Acid mine drainage is an unavoidable consequence of some coal mining operations. Typically runoff pH is below 3.5 and at these pH levels heavy metals are mobilised. Leachate from coal reject dumps may require collection and treatment to raise the pH and precipitate the metals before being discharged. A bi-product of coal mining operations at Clarence Colliery is coarse washery reject. At present the coarse reject is deposited above ground and rehabilitated. Adjacent to Clarence Colliery is the Kable's Transport Pty Ltd sand mining operation. It has been proposed that co-disposal of the rejects from both operations may produce a product whose leachate has near neutral pH. The University of Western Sydney undertook laboratory experiments to investigate the chemistry of leachate water from 22 co-disposal options. Reject material was placed in 205L drums. Each drum contained coarse reject and either sand or clay, either mixed or layered. Three control drums were used, being 100% coarse reject, 100% sand and 100% clay. Deionised water was introduced to the co-disposed material at approximately 4mL/min for one month and the leachate tested for pH and conductivity. On two occasions samples were collected and analysed for metals concentration using Inductively Coupled Plasma Mass Spectrometry .This paper presents the results of the metals analysis, comparing the materials, quantities and modes used for co-disposal.