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Home My WebLink About4.1 Village Board discussion of rehabilitation options for the Fairview Gardens Sewer Pump Station.Mr�GauC �'d'+rt;�iect Item Cover Page Subject Village Board discussion of rehabilitation options for the Fairview Gardens• Station. Meeting July 12, 2022 - COMMITTEE OF THE WHOLE - Fiscal Impact true Dollar Amount Varies Budget Source Not applicable at this time. Category DISCUSSION ITEMS Type Discussion Item Fairview Gardens is a residential subdivision comprised of approximately 292 single-family homes. It is located near the intersection of Central Road and Wolf Road. This area was annexed to the Village in 1969 after streets, utilities, and most of the homes were already constructed. Originally, the sewer system was owned and operated by a private utility company (the Utility Sewer Company). The Village purchased the utility shortly after the area was annexed. The sewer conveyance system in the area is comprised of separate sanitary sewers and separate storm sewers. However, the sanitary sewer accepts a significant amount of storm water during rain events as a consequence of directly connected footing tiles from some neighborhood homes. To accommodate these flow peaks, the sanitary sewer system features a relief storage pipe (installed in 1992) and a high capacity pump station that discharges to a Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) interceptor sewer in the Central Road right-of-way. The MWRDGC interceptor carries the waste to treatment plants for processing. To further mitigate the impact of wet weather flows, the Village has lined 100% of the sanitary sewers and manholes in the drainage basin. Staff has also performed 1 smoke testing on separate storm sewers to confirm no illicit cross connections with the separate sanitary sewer system exist. In summary, all extraneous wet weather flow enter the separate sanitary sewer system through private property sources (i.e. footing tiles, directly connected sump pumps, and service line defects). There are no publicly owned sources of wet weather flow. In 2019, staff began a process to replace the pump station. This process was part of a comprehensive end -of -lifecycle program to replace all of the Village's 10 sewer pumping stations. To date, six (6) sewer pumping stations have already been replaced. One (1) is underway this year (Cottonwood Lift Station), and two (2) more are pending in future budgets. To replace a sewer pumping station, a permit is required from our receiving system (MWRDGC). The MWRDGC will not issue a permit to replace the Fairview Lift Station in kind because the existing rate of discharge exceeds the new limits established in the 2014 Cook County Watershed Management Ordinance (WMO). To obtain a permit,, the discharge capacity of the pump station would have o be reduced by approximately -thirds (66%). This reduction would result in frequent basement back-ups during common rain events. The existing lift station has three (3) pumps capable of pumping a maximum of 1.656 MGD. If the Village were to reconstruct the lift station at the Allowable Permit Capacity per the Cook County Watershed Management Ordinance, this maximum flow rate would reduce to 0.5314 MGD. In order to quantify what this impact would mean to the basin, a wet weather analysis (computer modeling) was conducted. Lift station SCADA data was analyzed during storm events with the highest recorded rainfall totals since 2014. Flows generated from these storms were simulated through the lift station as if it had been reconstructed with the Allowable Permit Capacity and maximum system surcharge was calculated. The following table illustrates this analysis. Storm Datesi Recorded Rainfall (In)2 ( ) Estimated Rain Event Estimated Estimated 9 e (Acre-Feet4) 1 6/30/14 - 7/1/14 2.6 over 1 day 1 -yr 0.76 2 7/19/17 - 7/23/17 4.55 over 5 days 5 -yr 5.5 3 10/13/17 - 10/16/17 4.39 over 2 days 5 -yr 5.6 It U/0/10 — 0/1L/10 L./J VVCI L uc1VJ 1 -VI D. It 2 5 4/28/19 - 5/2/19 14.29 over 4 days 5 -yr 17.93 1. Analysis dates included dry days before and after the event to observe residual I&I behavior. 2. Rainfall data from O'Hare Weather Station, approximately 6 -miles south of the lift station. 3. Analysis not utilized. SCADA data likely impacted by floats stuck in the "pump on" position. 