Innovative Plant Manages Excess Flow
In A Residential Neighborhood

By RICHARD J. NOGAJ, P.E
President of RJN Environmental Associates, Inc.

The Village of Villa Park, a western suburb of Chicago, is a residential community with population of 24,000. Older sections of the Village were originally built with combined sewers which discharged directly to Salt Creek. When regional treatment requirements were mandated, the Salt Creek Drainage Basin Sanitary District was formed to provide wastewater treatment. Previously, during wet weather, it was acceptable to bypass excess flow from the combined sewers directly to Salt Creek. When the State of Illinois disallowed the practice of construction of new combined sewers, new areas of the Village were constructed with separate sanitary sewers.

The resulting sewer system was generally adequate during dry weather conditions, but severe problems were experienced during wet weather conditions. During wet weather periods, overflows from both the combined and separate sewer areas frequently discharged to Salt Creek. In addition, sewage back-ups into basements and localized surface flooding occurred from an overloaded sewer system. Sewage overflows violated current state and federal regulations regarding pollution of the receiving stream. Downstream of Villa Park, Salt Creek extends through several public recreational lands including Butler National Golf Course, the historic Graue Mill area, Brookfield Zoo and forest preserves containing hiking/hiking trails. Not only did Salt Creek flood on a regular basis, but the flood waters contained sewer overflows which affected the surrounding recreational waters and land.

Faced with these environmental concerns and State/Federal requirements, the Village of Villa Park retained RJN Environmental Associates, Inc. to conduct the preliminary studies, develop alternative solutions, perform final design and monitor the construction activity.

A Combined Sewer Overflow Study was conducted in accordance with Federal and State requirements to determine the level of treatment required for combined sewer overflows which previously entered Salt Creek without treatment. A cost-benefit analysis determined that primary treatment and disinfection of wet weather flow, up to 10 times dry weather flow from the combined sewer areas, would meet regulations established by the State of Illinois Pollution Control Board. This would enhance water quality in Salt Creek in a cost-effective manner.

There were numerous sources of infiltration and inflow in the separate sanitary sewer system which overloaded the system causing basement back-ups and sewage overflows to Salt Creek. The purpose of the study in the separate sanitary sewer system was to determine which infiltration/inflow sources were to be repaired and what additional sewer requirements were needed to transport the remaining flow. The degree of treatment required by the State of Illinois for excess flows from separate sewer systems is equivalent to that provided by a secondary treatment process.

The study for the separate sanitary sewer area was complicated by the fact that when homes were originally constructed, it was acceptable practice to connect storm sump pumps to the separate sanitary sewers. As part of the study, 2,664 buildings were inspected in the separate sanitary sewer areas and 1,077 infiltration/inflow sources were identified as being cost-effective to remove. Since there would be a public benefit in removing the excess flow from the sewer system, a program was established to pay a portion of the cost incurred by each homeowner for plumbing modification required to remove the excessive flow from the separate sanitary sewer system.

In accordance with these studies, the total required capacity of the treatment facilities is 25.9 mgd (18.3 mgd for Combined Sewer Overflows and 7.6 mgd from Sanitary Sewer Overflows). Treatment of wet weather flow consists of coarse screening, storage and

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aeration of first flush volume, and flocculation with polymers, primary settling, and chlorination for excess flows.

Although the Salt Creek Drainage Basin Sanitary District provides treatment of dry weather flow, facilities were not available to treat wet weather flow. An off-site facility was recommended that would treat wet weather flow while the Salt Creek plant would continue to provide dry weather treatment. Several treatment alternatives were evaluated during the preliminary design phase. Major considerations which were addressed included location of the plant, process requirements, odor control, and cost.

The only suitable site available for construction of the Wet Weather Flow Treatment Facilities (WWFTF) was a one acre parcel in a predominantly residential area of the Village immediately adjacent to the Illinois Prairie Path. Given the residential character of the area, it was necessary to make the new facilities aesthetically pleasing and architecturally compatible with the neighborhood. Several treatment alternatives were evaluated during the preliminary design phase.

The exterior of the structure is brick, accented with cedar siding and has a low profile facade to maintain residential character. The entire treatment plant was also enclosed and equipped with odor removal equipment as part of the ventilation system. Sound abatement materials were utilized to control noise pollution.

To take advantage of different effluent criteria established by EPA for combined sewer overflows and excess flows from separate sanitary sewers, the WWFTF was designed to treat each flow stream separately. Variable flow pumps are used to improve the performance of primary treatment for the excess sanitary sewer flow. Polymers, used for flocculation of excess sanitary sewer overflows, are not required to meet the less stringent effluent standards for the combined sewer overflows.

Space limitations mandated a "shoe-horn" design and prevented construction of a chlorine contact tank on the site. Therefore, the outfall had to be increased from a 48 inch diameter pipe, to an 84 inch diameter pipe, to provide necessary volume to ensure that adequate chlorine contact time was obtained for disinfection. Since the structure covered most of the site, stormwater detention for the facility itself was incorporated into the roof of the structure with controlled release to Salt Creek.

An innovative mix of electronic controls were included in the design of the treatment facilities since the facilities would only operate intermittently, and only

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one person would operate the facilities. A programmable controller activates opening of influent sluice gates, starts pumps, starts the mechanically cleaned bar screens, energizes the chlorine evaporators, controls air cylinder operated valves, activates the ventilation system, starts the influent and effluent wastewater samplers, and controls many of the operations. The programmable controller is also used to monitor valves, meters, and equipment. A graphic instrumentation panel is connected to the programmable controller so that the status of valves and equipment is indicated on the panel along with indicators from the plant flow meters. The panel gives the operator an instant update on the operating status of the facilities. A telemetry system communicates information between the Villa Park WWFTF and the Salt Creek Drainage Basin Sanitary District Treatment Plant. An automatic telephone dialer relays 13 customized alarm messages. For the convenience and safety of the operator, the facilities are supplied with an intercom system, oxygen detectors, combustible gas monitors, chlorine gas detectors, smoke detectors, and an illegal entry security system. Each of these systems is connected with the programmable controller and the automatic dialer. When wet weather overflows subside, the facilities deactivate automatically.

A significant achievement of the project was the cooperation between the Village of Villa Park, Salt Creek Drainage Basin Sanitary District, USEPA, IEPA, IDOT Division of Water Resources and the Army Corps of Engineers to successfully resolve a major water pollution issue. While the WWFTF treats excess wet weather flow, the Sanitary District continues to provide primary, secondary, and tertiary treatment of first flush volume and collected sludge from the WWFTF.

The Village of Villa Park recently was the recipient of the 1988 Local Project of the Year Award from the American Public Works Association.

In conclusion, sewer overflows encountered in Villa Park were many and varied. EPA established strict guidelines for water quality for both separate sanitary sewer overflows and combined sewer overflows. An innovative design satisfied the constraints of space limitations, sensitive site location, stormwater control, and inter-agency coordination. The process further included methods of continual communication, and coordination between agencies. Protection of the environment was achieved without adverse impact on the adjacent residential community. •

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