By Ibrahim Kasita
SCIENTISTS have found that the contentious mud-cuttings buried in Purongo sub-county in Amuru district did not contain heavy metals.
Soil tests carried out in July by the Uganda Wildlife Authority (UWA) showed unacceptable levels of heavy metals in the waste water and mud cuttings of 10 oil wells in Buliisa and Hoima districts. The heavy metals found were lead, zinc, chromium, cadmium, manganese, copper, nickel, iron, chloride and sulphates.
However, a new study specifically on the mud cuttings that were burried in Purongo, carried out earlier this month, showed that they contained no more toxic metals after they had been treated.
“The results confirm that disposing the treated drilling mud cuttings by burying did not result in negative impact on the soils ability to support proper plant growth, the major sources of animal fodder in the area,” read the study, carried out by the National Agricultural Research Organisation (NARO).
“This is important for maintaining the sustainability of the different components of the system.”
UWA spokesperson Lilian Nsubuga confirmed that the mud cuttings, burried in Purongo by Heritage Oil, did not contain heavy metals.
“They got permission from NEMA (the National Environment Management Authority) and I think they are complying with the regulations.”
Her boss, Moses Mapesa, last week told Business Vision that Heritage Oil paid a farmer in Purongo sh300,000 to dump their waste in his garden.He said NEMA had written to Heritage asking them to rectify the situation after neighbours had complained.
Mapesa said there was a danger of heavy metals getting into the ground water when waste water or mud cuttings were burried in community areas.
UWA wants the waste disposal issue sorted out before the oil companies start the second phase of testing. Efforts to contact NEMA were futile as the top managers were engaged in a day-long management meeting.
The study, commissioned by Heritage, explained that the oil company acquired the land in Purongo for disposing the mud cuttings, which originate from its exploration activities in Murchison Falls National Park, because it was the most environmentally acceptable way.
“Due to limited land size (at the exploration sites), it was not possible to dispose the treated mud cuttings from the two exploratory wells by either land spreading or land farming,” the study said. The two methods could not be used due to the strict conditions set by UWA, it said.
“The only option available was the transfer of the treated drilling mud cuttings to a site outside the conservation area for disposal,” the report noted.
“Consequently, Heritage Oil acquired land at Purongo, Amuru district, and a pit that was to be used as disposal site.”
All precautions were taken to avoid contamination of the ground water, it noted.
“Areas with shallow ground water were avoided. The soil profile dug during the excavation of the pit clearly indicated that the groundwater table is deep.”
The report said the pit was located at least 1.5m above any groundwater. In addition, it said, low permeasibility soil, such as clay, was used to surround the pit, and run-off and leaching were prevented by maintaining the vegetation over the pit.
Burying the treated waste, according the report, is a natural reduction process.
“The purpose is to contain wastes in a sanitary manner, protect them from animals and wind spread and finally to cover them sufficiently to allow re-vegetation and possible reuse.”
Prior to approval, NEMA gave Heritage Oil a condition to carry out soil and plant analysis on a regular basis, the report pointed out. The oil company is to submit a report every two months about the status of availability of plant nutrients and other pollutants to plants.
The NARO researchers found that the owner of the land had planted cassava and maize over the pit. Samples of those were analysed for lead, mercury and cadmium by the chemistry department of Makerere University.
“The waste did not affect the soil neutrality and organic matter content, the most important parameters used to evaluate soil suitability for plant growth under Ugandan conditions,” the study concluded. It only found that the levels of phosphorus, potassium and calcium had increased significantly.
However, the study noted that these have no negative effect on the environment and they are not toxic.
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