P1.3.2.2 Follow requirements Flush of the NZDS. of chemical well/bore until Residual determinands determinands chemical substances Ensure the bore is used in more than 50% determinand used in drilling well flushed before drilling. of MAV. releasing being put into use. less than health Evidence of 50% of their significant NZDS not MAVs. determinands having been (eg, barium followed. from baryte). Flushing not undertaken. Event: CONTAMINATED WATER GETTING INTO THE BORE/WELL FROM SHALLOWER DEPTHS Possible hazards: Germs and chemical determinands (eg, manganese, nitrate). Level of risk: High P1.3.3.1 Select appropriate High E. coli Withdraw casing material from quality. counts. casing and Poor joints, knowledge of the replace or cracks or Chemical Evidence of water chemistry. repair. corrosion, in determinands NZDS not the bore Ensure bore possible at having been casing. construction follows shallower followed. the NZDS. depths (eg, Inappropriate nitrate, casing manganese). material selected. No system for backflow prevention. P1.3.3.2 Carry out initial High E. coli Implement aquifer tests to quality. counts. conservation Drawdown determine a rate at measures and bringing Chemical Evidence of which water can be reduce contaminants determinands NZDS not abstracted without pumping rate. from shallower possible at having been excessive drawdown. regions of the shallower followed. aquifer. depths (eg, Inappropriate nitrate, casing manganese). material selected. No system for backflow prevention. CONTAMINATED WATER GETTING INTO THE BORE/WELL FROM THE SURFACE Possible hazards: Germs and chemical determinands appropriate to contamination sources. Level of risk: High
P1.3.2.2 Residual substances used in drilling releasing health significant determinands (eg, barium from baryte). Follow requirements of the NZDS. Ensure the bore is well flushed before being put into use. determinands used in drilling. of chemical determinands more than 50% of MAV. Evidence of NZDS not having been followed. Flushing not undertaken. Flush well/bore until chemical determinand less than 50% of their MAVs. Event: CONTAMINATED WATER GETTING INTO THE BORE/WELL FROM SHALLOWER DEPTHS Possible hazards: Germs and chemical determinands (eg, manganese, nitrate). Level of risk: High P1.3.3.1 Poor joints, cracks or corrosion, in the bore casing. Select appropriate casing material from knowledge of the water chemistry. Ensure bore construction follows the NZDS. quality. Chemical determinands possible at shallower depths (eg, nitrate, manganese). High E. coli counts. Evidence of NZDS not having been followed. Inappropriate casing material selected. No system for backflow prevention. Withdraw casing and replace or repair. P1.3.3.2 Drawdown bringing contaminants from shallower regions of the aquifer. Carry out initial aquifer tests to determine a rate at which water can be abstracted without excessive drawdown. quality. Chemical determinands possible at shallower depths (eg, nitrate, manganese). High E. coli counts. Evidence of NZDS not having been followed. Inappropriate casing material selected. No system for backflow prevention. Implement conservation measures and reduce pumping rate. CONTAMINATED WATER GETTING INTO THE BORE/WELL FROM THE SURFACE Possible hazards: Germs and chemical determinands appropriate to contamination sources. Level of risk: High
treatment-bores-and-wells-feb14-v2.docx