They were created by subdividing the previous oxidation ponds. This plant s effectiveness as a treatment species was shown by Marsh Pilot Project data. The treatment marsh s effluent is combined at a pump station where it is pumped to the disinfection facility. The three enhancement marshes cover a total of 31 acres. These marshes are managed to maintain the greatest diversity of aquatic plant species and to maintain or improve water quality.
Flow is directed through the enhancement marshes with sluice gates and wooden stop-log weirs.
After disinfection, the wastewater flows into George Allen Marsh, then Robert Gearheart Marsh, and finally Dan Hauser Marsh. The effluent from Hauser Marsh is pumped back to the disinfection facility. Chlorine gas is used to disinfect Arcata's waste water before it is discharged to the enhancement marshes and again before it is discharged into Humboldt Bay. Because of this double chlorination two chlorine contact basins are necessary. These basins are built as one unit, which is located immediately south of the headworks.