Waterway System
	Home Page
	CSO Main Page
	CSO Map Page

Collection System Inspection

The collection system is inspected with various frequencies, depending upon what portion or facility is being inspected.

All Tunnel and Reservoir Plan (TARP) control facilities are inspected locally every two months. This includes the Upper Des Plaines (UDP) structures located along Weller Creek in Mt. Prospect and Des Plaines, where the tunnel system is tributary to the Kirie Water Reclamation Plant (KWRP) and O’Hare CUP Reservoir. All ancillary equipment associated with the TARP structure is tested for operation. This equipment includes security alarms, dehumidifiers, sump pumps, and vault (or control room) flood alarms. The inspection of this equipment ensures that the motors and equipment, which power and control the gates which regulate flows to the tunnel system, are not damaged. TARP gates are exercised locally at the structure and remotely from the Kirie WRP in order to verify proper operation in preparation for precipitation events. Alarms of the tide gates, or backwater gates, associated with each respective structure are tested during the control structure inspection.

In addition to the procedures above, other routine maintenance is performed. The District contracts an electrical maintenance contractor to lubricate, inspect, and repair gate operators, disconnect switches, and electrical accessories associated with the TARP structures. This maintenance work is performed semi-annually. Furthermore, the Kirie WRP operators exercise the gates at a minimum of once per week to verify normal operations.

As part of the District’s Interceptor Inspection and Rehabilitation Program (IIRP), control structures and inverted siphons are inspected annually. Each intercepting sewer is inspected at least once every 10 years. If the sewer is showing signs of deterioration, the sewer is placed on a once every three years inspection schedule. Each year, in the North Area, approximately 25 miles of sewers undergo a television inspection using a competitively bid contract for television inspection services. Every manhole is inspected at least once every five years. Sewers or manholes will also be inspected if a District employee, contractor, government agency or private citizen informs the District that repairs may be needed.

Tide gates associated with the entire collection system are inspected semi-annually. This inspection includes the gates associated with TARP control structures as well as gates located on outfall sewers owned and operated by local municipalities. The condition of structural members and timbers, depending on the gate construction, is visually inspected. Gates are exercised and lubricated to ensure proper operation.

Connecting structures and local controlling structures (river siphons, slide gates, etc.) are inspected every two months. These structures divert and control flows from the local sewer system to the interceptor system. Inspections conducted ensure that flows are not obstructed and dry-weather flow is not diverting to TARP.

Drop connections (drops) for the entire collection system are inspected annually. Drops convey local sewer flows to the interceptors via a 90 ° connection in the manhole. This flow conveyance controls splashing, which can damage the structural integrity of the manhole and/or release hydrogen sulfide gas. If the flows are blocked from the drop, local sewers carry a greater flow than typical dry weather capacity.

Sewer Cleaning and Maintenance

The District contracts outside services to clean and maintain the collection system. Blocked drops, root intrusion, grease build-up, and mineral growth are cleaned/cleared when discovered during routine inspections. The Contractor is typically required to provide power rodding equipment, vacuum truck services, and high-pressure jetting services.

Inspections and Preventive Maintenance on Pump/Lift Stations

The collection system for the Kirie WRP has no pump/lift stations.

Collection System Rehabilitation and Replacement

The District initiated the IIRP to undertake the maintenance of the interceptor sewer system in a systematic plan. The goal of the IIRP is to increase the reliability of an aging interceptor sewer system as well as to reduce the incidents of cave-ins and the resulting emergency repair work.

Sewers to be inspected are classified according to criteria such as age, TARP diversion capability, brick construction (or otherwise noted as damaged), and industrial sewers. Inspections are performed by the District using physical inspections, television inspections, and infrared inspections, as needed. As noted previously, surface inspections are performed as part of IIRP. Flow metering will also be used to identify blockages and pipe cave-ins.

Based on the inspection reports, deficiencies in sewers and related structures will be repaired by the District on an emergency basis, or by competitive bid contracts. Manholes are repaired using a competitively bid manhole repair contract.

Detection and Elimination of Illegal Connections

The local sewer systems within the District are owned by the respective municipalities, townships, local sanitary districts or utility companies. These entities inspect and eliminate illegal connections to their sewers. The District’s Local Sewers Section and Industrial Waste Division inspect new work to assure that illegal connections are not made to the District’s intercepting sewers.

The Local Sewers Section will detect an illegal connection during routine sewer inspections, per reviews for new construction and television inspections of sewers. The Industrial Waste Division will detect an illegal connection by installation of automatic samplers and flowmeters at industrial site discharges and sewers tributary to industrial sites. Television inspections of sewers in industrial areas will also detect illegal connections.

Detection and Elimination of Dry Weather Overflow

Dry weather overflows, if any were to occur, would be detected by tide gate transmitted to the Kirie control room. Dry weather overflows have been eliminated because all flows are directed to the Kirie TARP tunnel system. Regular inspections insure that all components of the collection and tunnel system are functioning properly.

The Collection System is to be Operated to Maximize Storage Capacity.

The collection system consists of the Kirie TARP tunnels (70 MG capacity) and the more recently constructed O’Hare CUP Reservoir (343 MG capacity). The system is operated to maximize storage capacity. The tunnel is “drawn” down daily during dry weather, and also in anticipation of storm events. In 1972, the TARP system was designated as the District’s selected plan for the elimination of untreated CSOs or WRP bypasses.

The Treatment and Collection Systems are Operated to Maximize Treatment

The Kirie WRP is operated to provide maximum treatment according to the following protocol. During a rain event, treated flow is increased to a maximum of 110 MGD, and even higher flow rates as conditions permit, while maintaining compliance with NPDES Permit requirements. When the flow of combined interceptor sewers exceeds the treatment capacity of the Kirie WRP, the CSOs are stored in the excess capacity of the TARP tunnels and, if necessary, the CUP Reservoir, until they can be treated at the Kirie WRP after the rain event has subsided.

Minimize the Discharge of and Adverse Impacts from any Solids or Floatables Discharged from CSOs

TARP has been approved by the IEPA as the long-term control plan for addressing combined sewer overflows. The addition of the O’Hare CUP Reservoir has eliminated the occurrence of CSOs and, therefore, offers protection of the waterway.

06/16/05