Forging the Future Grinder Pumps in Pressure Sewers

Charles G. Stolberg, Submersible Wastewater Pump Association

An explanation of why the application of grinder pumps and pressure sewer systems provides a cost-effective, long life answer to allow more sites, existing and new, access to a public sewer system.

ince the early 1970s, pressure sewer systems have been an effective method to move residential wastewater through small diameter pipes to collection facilities S 1 where other methods are less economical or less feasible. The keys to understanding the differences between con- ventional systems and pressure sewer systems are the piping network and the reduction of solids size in the wastewater. Pressure sewer systems use grinder type pumps to reduce the solids present to particles, which can easily be moved through small diameter pipes. This discussion describes the use of pressure sewer system technology to solve challenging disposal requirements where other methods may be less economically feasible or environmentally unacceptable. Pressure sewers can be used where gravity systems just won’t work because of uphill topography, surface rock, high water tables, waterfront locations, very fl at land, extreme Aerial view of Levittown, Pennsylvania. Following WWII, subdivi- cold weather, stream crossings, restricted access, and con- sions such as this used septic tanks and soil absorption systems, straints on blasting. where sewage is digested in a large tank and then leached into Because the piping systems are sealed, pressure sewers the surrounding soil, instead of public sewers and water supply. offer freedom from infi ltration/infl ow. This provides a two- fold benefi t. The wastewater treatment plant can be built diately following the Second World War. This boom, epito- with smaller capacity since it is not necessary to allow for mized by William Levitt at his Levittowns on Long Island storm peaks, and the treatment process will not be upset by and in southeastern Pennsylvania, provided a fi rst home to storm related fl ows which can literally swamp out plants with millions of homecoming GIs. infi ltration/infl ow plagued gravity collection systems. Many of these subdivisions, in all parts of America, were Generally speaking, these systems are installed outdoors carved out of raw land adjacent to existing cities and towns. below grade. Indoor systems are also available. A typical Most provided only streets, electricity, and telephones. Such system includes a pump, basin, controls and piping and valv- niceties as curbs and gutters, streetlights, fi re protection, and ing. Let’s consider some well-known applications of submers- especially public sewers and water supply were notable by ible pressure sewer technology. their absence. Into this breach was thrown an old technology, devel- Failing Septic Tanks In Existing oped early in the 20th century by agricultural engineers for use on the farm: namely, septic tanks and soil absorption Subdivisions systems where sewage is digested in a large tank and then The biggest building boom in American history began imme- leached into the surrounding soil.

42 JULY 2007 www.pump-zone.com PUMPS & SYSTEMS Historical Timeline of Pressure Sewers successful and widely used methods is pres- sure sewer systems powered by grinder pumps. • ASCE-sponsored project (mid 1960s) inspired by Professor Gordon M. Fair Most public health offi cials, developers, con- of the Harvard School of Public Health (Fair 1968) sulting engineers, contractors, and public • Development (1963-66) at General Electric of world’s fi rst prototype grinder works personnel have had at least some pump. Field test of fi rst pressure sewer system (1969-70) by Environment experience with pressure sewer systems since One Corp. in cooperation with NYDEC and the US EPA (Carcich 1972) their development in the 1960s. • Introduction of fi rst commercial grinder pump at WEF (then WPCF) Hundreds of thousands of homes that Annual Conference in Boston, 1969 once suffered from marshy, odorous chil- • Other EPA-sponsored demonstration projects (early 1970s) in Pennsylvania dren’s play areas, lake water quality degrada- (Mekosh 1973), Oregon (Eblen 1978) and Indiana (Sanson 1973) tion, and even hepatitis and E-coli epidem- • Earliest projects approved by state regulatory agencies (1970-72) in Indiana, ics caused by failures are today New York, Ohio, Texas, Virginia the proud owners of successful grinder • Federal Construction grant eligible (c. 1970s) as an Alternative Technology pump pressure sewer systems. These are in • Adopted (early 1980s) into “Ten States Standards,” as well as most indi- everyday use in neighborhoods all over the vidual state guidelines. world. Out in the country, land was abundant. As long as the well was prudently located up hill and on the other side of the New Developments With Slow Rate Of house, there was no problem. A little odor or a soft spot in the Buildout middle of a fi eld, far from habitation, was no cause for concern. In a typical new development, all the lots are platted, roads Limited use of such septic systems had also been made in some built, and some community facilities put up initially in order to city neighborhoods with large lots, prime soil conditions and begin selling lots. This represents a large “up front” investment careful operation (limited loading and frequent pump outs). at the start of the project. Since only a few houses are actually In retrospect, septic tanks (when brought to town) were built and occupied each year, resulting in a proportionally small a very poor choice on these small “postage stamp sized” lots. revenue stream, the “up front” cost of gravity sewers is often Nonetheless, in the rush to provide criti- prohibitive. cally needed homes, millions of septic tanks were built. By the late 1950s the U.S. Public Health Service (USPHS) was conducting serious studies in the fi eld and in labs at the Taft Sanitary Engineering Center on behalf of the FHA. UPSHS reported that over 24 million septic systems were in ser- vice and that they were failing, on average, in 11 years – far less than the 20-year or 30-year term of the typical VA or FHA mortgage loan. These same USPHS studies showed that over 50 percent of the available build- ing land in the U.S. was unsuitable for septic tank systems. Despite these facts, and because of continuing tremendous pressure from the public and the home building and real estate industries, several million more septic tanks were installed. The sad fact that failing septic tanks are a ubiquitous feature of so many American suburbs today makes it clear that they have been misapplied and not properly main- tained or inspected. Fortunately there are several proven solutions to this need for affordable, dependable, safe sewers. One of the most Layout of a typical progressing cavity grinding pump system.

