Ross,
Two things ... one posted by you ... and another posted by highflyer ... speak to me.
The engineering study computed that our 40 foot spillway would need to be 170 feet wide to handle this rain event. That is wider than our dam.
AND
The 48 inches of rain measuring stick came from the Hurricane that dumped 36 inches in 12 hours way back in history. It was the event they are protecting to 150% in half the time as I recall.
Given these, I have to wonder if your community's dam could withstand the actual event that highflyer is referring. This is a known event with metrics that come from a very small window of geologic time. If you stop for a moment and wear the shoes of the task force burdened to prevent ANY dam failures in Texas private lakes ... I think that you would probably also base the yard stick on a known event with some level of overbuild (engineer's safety factor). The crap situation is that your location may not receive the known maximum event in 10,000 thousand years, or perhaps longer. BUT some location in Texas probably could within the next several decades. Given it is unknown where such events will occur ... what choice do they have but to make everyone comply with the standard?
$100,000 is fair sum of money but consider this. What would it cost in today's dollars to rebuild? How much would one human life be worth? Or a washed away home be worth? The risks do greatly outweigh the cost of buttressing the dam. I was once told that a good business agreement benefits everyone. While your community doesn't stand to profit from complying it could ensure the dam has a very long life and it could demonstrate, if the dam ever failed, that it worked willingly on compliance and made appropriate and recommended alterations. If the community plays games ... and the dam later fails ... there could be lots of liability and culpability floating around.
