To: Members of the Castle Rock Water Commission
From: Mark Marlowe, P.E., Director of Castle Rock Water
Title
Resolution Waiving Formal Written Bidding Requirement Based on Sole Source and Approving an On-Call Equipment and Services Agreement with Evoqua Water Technologies LLC. [Entire Castle Rock Water Service Area]
Town Council Agenda Date: June 16, 2026
Body
________________________________________________________________________________
Executive Summary
Castle Rock Water (CRW) seeks Town Council approval of a Resolution (Attachment A) approving an On-call equipment and services agreement (Exhibit 1) with Evoqua Water Technologies LLC (Evoqua), for a total authorization amount of $600,000, as a sole source justification (Attachment B). In previous years, the total annual amount of Bioxide use from Evoqua has been on the order of $XXX,XXX. Changes in Bioxide usage have been recommended as a result of studies on the Woodlands Seweer Interceptor which runs through the Woodlands and Escavera neighborhoods. Based on these changes, the estimated cost of Bioxide for implementation in 2026 is $600,000.
Notification and Outreach Efforts
Customer outreach has been conducted for the Woodlands Sewer Interceptor and Odor Control station near the Woodlands and Escavera neighborhoods, including CRW staff attending several Woodlands Homeowner Association (HOA) meetings to provide updates on the findings from sampling and modeling efforts conducted on the sewer interceptor, Castle Oaks Lift Station, and Mitchell Creek Lift Station.
History of Past Town Council, Boards & Commissions, or Other Discussions
There have been Town Council discussions regarding customer complaints and Bioxide use for odor and hydrogen sulfide (H2S) control at Town wastewater lift stations and force mains. Most recently, meetings and customer interactions have occurred regarding Woodland’s main interceptor, and the sewer odors generated in the Escavera/Woodland’s bowl open space.
On May 29, 2025, the Town approved a professional services agreement with Carollo Engineers, Inc. to collect and analyze wastewater liquid gas samples, model odor generation based on sampling results, and make recommendations to CRW for operational changes and facility upgrades.
On May 29, 2025, the Town approved a professional services agreement with Carollo Engineers, Inc. to collect and analyze wastewater liquid gas samples, model odor generation based on sampling results, and make recommendations to CRW for operational changes and facility upgrades.
On October 21, 2025, the Town authorized an amendment to Carollo’s service agreement to evaluate taking Castle Oaks Lift Station sewer flows by gravity to the Pinery Wastewater Treatment Plant.
Discussion
Bioxide is a chemical that reduces the production of H2S that CRW utilizes at four of our sewer lift stations. They are Mitchell Creek, Castle Oaks, Maher Ranch, and Castlewood 1. The chemical is injected into the lift station wet wells to decrease the development of sulfides in the force mains. This process reduces the release of toxic, corrosive, and odorous H2S gas in the collection system. Bioxide is currently CRW’s only chemical additive option for odor and H2S control, and Evoqua Water is the sole nationwide provider of the proprietary chemical.
The Woodlands Interceptor sewer line runs through a valley, starting in Escavera and continuing through the Woodlands neighborhoods. This sewer interceptor has several drops, causing turbulent flows in the sewer. These flows allow excessive sewer odor to accumulate in the manholes, creating an off-putting odor that is detectable by surrounding residents and trail users.
This condition has worsened over time, leading to increased customer and HOA complaints about sewer odor. In response to these complaints, CRW contracted with Carollo Engineering to collect liquid and gas wastewater samples at the Castle Oaks and Mitchell Creek lift stations, perform odor-generation modeling based on the sample results, and recommend operational changes and facility upgrades to CRW. Carollo generated short and medium-term recommendations during this analysis. Below are the short-term recommendations, summarized:
• Seal off and discontinue use of the current odor control system, capping any foul airflow into the building or surrounding neighborhood.
• Improve Bioxide dosing method through the use of flow pacing and saddle taps for ideal mixing
• Increase the quantity of Bioxide dosing until the desired H2S levels are reached in the gravity sewer.
CRW immediately implemented the first recommendation and shut down and capped the existing odor control facility located along the Woodlands Sewer Interceptor in the Woodlands neighborhood. The investigation also revealed that increasing the dose of Bioxide at two Town lift stations (Michell Creek and Castle Oaks) that flow through the Woodlands interceptor and improving chemical mixing were the next immediate solutions to reduce H2S production and associated sewer odors in the area. Carollo recommended increasing Bioxide dosing to as much as double the current dosage of Bioxide at each lift station while CRW continued to coordinate optimizing chemical mixing. Once the mixing system was in place, a sustained 25% increase in Bioxide was recommended to fully control liquid phase sulfide formation.
In addition to supplying the chemical and feed system, Evoqua will also provide testing for H2S and Nitrate levels at downstream sample sites and Vapor Link monitoring services. Vapor Link monitoring provides real-time atmospheric H2S data displayed on the Evoqua Link2Site website. Woodland’s Link unit is deployed in the Woodlands interceptor downstream of the Castle Oaks and Mitchell Creek outfalls. Evoqua Link2site also provides data on Bioxide levels and feed rates at the Castle Oaks and Mitchell Creek lift stations.
This information allows staff to adjust Bioxide dosage manually via remote control or by visiting the site to respond to changing H2S levels in wastewater force mains. Unusual data, such as H2S spikes, will also alert operators to potential increases in odors in the collection system. This ensures that corrosive H2S levels and customer odor complaints are kept to a minimum. This monitoring service is included in the Bioxide agreement, at no charge.
Budget Impact
Funding for this agreement will come from the Wastewater Field Services Chemicals & Fertilizer line item, after a budget transfer from the Wastewater CIP Operations & Maintenance Replacement fund, as follows:
|
Fund Name |
Account Number |
Budget Transfer |
Current Balance |
Cost |
Balance After Transfer |
|
O&M Replacements |
213-4575-445.40-90 |
$500,000 |
$311,000 |
|
$0 |
|
Chemicals & Fertilizer |
213-4540-445.61-26 |
|
$100,001 |
$600,000 |
$600,001 |
Proposed Motion
“I move to recommend to Town Council approval of the Resolution as presented”
Attachments
Attachment A: Resolution
Exhibit 1: Agreement
Attachment B: Evoqua Water Technologies Sole Source Justification