PUMPS & SYSTEMS www.pump-zone.com JULY 2007 43 Forging the Future

On the other hand, if pressure sewers and grinder pumps are chosen, all of the small diameter shallow buried pressure piping system can be installed initially at very low cost per foot. The grinder pump station, which comprises the majority of capital cost, needs to be purchased and installed only as each house is built. This is especially critical in providing an afford- able and effective sewer system, initially to the fi rst few houses — often scattered throughout a large tract far from their nearest neighbor.

Projects With Large Lots And Consequent High Cost Per Dwelling Unit The cost difference between gravity and pressure sanitary sewers is a function of the size, depth, and the necessity to deeply bury gravity sewers to ensure down- hill fl ow. Pressure sewer piping, besides being smaller and shallower, need not be laid on a downhill grade, but can follow the contour of the land at a constant shallow depth dic- tated by the local frost penetration depth or, in very mild climates, by the need for protection from mechanical damage. Layout of a typical centrifugal grinding pump system. Since costs are assessed to serviced properties on a dollars per front foot basis, the cost advantage for pressure sewers increases rapidly as lots become larger.

Diffi cult Terrain Conditions In steep terrain, especially on uphill runs, gravity sewers very quickly become too deep and costly to be feasible. The only answer is to put at least one on each signifi cant uphill reach. Gravity can usually be used on the downhill sections, but the capacity of pump stations become successively larger as the piping progresses toward the ultimate discharge point. Pressure sewers can be designed to work successfully and economi- cally in either situation. A useful analogy to water system hydraulics can be drawn which shows that appropriate attention must be paid to the need for air and vacuum release valves at signifi cant high points in the profi le, as well as at the beginning of long downhill runs discharging to atmosphere. The ability to construct sewers that follow the contour of the land not only makes development affordable, but has also preserved natural Design fl ow, in any given downstream section of line, as rolling topography and trees. a function of number of pumps contributing, has been determined empirically and is available in tabular or Rocky Soil Conditions graphic form. Here are these criteria as suggested by Rock can be one of the most costly and diffi cult factors in construction. several competent authorities. Gravity sewers have wide excavated trenches and go deeper with each

44 JULY 2007 www.pump-zone.com PUMPS & SYSTEMS lower trenches makes it feasible in places like solid rock where gravity systems are liter- ally impossible.

High Groundwater Levels Locations with high groundwater, whether seasonal or year round, present other chal- lenges in both construction and operation of gravity sewers. During construction, the work site must be dewatered by generous use of pumps and well points distributed along the proposed trench route, and powered 24 hours a day. Such dewatered soil can be very unstable and potentially dangerous to work in. Therefore, continuous shoring and bracing are usually required. Layout of a typical 230-volt grinder pump control panel circuit. Even if these obstacles are overcome foot of length. This means the price per foot is signifi cantly by expenditure of much money, care and higher than installations in normal soil. effort, there remains the necessity to successfully operate the Installation in areas of solid rock can make system costs completed gravity sewer for the next 40 or 50 years. Consider economically unfeasible. In cases such as these, contractors rec- that once the dewatering pumps are shut down and the ground ommend alternatives such as pressure sewer systems. The fact water returns, the sewer must operate in what is tantamount that this alternative requires dramatically narrower and shal- to a submerged condition – this without causing infi ltration

