EP 1110-1-27
27 Jan 00
All surfaces potentially in contact with cleaning solution should be nonreactive with its components.
Chemical-resistant hose, stainless steel, PVC, and high density polyethylene (HDPE) plastics in tanks,
fittings, and pumps will provide good service.
5. After batch mixing, tremie into the screen zone by gravity from the bottom up across the screen
surface. Apply very slowly (~ 10 gpm ( ~ 0.0379 cu m/min)) through a 1- to 2-in. ( 2.54- to 5.08-cm) -
diameter pipe made of nonreactive materials.
6. Surge in place and leave overnight (12 to 24 hr). Do not leave in place more than a weekend.
NOTE: Surge tool and applications of conventional ground water technology for well development
surging apply to HTRW well cleaning. For example, surge blocks should have size and weight to permit a
1- to 2-ft/sec (0.3- to 0.6- m/sec) fall.
VARIATION (pump in place): Remove the well cap, disengage pitless adapter, and pull up pumping
discharge assembly to surface. Use a reversible friction pump puller to move the pump slowly up and
down to provide a surging action. Pump at a low rate during surging, recirculating back down the well
(monitor pH - treatment is finished if pH rises above about 5 or if water clears). Note: Watch for lockup
and stop immediately if it occurs.
7. If satellite wells are installed around a pumping or injection well for treatment application (highly
recommended), treat each 2- to 4-in (5.08- to 10.16-cm) -diameter well with a solution as in step 4, but
six times the satellite well's screen diameter. Surge in place and leave overnight (see step 6).
8. For both the target and satellite wells, sound wells to determine depth and safety to insert development
tools. Surge and pump to containment and necessary pretreatment prior to release to water/wastewater
treatment. Release water should pass through the site's remediation treatment facility prior to release to
the open environment.
NOTES:
Know the specific release and treatment requirements of the jurisdiction, project, and site.
Check pH and treat as needed to within 1 pH of background (pH 6.5 to 8.5 for wastewater treatment
plants).
Tanks for containment should be sufficient in size to handle the expected discharge water volume
requiring treatment without shutting down development. The system for neutralizing should permit
continuous and not batch treatment.
If site remedial treatment is digestive, expect a radical increase in BOD and COD. Expect and plan for
pretreatment for a large increase in mineral and encrustation-debris solids content.
9. Continue surging until a set standard for clarity is met (standard set realistically based on site
experience. Some standards used are < 5 NTU turbidity, < 5 ppm sediment, and a predetermined percent
recovery of specific capacity. Sound wells periodically and remove accumulated debris. Examine to
determine the nature of solids (filter pack? formation?). If excessive filter pack is brought in, examine
with downhole TV to determine if a screen or casing breach has occurred.
NOTE: This can be a lengthy process, especially if wells were not developed sufficiently when installed,
or during remediation attempts. Frequent maintenance treatments should reduce the necessary
C-3
Previous Page
