Dewatering Wells.docx

Borehole Methodology Using Used HQ Rods as Casing

1. Drill PQ (122mm/4.8”) to 1.5m past target depth (100m) so 101.5m creating sump for fall in material 2. Pull back to 9-12m and air lift hole to test for water corrosiveness and flow 3. Pending Client requirement on hole diameter to get hole to 6” OD either reaming HWT Casing shoe or hole widening tool if diamond drilling or using hammer and air with Hanjin rig to widen hole. Using hammer will mean hole will be left open when RC rods are pulled and could create fall in. Or if PQ (4.8”) is ok then simply run PQ back into hole and flush before running HQ. 4. Run in HQ casing (89mm/3.5”) to bottom. Screened/slotted section and depth to be advised. 5. Sand/gravel pack slotted section to 3m above top of slotted section 6. Bentonite cap above (1m) slotted section 7. Fill remainder of annulus with course sand until 2m from surface 8. Bentonite cap (0.5m) again 9. Cement last 1.5m and top of hole casing into ground

Borehole Methodology Using Stainless Steel 4” and 6” Casing 1. Drill PQ (122mm/4.8”) to 3m past target depth (100m) so 103m creating sump for fall in material 2. Pull back to 9-12m and air lift hole to test for water corrosiveness and flow 3. Have to use hammer drilling to get required diameter for 6” Stainless Steel casing at top of hole. HWT maybe can do diamond but maybe too tight in loose ground run in the 6” casing again. 4. Run in PQ again with casing shoe to bottom and flush hole 5. Run in 4” Stainless Steel casing to bottom welding pieces as lowered into hole. Screened/slotted section and depth to be advised 6. Sand/gravel pack slotted section 3m above top of slotted section 7. Bentonite cap (1m) above slotted section 8. Fill remainder of annulus with course sand until 2m from surface 9. Bentonite cap (0.5m) again 10. Cement last 1.5m and top of hole casing into ground

Estimated Material Costs Per Hole based on 100m of casing in hole to target depth (9m screened/slotted), 12m top of hole casing Option 1-Using used drill rods as casing if water is deemed ok. Option 2-Using Stainless Steel casing. Please also note using Stainless Steel casing will cause significant delay as stainless steel casing not yet ordered and will not be ordered until reimbursement made

Option 1

Item Used HQ Rods Used HQ Rods cut into screen/slotted USED HW Casing Total Casing Cost Per Hole

Cost USD$60/3m USD$80/3m

Quantity 31 pieces (93m) 3 pieces (9m)

Total Cost $5,580 $240

$140/3m

4 pieces (12m)

$560 $6,380+10% Handling =$7,018

Option 2 Item

Cost

Quantity

Total Cost PHP

Stainless Steel 4”

PHP31,157/6m

PHP467,355

Stainless Steel 4” sceened/slotted Stainless Steel 6”

PHP32,500/6m (Includes Slotting) PHP55,203/6m

15 pieces (90m) 2 pieces (12m) 2 pieces (12m)

Total Casing Cost Per Hole

Total Cost USD

PHP75,000 PHP110,406 PHP652,761+10% $13,500 Handling=PHP718,037