Former Chemical Manufacturing Superfund Site Confidential Client

Portland, Oregon

Arrowhead was selected to implement a $5.9M design-build groundwater remedial action at a Former Chemical Manufacturing Superfund Site located in Portland, OR. The project included remedial system design, construction, and operation & maintenance of a remediation system for groundwater source control that prevents offsite migration of site related contaminants. The site contains a wide variety of contaminants related to the former chemical manufacturing process, including perchlorate, pesticides (DDE, DDD, and DDT), metals, volatile organic compounds (VOCs), and semi-volatile organic compounds (SVOCs). Primary components of the remediation system include a containment barrier wall that physically separates the affected upland portions and in-water portions of the site; a network of extraction wells to provide hydraulic control that prevents contaminated groundwater from moving around, over, or under the containment barrier wall; and, management of treated groundwater from the ex site treatment system. Treated effluent is discharged to the Willamette River under a National Pollutant Discharge Elimination System (NPDES) Permit.

The groundwater extraction system utilizes a network of 22 extraction wells designed to remove groundwater containing the site-related contaminants from three different zones of the aquifer. The extraction wells and wellhead are each fitted with a VFD controlled submersible pump, level transducer, and magnetic flow meter. A network of 36 piezometers fitted with level transducers was also installed to monitor and facilitate control of the hydraulic conditions.

Process equiment includes:

  • A chemical precipitation reactor with aeration and pH adjustment via sodium hydroxide (caustic) to remove metals; includes the option for ferrous sulfate addition to enhance metals removal via iron co-precipitation.
  • The precipitation reactor is vented through two vapor phase granular activated carbon units in series, to remove VOCs.
  • A solids handling/dewatering system including a plate separator (Lamella-type clarifier) with polymer feed, sludge holding tank, solids bin filter, and associated equipment to dewater and prepare precipitated solids for transportation off site and disposal.
  • Multi-media sand filters to remove suspended solids that may have been carried over in the plate separator effluent. The sand filtration unit is equipped with pneumatically actuated flow control valves and a local control panel which provides fully automated backwash operation.
  • A fluidized bed reactor with carbon feed, nutrient feed, and pH adjustment (if required) to anaerobically biodegrade chlorate, perchlorate, and potentially biodegradable organics present in groundwater.
  • A solids handling system, including a continuous backwash sand filter with polymer feed to remove bio-solids that may have been carried over in the fluidized bed reactor effluent, and solids holding tanks to prepare precipitated solids for transportation off site and disposal.
  • Two liquid-phase granular activated carbon units, in series, to remove VOCs, SVOCs, and pesticides.