Lake Pocotopaug Lake and Watershed Restoration Evaluation ...

Lake Pocotopaug water quality was sampled on ten dates starting in April 2001. Two stations(LP-1 and LP-2, Figure 6) were sampled on each visit. At each site, samples were collected atthe surface (0-0.5 m) and near the bottom with the help of a Van Dorn sampler. Samples werecollected at the thermocline depth (usually 5-6 m) during periods of stratification. Water qualityvariables measured on site included pH, conductivity, and turbidity. Additionally, temperatureand dissolved oxygen (DO) profiles were determined at 1 m interval depths at each site. SDTwas also determined, and a depth-integrated (~ 6 m) water sample was collected at each sitefor chlorophyll a analysis and phytoplankton identification and quantification. Sampling namingconvention was as follows:LP-1S or LP-2S – surface water samplesLP-1M or LP-2M – mid-depth (thermocline) water samplesLP-1B or LP-2B – bottom water samplesLP-1I or LP-2I – integrated water samplesChlorophyll samples were filtered through a 0.45 µm glass fiber filter within 12 hours fromcollection and frozen until spectrophotometric determination of chlorophyll a content. Thesurface, mid- and bottom depth water samples were collected and sent to an independentanalytical laboratory for determination of total and dissolved phosphorus, and alkalinity.Dissolved and total aluminum was sampled in May. Dissolved aluminum was measured at allthree water depths and total aluminum was measured at the surface and bottom. Also inAugust, dissolved iron was measured at all three depths. Arsenic, cadmium, chromium, copper,nickel, lead, and zinc were measured in May at the surface and bottom.Tributaries and storm water pipes were sampled during four dry weather and four wet weathervisits. The first visit occurred in May 2001, when all potential stations were located, identified,and described. Actual sampling of the stations on subsequent dates was contingent uponexisting conditions (i.e., whether the station was active or not) and budgetary constraints.Location of the water quality sampling stations is provided in Figure 6.A total of 60 samples were collected from tributaries and storm drains, not including QA/QCduplicates. Descriptions of the locations, corresponding VLSG sampling identifier, and drainageareas (VLSG 1992) are provided in Table 9.Tributary stations were not sampled when flow was too low to cause any appreciablecontaminant load to the lake. Water quality variables included temperature, pH, DO,conductivity and turbidity (determined in the field by ENSR personnel), suspended solids,alkalinity, chloride, total and dissolved phosphorus, nitrate nitrogen, ammonium nitrogen, andtotal Kjeldahl nitrogen, and alkalinity (determined by an independent analytical laboratory).Aluminum, arsenic, cadmium, chromium, nickel, lead, and zinc were analyzed once during dryand once during wet weather.Lake Pocotopaug Restoration Evaluation 23May 2002