8/14/2019 Black & Veatch WEFTEC.09 Targeting Low Cost and Value-Added Rehabilitation of Large Diameter Sewers

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ABSTRACTFor many years, the City of Indianapolis has experienced cost effective and effi-cient bidding of large diameter sewer rehabilitation projects using shotcrete liningtechnologies. In the region, Indianapolis has embraced the use of shotcrete for large diameter sewer rehabilitation projects and the costs just keep getting lower.Bid prices as recent as March 2008 are coming in lower than shotcrete rehabilita-tion projects more than five years ago. Shotcrete rehabilitation of large diameter pipelines sometimes receives a bad rap, but the technology is efficient and gets better all the time with additional additives for corrosion resistance and increasedstructural strength. This paper discusses shotcrete rehabilitation for a large diame-ter sewer, and construction on two miles of 42-inch through 72-inch diameter brick and concrete sewer from design inception through construction.

THIS POSTER WAS PRESENTED AT WEFTEC 2009

FOR MORE INFORMATION WRITE weknowwater@bv.com OR VISIT www.bv.com

TARGETING LOW COST AND VALUE-ADDED REHABILITATION OF LARGE DIAMETER SEWJ. MORGAN: DEPARTMENT OF PUBLIC WORKS, INDIANAPOLIS, INDIANA J. TRYPUS, S. FAIRFAX: BLACK & VEATCH E. HAENLEIN: M. D. WESSLER & ASSOCIATES, INC.

BUILDINGAWORLDOF DIFFERENCE

WHITERIVER COMBINED SEWERREHABILITATION PROJECTThe project involved the design and construction for the rehabilitation of theWhite River Combined Sewer (WRCS) for the City of Indianapolis DPW. TheWRCS includes sewer segments that range in size from 42-inch to 72-inch diame-ter, located along the eastern side of the White River. The WRCS is approximately12,000 feet long and begins at 10th Street and Elmwood Street, runs generally in asoutheasterly direction, and ends at McCarty Street and Church Street.

The WRCS alignment is ina mixture of industrial,commercial, healthcare,recreational sporting andeducation use areas. The

sewer rehabilitation begannear 10th Street andElmwood Street immedi-ately west of WishardHospital and continuessouth through the campusof Indiana University-Purdue UniversityIndianapolis (IUPUI) toCSO 039. From there, the

sewer rehabilitation continues in a southeasterly direction through the White River State Park and Victory Field, crossing West Street and going through industrialareas before ending near the intersection of McCarty Street and Church Street.

CONCLUSIONS

The construction of the project began in June2008 and was completed inAugust 2009. Thedesign information developed, as well as theCity of Indianapolisdrive to complete rehabili-tation of large diameter sewers in an efficientand cost-effective manner, resulted in a benefi-cial project. The project was bid at approximate-ly $700,000 below the engineers cost opinion,and the bids were very competitive. Based onIndianapoliss history of successful s hotcrete projects for large diameter sewers at an extreme-ly low average cost per linear foot of sewer,future success stories are expected to continue.

DESIGN PHASEInitially, two rehabilitation methods, cured-in-place pipe(CIPP) and shotcreting, were recommended as the mostfeasible methods for correcting present problems incombined sewers. Both methods are minimally inva-sive, will have minimal socioeconomic and environ-mental impacts during construction, and will providecost-effective solutions for correcting structural defi-ciencies. However, after technical discussions betweenthe Engineer and the Client, shotcreting was selected asthe best method for rehabilitation of all sewer segments.Segments recommended for CIPPlining resulted in ahigher cost and would require surface flow bypassing,as opposed to the internal bypassing completed duringshotcreting. Shotcreting was determined to provideequivalent rehabilitation for those segments whereCIPPlining was previously recommended.

Prior to the installation of shotcrete lining, the sewer was cleaned and sandblasted. Cleaning is completed to removesolids, roots, deposits and other matter that would preclude the installation of the shotcrete liner. Shotcrete for the projectis composed of Portland cement, aggregate, water and fibers, proportioned to produce a suitable mixture for pneumaticapplication. Shotcrete was placed with a minimum thickness of four (4) inches for a maximum of 400 feet from the man-holes. Shotcrete component materials will be selected and proportioned to produce a minimum 28-day compressivestrength of 5,000 pounds per square inch (psi) and a minimum 28-day flexural strength of 800 psi. The shotcrete can be placed using either a wet or dry mix, as both applications were used for this project. Pre- and post-installation televisioninspections of the sewer segments were planned to evaluate conditions.

There are approximately 45 manholes identifiedon the sewer alignment with detailed inspections performed at accessible manholes. Manholes are

typically located at intersections of two or moresewers, at changes in alignment or grade, at thehead end of the sewer and at immediate intervals.Manhole investigation reports were prepared andincluded in the bid documents. Based on theseverity of the defects, manholes along the sewerswere rehabilitated using shotcrete lining, and/or frame and cover replacement and internal chim-ney seals. The thickness of the shotcrete liner for manhole rehabilitation will be at least one (1)inch with a minimum compressive strength of 4,000 psi at 28 days and a minimum flexuralstrength of 600 psi at 28 days.

RISK MANAGEMENTUnderground projects have unique aspects that differentiate as pump stations and treatment plants. These factors includemay or may not occur during construction, and significant vaContractor. Because these factors do not exist in abovegrounallow certain variations in means and methods while providencountered during construction and design.Risk management activities were completed by the Engineer

I Review and response to Contractorssubmittals andrequests for information.

I Review and technical commentary on alternatives byContractor.

I Review and discussion of Contractors progress.I Provide input and raise questions concerning

Contractor progress, equipment, personnel changesand other issues related to technical aspects affecting project completion.

I Technical review and consideration of any claims or change orders.

Risk management was discussed and implemented dur-ing the pre-bid meeting, as well as throughout the proj-ect phases, to reduce any potential impact to the City, aswell as maintain a safe project throughout construction.

SHOTCRETEMETHOD PRIMARILYUSED FORWRCS PROJECT

TYPICALDRAWINGFROM WRCSPROJECTBID DOCUMENTS