§ Mr. BreedTo ask the Secretary of State for Environment, Food and Rural Affairs, pursuant to her answer of 23 November 2001,Official Report, column 517W, on river quality, what chemical levels of (a) biochemical oxygen demand and (b) concentrations of dissolved (i) oxygen and (ii) ammonia are deemed to be (A) good, (B) fair, (C) poor and (D) bad in the Environment Agency's general quality assessment scheme for rivers. [19237]
§ Mr. Meacher[holding answer 30 November 2001]: The Environment Agency's General Quality Assessment (GQA) scheme assigns stretches of rivers and canals to one of six quality grades (ranging from A for water of very good quality to F for water which is of bad quality) based on the monitoring results for biochemical oxygen demand and concentrations of dissolved oxygen and ammonia. The overall grade is that of the poorest of the three determinants. The grade classes are expressed as percentiles as set out in the table.
Standards for the chemical GQA GQA grade Dissolved oxygen (% saturation) 10-percentile Biochemical oxygen demand (mg/l) 90-percentile Ammonia (ntgN/l) 90-percentile A (very good) 80 2.5 0.25 B(good) 70 4 0.6 C (fairly good) 60 6 1.3 D (fair) 50 8 2.5 E (poor) 20 15 9.0 F (bad) less than 20 — —