Study Design

A water quality monitoring program was conducted on Lake St. Clair and the Clinton River Watershed during the spring, summer and fall of 2003. The overall purpose of this project was to collect data and characterize water and sediment quality in the Lake and Watershed.

The project included five complementary monitoring activities; near shore, off shore, watershed, bathing beach and wet weather. The near shore testing was conducted at 23 major inputs to the lake, including the mouths of the Clinton River and Spillway, urban storm drains, smaller rivers and creeks and retention basin discharge points. Near shore sampling was conducted immediately adjacent to the outfalls; however, many samples were collected further from the outfalls than during previous years due to lower lake levels. Off shore sampling was conducted at 13 sites. Seven of the off shore locations corresponded to major near shore sample locations, two were adjacent to public beaches, two were municipal drinking water intake sites and the mouths of the North and South Channel. Water chemistry samples were collected during the spring, summer and fall seasons at 20 near shore and all off shore sites. Aqueous bacteriological samples and water quality meter readings (temperature, dissolved oxygen, conductivity, pH and turbidity) were collected weekly from April 24 through September 25 at all 23 near shore sites. Off shore water bacteriology testing and water quality meter readings were collected during the spring, summer and fall seasons. Sediment E. coli samples were collected during the summer and fall from 7 near shore and 7 off shore sites. Sediment chemistry samples were collected at 13 near shore locations. Aqueous samples for trace mercury analyses were collected at ten sites on the lake and six sites in the watershed.

Concurrent sediment and water samples were collected at 20 locations in the watershed for bacteriological examination during the spring, summer and fall. Sediment chemistry samples were collected at 5 locations. Water chemistry samples were collected at five locations during wet and dry weather conditions.

Bathing beach water and sediment sampling was conducted at 15 sites on the public beaches along Lake St. Clair (Blossom Heath, Memorial Park, HCMA Metropark, and New Baltimore). The sampling was performed at locations established for the Bathing Beach Water Quality Monitoring Program. Samples were collected monthly from July through September, and analyzed for water and sediment bacteriology.

Event sampling was conducted in the watershed in response to rain events exceeding one half inch in a 24-hour period. Water samples were collected for bacteriological analysis at 20 strategic locations between April and September. Sample locations were selected based on three criteria: proximity to known sewer overflows, locations of frequently high bacteria counts and at the most downstream sample site of each major sub-watershed drainage area of the Clinton River.

Executive Summary

Key Findings in the 2003 Lake St. Clair Assessment

Six sample sites had average annual nitrate values over the critical value of 0.30 mg/L. They include the Clinton River (n23), Salt River (n28), Milk River (o11), North Channel (o12), South Channel (o13) and Metropolitan Beach (o6). The inclusion of Metropolitan Beach on this list is likely due to the influence of the Clinton River. All of this suggests that major sources of water coming into Lake St. Clair are a significant source of the nitrate.

The seasonal geometric mean of the E. coli levels at any near shore or off shore site did not exceed the 30 day Total Body Contact Standard of E. coli CFU/mL, nor did the geometric mean for all near or off shore sites during any individual sampling event.

A statistically significant decrease in the daily geometric means of the E. coli levels at all near shore sample sites was observed between 1998 to 2003, using an exponential regression.

The critical value was exceeded for all sediment metal concentrations except mercury at the Clinton River (n23), At the Milk River site (n1) all sediment metal critical values were exceeded except arsenic.

There were no all-site averages that demonstrated a statistically significant trend in sediment metal concentration between the years 1998 and 2003. The only site with a statistically significant sediment metal decrease was the Martin Drain (n6).

Among the off shore sample sites, Metropolitan Beach (o6) had the highest average concentration for all aqueous chemistry parameters except nitrate. The nitrate concentration at Metropolitan Beach was only slightly lower than the highest off shore nitrate concentration. This is likely due to the influence of the Clinton River.

The highest aqueous mercury concentration (33 ng/L) was recorded at Liberty Drain (n2). This value was almost ten times higher than any other Lake St. Clair sample site and significantly greater than the critical value of 1.3 ng/L.

Analysis revealed that the E. coli level at some sites was related to turbidity. For instance, at the 12 Mile Relief Drain (n10), Clinton River (n23) and Salt River (n28), the E. coli levels were found to be significantly correlated with turbidity. At the Milk River (n1), Liberty Drain (n2), Clinton River Spillway (n19) and Irwin Relief Drain (n24), E. coli levels were found to be independent of turbidity readings.

Statistically significant trends were observed between 1998 and 2003 for three aqueous chemistry parameters. Average near shore values for ortho-phosphorous, biochemical oxygen demand and total organic carbon were all found to be decreasing over this time period. The total organic carbon concentration at the Clinton River (n23) was also found to have a statistically significant decreasing trend during these years.

Elevated PNA levels were found in the sediments at the Stephens Relief Drain (n4) in each of the last four years. The PNA concentration found at this site in the year 2000 sampling was twice as high as that for any other near shore site sample tested for PNA.

TO VIEW THE 2003 SITE SUMMARIES click here

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