JULY 2009 WATER QUALITY SUMMARY

The 2009 July water tests were completed on the 15th for the streams and the 17th for the lake. These tests followed a three week period of well above average rain fall. This wet weather increased the stream flows, raised the lake by approximately 1ft., and affected the water test readings for the month. When tested this week, the flows had slowed and the lake has started to drop in level as the dam outflow now surpasses the stream inflow rate. This create an unusual set of readings because the top layer of water above thermal layer has been refreshed by the rain and wet weather. A brief summary follows for each characteristic tested:

Conductivity – (a measure of salinity) – While all readings were in the normal range, North Pond yielded readings about 40% higher than Middle and South Pond. The streams did not reflect higher readings when tested this week but may have been the source of the increased salinity level over the past few weeks when they were flowing at much higher rates then was present the day they were tested.

Nitrates – (Indication of nutrient loading) - Nitrates showed elevated levels from the surface down to the thermal barrier which was around 18-20 ft across the 3 ponds for this month’s test. The Troll sensor showed higher readings than the Colorimeter tests but both showed elevated Nitrate levels in the upper layer of water in the lake. The streams tested low with the exception of the runoff stream that enters the lake at the corner of Wakefield and Lakeside Ave which is the location at which it was tested.

Dissolved Oxygen (DO) – DO levels above the thermal barrier yielded fairly good readings in the 8mg/L range but dropped to virtually zero quickly below the thermal barrier. The drop from normal levels to near zero level is sharp and not normally seen as dramatic at this. It may be due to the upper layer being refreshed with rain, stream, and runoff water, over the last few weeks, but below the thermal barrier it has not been refreshed. Oxygen levels are near zero from 20ft of depth on down which again is highly unusual. This suggest that an algae bloom is occurring below the thermal barrier but has been truncated above the thermal barrier due to the wet weather causing low DO levels. DO readings in all the streams were very good.

Oxygen Reduction Potential (ORP) – ORP measures the water’s ability to store electrical energy which is a direct indication of the waters ability to oxidize nutrients, impurities, and bacteria. ORP readings showed good values from the surface down to the thermal barrier. Below the thermal barrier, ORP levels dropped rapidly. The rapid decline of DO and ORP readings below the thermal layer suggest that an algae bloom exists below the thermal barrier. ORP levels in the streams were good with the exception of Brown Brook which enters Smith Cove near Indian Ranch. It is unclear why Browns showed these lower readings.

pH – pH readings in the streams were all normal. In the lake, pH readings from the surface down to the thermal barrier showed elevated readings. Normal pH readings are 6.5-6.7. All three ponds showed elevated pH readings in the 7.0–7.15 range in the top layer from the surface down to the thermal barrier. Below the thermal barrier, pH readings tested normal. The higher pH readings in the top layer are likely due to the wet weather.

Temperature – The water is warming up. In the last month, the water temps have risen from the 65-67 degree range to 74-75 degrees near the surface. The temperature is above 70 degrees down the thermal barrier which was approximately 18ft in depth. Below the thermal barrier, the temperature drops steadily with temperatures at the bottom of South and Middle pond reading approximately 60 degrees and the deeper North pond readings were 52 degrees.

Phosphorus – Phosphorus levels tested normal in both the streams and the lake. Water samples for Phosphorus are taken from each of the streams and in each of the 3 ponds at the surface, at the thermal barrier, and at the bottom. This test is performed on the collected samples using Colorimeter equipment that used chemical reduction to free any Phosphorus that is bound in other solids. Optical readings are then taken and compared with a reference standard to yield the readings for Total Phosphorus.

Chlorophyll-a – (a indicator of algae content) - Water samples are collected for Chlorophyll-a. Results are not available for this test since samples are sent to Microbac labs in Worcester and take a couple of weeks to get the results back.