The cleaning occurs in two stages:1. Conventional sedimentation, when conventional sedimentation is done it is called primary treatment. filtering and chlorine treatments are given.2. After this stage, lots or danger pollutants like dissolved heavy metals still remain. To combat this, an innovative approach was taken.3. The biologists produced a series of six marshes that were connected to each other over 60 hectares of marshland. The suitable plants, algae, fungi and bacteria were planted and grown into this area, which neutralise, absorb and assimilate the pollutants. So, when the water flows through the marshes that were developed over 60 hectares of land the water gets purified naturally.4. The marshes are the composition of a sanctuary, that contains a high level of biodiversity in the form of fishes, animals and birds that now are living there and are shelter for them. A citizen group called Friends of the Arcata Marsh (FOAM) are responsible for the uptake and safeguarding of this wonderful project.