Another Cost of Sprawl
The Effects of Land Use on Wastewater Utility Costs
Study Protocol and Design
Originally intended as two separate studies of linear infrastructure costs and land use in the Chicago and Cleveland regions, these related, but independent efforts were combined due to necessity. Much of the study design for each of these individual efforts was dependant upon conditions that existed in the field, but that were largely unknown at its inception. Although a general study protocol for each region was initially conceptualized, there was a high likelihood the study design would have to be adjusted based on conditions in the field as they became known. As it happened, this was the case.
From the beginning, the two study efforts shared a similar objective - to determine and quantify the extent (if any) to which different types of land use affect linear utility service costs. It was generally assumed the study would utilize either a case study, cross-sectional or time series approach, although cross-sectional or time series techniques were most preferred, since they are considered to be more conclusive. Moreover, the relationships revealed through these techniques are generally applicable to systems in other communities with similar characteristics.
The systems to be included in each study were to be located in the Chicago and Cleveland metropolitan areas. Initial site visits took place in communities located in the western Chicago region to attempt to locate a community with the land use patterns, service characteristics and budgetary practices that could serve as a "stand-alone" case study. Elgin, Illinois was examined first to determine if conveyance costs for subareas representing different land use patterns within the same system could be accomplished. But Elgin's water and wastewater systems exhibited a complex series of physical and budgetary inter-relationships with other regional utility systems. Accounting and budget data for conveyance costs were found to be lacking, and the ability to link these costs to discernible subareas was not possible. Furthermore, there was a large age difference between the conveyance facilities serving subareas with significantly different land use patterns. Such age differences would have likely confounded and obscured the ability to determine the influence of other factors on conveyance costs for the subareas. Accordingly, Elgin was not considered further for a sub-system case-study analysis.
As a second approach, it was decided to attempt to find two utility systems that exhibited the following characteristics: 1) conveyance-only costs were available, 2) both had experienced recent development, and 3) development had occurred with substantially varied land use patterns and densities. If two such communities could be found, then a comparative time-series analysis could be done.
Naperville, Illinois did have time series data for conveyance costs and, since it had undergone significant development in the last few years, it was further investigated to determine if a time series analysis would be possible. Upon further examination, however, there were too many data-reconciliation problems for a time series study.
Specifically, Naperville's conveyance costs had not been reported in a consistent fashion over a ten year period. There had also been a change in the source of water that affected other data. Exceptionally rapid growth rates in the last ten years presented other difficulties with the reported data that were the equivalent of trying to take a still photo of a rapidly moving subject. Naperville also provides some water and wastewater treatment for an adjoining community, thereby creating additional data problems. And, critically, land use data such as acreage of developed land, was not consistently available for the necessary ten years to develop statistically significantly results.
While these problems were being encountered with Naperville, site visits were made to four other utility systems in the Chicago region. Oak Park, an older, inner suburb of Chicago, was found to have conveyance-only data and represented a more traditional grid-form of development. However, since the community had achieved build-out in the 1940's, it did not present an opportunity for a time series study of a developing community.
Accordingly, work on the Chicago-area study was temporarily suspended pending discussions with sponsoring agencies, and to explore further options for accomplishing the study.
In the meantime, initial data collection efforts had begun for the Cleveland area study which was to focus on how local and regional land uses in Northeast Ohio affect the cost of water service. With a few exceptions, the Cleveland Division of Water (CDOW) is the water provider for virtually the entire Cleveland metropolitan region. Interviews with CDOW officials were held and budgetary, system, and capital improvements data were obtained. Although the course of the study appeared promising at first, it was stymied by the lack of functional accounting and budget. Such data are critical to determine the effect of changes in land use on a utility's service costs. Despite being one of the few utility systems in the U.S. to charge geographically distinct rates, conveyance-only cost data were unavailable from CDOW.
Despite these obstacles sufficient data were obtained from these and subsequent data collection efforts to perform a broader spectrum analysis on the effect of the region's outward growth on CDOW's geographic-based user rates. Although not conclusive, the results of this analysis are suggestive, and point out the need for better cost accounting data on the part of the CDOW so that it can more closely link its geographic based rates with actual costs incurred for these areas. The results of this analysis are presented in Appendix E.
Still, this did not fulfill the original objective of the Cleveland-area study, which was to determine the extent to which land use patterns affect utility conveyance costs. Although CDOW's zone-based rates are an acknowledgment of the presence of spatially distinct service costs, the ability to identify these costs and link them to individual areas was not possible. Accordingly, it was decided to investigate the area's wastewater service characteristics to see if such an analysis could be prepared for this service.
Upon investigation, it was found that the wastewater service patterns are significantly different than those for water service in the Cleveland region. Specifically, five independent wastewater collection-only systems and two combined conveyance and treatment systems with identifiable conveyance costs were found in the Cleveland area. These seven systems represent a range of land use patterns: rural/suburban, suburban, and high density urban. 
Additionally, all but one of these systems obtain water from the CDOW, and CDOW maintains excellent community-level water consumption and account data. Having consistent water consumption data is critical, because wastewater flows and costs are best equated to cost per unit of water consumption.
While this produced the first substantial progress towards realizing the goals of this study, eight data points (seven individual systems plus four consolidated systems) is not a sufficiently large sample for purposes of obtaining statistically significant results. Although results from eight systems would be suggestive, they would not be conclusive so an attempt was made to locate at least two additional systems in the Cleveland region with identifiable wastewater conveyance costs. Unfortunately, none were found.
After consultation with the organizations sponsoring the Chicago and Cleveland studies, Naperville and Oak Park were joined with the Cleveland-area systems. This provided the minimum ten systems necessary to obtain statistically significant cross-sectional results. Before this was accomplished, other factors that might influence costs between the two areas were examined. While there is some variation in these factors between the two areas, most of the variations were found to be within the range of conditions within the Cleveland communities. Accordingly, no adjustments were deemed to be required to "normalize" between systems from each of the two regions.
Specifically, for all systems, topography is essentially flat to gently sloping, thus pumping costs are not a significant distinguishing factor. In addition, wages for utility workers are also similar between Cleveland and Chicago. For example, the average salary for a wastewater collection system employee is essentially the same for both Oak Park, Illinois ($32,240) and Lakewood, Ohio ($32,466), the two most urbanized communities.
Temperature and rainfall were also found to be similar. Mean average temperatures for Chicago are reported to be 21 degrees in January, and 73.2 degrees in July.  In 1995, the warmest day at O'Hare airport was 104 degrees and the coldest was -4.0 degrees, with a year round average of 49.9 degrees. In 1995, the mean year-round average temperature at Cleveland's Hopkins Airport was 51.0 degrees, with precipitation of 39.05 inches. The warmest day was 98 degrees and the coldest was -1.0 degree.  The only potentially significant difference between the two areas was annual precipitation. Total precipitation at Chicago's O'Hare airport was 32.88" but was more in Cleveland, due mostly to "lake effect" snowfall. Thus, climatic conditions are not seen to have a significant influence in imposing greater or lesser wastewater collection costs for either region.
With ten data points representing ten separate communities with a range of land uses and their respective wastewater collection systems, it became possible to conduct a statistically significant cross sectional analysis of these systems.
50. Four of these systems also own and operate a joint venture wastewater treatment facility. Combined, these four systems represent one large conveyance system. Accordingly, eight wastewater systems which met the criteria for performing a cross-sectional study were found in the Cleveland area.
51. The Weather Almanac, 7th Edition, 1996.
52. Public Information Statement, National Weather Service, Cleveland Ohio, January 1, 1996.
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Kaid Benfield writes about development, community and the environment on Switchboard.
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