel and in the lake's deep water indicating low oxygen levels. It is noted that an aeration device was in use in the channel at the time to combat this problem. (The aeration device has been removed). Nitrate-nitrogen was in low concentrations in the rest of the lake probably due to plant uptake. Nitrogen compounds encourage excessive plant growth.
7. Phosphate (dissolved orthophosphate) were low through the lake but higher in stormwater entering the lake. Phosphate encourages excessive plant growth.
8. The watershed is primarily urban and contains virtually no wetlands. This leads to higher nitrogen and phosphate levels in the lake along with silts in run-off water.
9. Dissolved oxygen levels were too low for aquatic life in the 7-10 foot depth and especially in July and August.
10. The lake's fishery is in an undesireable condition though in 1988 encouraging levels of grass pickerel were observed.