Cleveland progressing its CSO network 17 Sep 2020

Two deep storage tunnels are under construction in Cleveland, Ohio, with two completed and three more in planning as part of its USD$1.37 billion Federally-mandated Project Clean Lake. When fully completed in 2035, the project will comprise a CSO interceptor network of more than 22 miles (35km) to reduce combined sewer overflow events into Lake Erie by 4 billion gallons per year.

Fig 1. Project Clean Lake deep storage tunnels

In June 2020, the project marked the completion of the 2.8 mile x 24ft i.d. (4.8km x 7.3m i.d.) Dugway storage tunnel. Completed under its $153 million budget, Dugway follows completion of the 3.4 mile x 24ft i.d. (5.5km x 7.3m i.d.) Euclid Creek tunnel, which was finished in 2015 (Fig 1 and Table 1). A third project, outside the remit of Project Clean Lake works programme, for the Mill Creek tunnel came online in 2012.

Both Dugway and Euclid Creek alignments are located within the easterly service area of the Northeast Ohio Regional Sewer District, NEORSD. Four of the seven tunnels are located in this service area which covers the eastern half of the city and the suburbs of Bratenahl and Cleveland Heights.

Dugway and Euclid Creek run at about 200ft below grade through Chagrin Shale. They were constructed using a single-pass excavation-and-lining process with a 1ft (300m) thick fibre-reinforced precast segmental lining. This method was a required by NEORSD and project designer Hatch Mott MacDonald to limit gas infiltration and overbreak. The method has been used on all the main project drives and will be used on the remaining deep tunnels.

The Euclid Creek and Dugway projects were constructed by different contractors, using the same Herrenknecht TBM. After excavation of Euclid Creek by McNally-Kiewit JV in August 2013, the machine was purchased by Dugway contractor Salini-Impregilo Healy DST JV. It was refurbished with the support of the manufacturer and relaunched in early March 2016. Breakthrough was achieved two years later in mid-March 2018.

The two remaining Project Clean Lake excavations in the easterly service area are the Doan Valley system, which is currently under construction, and the Shoreline project. Both will connect to the Dugway alignment. When complete, the easterly tunnels will capture almost 1.7 billion gallons of overflow per year.

The Doan Valley system with six shafts, comprises the main 1.9 mile x 18ft i.d. (3km x 5.5m i.d.) storage system, plus the 0.6 mile x 8.5ft i.d. (900m x 2.6m i.d.) Martin Luther King and the 1.2 mile x 8.5ft i.d. (2km x 2.6m i.d.) Woodhill conveyance alignments. Excavations on the $142.3 million contract were completed earlier this year (2020) by contractor McNally-Kiewit JV using two TBMs. A new 21.5ft (6.6m) diameter single-shield Herrenknecht TBM completed the main Doan Valley alignment in September 2019. A Robbins machine, first manufactured in the 1970s and subsequently refurbished in 2009, completed the Woodhill drive in December 2018 and the Martin Luther King drive in January 2020; the excavated tunnels finished with an inner cast-in-place final concrete lining.

Dugway TBM broke through in March 2018

All three Doan Valley drives were constructed from a single site within the University Circle neighbourhood. This posed several design and construction challenges that included protection of trees and sculptures, as well as the use of a small-diameter helicoidal shaft excavation method to minimize impact. The contractor has also had to deal with several utilities in the TBM launch site that could not be relocated, due to a prohibition on service disruptions, requiring the installation of protective measures in the work area. The project is due to begin capturing CSO overflows in mid-2021.

The planned 2.7 mile x 23ft i.d. (4.3km x 7m i.d.) Shoreline storage tunnel is the fourth and final tunnel within the easterly service area and is likely be constructed by EPBM through softer ground conditions and under the watertable. This is yet to be finalised. The project includes three online shafts, with two drop shafts – one an offset internal vortex drop and the other a baffle drop. The third will feature an upper and lower gate to help control dewatering of the tunnel. Currently in design by McMillen Jacobs, bidding for the construction contract is expected in 2021 with completion in 2025. The estimated project cost includes US$18 million for the design and $204 million for construction.

Flows from the easterly tunnels system are pumped by one of the largest CSO pump station projects in the USA, to the easterly wastewater treatment plant. Designed by MWH, now part of Stantec, and constructed by the Walsh-Atkinson JV, the pump station is located 230ft underground, 22ft below the Euclid Creek and Dugway tunnel storage system invert, in a cavern of 185ft long x 45ft wide x 60ft high (56m x 14m x 18m). Nine pumps provide a capacity of 160 million gallons per day to entirely dewater the storage tunnels. The pump station was completed in 2018.

Westerly and southerly service areas

In addition to the easterly system, Project Clean Lake includes three additional tunnels in the westerly and southerly service areas.

Construction of the 1.8 mile x 25ft i.d. (2.9km x 7.6m i.d.) Westerly storage tunnel began in 2018 by the Jay Dee-Obayashi JV and is about halfway complete. Running at 200ft-250ft (61m-76m) below grade, the alignment is being excavated by a 28.1ft (8.56m) diameter Lovsuns TBM. The project also includes three shafts excavated using diaphragm wall construction. WST-3 and WST-1 are both online and function as the TBM launch and reception shafts. When complete, WST-1 will house the Westerly tunnel dewatering pump station. The middle drop shaft is offline with a two-pass TBM construction excavation anticipated for the adit. Construction is expected to be completed in 2021 at a cost of $135 million.

Lowering Lovsuns TBM for Westerly tunnel drive

The Southerly and Big Creek tunnels are currently in planning with bidding for construction expected in 2023 and 2026 respectively.

Excavation of the 3.4 mile x 23ft i.d. (5.5km x 7.0m i.d.) Southerly alignment is likely to be by EPBM, and there will be at least four shafts along the main alignment, all online. The launch shaft will subsequently house the Southerly tunnel dewatering pump station, which will be constructed under a separate contract and will feed to the Southerly wastewater treatment centre. When complete, the estimated $326 million project will hold 54 million gallons and is expected to be operational in 2027.

The last element of the Project Clean Lake is the 4.2 mile x 20ft i.d. (6.8km x 6m i.d.) Big Creek tunnel which is currently planned to include at least seven shafts, five of which will be offline. Estimated at $222 million, completion is required by mandate by 2035. It will hold 46 million gallons and will be dewatered via a downstream gate leading to a gravity flow interceptor to the Southerly wastewater treatment centre.