Chromic Acid Line and the River 60 Metres Away
Brenton Metal Finishing operates a chromic acid anodising line at a site 60 m from the River Calder. The main process tank holds 2,000 litres of chromic acid solution. Secondary containment is a 110% bund, but the bund has a hairline crack and the drain valve was left open after maintenance last month. The surface-water drainage system discharges directly to the river; the foul sewer has an interceptor but no trade-effluent consent covers chromium. A public water-supply abstraction is 300 m downstream, and the site lies in Flood Zone 3. The spill kit is stored 20 m away in the main workshop, and only two of fourteen operators have received spill-response training. The environmental risk assessment scores each activity for likelihood and consequence and multiplies the two scores; it does not record pathways or receptors. The regulator has requested a pollution-prevention review after a nearby incident at another site.
1. Critique the current risk assessment approach and explain how source-pathway-receptor analysis changes the controls you would recommend.
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The likelihood-times-consequence matrix is not sufficient because it produces a score without showing how a source can reach a receptor. For chromium, the source is 2,000 litres of chromic acid solution containing Cr(VI). Pathways include leakage through the cracked bund, the open drain valve, the surface-water drain, floodwater and infiltration to groundwater. Receptors include the River Calder ecology 60 m away, the public abstraction 300 m downstream and flood-zone receptors. A high score may be recorded, but the controls may still be wrong because the pathway is not interrupted. Source-pathway-receptor analysis changes the decision: the highest priority is to break the pathway by sealing the bund, locking the drain valve closed and isolating the surface-water drain. Then reduce source inventory, plan substitution to trivalent chromium and add leak detection. The current spill kit 20 m away and untrained staff is a response weakness, not a primary control. The assessment should also examine maintenance activities, because the valve was left open after maintenance. Record assumptions, residual risk and monitoring arrangements.
2. Recommend and justify a prioritised improvement programme within a 60,000 GBP budget and a 12-week regulatory deadline.
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Immediate, week 1, under 2,000 GBP: close and lock the drain valve, seal the crack temporarily, relocate the spill kit to the line, train all fourteen operators, cut inventory to 1,000 litres and map the drains. These are low-cost actions that directly interrupt the pathway. Weeks 2-4, about 10,000 GBP: integrity-test and line the bund, install a high-level alarm and drip tray, and fit a locked penstock on the surface-water drain. Weeks 5-8, about 25,000 GBP: install a conductivity or UV monitor on the drain with automatic isolation, and create a bund sump pump-out procedure. Weeks 9-12, about 15,000 GBP: concrete repair, signage, an emergency drill and a groundwater monitoring point. Keep about 8,000 GBP as contingency. Do not spend the whole budget on trivalent substitution, quoted at 150,000 GBP; plan that in next year's capital budget because it eliminates the Cr(VI) source. Justify the sequence by risk: pathway interruption first, then source reduction, then monitoring. The regulatory deadline is met with evidence of immediate risk reduction, not just a purchase order.