When water shows up unexpectedly in your drill holes, you have to make some compromises. If you have access to repump emulsion you can evaluate your ground and judge if that is an appropriate solution for your conditions. If that product isn’t an option, you can consider cartridges of various water-resistant products and load into the water. The down side to that choice is considerable additional expense and less than optimum blast results. Your shot won’t be as good because your powder factor using cartridges will be significantly less that what you calculated for your drill pattern and hole size.
Even if you need to use cartridges, getting the water out will make your loading easier and surer. The chances of cartridge separation will be lessened when you don’t have to drop them into or push them thru the water. If you don’t try to dewater, just a few feet of water will come right up the hole as it’s displaced be each cartridge. So if you’ve got 5 ft. of water, you’re going to need close to 15 ft. of cartridges to dry up the hole.
If you originally intended to load with ANFO, your best bet is to dewater and use WR-ANFO in that portion of the hole that was wet. Dewatering and using regular ANFO is a risky business. That product is almost instantly soluble and when affected by moisture, most likely will produce a low-order detonation at best. WR forms a water-resistant gel coating where it touches the part of the borehole that was wet. Dewatering and using WR will give you the identical powder factor that you intended when you established your drill hole spacing and burden.
Pump it Out
The pneumatic displacement pump from Blasthole Dewatering Systems (BDS) is designed specifically to dewater small to medium diameter drill holes. The pump will easily lift water from more than 100 ft. with the air delivered by a small compressor of about 20 cfm at 100 psi or so.
Using the pump is easy. Connect the regulator/valve assembly to the two-lug connector on the hose from the compressor and the quick connect hose fitting to the pump air hose.
Clear any loose debris from around the hole collar. Since you’re lowering a device down the hole, which can get stuck if some loose rock should fall in above it, it makes good sense to inspect the collars and to be sure they’re tight. If they’re not, use the collar saver tube furnished with the pump. This will prevent the pump or the hoses from dislodging or pulling loose material into the hole.
When you’re ready to pump, lower the entire assembly into the hole until you either reach the bottom with the intake tube, or until the sleeve reaches the top of the water. Pull up on the hoses slightly to insure that they are not kinked right above the pump or that the intake screen is not buried in the cuttings.
Stand away from the top of the hole and open the valve. Keep some slight tension on the hoses as the water rushes up and fills the discharge line. The water will discharge forcibly from the open end of the discharge hose within a couple of seconds. Be sure to hold that end, or secure it in some manner to prevent it from whipping. The sleeve is inflated and is being held against the outer wall of the borehole by the pressure inside of it. The compressed air is forcing the water into the easiest route to the surface (your intake line).
When all the water is forced from that section up and out through the discharge line, you will feel the discharge hose vibrate in your hand as the last of the water and the front of the air passes through the hose. Watch the discharge and as soon as the burst of air blows from that end, close the air valve.
After you feel the sleeve relax, and the pump is loose in the hole, you can move the device and repeat the process if necessary. If you hadn’t reached the bottom of the hole with the lower end of the intake tube, you can lower the pump assembly further into the hole until it reaches bottom, or until the sleeve again reaches the water.
Take up the slack in the hoses, move clear of the hole, and proceed as above. Continue the procedure until you have pumped with the intake tube positioned at the hole bottom. The entire pumping sequence will take less than 30 seconds. When you’re finished, withdraw the assembly from the hole, then prime and load right away, because the water in the formation will start moving back in as soon as you remove the pump.
Blasthole Dewatering Systems, www.bds-usa.com