CityNews – Silt from the construction of a social security office in the city hall was reported as the cause for the dozens of dead fish found in Mae Kha canal last week.
Chiang Mai Municipality has been investigating a case of many dead fish found collecting at a water gate along the Mae Kha canal near Lanna Hospital, suspected of dying from an unidentified pollutant in the water.
Locals had reported that the water had turned a milky colour and was turbid. The authorities traced the source of the turbid water back along the canal to a construction site at Chiang Mai City Hall where construction workers were draining groundwater into the canal to clear the area to build foundations for a new Social Security Office.
Chiang Mai municipality issued an immediate cease of operations, stopping all drainage of water into the canal March 8th, and monitored the canal to see if any more fish were found dead. On March 11, officials conducted a water quality test at the water gate where the dead fish were found to check the water was clean of pollutants. The reported all safe levels, recorded as follows;
Dissolved oxygen 2.2 mg/L with nitrate at 4.0 mg/L (safe level is set at below 10 mg/L for nitrate)
Ammonia 0.01 mg/L – safe level (maximum safe level is 0.5 mg/L)