You should at least try to ensure that vandalism doesn’t happen. From the Association of State Dam Safety Officials, we get Case Study: Maple Grove Dam (Colorado, 1979).
The dam was built in 1955. In 1960 the spillway was redesigned to handle a larger discharge, on the order of 1100 cubic feet per second.
The dam was doing a fine job of controlling floods. This was actually an “unintentional” side effect of the dam, and not part of its original design.
So since more of good thing is a better thing the local powers-that-be decided to see if they couldn’t improve the ability of the dam to deal with flooding. So in the 1970s a decision was made to add two Fabridams in the spillway, to increase the ability of the dam to deal with rare floods.
This new design included the addition of two Fabridams, one 30 foot long by 6 foot diameter and one 40 foot long by 10 foot diameter, placed within the newly enlarged spillway beneath the W. 27th Avenue bridge. The Fabridams were able to be filled with either water, air, or a combination of both and included automatic controls for ease of maintaining desired heights of both dams.
Fabridams are basically long tubes made of neoprene, laminated rubber, and nylon (the sort of material that inflatable boats are made from) that could be changed to increase and then decrease the holding capacity of the reservoir to attenuate floods. But there is a problem with that material, and any boater can tell you if they have an inflatable dinghy. That material can be punctured.
During a routine inspection of the Fabridams on March 17, 1979 around 11:45 PM, personnel of the CMWC noticed one of the Fabridams was collapsing and allowing water in the reservoir to be suddenly released down the spillway. The CMWC personnel immediately contacted the Wheat Ridge Police Department, who began evacuations of approximately 2,000 people from residential units along Lena Gulch in the 2.3 mile river reach immediately below the dam. Approximately 100 acre-feet of water was released during a period of about 2.5 to 3 hours before the spillway flows ceased, lowering the reservoir by about 3 feet.
There was no loss of life, but basements and first floors of homes and businesses were flooded. You can find an image of one of the points where the Fabridam was damaged at this link.
The punctures were determined to be the work of vandals. Temporary repairs were made, and later permanent repairs were made, but that isn’t the what addressed the cause of the failure.
Starting March 18, 1979, personnel surveillance was notched up to half-hour intervals without pattern. Security lighting was installed on March 27, 1979. On April 2, 1979, a seasonal changeover was made filling the Fabridam with water instead of air, a mode of operation less likely to be tampered with. On June 4, 1979, a low pressure monitor and alarm system was put into operation which activated a visual and audio alert in the treatment plant anytime the pressure system in the Fabridams operated for longer than two minutes. Alternative designs for supplying emergency power were initiated on June 14, 1979. On August 1, 1979 fencing was placed on top of the concrete walls of the spillway that included a barbed wire overhang in an effort to deter entry into the property
An erodible coffer dam was installed downstream of the Fabridams in 1980, and in 2004 the system was upgraded.
In 2004, the Fabridams in the Maple Grove Reservoir were reaching the end of their service life. A replacement system was put in place that uses hydraulic cylinders to raise and lower two independent steel crest gates. They operate under the same discharge parameters as did the Fabridams, but are less susceptible to vandalism and are simpler to operate and maintain than the Fabridams were, allowing greater confidence in the integrity of Maple Grove Dam and ultimately a safer option for the public.
This isn’t the only example of an inflatable dam being damaged by vandalism. In 2015 a dam that was part of a freshwater system in California was damaged in spite of some security. Nearly 50 million gallons of water lost due to vandalism in East Bay. The video starts with an annoying advertisement.
So what is the moral of the story? Our infrastructure is under attack. And while that may not have been so apparent in 1979, by 2015 it should have been apparent. They make reference to the fact that the security which was in place decades in that California article had worked without incident. “We’ve always done it that way,” should not be your guiding principle.
You should consider how vulnerable any infrastructure you maintain is, to accident, to vandalism, whatever. You should have some security in place and you should review it. You should have monitoring in place, and you should know ahead of time what you are going to do if something goes wrong. And it should go without saying, but you should know what is important, and not just if you own infrastructure, but the stuff you rely on. What would you do in the event of a long-term power outage? What if your communications are disrupted? What if you can’t get back into the office building because of fire or other hazard? In short, you need to plan for what can go wrong.