Shoring underwater dredge holes

[Mgumby16]

Hi everyone,

I wanted to know if any of you have any experience shoring up underwater dredge holes when you are trying to get through approximately 4 to 7 feet of overburden to get to the pay layer ontop of bedrock. I have a few ideas but I also dont want to reinvent the wheel if it has already been done.

I have a 4 inch dredge, the largest allowed in my state without a permit and the overburden is reported to be a sandy gravel with no boulders or mud. It might take a day or two but if I can shore at least three of the sides I believe it would be doable. Any ideas are appreciated.

Thank you,

 

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[2cmorau]

just taper/angle/slope your holes

 

[rodoconnor]

I can't imagine that shoring would be worth the effort as opposed to just hogging your hole out like 2cmoreau just said. Whatever you do stay safe . G/L

 

[rebel003]

A lot depends on how fast the water flowing as to just how large to hog out the hole, and the type of over burden your working with, a good rule of thumb is 1 foot out in each direction for every foot of depth.

 

[russau]

Mgumby16 what state are you in??

 

[Mgumby16]

The main reason for shoring the hole is so I can limit the amount of material moved to get to bedrock. If I take a 7 foot deep hole and use conventional benching methods the hole will be at least 15 ft wide and that would only give you a 1 foot area of exposed bedrock. And the hole would be almost as wide as the creek.

The stream is slow moving and the overburden according to historical records is a sandy gravel with no boulders or clay.

I am located in central virginia almost in the heart of the states gold pyrite belt.

Thank you for the comments so far.

 

[Hoser John]

No shoring needed. 1 foot down and one foot out. A step every 2 feet,2 feet wide in deeper gravels as the hole expands. Once on the bottom you need a big clean area to put your body,hands and feet safely. One knuckle buster can ruin your season healing or cause damage for life. Dredge upstream and cobbles behind as then your hole stays safe,less smoke to ruin your clarity as MOST important to see that wall and anything coming down to/on you. A 7' deep hole gives a boulder plenty of time,even with weight reduction underwater, to build up momentum and adios the fingers,toes or upside your head and your dead. Seen the death part too many times. Always err on the side of caution and stay safe to fight yet another day-John...PS-Nothing wrong with a 4" UNLESS no blaster nozzle then your just a mutzing and a putzing with any size dredge.

 

[Reed Lukens]

What John said along with... You can't safely shore up loose gravel and sand under water, I've tried. If it's all loose then just start a hole with the dredge running full blast and take it down as fast as possible. With slow water you will be daming up the flow with tailings so you will have to stack them. Use a piece of old roofing at the bottom of your box and move it left and right to stack the tailings evenly.
This link will show you how to work low flowing areas quickly.
http://www.treasurenet.com/forums/gold-prospecting/417245-black-water-gold.html

 

[Oakview2]

Love the pics of that Hydraulic site, hope all is well. Good health and good hunting.

 

[Hoser John]

And GOOD wife too?-John

 

[Reed Lukens]

Yea John, Karen & I are both doing great now. I'm 200% better than I was last year after the accident with another 40% of recovery possible. Karen is still hurting but all is good now. It took a year to mostly heal. Even after a year my ribs are still itching so there is still more healing going on

 

[Mgumby16]

Thanks for the input. I was able to get out and walk the creek this weekend lots of sand with areas of cobbles and some exposed bedrock.

I just need to find the time now to get the dredge out there and start sinking sample holes. Here's to hoping that the historical papers are correct about the average gold being the size of wheat grains.

 

[Hoser John]

The older we get Reed the longer it takes but old dredgers are TOUGH and will achieve about any goal. Take care-and tons a au 2 u 2-John