Portland City Hall says reservoirs are falling apart
Admiral Randy and his henchpeople in the Portland water bureau -- currently in litigation over their propensity for spending water revenue illegally -- are hellbent on replacing the city's open air reservoirs with outrageously expensive underground tanks. The reason given up until now is that the open reservoirs are a safety hazard, and every once in a while a boil water scare has been thrown in to make their point.
But now there's a different point. In response to city commissioner Amanda Fritz's suggestion that the city merely cover the reservoirs with plastic -- a cheap solution that would last at least 15 years -- the Admiral and his bureaucrat buddies say that the reservoirs are not only unsafe, but deteriorating:
To the casual passer-by the reservoirs may look fine, particularly when full. From an engineering perspective, that is not the case. These century old reservoirs are rated in "Poor Condition" as bureau assets. Over 100 years of the combined effects of temperature changes, weathering and loading have literally worn the reservoirs out. Each time the bureau drains the open reservoirs, every 6 months or so, the bureau patches and repairs. Severe joint failure is becoming more and more common. Cracking and spalling (chunks breaking off), particularly in the wetted zones, is evident everywhere.
Flexible liners have been added to three (two hypalon and one asphalt) of the five reservoirs to both reduce leakage from the reservoirs and prevent the intrusion of groundwater. Properly functioning concrete reservoirs do not need flexible liners. It is telling commentary on the poor condition of the reservoirs that liners had to be added. It is similarly telling how long ago the liners started being added. In the case of Reservoir 6 the asphalt liner was added in 1965 to repair leaks. Reservoir 3 had a hypalon liner installed first in 1978 and then replaced in 2003. Reservoir 5 had a hypalon liner installed in 1998. The life of the hypalon liners is about 15-20 years.
The liners do not solve the long term problem. They stop leakage and intrusion for a time. But the reinforced concrete continues to undergo all the effects listed above. Structurally, the reinforced concrete basins continue to deteriorate. Risk increases for more damaging types of failure and the bureau is at a disadvantage because personnel cannot see under the liners. Liners obviously do nothing for the risks associated with open exposure to the environment outlined above.
Design standards have advanced greatly since the 1900s. Design standards and formulae used in the 1900s were much simpler and did not account for many of the risks and conditions that are common practice today. Current analytical tools result in much stronger designs, designs that can handle a wider variety of conditions. Of particular relevance, is the improved understanding of earthquakes, the forces earthquakes generate and solutions to resist earthquake forces. The open reservoirs do not meet current seismic design standards. The Water Bureau's open reservoirs would likely be severely damaged and likely not hold water in the event of a significant earthquake like an earthquake occurring on the East Bank Fault, West Hills Fault or from the Cascadia Subduction Zone.
If the reservoirs are to remain operational for any length of time, they need extensive infrastructure repairs, renewal and modernization. All of the open reservoirs are over 100 years old and have exceeded their life expectancy and are due for replacement regardless of what happens with LT2.
Due to the condition of the floors and walls of the reservoirs, liners and covers would be required. Liners and floating covers whether temporary or permanent limit access to the reservoir for making repairs and maintenance of the structure itself. The necessary repairs and improvements should all occur before covering the reservoirs; otherwise the investment in liners and covers will be lost until some future Council authorizes the needed work.
As usual, there's only one workable solution, and that's to do as Randy tells you.