OVERVIEW OF WATER QUALITY INVESTIGATIONS, 1994 - 1996
I. INTRODUCTION
A. Objectives
Water quality monitoring of southern Cayuga Lake was conducted over a three-year period (1994-1996) in support of the Lake Source Cooling project. Overall objectives included:
1. Gather data necessary to complete a comprehensive analysis of the aquatic environmental impacts of the LSC project on Cayuga Lake.
2. Provide information to the project engineers regarding optimal location of the intake and outfall.
3. Provide information to the project engineers regarding the need for mitigating measures to reduce identified adverse impacts, and identify design parameters for necessary mitigating measures.
4. Collect data necessary to complete applicable regulatory permits associated with the LSC project.
B. Sequence of Investigations: 1994-1996
The first year of water quality monitoring (1994) was designed to assess current lake conditions, compare the 1994 results with historical data, and identify potentially adverse impacts of LSC on the lakes thermal structure, chemistry, and biota. As such, the 1994 field program was broad in scope. The 1995 program was more focused and concentrated on the potentially significant aquatic issues identified through the 1994 screening analyses. In the final year (1996), we concentrated on expanding the database for parameters of concern and quantifying the efficacy of mitigating measures. Each year, our work plan was reviewed by appropriate divisions of the New York State Department of Environmental Conservation (NYSDEC) and by the projects Scientific Advisory Committee, convened by Cornells Center for the Environment (CfE).
II. MONITORING PROGRAM
A. Sample Locations
We established a network of monitoring stations in southern Cayuga Lake. Various chemical, thermal, and biological parameters were measured at the stations, as described in detail. Table C-1-1 summarizes the locations and depths of the monitoring stations, which are plotted in Figure C-1-1. The field team used electronic satellite-based location technology (Global Positioning System [GPS]) to locate the stations and facilitate replicate sampling. A benchmark located at the southern end of Cayuga Lake was used to determine the accuracy and precision of the GPS.
B. Summary of Analytical Parameters by Year, Depth, and Sampling Location
The 1994 monitoring program for water chemistry and biological parameters is summarized in Table C-1-2. Note that the monitoring programs to assess sediments and Mysis relicta are not included. The protocols for data acquisition related to these parameters are presented in separate appendices to this DEIS.
The 1995 program is summarized in Table C-1-3; the 1996 program is summarized in Table C-1-4.
C. Field Methods
1. Water Samples for Laboratory Analysis. Water samples were collected using a 4.5LVan Dorn bottle on a calibrated line. Water was poured directly into the laboratory bottles, which contained required preservatives. Sample bottles were stored on ice and transported to the analytical laboratory at the end of each sampling day. Chain-of-custody procedures were observed.
2. Hydrolab Profiles. A multi-probe field instrument manufactured by the Hydrolab Corporation of Austin Texas was used to measure and record temperature, pH, specific conductance, dissolved oxygen (percent saturation and concentration), and oxidation reduction (redox) potential. The Hydrolab surveyor system that was used in the LSC investigation has a multiprobe attached to 75 meters of cable for measurements through the water column, and a data display logger that interfaces with standard computers.
3. Secchi Disk Transparency. Secchi disk measurements were obtained with a black and white disk, 20 centimeters in diameter, attached to a calibrated line. Observations were made by lowering the disk through the water column on the shady side of the boat and recording the depth at which the disk disappeared from sight. A second reading was obtained by lowering the disk an additional meter, then raising the disk, and recording the depth at which the disk again appeared. The final Secchi disk recorded was the average of the two measurements.
4. Phytoplankton. Phytoplankton were sampled using a 3/4 inch (inner diameter) tygon tube suspended through the photic zone, poured into glass jars and preserved with acid-Lugols solution. Cell counts and identification of major taxa was conducted by Dr. William Schaffner. Dr. Schaffner concentrated 50 ml of sample into 10 ml by allowing the sample to settle in a graduated cylinder for at least 24 hours. He then pipetted 2 ml of the concentrated sample into a shallow counting chamber, and allowed another one-half hour for the cells to settle. Phytoplankton cells and colonies were identified and enumerated by the Uttermohl method using an inverted microscope. Transects across the chamber were made at 400x magnification to identify the small cells, typical of the Cayuga Lake flora. Cell counts were made at 100x to identify rarer large cells and colonies. Numbers are reported in units of cells per ml of sample, after adjustments are made for the volume of sample concentrated and the number of transects counted. Biovolume calculations were made by direct measurement using a calibrated grid.