4. Acre-feet: one "acre-foot" of water covers an area the size of one acre (43,560 square feet) with water to a depth of 1 foot. One acre-foot is 325,851 gallons of water. MWRDGC allows for a maximum peak factor for sanitary flow rates of 4.0 in new designs, normal daily flow rate has a factor of 1. Peak factors for the Fairview basin were found to be as high as 14.3 for the analyzed storms. This difference in peak factors points to infiltration and inflow of non -sanitary flow, or stormwater. - . • • • • - • - • . - _ The Clean Water Act of 1972 and MWRDGC Watershed Management Ordinance prohibit stormwater flow in separate sanitary sewer systems because the clear water does not need to be treated at wastewater treatment plants. Removing clear water from separate sanitary flows reduces the capacity requirements for treatment plants and, perhaps most importantly, reduces the frequency of wastewater treatment by-passes. As noted previously, all sources of wet weather inflow or infiltration in the Fairview basin are from privately owned property; mostly single family homes. All defects in the Village owned portion of the separate sanitary sewer system have been corrected. All 292 homes in the basin were inspected by Public Works staff and/or a Public Works contractor. 74 of these properties likely have footing drain connections connected into the sanitary sewer, resulting in the high non -sanitary flows during wet weather periods. In order to replace the pump station, these wet weather flows need to be eliminated or temporarily stored until the pump station can catch up with the high KI incoming volume. For the purposes of this analysis, this volume is defined as 5 - acre feet based on the wet weather analysis summarized in the table above. Staff appealed MWRDGC's position in an August 2019 letter. Staff's appeal was predicated on pre-existing conditions constructed prior to both the 1972 Clean Water Act and the 2014 Watershed Management Ordinance as well as previous permitting by the MWRDGC. In addition, staff argued that the subdivision was developed prior to Village annexation. Furthermore, sanitary sewers were inspected directly by MWRDGC personnel; not Village staff. The Village's appeal did not prevail. Four (4) alternative solutions have been identified. Three (3) of the solutions involve constructing storage facilities to temporarily store peak surges (see exhibits labeled Alternative 1, Alternative 2a, and Alternative 2b). Alternative 1 presents a solution that only utilizes existing Village -owned public rights-of-way to temporarily store excess water. Alternatives 2a and 2b utilize both public rights- of-way and existing open spaces such as Bluett Park and an existing parking field adjacent to St. Emily's Catholic Church. All of these storage solutions are expensive to implement, costs range from approximately $4 million to $8 million, and do not offer relief from storms larger than a 5 -year recurrence interval. There is a 20% chance of exceeding a 5 -year storm in any given year. By extension, there is a 100% chance of a 5 -year storm over the course of 5 years. The fourth option is unusual and a little innovative. It involves permanently eliminating the clear water that the pump station has to handle. This will be accomplished by disconnecting existing foundation footing tiles from sewer service lines, installing a sump pump, and redirecting the clear water flow to discharge on the ground instead of being conveyed into the sanitary sewer system. This option should allow the sewer system to handle any storm event without basement flooding. This option is unusual and innovative because it resolves a neighborhood flooding problem by performing rehabilitation work exclusively on private property. To be effective, all homes with direct footing the connections would have to be disconnected. Partial participation would likely still result in increased structure flooding. Staff has determined that 72 of the 292 homes in the subdivision have direct footing the connections. The estimated cost to disconnect these footing tiles, and replace them with a sump pump and overhead sewers, is $1,850,000 (or about $26,000 per home). Exhibits depicting each alternative are attached. Exhibits labeled Alternative 1, Alternative 2a, and Alternative 2b depicts temporary storage solutions constructed in public rights-of-way and/or other public property. The fourth option, labeled as 4 Alternative 3, depicts homes that would be required to participate in a direct footing the disconnection program. One approach to attenuate the surcharge is the construction of relief storage. Similar to a 1992 project that was constructed in the area due to this condition, additional relief sewers could be constructed to hold the sewer surcharge as the station catches up with the inrush of flow caused by storm flows entering the system. This work would require the construction of approximately 13,700' of 54" storm sewer with an average depth of about 14 -feet. Assuming a pavement patch approach to restoration, this Alternative concept is estimated at ,020,000 including construction contingencies and engineering costs. This alternative would provide protection for a 5 -year recurrence interval storm. Relief storage can also be constructed in underground storage structures. The alignment of the 1992 relief sewer offers two potential locations for this type of structure. The first location is