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PUMPS & SYSTEMS www.pump-zone.com JULY 2007 45 Forging the Future and or infl ow, both notorious enemies of overall water quality capacity for the additional fl ow. goals. Indoor Installations Lakeside Or Oceanfront Properties As strange as it sounds to us today, when fl ush were One of the most desirable properties, sought out by millions fi rst invented, they were installed in the outhouse. Now, more of people around the world, is “a place beside the water.” It than a century later, the fl ush and other convenient water doesn’t really matter whether it’s a pond, creek, lake or reservoir, using fi xtures are fi rmly ensconced as not only necessities, but riverfront, an estuary or an ocean. People desire to live near also beautiful adjuncts to the modern American home. water. However, we still seem to have a residual mental block The topographical features, which create these precious from those days which whispers, “anything to do with sewage water bodies, are dominated by the fact that the land almost goes out in the yard.” Some manufacturers have systems specifi - always slopes down toward the shore. With failing septic systems, cally designed to be installed indoors in basement areas. the untreated wastewater can potentially pollute the body of water. Elimination Of Infi ltration/Infl ow Since these systems must be down slope from the houses, Pressure sewers are constructed of pressure pipe and leak tested they cause the disturbance, degradation and sometimes destruc- to the same American Water Works Association (AWWA) tion of the most important feature of waterfront properties; standards used for potable water supply; thus, they are, for all namely, the “front yards” facing the shore. In some cases, land practical purposes, watertight. This eliminates most infi ltration is so precious and the demand so great that tiny cabins are problems so characteristic of old gravity sewers. crowded against each other and literally pressed down as close New collection systems consisting entirely of pressure lines as they dare to the water. It is very expensive, environmentally fed by grinder pumps have been shown to be entirely free of damaging, and seldom entirely satisfactory to put gravity sewers extraneous water fl ows. in such waterfront locations. The pressure sewer has proven to be an environmen- Conclusions tally friendly, cost-effective solution in these waterfront • It has taken three decades for pressure sewer systems to applications. begin to take their proper place within the public health engineering fi eld. Today, there are hundreds of thousands of Lots On The Wrong Side: Sewer Must Go grinder pumps in routine daily operation in systems ranging Under A Stream Or Highway in size from a single pump to thousands of pumps. Sometimes, property is developed in a strip along one side of a • Extremely low operating and maintenance (O&M) costs highway, road or stream. Often there are highly desirable, per- have been documented. Data is now available from many haps isolated, building lots on the “wrong side of the street.” successful systems – some in operation for more than 20 Until pressure sewers came along, these choice lots were listed years. By taking advantage of the experience which these as “unbuildable” and might be ignored for decades with a casual systems offer, a new system can be planned which will have “that’s too bad.” good performance, high reliability, and reasonable O&M Pressure sewers bored under the stream or highway using costs. a trenchless technology, or carried overhead on a bridge cross- • Pressure sewer systems using grinder pumps are particu- ing, make such diffi cult sites easily accessible to whatever sewers larly useful in new construction of subdivisions and second already serve the strip community. home communities, and in existing communities with failing septic tanks. The problems of failing septic tanks, Houses Near But Not Directly Serviceable unsatisfactory soil conditions, and an increased emphasis By An Existing Gravity Sewer on environmental issues can be economically solved with It is always desirable, and sometimes absolutely mandatory, that pressure sewers. Pressure sewers are compatible with other public sewers be deep enough to serve fi xtures at, or just under, collection system techniques. The advantages of each the basement fl oor level. technology can be blended into site-specifi c designs using It often happens that when a gravity sewer is designed to grinder pumps, gravity, large submersible pumping stations, serve a certain area, the basements of houses at the ends of the and force mains. There is virtually no limit to the type dis- served streets end up just level with the sewer. If such streets are charge point to which a pressure sewer using grinder pumps later extended “further out into the country,” the new houses can be connected. P&S will be too low to have basement sewer connections. Or the distance to the gravity sewer may require a pump system. References 1 Adapted from “The Secret Life of Pressure Sewers” by R. Paul The answer is to put grinder pumps in or next to these Farrell, Consulting Engineer Niskayuna, NY, USA. Presented basements and create a pressure sewer line that can pump into at the Small Drinking Water and Wastewater Systems Conference, the nearest gravity pipe or pumping station with available January 12-15, 2000 Phoenix, AZ.

