Decant of sigma colliery

Abstract

English: This study of Sigma Colliery was intended: • To determine the water quality of each aquifer associated with the mining area. • To determine the overall electrical conductivity profile of the mine to aid in the overall management of the mine. • To delineate possible decant positions with the help of water levels and to determine what the water quality of the possible decanting water will be. • To discuss the use of fly ash as a backfilling material in underground mines with the help of case studies. • To determine if ashfilling is a viable option for Sigma Colliery. From the study of Sigma Colliery, the following conclusions and recommendations could be made in this document: • A total of 12 samples were obtained from the shallow aquifer, classified according to the SANS 241 :2006 drinking water standards and discussed in this document. Only sample WW024D was classed as above the maximum allowable limit and not suitable for human consumption. Four samples were classed within Class 2, suitable for human consumption for a limited duration use only. A total of seven samples were classed as Class 1, suitable for human consumption. • A total of 23 samples were obtained from the intermediate aquifer, classified according to the SANS 241 :2006 drinking water standards and discussed in this document. Samples WW036, NW021, NW037 and UG001 were classed as above the maximum allowable limit and not suitable for human consumption. Three samples were classed as Class 2, suitable for human consumption for a limited duration use only while 16 samples were classed as Class 1, suitable for human consumption. • A total of 21 samples were obtained from the deep aquifer system, classified according to the SANS 241 :2006 drinking water standards and discussed in this document. Samples NW006, NW036, NW040, NW041, NW042, NW044, NW046, NW051, UG027D, UG071, UG072D and UG072M were classed as above the maximum allowable limit and not suitable for human consumption. Two samples were classed within Class 2, suitable for human consumption for a limited duration use only and seven samples were classed as Class 1, suitable for human consumption. • A total of six samples were obtained from the disturbed aquifer system, classified according to the SANS 241 :2006 drinking water standards and discussed in this document. Samples UG014 and UG023 were classed as above the maximum allowable limit and not suitable for human consumption. Two samples were classed within Class 2, suitable for human consumption for a limited duration use only and two samples were classed as Class 1, suitable for human consumption. • A total of 20 samples were obtained from the ashfill boreholes, classified according to the SANS 241 :2006 drinking water standards and discussed in this document. Samples UG033, UG034, UG044, UG069, 812/179, 812/1830, 812/183M and 812/183S were classed as above the maximum allowable limit and not suitable for human consumption. Only one sample (sample C316/47) was classed within Class 2, suitable for human consumption for a limited duration use only and 11 samples were classed as Class 1, suitable for human consumption. • A total of 19 samples were obtained from the mine boreholes, classified according to the SANS 241 :2006 drinking water standards and discussed in this document. Samples UG0130, UG024, UG0370, UG046, 812/530 and 812/53S were classed as above the maximum allowable limit and not suitable for human consumption. Five samples were classed within Class 2, suitable for human consumption for a limited duration use only and eight samples were classed as Class 1, suitable for human consumption. • All 94 boreholes were profiled and a three-dimensional image of the whole area was created with the use of the electrical conductivity profiles. From this image created, varies possible decant areas were identified and the water quality of these possible decant areas were discussed. • The ashfilling used turned out to be a viable option when there was still mine void space available before the mine was filled up with water from the flooding. • Since the mine voids were filled with water and the fine ash slurry was pumped into the mine voids, the conditions was disturbed in that the void space in the mine was decreased with some volume of water. • The storage of the strata above is not enough for the water that was pumped in with the ash and the water is therefore forced to decant. • The only place where decant and pollution of the shallow aquifer is evident is where ashfilling has been done. • The situation improves as soon as the ashfilling is ceased and this can be substantiated by the water level and water quality behaviour of borehole UG069. The water levels of borehole UG069 has been at decanting levels from September 2009 to March 2012 (Figure 15-3) after which the water level started to decrease again after the ashfilling was ceased. From the electrical conductivity profiling done of borehole UG069 (Figure 15-2) (after the ashfilling was ceased) the profile already indicates that the upper part of the water column is of a better quality than deeper down. • In this document it is therefore recommended that in the event that the company would like to continue with the ashfilling, they should pump water out of the mine to provide void space and prevent decant. • The ash slurry should simultaneously be injected into the mine with the water that is pumped out. This should be pumped in equal volumes, which will prevent other problems such as the collapsing of the mine roof.