5. Zooplankton. Zooplankton were sampled by towing a one-half meter diameter x 2m length, 130 microns mesh Peugot Sound zooplankton net to the surface.
Samples were poured into bottles and preserved with 4 percent formalin (later, methanol) solution until identified and enumerated by Dr. William Schaffner. He sieved the samples through a fine net, then diluted the samples based on the density of the organisms. Five ml samples were placed in a Bogorov counting chamber, and enumerated using a Wild stereo microscope.
6. Benthic Invertebrates. The benthic invertebrates were sampled on July 22, 1994. This sampling date was selected to be comparable to the existing benthic invertebrate data base for Cayuga Lake. Dr. Edward Mills of Cornells Biological Field Station, at Shackleton Point, NY, conducted the benthic invertebrate analysis.
Samples were collected using an 22.5 cm2 Eckman dredge, emptied into clean buckets, and transported to the Cornell Biological Field Station for processing, identification, and enumeration of animals. In the laboratory, each sample was split into fractions of 1/2, 1/4, 1/8, 1/16, and 1/32. All animals were first counted in the smallest fraction of sample. When 50 or more of any one organism was counted, no more of that taxon was counted in the remaining sample fractions. If fewer than 50 animals of a taxon were counted, all animals were counted until 1/4 of the sample had been processed.
D. Laboratory Methods
The analytical procedures used during the LSC monitoring program are summarized in Table C-1-5. Low level phosphorus analyses were performed by two laboratories (Life Sciences Laboratory of Syracuse, NY, and Ichthyological Associates [IA] of Lansing, NY). The following text is a description of IAs procedures for SRP and TP.
To determine soluble reactive phosphorus (SRP), Ichthyological Associates employed Standard Methods, 424 F. Ascorbic Acid Method from APHA 16th Edition. Because SRP is very labile, samples were chilled in the field and processed immediately. Analysis began within one hour of reception of the samples and was completed on that day without delay. Samples were filtered through Gelman Metricel filters (0.45 micron) that had been soaked in 500 ml distilled water and washed with 250 ml of double deionized water prior to dispensing for analysis. Standards and blanks were filtered in the same manner as the samples. A four point standard curve was obtained and blanks were measured in duplicate.
Samples were only exposed to dedicated glassware that was washed with concentrated sulfuric acid and thoroughly rinsed with deionized water; the last five rinses were made with double deionized water. Analysis differed from that described in APHA (1985) in that phenolphthalein was generally added to subsamples to assure that there was no phenolphthalein alkalinity, instead of to the samples directly. We used a 5 cm cuvette for determination of absorption. At very low concentrations of SRP, this cuvette was refilled with distilled water and the spectrophotometer reset to zero between sample readings to assure that the cuvette was not adsorbing materials from the samples and causing drift.
Total phosphorus was determined using the ascorbic acid method as above preceded by Method 424 C III - Persulfate Digestion Method (APHA 1985) using an autoclave. The method used was as described with one exception. After titration with NaOH, the samples were placed in a graduated cylinder and brought up to 70 ml instead of the 100 ml called for in order to keep them as concentrated as possible. After treatment, no samples or standards exceeded 70 ml volume. After the digestion and titration, analyses were completed using the ascorbic acid method as given above.
For each days sampling, the results from one blind duplicate sample and one matrix spike and matrix spike duplicate were provided.
According to APHA (1995), there are several terms in use to describe the minimum concentration of any analyte that can be detected above analysis noise at a stated confidence level. According to current practices, there is a hierarchy of detection levels; consequently, it is important to define any level used. These levels include the instrument detection level (IDL), which is defined at concentration of the constituent that produces a signal greater than three times the standard deviation of the blanks. The lower level of detection (LLD) is the concentration of constituent that produces enough of a signal so that 99 percent of the trials will produce a detectable signal. Determining this level requires repeated trials with a very low concentration standard. These trials do not utilize samples that have gone through the whole method process, but measure the ability of the instrument to detect the constituent.