46 JULY 2007 www.pump-zone.com PUMPS & SYSTEMS Pressure Sewer System Technology Bibliography 50.3, May 1999, 76(1) Almquist, Carl, Chief Operator, Town of Groton, CT, personal com- Mayhew, Chuck and Fitzwater, Richard, “Grinder Pump Sewer munication, December 1991 System Saves Beach Property”, Water Engineering and Management, Bendixen, T.W., and Weibel, S. R., “Study on Septic Tanks and Septic 4p, September 1999 Tank Disposal Systems”, NTIS Report Number PB-216 760, 24p, Mekosh, G. and Ramos, D., “Pressure Sewer Demonstration at 1951 the Borough of Phoenixville, PA”, EPA-R2-73-270 (NTIS PB- Carcich, ltalo G.; Farrell, R. Paul and Hetling, Leo, “A Pressure Sewer 224456/4), 71 p, 1973 System Demonstration”, EPA R2-72-091, 218p, November 1972 Milnes, Thomas R. and Smith, Nacky, “Community Action at Coulter, J.B., “Sewage Disposal Systems Applicable to Subdivisions”, Quaker Lake”, WPCA of Pennsylvania Magazine, 6p, November/ NTIS Report number PB-217 475, 12p, 1957 December 1978 Eblen, J.B. and Clark, L.K., “Pressure and Palmer Lynn H., “Preserving the Antietam Battlefi eld at Affordable Demonstration Project – Bend, Oregon”, EPA 600/2-78-166, Cost” in WEF Specialty Conference on Collection System 1978 Operation and Maintenance, Tucson, AZ, pp377-383, 1993 Environment One Corporation, “GP Report”, Summer 1988 Sanson, R.L., “Design Procedure for a Rural Pressure Sewer System”, Fair, Gordon M., “Converted Sewer System” – US Patent 3,366,339, Public Works, (I 04)1 0, pp86-87, 1973 fi led Nov. 26, 1965, issued June 30, 1968, assigned by the inventor Wetsel, David A., “The O&M History of the Low Pressure Sewer to the public Systems for the Towns of Parish, West” Gray, Donald D., “TN Community’s Grinder Pumps Provide Positive Monroe, and Cleveland, New York, at NYWEA Environmental O&M Statistics”, Small Flows Clearing House, 5(4), October 1991 Technical Conference, Saratoga Springs, NY, 11 p, June 12-14, Gray, Glenn C., “Environmental Constraints Challenge Designers 1995 of Shoreline Community Near Kansas City”, Professional Engineer 45(6) pp42-44, 1975 Charles G. Stolberg is the executive director of the Head, A. L. et al, “Low Pressure Sewer System Replaces Septic System Submersible Wastewater Pump Association (SWPA), 1866 in Lake Community”, http://towtrc.tamu.edu/sewer.htmi, 8p, Sheridan Road, Suite 201, Highland Park, IL 60035- 1998 2545, 847-681-1868, Fax: 847-681-1869, swpaexdir@ Ierley, Merrit, “The Bathroom an Epic”, American Heritage magazine, sbcglobal.net, www.swpa.org.

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PUMPS & SYSTEMS www.pump-zone.com JULY 2007 47 Forging the Future The State of the Association

A profi le of the Submersible Wastewater Pump Association and current projects it is developing for its members.

WPA is truly forging the future of the submersible waste- Components Integration for Use in Submersible Wastewater water pump industry. The three critical functions of the Pump Stations) SAssociation are to 1) identify the common self-interests • Funding proposed research by Dr. Robert Sanks entitled of its membership and the industry, thereby creating a vision The Next Generation of Small, Round Wet Well Design and for the Association; 2) develop, update and approve programs creating educational programming, publications and other to serve those needs as the dynamic components of a strategic technical resources based on the results of that research. plan; 3) implement the strategic plan and monitor progress as • Developing for sale technically-oriented products and those programs carry forward. services on pressure sewer systems to educate specifi c target audiences. • Developing website links to grinder pump and low-pressure Purposes and Objectives sewer system information. • SWPA promotes increased use and consumption of the • Creating a PowerPoint tutorial on Grinder Pumps in products of the submersible wastewater pump industry. Pressure Sewers and an accompanying Business Plan to • SWPA performs such functions as shall promote and pro- establish goals and objectives for the program. vide for the welfare of the industry and engage in all lawful • Creating plans for the development of additional activities appropriate for an industry trade association, standards/guidelines/tutorials. including but not limited to analyzing and discussing con- • Developing a plan to work more closely with national, ditions affecting or which may affect the industry; studying regional, state and local code setting bodies to ensure their improved operating methods and procedures; conducting standards and regulations are current, accurate and conform education and research activities; formulating or assisting in to SWPA’s recommendations for Grinder Pumps in Pressure the formulation of tests and test methods for industry prod- Sewers. ucts; and representing the industry in contacts and relations • Refi ning its Strategic Initiatives related to “The Systems with other organizations, the government, and the public. Approach” and developing standardized language on those • SWPA cooperates with other associations and groups where efforts to appear in all SWPA Technical Resources. necessary or desirable in carrying out the purposes and • Developing System Component Guidelines in a series of objectives of the Association. documents that provide descriptive information on the • SWPA does any and all lawful acts and performs and components in a total submersible system furnishes any and all lawful services which may be deemed and how those components interact with, impact on, and to be useful and desirable in order to effectuate any of the affect each other, in a standardized format. above purposes and objectives or to conduct any of the • Coordinating and ensuring the consistency of terminology above activities. within all SWPA publications as well as between SWPA publications and accepted industry nomenclature. Current Projects Under Development • Expanding the SWPA Field Start-Up and Check-Out • Creating a comprehensive Strategic Plan, based on the Procedures Manual to include a section on Grinder Pumps. results of the Association’s recent Member Needs and • Creating a series of training modules based on the SWPA Opinions Survey. Handbook. • Publishing a comprehensive Submersible Wastewater • Expanding the SWPA Statistical Reporting Program to Pumping Systems Manual (Engineering, Applications and include Submersible Mixers, Submersible Choppers, Packaged Systems and wastewater valves.

