ACASAK Aquatic Monitoring Consulting 380 W Roxbury Pkwy, West Roxbury, MA 02132 www.acasak.com September 2, 2022 Monitoring Results For: Wayland Surface Water Quality Committee DUDLEY POND MONITORING Enclosed with this report are results from monitoring Dudley Pond on 9/1/22. YSI meter data are provided for surface and bottom measurements at three locations: DUD-024, DUD-025, and DUD-027. The meter data includes temperature, dissolved oxygen saturation, dissolved oxygen concentration, and pH. Conductivity, specific conductance, ORP, and turbidity were added because the sensor included them. Secchi depth is relevant for DUD-025 only, because the other two sites were not deep enough to exceed the visibility depth. Pages 2-4 of this report include analyses of all data collected since 2020. Profile measurements at DUD-025 have been added to this report because they were easy to collect. Also enclosed are calibration records for the YSI meter. All sensors performed within the target range of accuracy. Observations: • This September survey aligned closely with the survey we did in August 2020. See the Data by Sampling Date graph below. It is interesting to note that DUD-024 differed from DUD-027 with higher DO, pH, and Conductivity, and that this same difference can seen in the August 2020 data. DUD-027 is near the outlet of the pond, while DUD-024 is confined. There was very heavy growth of tape grass everywhere during this survey, but the higher DO and pH levels could be an indication that the heaviest vegetation is near DUD-024. • There was a small but distinct difference in DO and pH between the surface and bottom at DUD024. This could also be an indication of very active vegetation. Since it was early in the morning, the bottom waters could still be reflecting lower DO levels from nighttime respiration. • The Surface Data by Month graph below shows how our surveys are starting to display a distinct annual pattern. The one point that doesn’t seem to fit that pattern is the secchi depth in the April 2022 survey. Secchi depth was also quite low this month and may be related to that April condition. • The extremely high pH value at DUD-025 is concerning. See the DO vs. pH graph below. Mass DEP defines the healthy range for pH in freshwater as 6.5 to 8.3. Both DUD-024 and DUD-025 had pH values well above 8.5. This is a direct result of the extremely high levels of plant growth, which remove carbon dioxide from the pond and raise pH. • There is a strong stratification at DUD-025 at about 15 feet depth. This is evident from the distinct 1.5° C thermocline and it corresponds to the point where DO and pH both start dropping and turbidity starts to spike. The layer below 15 feet is most likely highly turbid stagnant water with suspended organic matter. All supporting graphs are on the following pages. Please let me know if I can provide any more information. Sincerely, Benjamen Wetherill, bwetherill@acasak.com, 617-390-3151
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ACASAK Aquatic Monitoring Consulting 380 W Roxbury Pkwy, West Roxbury, MA 02132 www.acasak.com Dudley Pond – All Data by Sampling Date
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ACASAK Aquatic Monitoring Consulting 380 W Roxbury Pkwy, West Roxbury, MA 02132 www.acasak.com Dudley Pond - Surface Data by Month
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ACASAK Aquatic Monitoring Consulting 380 W Roxbury Pkwy, West Roxbury, MA 02132 www.acasak.com Dissolved Oxygen vs. pH and Temperature (2020-2022) (Points with black outlines are from the most recent sampling)
DUD-025 – 9/1/22 Profile measurements (depths are estimated)
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