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Return Activated Sludge Building
Three-Channel Oxidation Ditch Aeration Basin
Grit Dewatering Building
New Headworks
Orbal Basin

WWTP Upgrades Ensure Community Health

The City of La Junta’s municipal wastewater treatment plant (WWTP) was oversized, aging, and in need of significant upgrades. Farnsworth Group evaluated the WWTP to determine needed improvements. Following the evaluation, our team provided the architecture and engineering design for all of the new plant infrastructure. 

Existing WWTP Evaluation and Vulnerability Analysis

Farnsworth Group performed a comprehensive plant evaluation to determine areas needing improvement or replacement. Each process component was evaluated regarding its current condition, service life remaining, maintenance requirements, current code compliance and its suitability to meet proposed CDPHE Discharge Permit limits.

Discharger Specific Variance

Population decline and loss of a large industrial contributor resulted in excess capacity at the plant. In addition, new effluent limits that the existing plant was not capable of meeting were slated to be implemented by the Colorado Department of Public Health and Environment (CDPHE). The City of La Junta experiences high levels of selenium in their ground water and wastewater due to geologic conditions. Our team applied for a water quality Discharger Specific Variance for selenium on behalf of the City. After considering multiple factors, the Commission granted the variance. This was the fourth variance ever granted in the state of Colorado.

Improvements Design

Farnsworth Group provided engineering design for La Junta’s new 1.6 MGD average and 4.13 MGD peak flow WWTP, and architectural building design services for four new buildings (Returned Activated Sludge (RAS) Building, Grit Building, Headworks Building and UV Disinfection Building).

Design included:

  1. Influent headworks with mechanically cleaned bar screen, wet well equipped with three submersible sewage pumps with firm capacity of 4.13 MGD, and flow metering;
  2. New forced-vortex-type grit removal structure
  3. New grit dewatering building;
  4. New three channel oxidation ditch aeration basin
  5. Two new final clarifiers
  6. New UV-disinfection building
  7. New RAS building with sludge transfer pumping and chemical feed equipment
  8. New gravity thickener
  9. New aerobic sludge storage basin.

Additional work included the conversion of an existing aeration basin to aerated sludge storage and provision of a Supervisory Control and Data Acquisition (SCADA) system.

Our team also performed construction phase services including serving as the Owner’s Representative for pre-qualification and selection assistance for contractors, construction contract administration and construction observation.