48 JULY 2007 www.pump-zone.com PUMPS & SYSTEMS Featured SWPA Members The Mission of SWPA Enhance the global wastewater environment by Environment One Corporation 2773 Balltown Rd., Niskayuna, NY 12309 informing, educating and providing leadership Phone: 518-346-6161 Ext. 3028 in the design, procurement and operation of Fax: 518-346-6188 submersible wastewater pumping systems. Website: www.eone.com/sewers Email: [email protected]

• Developing membership within the Association, including both current membership retention and prospective mem- Fairbanks Morse Pump bership recruitment. 3601 Fairbanks Avenue, Kansas City, KS 66106 • Promoting current membership retention by enhancing the Phone: 913-371-5000 programs, services and benefi ts provided to members. Fax: 913-748-4025 • Promoting prospective membership by creating new pro- Website: www.fmpump.com grams and activities to attract new members. Email: [email protected] • Ensuring consistency in membership development – retain- ing current members and attracting new ones – and promo- tional activities. Hydromatic • Creating a membership development campaign under the 740 East 9th Street, Ashland, OH 44805 banner “SWPA is forging the future of the industry and, as an Phone: 419-289-3042 industry leader, your company needs to become involved (or Fax: 419-281-4087 more involved) and incorporate SWPA’s plans and programs Website: www.hydromatic.com into your company’s marketing strategy.” The components of the campaign are expected to include: 1. Encouraging current members to become more involved ITT Flygt and to increase their participation in the Association’s 35 Nutmeg Drive, Trumbull, CT 06611-0943 programs and activities. Phone: 203-380-4700 2. Reviewing the potential of developing additional “value Fax: 203-380-4705 added services” to attract specifi c categories of potential Website: www.fl ygtus.com members. Email: fl [email protected] 3. Attracting a broad base of members in the Associate Member (non-manufacturer) classifi cation. Ronk Electrical Industries, Inc. • Creating a SWPA Engineering Scholarship Program for the P.O. Box 160, Nokomis, IL 62075-0160 children of employees of SWPA member companies. Phone: 800-221-RONK • Creating an Internet based technical Discussion Fax: 217-563-8336 Group/Forum. Website: www.ronkelectrical.com • Seeking out additional distribution channels for SWPA’s Email: [email protected] technical resources. • Translating SWPA’s technical resources into Spanish. • Publishing a condensed version of the SWPA Handbook, a SJE-Rhombus tutorial/guideline created as an introduction to the design 22650 County Highway 6, Detroit Lakes, MN 56502 and proper application of submersible pumps. Phone: 888-DIAL-SJE (342-5753) • Exploring additional Partnering Agreements with industry Fax: 218-847-4617 organizations, the trade press and others. Website: www.sjerhombus.com • Conducting market research on the “drivers” in the waste- Email: [email protected] water business. P&S Yeoman Chicago Corporation The Submersible Wastewater Pump Association, 1866 3905 Enterprise Ct., Aurora, IL 60598 Phone: 630-499-6918 Sheridan Road, Suite 201, Highland Park, IL 60035- Fax: 630-236-5511 2545, 847-681-1868, www.swpa.org. Website: www.yccpump.com Email: [email protected]

PUMPS & SYSTEMS www.pump-zone.com JULY 2007 49