Draft aug 3, 2014 dp wq report

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DRAFT August 3, 2014 Report Dudley Pond Water Quality Sampling Program Author - Toni Moores This document is part of an ongoing Surface Water Quality Committee (SWQC) water quality sampling program initiated for Dudley Pond. The objectives of the Program are to gather Dudley Pond water quality data that will be used to:  Compare to similar water quality data gathered in the past at Dudley Pond.  Track the trophic index of Dudley Pond during the spring, summer and fall of each year. Summary  

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On August 3, 2014 water quality data was gathered at three depths at three sample points. Water quality parameters such as, pH, oxidation – reduction potential (ORP), dissolved oxygen (DO), dissolved oxygen % saturation and temperature were measured at three depths at each of the three sample points by SWQC members using a YSI Multimeter. Water and Secchi depths were measured at each of the three sample points. Samples were gathered by SWQC members and analyzed by Nashoba Analytical LLC. Based on a number of parameters shown below the water quality found on August 3, 2014 was much better than August 24, 1981, but one of the worst since 2011 when the SWQC started gathering water quality data. Water quality data found on August 3, 2014 including DO Percent Saturation, OxidationReduction Potential and the Total Nitrogen concentrations were significantly different than in the summer samplings of the past. The “abnormal” water quality parameters on August 3, 2014 may have been negatively influenced by a large amount of surface water runoff from a large rain event that occurred approximately 36 hours prior to taking data and gathering samples. Historical Dudley Pond water quality data appears below.

Date TSI * August 24, 1981 49 - 54 Sept. 11, 2011 44 - 48 August 5, 2012 48 - 52 August 5, 2013 43 - 48 August 3, 2014 47 - 53 * Above the thermocline (~ 12 feet) **Contaminated sample

Chlorophyll a * 7.0 4.41 – 6.3 ppb 2.9 – 17.29 ppb 4.65 – 13.03 ppb 7.48 – 10.83 ppb

Secchi Depth 2.1’ 9.83’ 6.75’ 10.75’ 8.24’

Total Phosphorus* 30 ppb ND ND 20 ppb ** ND

Background Historically Dudley Pond has been sampled most frequently at the “deep hole” (Sample Point 25) on Dudley Pond. In order to have data sets that are comparable to historical data, samples were gathered at locations 24, 25 and 27 as indicated in Figure 1. Two of these sample locations correspond to the sample locations used in the Larkin (1978) and IEP (1983) reports. Line-of-site intersections were used to locate sampling points.


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