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2020 Eugene Wastewater Master Plan Chapter 5: Rehab of Existing Systems 35
<br />Chapter 5 - Rehabilitation of Existing Wastewater Systems
<br />PURPOSE
<br />The purpose of this chapter is to document current and past pipe rehabilitation efforts, outline methods
<br />for determining future rehabilitation priorities, and propose a level of funding necessary to fully address
<br />long-term preservation of the system based on projected design life and capacity of system components.
<br />GENERAL
<br />The preservation needs of the wastewater system fall into two categories: structural problems and
<br />excessive I/I.
<br />Structural problems: As detailed in Table 5-1, 29 percent of the system, which is approximately one
<br />million feet of pipe, was constructed at least 50 years ago and not rehabilitated as of 2019. Studies
<br />indicate that this may approach the design life of concrete pipe materials, particularly those installed
<br />before advanced gasket technology was available. Prior to the mid-1970s, wastewater pipe was
<br />constructed with concrete, clay, or transite. Although these materials are generally good for this
<br />application, over decades they are subject to chemical erosion, and the jointing materials deteriorate,
<br />allowing ground water to infiltrate. Investigations into the older parts of the system indicate that the
<br />majority of infiltration is coming from these older pipes. Today's installations only allow PVC, HDPE and
<br />ductile iron pipe which are chemically resistant, and have superior jointing materials.
<br />Currently, the City of Eugene rehabilitates approximately 9,000 feet of old pipe per year. However, the
<br />collection system is aging much faster than we can rehab it. As of 2019, 34 percent of the system was at
<br />least 50 years old. By 2029 that number jumps to 49 percent. As a result, Eugene can expect more
<br />structural problems and emergency repairs unless an accelerated rehabilitation program is established.
<br />Table 5-1: Age of Unrehabilitated Gravity Pipe Collection System
<br />Decade of
<br />Construction
<br />Length of Pipe
<br />Constructed
<br />Rehabilitated
<br />Pipe
<br />Unrehabilitated
<br />Pipe
<br />Percent
<br />Unrehabilitated
<br />1912-1919 43,685 24,531 19,154 44%
<br />1920-1929 90,958 65,291 25,666 28%
<br />1930-1939 23,804 12,041 11,764 49%
<br />1940-1949 141,521 75,167 66,354 47%
<br />1950-1959 336,789 200,876 135,913 40%
<br />1960-1969 925,151 112,844 812,307 88%
<br />1970-1979 617,267 41,605 575,662 93%
<br />1980-1989 337,284 9,200 328,084 97%
<br />1990-1999 850,484 6181 844,304 99%
<br />2000-2009 273,154 1465 271,689 99%
<br />2010-2019 88,218 147 88,071 100%
<br />Total 3,728,314 549,347 3,178,967 85%
<br />50 years or older (as of 2019) 490,750 1,071,157 69%
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