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The Toms Creek sewage interceptor has become a major issue in Blacksburg. In the interest of providing factual information to residents, and also, we hope, correcting misinformation that has been published, we, as practicing professional engineers and engineering professors in Blacksburg, would like to clarify and enumerate the facts of many issues that have been reported in this and other newspapers.

During our careers, many of us have actually designed miles of gravity sewers and pressure sewers. Others of us have studied the overall lifetime efficiency and effectiveness of these conveyance alternatives. Collectively, we have hundreds of years of experience in this field and would like to convey to residents and voters of Blacksburg our assessment, as practicing professionals, regarding the current controversy over the Toms Creek interceptor sewer.

In general, a pressure or pumped conveyance system is going to be much more expensive than using the energy provided by Mother Nature: that of gravity. The gravity interceptor sewer along Toms Creek has been planned for more than 30 years and has always been, and remains, the most efficient and cost-effective method of conveying wastewater from the basin into the wastewater treatment plant.

"Oversizing" of the interceptor has been criticized. It is a generally accepted principle within the engineering profession, no matter the discipline, that engineering designs be conceived to not only serve the present, but be designed with reasonable growth expectations. This is especially true with a gravity sewer line. If the trench is opened to accept a pipe, it is a cost-effective approach to place a pipe that will serve the community for as much as 50 years into the future.

Modern sewer materials and construction techniques preclude the leakage of any wastewater from a gravity sewer system. Construction techniques dictate that all pipes be tested and proved watertight. Maintenance procedures into the future will ensure integrity. Also, strict specifications are followed as regards cleanup and restoration following any type of construction such as this. In other words, once the pipe is in the ground, properties will be restored such that little or no evidence exists indicating the presence of the line.

Recent points from letters to the editor from James Marchman and John Novak deserve repeating and re-emphasis:

- The STEG-hybrid system (proposed as an alternative to the gravity sewer) does not eliminate a central collection system along Toms Creek. In fact, because velocity and pressure in a pressure line are so critically limiting, there is an excellent chance that, due to flow changes in the North Main drainage basin alone, the town will some day face installing a parallel system along Toms Creek. Who picks up this expense? Answer: All of the residents of Blacksburg.

- Somewhere between 11 and 16 pump stations must be constructed and operated to accommodate the STEG-hybrid system. How can this be cheaper than nature's own gravity? Who picks up this expense? Answer: All of the residents of Blacksburg.

- The STEG-hybrid system will require the installation and maintenance of 2,000 septic tanks. This will result in more immense expense for both installation and maintenance. Who picks up this expense? Answer: All of the residents of Blacksburg.

- The 11 to 16 pump stations will all be small methane generators, thereby creating the potential for air pollution and certainly odors. Who picks up this expense? Answer: All of the residents of Blacksburg.

- The cost for the STEG-hybrid system will, over the life of the project, greatly exceed that of the conventional system. Who picks up this expense? Answer: All of the residents of Blacksburg.

- And finally, to quote Marchman's letter: "But you have to wonder why people worry that a 'once in a blue moon' drip from a sewer pipe might somehow do something that the urine and feces of hundreds of grazing cows, sheep, horses and all those other wild fauna are not already doing." A point well taken.

It is evident that this entire matter is not an issue of one engineering solution vs. another, but simply an issue of growth vs. no growth. In this type of emotionally charged debate, common sense, and what makes economic sense to the greatest majority of residents, sometimes is overlooked.

All of us are fortunate to be living in a vibrant and economically attractive area. The Blacksburg area is going to grow, and effective growth management dictates that growth occur in the areas where utilities are available. Efforts to prevent this growth should not be at the expense of the rest of the town but should be directed through the comprehensive planning and zoning process.

We believe the council members, both present and future, who are proponents of the gravity interceptor along Toms Creek are representing all of the residents of Blacksburg in a fiscally responsible way. Any other solution will be paid for by generations to come.

This commentary was written by William A. Aden, president of Draper Aden Associates, and endorsed by Richard DiSalvo, vice president of Draper Aden; consulting engineer Robert R. Roberts; engineer J. Beverly Jones; former engineering professor and Virginia Tech President Paul Torgersen; Clifford Randall, professor emeritus of civil engineering at Tech; and Tech engineering professors Richard D. Walker, John T. Novak and James Marchman.