The method detection level (MDL) uses low level standards that have gone through the whole process and includes errors associated with extraction, digestion, application of reagents, etc. It is defined as the smallest concentration that can be determined in a laboratory at a stated level of confidence. To determine the MDL for soluble reactive phosphorus (SRP) and total phosphorus (TP), we determined the standard deviation for multiple trials of standard with a concentration of 6.25 µg/l, a level near the stated minimal detectable concentration (APHA 1995). The resulting standard deviation is multiplied by a one-sided t-statistic for the appropriate degrees of freedom (n - 1) and level of confidence (99 percent). The resulting MDL for SRP for 1.4 for both 1995 and 1996, and for TP, was 1.35 for both years. This level of confidence applies only to Ichthyological Associates, Inc.s laboratory. We have included this calculation with our phosphorus results because we have reported concentrations below the stated multi-laboratory minimum detection level provided in APHA (1995). The minimum detection concentrations for analyses conducted by multiple laboratories are considerably higher than for a single laboratory, a factor of about five according to APHA (1995). These calculations are presented in Table C-1-7.
Literature Cited
American Public Health Association (APHA) 1985. Standard Methods for the Examination of Water and Wastewater. 16th Edition. Washington, DC. 1268 pp.
III. QUALITY ASSURANCE/QUALITY CONTROL PROGRAM
A. Introduction
The objective of the project quality assurance/quality control (QA/QC) plan is to ensure that the data collected meet the standard data quality objectives: precision, accuracy, representativeness, comparability, and completeness. Choices made in the design of the sampling program (spatial and temporal), field and laboratory procedures, and data evaluation techniques can influence the ability to draw valid conclusions from field data. In this section, the quantitative and qualitative criteria to ensure data quality are briefly described.
B. Field Replicates
Precision was assessed by a program of field replicates. Replicate field parameter (Hydrolab) data was obtained at one of the 16 stations each sampling trip. Replicated stations were rotated throughout the field season. In addition, one of the 16 stations for chemical parameters was replicated for the complete suite of parameters during each biweekly sampling event. Phytoplankton and zooplankton samples were collected in duplicate. The data quality objective was for replicates to be within 20 percent relative percent difference. If the replicates were not within this control limit, data was screened to evaluate whether proper field procedures were implemented. Resampling was conducted when the data was considered critical to the project teams ability to draw conclusions.
C. Proficiency Samples and Matrix Spikes
Accuracy refers to how close reported concentrations are to "true" concentrations. Accuracy was assessed through a program of laboratory audit samples, including proficiency samples and matrix spikes. The required frequency were two sets of performance samples, and two sets of spiked samples over the field monitoring season. The data quality objective was for the performance samples and the matrix spike recoveries to be within 20 percent relative percent difference. If the results were not within this control limit, the laboratory was notified and resampling was required. For the Target Compound List sampling, additional blanks were included in accordance with USEPA methods (trip blank required for each day volatile organics are measured in water, field blank required when non-dedicated sampling equipment is used).
D. Hydrolab
Accuracy of the field instrumentation was evaluated through a program of standardization and calibration. The Hydrolab was calibrated at the beginning of each monitoring day. In addition to the calibration procedures recommended by the Hydrolab manufacturer, the field team cross-checked instrument readings for pH, temperature, and dissolved oxygen against other field and laboratory instruments. At the end of each monitoring event, the calibration of the Hydrolab was rechecked and drift was recorded in a bound project field book.
E. Summary of QA/QC for Field Program
Quality assurance/quality control for the field work component of the LSC project has included:
· Confirming presence of sample preservative as indicated on laboratory chain of custody.
· Recording collection dates and times on bottles to ensure samples are analyzed within holding times.
· Calibrating Hydrolab before and after each sampling event and recording drift; charging Hydrolab battery.
· Using GPS to locate sampling site.
· Rinsing Van Dorn bottle and funnel and bucket used for collecting chlorophyll a and phytoplankton samples with lake water prior to sampling to remove potential residual contamination.
· Rinsing all lab bottles which do not contain preservative with sample water prior to filling.
· Storing all samples in ice in coolers immediately after collecting the sample.
· Taking duplicate samples of all parameters during each monitoring event (this includes separate duplicates for both labs).
· Conducting matrix spike/matrix spike duplicate analyses for each sampling event. Results are examined for acceptable recoveries.
· Conducting field audits. The field auditor is responsible for observing sample collection techniques and making recommendations for sample quality improvement. The 1995 audit was completed by Rob McCabe after he accompanied field staff during a sampling event, and in 1996, Michelle Gold completed the audit.
· Stearns & Wheler internal QA/QC procedures:
- A consistent laboratory contact, Ray Apy, reviews all laboratory results as they arrive.
- Michelle Gold reviews all laboratory results as part of data analysis.
- Liz Moran reviews all laboratory results and data analyses.
F. Summary of Life Sciences Laboratory QA/QC Program
The QA/QC program and results from this contract laboratory are summarized in Table C-1-6.
