Rock Ripping and off site damage

[oldestguy]

I'm being asked to be an expert in a case where a trout pond, spring fed, some 800 feet away is claimed to be affected by ripping of rock for a borrow area.

Sounds fishy, but other than blasting, I believe this sort of "damage" claim is without merit.

Any info on this subject verifying such claims would be of interest to me.

 

[Ron]

OG...What kind of damage can you do to a trout pond? Do they stop biting? With my fishing luck I'd never know the difference.

If it is losing water, there's a possibility of rock fracturing/fissures opening or some other type of subsidence issue, but at 800 feet, I would expect any vibrations to have significantly dissipated.

You might check C.H. Dowding's book on Construction Vibrations (2nd ed.)

 

[oldestguy]

I am learning more. The claim is that vibrations shook the bedrock and former fractures, which carried water, now are somewhat filed and the spring water source flow is way down. It is assumed the flow path to the pond spring goes under the borrow pit site. No info on past versus present rock fracture conditions, just a theory, but by a state hydrogeologist employee. Kinda neat to be able to state an opinion and then the defendant has a job to do to refute that.

Rock is a shale-sandstone which is very weak in compressive strength. Higher rock was a dolomite, hauled away for road making purposes.

 

[Ron]

OG...one of the things I like about forensics...you get paid to learn! I was thinking flow interruption (see previous post), so that's at least one place to start.

 

[jheidt2543]

One thing I would check is the state's hydrologic records for rain fall and stream flow data. You could also check the state's water well records in the area or with the USGS.
The lost of water flow could be due to drought conditions.

As a fly fisherman, my sympathies are with the trout, but 800 feet is a long way - 2-1/2 football fields! Vibration seems a stretch.

 

[oldestguy]

OK on the flow records. The main claim is a change in spring flow from 300 gpm to 76 gpm. I think the historical 300 may be a crummy test, who knows. Exploring seasonal changes will be an obvious effort, but so far no immediate site records known.

The factor I need to spend some time on is the vibration aspect and clogging of fractures. An interesting subject of which I surely would like to see some experience elsewhere. Even blasting experience would be helpful.

I'm wondering if solution channel short term changes in soluble rock also might have some studies somewhere.

 

[emmgjld]

Groundwater changes. One of the more difficult problems. When all goes well, no one actually keeps any records to prove the condition.
I can't think of any published papers or unpublished research dealing with changes of water flow through fractures. Here in Colorado, I would probably try to find old hands (like oldest guy) who either worked in or consulted with some of the hard rock mines in the area.

I would be looking around the area, with similar geology, trying to find any records, even anecdotal, which could tie together or not, groundwater levels, seepage or spring flow with published weather/precipitation records.

 

[BigH]

'ellova problem, OG. I will send this to an engineering geologist I know - who is quite the "geological" goat. I did find a paper that hints at closing dispersions due to blasting but may not be practical enough but may lead to some varying thoughts. It would be interesting to know if they had maintained any records of particle velocities at various distances from the blast - how big of a "pop" was it, etc. I'll keep thinking but this is all new to me too.

http://www.grainflow.com/index_files/Walton_AMD-Vol_117_1991_p65_Waves...Joint_Sets.pdf

 

[oldestguy]

No action yet waiting for the attorney in giving authority to do some area, on site, evaluations of spring flow changes. Springs are common in the general area, meaning they may be found say 5 to 20 miles spacing and usually in similar bedrock situations. Watersheds usually 25 to 50 square miles.

One paper I found indicates that earthquakes tend to allow more rapid flow of water in bedrock. Not sure how much good that will be in court.