A portable unit for treating washout, the unit comprising: a region for receiving the washout, and separating and storing concrete solids from the washout while transferring a washwater component from the washout receiving region, characterised in that the portable unit further comprises: a washwater containment region for receiving the washwater component transferred from the washout receiving region and for the storage and treatment of washwater, a neutralising agent source accommodation region for accomodating a source of a neutralising agent (44,45), and a pH adjuster for neutralising the washwater, wherein the pH adjuster is arranged to be connectable to the neutralising agent source, and wherein the pH adjuster is arranged to supply the neutralising agent to the washwater stored in the washwater containment region wherein the washout receiving region and the washwater containment region are arranged such that the solids in the washout are retained in the washout receiving region, and washwater in the washout is drained from the washout receiving region into the washwater containment region, wherein the pH adjuster is arranged to supply a neutralising agent to the washwater in the washwater containment region, wherein the ratio of the volume of the washwater containment region to the volume of the washout receiving region is between 3 and 8, and wherein the washout receiving region is arranged to accommodate a permeable container (21,22), such that when washout is received in the permeable container (21,22), washwater in the washout drains through the permeable container (21,22) into the washwater containment region and solid material in the washout is retained in the permeable container (21,22) a region for receiving the washout, and separating and storing concrete solids from the washout while transferring a washwater component from the washout receiving region, characterised in that the portable unit further comprises: a washwater containment region for receiving the washwater component transferred from the washout receiving region and for the storage and treatment of washwater, a neutralising agent source accommodation region for accomodating a source of a neutralising agent (44,45), and a pH adjuster for neutralising the washwater, wherein the pH adjuster is arranged to be connectable to the neutralising agent source, and wherein the pH adjuster is arranged to supply the neutralising agent to the washwater stored in the washwater containment region wherein the washout receiving region and the washwater containment region are arranged such that the solids in the washout are retained in the washout receiving region, and washwater in the washout is drained from the washout receiving region into the washwater containment region, wherein the pH adjuster is arranged to supply a neutralising agent to the washwater in the washwater containment region, wherein the ratio of the volume of the washwater containment region to the volume of the washout receiving region is between 3 and 8, and wherein the washout receiving region is arranged to accommodate a permeable container (21,22), such that when washout is received in the permeable container (21,22), washwater in the washout drains through the permeable container (21,22) into the washwater containment region and solid material in the washout is retained in the permeable container (21,22) a washwater containment region for receiving the washwater component transferred from the washout receiving region and for the storage and treatment of washwater, a neutralising agent source accommodation region for accomodating a source of a neutralising agent (44,45), and a pH adjuster for neutralising the washwater,