Afrikaans: Die doel van die studie van Sigma Steenkoolmyn was die volgende: • Om die water kwaliteit van elke akwifeer, wat geassosieer is met die myn area, te bepaal. • Om die algemene elektriese geleidingsvermoë profiel van die myn te bepaal om te dien as hulpmiddel in die bestuur van die myn. • Om moontlike areas van myn-oorloop te identifiseer met behulp van water vlakke en om die water kwaliteit van die moonlike myn-oorloop areas te bepaal. • Om die gerbruik van vliegas as In terugvullings material in ondergrondse myne met behulp van gevallestudies te bespreek. • Om die lewensvatbaarheid van terugvulling van Sigma Steenkoolmyn met vliegas te bepaal. Vanuit hierdie studie van Sigma Steenkoolmyn kon die volgende gevolgtrekkings en aanbevelings gemaak word: • In Totaal van 12 monsters was van die vlak akwifeer geneem, geklassifiseer volgens die SANS 241 :2006 drinkwater standaarde en in hierdie dokument bespreek. Slegs monster WW024D was geklassifiseer as bo die maksimum toegelate waarde en is dus nie geskik vir menslike verbruik nie. Vier monsters was as Klas 2 geklassifiseer en is geskik vir menslike verbruik vir slegs In beperkte duur. In Totaal van sewe monsters was geklassifiseer as Klas 1 en is dus geskik vir menslike verbruik. • In Totaal van 23 monsters was van die intermediere akwifeer geneem, geklassifiseer volgens die SANS 241 :2006 drinkwater standaarde en in hierdie dokument bespreek. Monsters WW036, NW021, NW037 en UG001 was geklassifiseer as bo die maksimum toegelate waarde en is dus nie geskik vir menslike verbruik nie. Drie monsters was as Klas 2 geklassifiseer en is geskik vir menslike verbruik vir slegs In beperkte duur. In Totaal van 16 monsters was geklassifiseer as Klas 1 en is dus geskik vir menslike verbruik. • In Totaal van 21 monsters was van die diep akwifeer geneem, geklassifiseer volgens die SANS 241 :2006 drinkwater standaarde en in hierdie dokument bespreek. Monsters NW006, NW036, NW040, NW041, NW042, NW044, NW046, NW051, UG027D, UG071, UG072D and UG072M was geklassifiseer as bo die maksimum toegelate waarde en is dus nie geskik vir menslike verbruik nie. Twee monsters was as Klas 2 geklassifiseer en is geskik vir menslike verbruik vir slegs 'n beperkte duur. Sewe monsters was geklassifiseer as Klas 1 en is dus geskik vir menslike verbruik. • n Totaal van ses monsters was van die versteurde akwifeer geneem, geklassifiseer volgens die SANS 241 :2006 drinkwater standaarde en in hierdie dokument bespreek. Monsters UG014 and UG023 was geklassifiseer as bo die maksimum toegelate waarde en is dus nie geskik vir menslike verbruik nie. Twee monsters was as Klas 2 geklassifiseer en is geskik vir menslike verbruik vir slegs 'n beperkte duur. Twee monsters was ook geklassifiseer as Klas 1 en is dus geskik vir menslike verbruik. • n Totaal van 20 monsters was van die boorgate in die vliegas geneem, geklassifiseer volgens die SANS 241 :2006 drinkwater standaarde en in hierdie dokument bespreek. Monsters UG033, UG034, UG044, UG069, B12/179, B12/183D, B12/183M en B12/183S was geklassifiseer as bo die maksimum toegelate waarde en is dus nie geskik vir menslike verbruik nie. Slegs een monster (monster C316/47) was as Klas 2 geklassifiseer en is geskik vir menslike verbruik vir slegs 'n beperkte duur. 11 monsters was ook geklassifiseer as Klas 1 en is dus geskik vir menslike verbruik. • 'n Totaal van 19 monsters was van die boorgate in die myn geneem, geklassifiseer volgens die SANS 241 :2006 drinkwater standaarde en in hierdie dokument bespreek. Monsters UG013D, UG024, UG037D, UG046, B12/53D en B12/53S was geklassifiseer as bo die maksimum toegelate waarde en is dus nie geskik vir menslike verbruik nie. Fyf monsters was as Klas 2 geklassifiseer en is geskik vir menslike verbruik vir slegs 'n beperkte duur en agt monsters was ook geklassifiseer as Klas 1 en is dus geskik vir menslike verbruik. • 'n Drie-dimensionele figuur van die hele area is met behulp van die elektriese geleidings profiele van die 94 boorgate geskep. Met behulp van hierdie figuur kon verskeie moontlike myn-oorloop areas geidentifiseer word en die water kwaliteit van die areas is bespreek. • Die terugvulling met vliegas was nog 'n lewensvatbare opsie toe daar nog myn leemte ruimte beskikbaar was voordat die myn opgevul was met water as gevolg van die oorstroming van die myn. • Vandat die myn leemtes gevul is met water en die vliegas in die myn leemtes ingepomp is, het die toestande verander, in dat leemtes in die myn afgeneem het met In sekere volume water. Die strata bo die myn het nie genoeg storings vermoë om die water wat saam met die vliegas ingepomp is ook te hanteer nie en die water word dus geforseer om uit te loop. • Die enigste area waar myn-oorloop en besoedeling van die vlak akwifeer sigbaar is, is waar terugvulling van die myn met vliegas plaasgevind het. • Hierdie situasie verbeter sodra die terugvulling met die vliegas gestaak word en hierdie stelling kan deur die water kwaliteit en water vlak gedrag van boorgat UG069 beaam word. Die water vlak van boorgat UG069 het van September 2009 to Maart 2012 oorgeloop (Figure 15-3). Die water vlak het weer begin afneem na die terugvulling met vliegas gestaak is. Die elektriese geleidings profiel (Figure 15-2) van boorgat UG069 (na terugvulling met vliegas gestaak was) dui alreeds aan dat die boonste deel van die water kolom van 'n beter kwaliteit is as die dieper deel van die water kolom. • In hierdie dokument word dit aanbevel dat indien die maatskappy wil voortgaan met die terugvulling van die myn met vliegas, water uit die myn gepomp moet word om myn leemte spasie te verskaf en dus sodoende myn-oorloop te voorkom. • Dit word ook aanbeveel dat die inpomp van die vliegas mengsel tegelyk met die uitpomp van water uit die myn moet plaasvind. Gelyke volumes moet in- en uit gepomp word om sodoende ander moontlike probleme, soos byvoorbeeld die ingee van die dak van die myn, te voorkom.