in the north parking lot of the St. Emily School. This facility would need to be installed at an approximate depth of 12 -feet to the structure top, and an overall excavation depth of almost 20 -feet and would require a footprint of 1.13 acres. The majority of the parking lot would need to be removed and replaced. This Alternative concept is estimated at $4.,870,,000 including construction contingencies and engineering costs. The estimate does not include property acquisition costs which would be determined with negotiations with the church and school. This alternative would provide protection for a 5 -year recurrence interval storm. The second potential location for underground relief storage is Bluett Park, north of the Horner Lane and Thayer Street intersection. This facility would need to be installed at an approximate depth of 7.5 -feet to the structure top, and an overall excavation depth of almost 15 -feet and would also require a footprint of 1.13 acres. Although no parking lot replacement is required, restoration would need to be coordinated with the Mount Prospect Park District. 5 This Alternative concept is estimated at $3.,925,000 including construction contingencies and engineering costs. The estimate does not include property acquisition costs. This alternative would provide protection for a 5 -year recurrence interval storm. - - • . -I MT a 77 r • A third approach is to correct the source of inflow on the private properties. Based on the Village's inspections, it is estimated that 74 properties have footing the and / or property drains directly connected to the public sanitary sewer as a gravity system. The proposed model for disconnection would follow that established for Basin 14 in 2010 to convert gravity systems to overhead systems. This approach would include the Village identifying organizing bid pricing with contractors for the sewer reconnections. All residents with direct footing tile connections would be required o permanently disconnect footing tiles and install overhead sewer systems. • secure 11' • participation,. - • . the Village provide .' in an amount notto exceed 1 1 1 per home.11' • of . - aid will • in the form of a direct grant that does nothave to be repaid.Only costs directly • - the disconnection of the footing tiles and installation •i overhead sewers would be eligible • -• - • • •- responsible •r all interior restoration). This Alternative concept is estimated at $1,850,000 ($25,000 per home @ 74 homes). This solution is the most cost-effective and provides sanitary back-up protection from almost any storm. Staff considers this fix the preferred solution. Appropriate Village staff, along with the Village's engineering consultant from Ciorba Group, and a representative from the MWRDGC will be on hand to present the issue and facilitate discussion. Additional information and supporting documents can be viewed on the project website: www.mountprospect.org/fairview Alternatives 1. Discuss options to rehabilitate Fairview Garden Sewer Pump Station. 2. Action at the discretion of the Village Board. 11 ATTACHMENTS: Fairview Basin Wet Weather Alternatives _ MAPS.pdf BASIN SS44 Map Info as of July 2018 F : \Projects\CASEY\2 018\SS44 ALTERNATIVE 7 Concept Est: $8,020,000 m i 431 21 N24 z 350 Y 20N18 R 20N20 177 0 32 Of LL J O 1INN E GR ORY ST 0 00 O r O O 00 O N W O J 11L� J El 3 11 L�ir [�i �r aii OrO r Ill N02319 310 11NO3 317 30 0 i-012NO16 11N51 0 11N52 1111455 11N53 11 N57 11N56 1992 48" Relief Sewer BASIN SS44 Map Info as of July 2018 F : \Projects\CASEY\2 018\SS44 E CENTRAL RD Underground Relief Storage 54" Relief Sewer ALTERNATIVE 2A Concept Est: $4,870,000 m JEFFRE i TV llN3 3 FIO 4. 11N59 1IN65. 0' 12W� D2 0 11N51 0 11N52 1111455 11N53 11 N57 11N56 1992 48" Relief Sewer BASIN SS44 Map Info as of July 2018 F : \Projects\CASEY\2 018\SS44 E CENTRAL RD Underground Relief Storage 54" Relief Sewer ALTERNATIVE 2A Concept Est: $4,870,000 m i 431 21 N24 z 350 Y 20N18 R 20N20 177 0 32 Of LL J O 1INN E GR ORY ST 0 00 O r O O 00 O N W O J 11L� J El 3 11 L�ir [�i �r aii OrO r Ill N02319 310 11NO3 317 30 0 i-012NO16 11N51 0 11N52 1111455 11N53 11 N57 11N56 1992 48" Relief Sewer BASIN SS44 Map Info as of July 2018 F : \Projects\CASEY\2 018\SS44 E CENTRAL RD Underground Relief Storage 54" Relief Sewer ALTERNATIVE 213 Concept Est: $3,925,000 m JEFFRE i 11N33 F14. —�FVIN13 63/ 11N59 DN4� 12 11N51 0 11N52 1111455 11N53 11 N57 11N56 1992 48" Relief Sewer BASIN SS44 Map Info as of July 2018 F : \Projects\CASEY\2 018\SS44 E CENTRAL RD Underground Relief Storage 54" Relief Sewer ALTERNATIVE 213 Concept Est: $3,925,000 m i 431 21 124 Z 350 Y 20N18 O� 20N20 177 0 32 Of LL J O 11N01 E GR ORY ST 0 A O l0 00 O N w 00 OOr r r N �A �rr�- J3� 13JAJ T � � r C�aaa � C 11102319 310 Ai 11 NO3LUWUEN LN 317 30P, 1012Nos BASIN SS44 Map Info as of July 2018 F AProj ects\CASEY\2018\SS44 ALTERNATIVE 3 Concept Est: $1,850,000