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DATA AVAILABILITY, QUALITY, METHODS, AND SOURCES

For simulation purposes, the ideal or desired condition is to obtain all required data by direct measurement or observation. In reality, however, necessary data are not routinely available by direct measurement or observation and must be synthesized using generally accepted engineering analyses and methods. Issues of data sources and the methods used to obtain data that cannot be directly measured reflect, ultimately, on the credibility of simulation results. To address these issues for the historical reconstruction analysis, the methods for obtaining the necessary data were grouped into three categories (Table 12):

• Direct measurement or observation—Data included in this category were obtained by direct measurement or observation of historical data and are verifiable by independent means. Of the three data categories, these data were the most preferred in terms of reliability and least affected by issues of uncertainty.
• Quantitative estimates—Data included in this category were estimated or quantified using computational methods.
• Qualitative description—Data included in this category were based on inference or were synthesized using surrogate information. Of the three data categories, data derived by qualitative description were the least preferred in terms of reliability and the most affected by issues of uncertainty.

Of the six specific types of information required for the historical reconstruction analysis previously described, the network pipeline, groundwater well-location, groundwater well-production, and storage-tank data were obtained by direct measurement or observation (Table 12). These data were available throughout the entire historical period and could be assessed for quality and verified by independent means such as state reports or field observations. For example, groundwater well-production data were available for every well for every month of the historical period (Appendix B) and these data were measured by the water utility using in-line flow-metering devices at groundwater wells (George J. Flegal, Manager, United Water Toms River, Inc., oral communication, August 28, 2001).

Data for historical consumption and the spatial distribution to pipeline nodes consisted of two components—monthly volumes (quantity) and spatial distribution (location). The monthly volumes were obtained by using the quantitative estimation method previously described (see section on Estimation of Historical Consumption). Data were available from metered billing records for October 1997 through April 1998 and verified through the calibration process described in Maslia et al. (2000a,b); the magnitude of monthly historical production was known based on measured flow data. Using these data, estimates of historical consumption were quantified by imposing the requirement that total consumption must equal total production.

Direct measurement or quantitative estimates of the spatial distribution of historical consumption were not available for the Dover Township area. Therefore, qualitative description methods were used to estimate historical data values. In doing so, estimates of the spatial distribution of historical consumption (point-demand values) were based on two assumptions: (1) historical water-use patterns were similar to the present-day (1998) patterns which are known from available metered billing records (Table 12); and (2) water-use patterns could be inferred from land-use classification using historical land-use classification as a surrogate indicator (see section on "Distribution of Historical Consumption"). To assess the validity of this approach, historical land-use classification and zoning maps for Dover Township were used in conjunction with pipeline network maps for 1962, 1967, 1978, 1990, and 1996. Using information obtained from the land-use classification and pipeline network maps, geospatial (Plates 46–51) and comparative analyses (Table 3) were conducted. Results of these analyses indicated that the distribution of land-use classification in Dover Township was relatively static and changed little during the historical period. These analyses substantially validated the qualitative description method used to estimate the spatial distribution of historical demand-point values.

The high-service and booster pump-characteristic data used during the simulation of historical network operations were derived using information obtained from the water utility (Flegal 1997). This information consisted of head values and corresponding pump flow values which were refined during the model calibration process (Maslia et al. 2000a,b). Consequently, these methods and the resulting pump-characteristic data are characterized as a "Quantitative estimate" (Table 12).

Table 12. Data characterization, availability, and method of obtaining data for historical reconstruction analysis.

The historical system-operation data were obtained using each of the three methods of obtaining data described previously. These methods apply depending on a specific period of time. For the early historical period (1962–77), investigators relied on hydraulic engineering principles and the "Master Operating Criteria" (Table 4). Because data describing specific operational practices were not available, operating schedules developed for these early historical networks (for example, Tables 5 and 6) were based on qualitative descriptions of system operations and are characterized thusly in Table 12.

For the period 1977–87, system-operation data were derived using hydraulic engineering principles, the "Master Operating Criteria," and from information provided by the water utility. The water-utility information consisted of descriptions of the general operation of the water-distribution system for a typical "peak" day (summer) and a "non-peak" (fall) day. For some of the years, the water utility also provided estimates of discharge to the distribution system from the high-service and booster pumps, such as the data listed in Table 9 (Richard Ottens, Jr., Production Manager, United Water Toms River, Inc., written communication, 1998). Accordingly, system-operations data for the period 1977–87 are characterized as both a "Quantitative estimate" and a "Qualitative description" (Table 12).

System-operation data for the most recent historical systems (1988–96) were obtained from direct measurement or observation, quantitative estimates, and qualitative descriptions of operating schedules. Data sources used to develop these operating schedules (for example, Table 7 and Table 8) included the generalized operating notes from the water utility (Richard Ottens, Jr., Production Manager, United Water Toms River, Inc., written communication, 1998), hourly operations data for 1996 (Flegal 1997), notes taken by ATSDR and NJDHSS staff during field-data collection activities in March and April 1998 (Maslia et al. 2000a), and the observation that the distribution system previously operated in a manner very similar to the present-day system (1998) for which detailed information was available. Given the spectrum of methods used to derive system-operations data for the most recent years of the historical period, data are consequently characterized as a "Direct measurement", a "Quantitative estimate", and a "Qualitative estimate" (Table 12).

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