2026 Excellence in Environmental Engineering and Science® Awards Competition Winner

Honor Award - Small Projects

Mighty Argo Cable Car Wastewater Reclamation Facility

Entrant:AquaWorks DBO, LLC - An Apex Company
Engineer in Charge: Adam Sommers, P.E.
Location: Idaho Springs, Colorado

Entrant Profile

AquaWorks DBO - An Apex Company is a design/build/operate firm dedicated to providing top-quality municipal waterand wastewater treatment facilities. Its primary focus is engineer-ing and installing cost-effective treatment systems that allow its clients to maintain long-term compliance with applicable environmental regulations. AquaWorks DBO caters exclusively to small systems, generally those that treat between 10,000 GPO and 1,000,000 GPO of potable water and/or wastewater. The majority of its projects have a construction budget of $300,000 to $10,000,000. AquaWorks DBO can provide a wide range of services, tailored to the client's specific needs, from small engineering evaluations to complete turnkey systems.

The Mighty Argo Upper Landing Wastewater Reclamation Facility was completedusing the Construction Manager at Risk (CMAR) delivery method. AquaWorks DBO served as the engineer of record, responsible for the environmentalengineering design, as well as project planning, preliminary engineering reports, and owner's representation services. Glacier Construction acted as the CMAR, and Newterra was the equipment manufacturer and supplier.

Other key stakeholders include the Mighty Argo Metropolitan District #2, which owns and operates the domestic wastewater reclamation facility in Idaho Springs,Colorado.The facility serves a new outdoor recreational and heritage tourismdevelopment accessed by a 1.25-mile gondola above the city. The district is governed by a five-member board of directors elected by the service area. AquaWorks DBO could not have completed the project without the endless contributions of the district's staff, board of directors, and the members of the contracting team.

Project Description

Introduction & Problem Statement

The Mighty Argo Cable Car Project (Argo) needed an innovative wastewater treatment and reuse facility to support a new outdoor recreation and heritage tourism destination in Idaho Springs, Colorado. The plant was required to treat 20,000 gallons per day and 95 pounds per day of BOD of high-strength wastewater with influent TKN concentrations expected as high as 290 mg/L.

The site, Argo Upper Landing, features an amphitheater, restaurant, and other amenities, and sits 1,300 feet above the town, accessible only by a 1.25-mile gondola or a steep 3-mile service road. With extremely limited land available, no municipal sewer connection, and no available surface water for discharge, a small, fully self-contained and environmentally sound wastewater treatment solution was essential.

Complexity

The Argo project presented extraordinary engineering and logistical challenges. All equipment had to be transported over 1,300 vertical feet and 3 miles on steep mountain roads, where construction space was limited. The system needed to fit within a tight construction footprint, minimize waste, enable water reuse, operate in harsh weather conditions at low ambient oxygen levels, and allow for rapid installation, all at the lowest possible cost.

With no access to surface water discharge and limited freshwater supply, all wastewater had to be fully treated and reused or infiltrated on-site. Any potable water or waste would need to be trucked 3 miles and 1,300 vertical feet. Additionally, the system had to function autonomously with remote monitoring and automated controls.

Originality & Innovation

AquaWorks DBO designed an affordable, highly compact membrane bioreactor (MBR) and reverse osmosis (RO) system, incorporating a unique configuration of cast-in-place concrete basins with modular treatment containers installed above them. Unlike conventional projects, the fully integrated wastewater treatment system is prefabricated off-site within a shipping container, delivered ready for installation, and brought online within a few months-all on less than a quarter acre.

Building an entire wastewater treatment system off-site In a container and delivering it on-site allowed for the design, permitting, fabrication, and construction to coincide with minimal land disturbance. A key innovation lies in the facility's dual-purpose effluent handling. The treated water meets stringent reuse and groundwater infiltration standards, allowing for reuse in toilet flushing and irrigation, and directing excess flow to a groundwater discharge infiltration field.

The MBR consistently produces higher-quality effluent than conventional systems due to the ultra filter at the tail of the process. The design integrates biological nutrient removal (BNR) through pre-anoxic, aerobic, and post-anoxic stages, using dissolved oxygen control and automated recycle loops to achieve precise nitrification and denitrification. A multi-stage chemical feed system enables the addition of supplemental carbon and aluminum sulfate to optimize nutrient removal under varying load conditions.

Contributions to Social, Public, Environmental & Economic Advancement

Socially and economically, the facility supports an effort to revitalize the National Historic Landmark into an educational, heritage, and recreational asset, and restore the mine's role as an economic engine.

Environmentally, the facility helps turn the historical site into a recreational development and preserves the integrity of the local watershed by ensuring that all treated water meets reuse and groundwater standards. By recycling water, the system significantly reduces the need to haul potable water up the mountain and the waste down.

Public health benefits include multiple treatment barriers-MBR, RO, and UV disinfection-ensuring reclaimed water is pathogen-free and preventing contamination of groundwater and recreation areas.

Comprehensive, Integrated Approach

AquaWorks DBO's approached the Argo project with a systems-thinking perspective, integrating environmental, technical, and operational considerations into a single, cohesive design. The facility simultaneously addresses water quality, air quality, land preservation, water use reduction, and energy efficiency in a genuinely integrated approach.

WATER QUALITY IMPROVEMENT

The MBR technology effectively removes high strength BOD (569 mg/L), TSS (600 mg/L), TKN ammonia (290 mg/L), and phosphorus (15 mg/L), achieving total suspended solids of less than 1 mg/L, total inorganic nitrogen of less than 10 mg/L, and total dissolved solids of less than 400 mg/L. The addition of the RO system ensures compliance with stringent requirements for groundwater infiltration.

LAND PROTECTION

Land disturbance impacts were minimized with a compact, containerized system placed on top of the below-grade facility. The entire system was installed within a footprint of less than one - quarteracre.

IMPROVED AIR QUALITY

Based on AquaWorks DBO's evaluations, reuse of water will offset 300 truck trips of freshwater 3 miles uphill and reduce the amount of water hauled downhill by up to 14,625 gallons per day. These combined reductions are estimated to prevent up to 31 metric tons of CO₂ emissions annually. (EPA, 2025).

Quality and Proven Performance

The facility meets all Colorado reclaimed water and groundwater discharge standards, producing effluent with exceptional clarity and nutrient control. Each process component-from the influent equalization basin to the membrane bioreactor and UV disinfection-is designed to ensure uninterrupted treatment under variable load conditions.

Quality assurance included factory testing of system equipment, programming, and verification of mechanical systems.

The facility's PLC-based control system uses real-time data from dissolved oxygen, flow, and pressure sensors to optimize aeration, chemical dosing, and overall treatment efficiency though P&ID loops. Chemical feed is proportionally dosed, minimizing waste, and telemetry provides remote monitoring and troubleshooting, ensuring reliable operation with limited on-site staffing.

Mighty Argo Cable Car Wastewater Reclamation Facility Project stands as a benchmark for innovation in small-scale, high-performance wastewater treatment. The project redefines what is possible for decentralized wastewater treatment.

Visit Clear Creek. (n.d.). Scenic gondola. https://visitclearcreek.com/activities/scenic-gondola/

Click images to enlarge in separate window.


Mighty Argo Cable Car Wastewater Reuse Facility Aerial View	Planning Area Map

Prefabricated Containerized System	Installing Treatment Basins onsite

Offloading of Precast Treatment System	Mighty Argo Cable Car Project Overview

Minimal Land Disturbance	Quality Control and Factory Testing

Process Flow Diagram	Automated systems