To: Board of County Commissioners
Through: Bryan Weimer, Director, Public Works and Development
Prepared By:
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Larry G. Mugler, Planner/Project Specialist, Planning Division, Public Works and Development
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Subject:
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Sky Ranch Site Location Application for New Outfall Location
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Purpose and Request:
recommended action
Rangeview Metropolitan District (Rangeview) is seeking approval from the Colorado Department of Public Health and Environment (CDPHE) for a site location for a new outfall facility to serve the Sky Ranch Water Reclamation Facility (WRF). As part of its application to CDPHE, Rangeview has requested the Board of County Commissioners, as the affected county and the 208 planning/management agency for Arapahoe County and under CDPHE Regulation 22, 5 CCR 1002-22, to review and provide comments on the site location application to CDPHE.
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Background and Discussion: This application is for a new outfall pipeline and discharge to serve Sky Ranch to be located in unincorporated Arapahoe County at approximately the 6th Avenue right-of-way and Box Elder Creek. The new outfall is needed to discharge treated wastewater that exceeds the capacity of the Sky Ranch reuse system.
The new effluent discharge outfall for the existing Sky Ranch WRF is to be used when reclaimed water is not being used for irrigation of Sky Ranch open space purposes, along with chemical addition to meet water quality discharge requirements. The pipeline will extend approximately four miles from the Sky Ranch effluent storage ponds to discharge into Box Elder Creek. The pipeline route will be constructed within private property and Arapahoe County-owned right-of-way. Rangeview provided the following explanation for the outfall location:
Rangeview has selectively chosen the outfall location for a variety of reasons including proximity to their existing reclaimed water system and physical characteristics of the Box Elder Creek drainage basin. Box Elder Creek has a thick sandy alluvium that will allow infiltration of the entire discharged flow and prevent discharged effluent from causing surface flows in a typically dry stream bed. This is advantageous compared to other proximate watersheds evaluated by Rangeview such as Coyote Run or First Creek that are primarily composed of silty soil. Discharging to these alternative drainages could cause erosion, soil plugging, unintended wetland formation, and odor issues due to septicity and stagnant/pooled water. Discharging in these other less permeable drainages could also cause other unforeseen issues associated with creating surface flows in a typically dry drainage.
The engineering report has been reviewed by the Arapahoe County Public Works and Development Department, the Arapahoe County Health Department, and the City of Aurora. Now the final stage is the signatures from these various agencies mentioned and the Chair of the Arapahoe County Board of County Commissioners, with authorization from the Board of County Commissioners.
The County’s review and comment and Board approval are part of the CDPHE process for its review of this wastewater facility plan and the proposed site location for the State permit to operate a wastewater facility.
For the site location application to CDPHE, the Board is asked to review and comment on the application and, under Regulation 22, CDPHE is interested in the County’s position as to whether the proposal is consistent with the water quality considerations contained in its local comprehensive plan and the location of the facility concerning the floodplain.
Towards this end, Arapahoe County Public Works and Development staff, Aurora staff, and Arapahoe County Health Department staff have reviewed LR24-002, Sky Ranch WRF Outfall Site Location Application, in detail.
Regarding the floodplain, the outfall will be in the 100-year floodplain of Box Elder Creek. Rangeview has designed the outfall structure to withstand any expected floodwaters. The preliminary effluent limits should be protective of the stream standards for Box Elder Creek.
The service area of the outfall line is the Sky Ranch development, previously approved by Arapahoe County and consistent with the Arapahoe County Comprehensive Plan.
As a result, Public Works and Development staff is comfortable that the application is consistent with the water quality considerations contained in the County’s local comprehensive plan and adequately addresses floodplain concerns (as specified in Regulation 22). Further, the Arapahoe County Health Department and the City of Aurora are comfortable with the application and have signed Rangeview’s application to CDPHE.
Staff, therefore, recommends the application favorably to the Board of County Commissioners with the findings listed below. If the Board concurs, staff requests that the Chair sign the application form for forwarding to CDPHE.
Recommended Findings:
1. The Colorado Department of Public Health and Environment (CDPHE) has to review the document before final approval for the construction of the wastewater outfall facility. Under CRS 25-8702. Approval for commencement of construction:
(1) No person shall commence the construction of any domestic wastewater treatment works or the enlargement of the capacity of an existing domestic wastewater treatment works, unless the site location and the design for the construction or expansion have been approved by the division.
(2) In evaluating the suitability of a proposed site location for a domestic wastewater treatment works, the division shall:
(a) Consider the local long-range comprehensive plan for the area as it affects water quality and any approved regional wastewater management plan for the area;
(b) Determine that the plant on the proposed site will be managed to minimize the potential adverse impacts on water quality; and
(c) Encourage the consolidation of wastewater treatment facilities whenever feasible.
2. In its role as the 208 Planning/Management Agency the County should determine that the outfall is consistent with the water quality management portions of the Comprehensive Plan and with floodplain regulations.
3. The Arapahoe County Health Department has requested that the final effluent limits for the discharge to Box Elder Creek include specific phosphorus concentrations.
4. The Arapahoe County Engineering Division will review the final design of the pipeline within floodplains and the right-of-way permit during an amendment to the applicant’s 1041 and Location and Extent application. The Mile High Flood District has requested the opportunity to review the final design.
An outfall sewer is defined by the Water Quality Control Commission’s Regulation 22 as “a sewer that receives treated wastewater from a treatment plant and carries it to a point of final discharge. This definition does not include reclaimed domestic wastewater distribution and transmission system piping. Outfall sewers are appurtenances to domestic wastewater treatment works.” Under that definition, the Rangeview proposal is subject to the site application process.
The Sky Ranch WRF has been in operation since 2020 but to date has reclaimed all of the flows as part of the water reclamation system. However, growth in Sky Ranch will soon exceed the capacity of the reclaimed water system, necessitating the discharge to a stream.
The wastewater to be discharged will be equal to or exceed the quality of the water being used for irrigation of open lands in Sky Ranch. With the upcoming regulations in Colorado concerning the discharge of nutrients to surface waters, Rangeview will be adding nutrient removal for the water being sent through the outfall.
The proposed site is shown on the map provided by the applicant and included in the Attachments. Since the site application was submitted, the applicant has confirmed that the landowner has agreed to the route shown in blue.
CDPHE regulations for site location of a wastewater treatment facility, Regulation 22, as regards county approval, provides two opportunities for comment:
Per Reg. 22, the county is being asked to comment as to:
(b) County if the proposed facility is located in the unincorporated area of a county. The county, through its commissioners or its designee, is requested to review and comment upon: the relationship of the treatment works to the local long-range comprehensive plan for the area as it affects water quality; the proposed site location alternatives including the location concerning the flood plain; and the capacity to serve the planned purpose. A recommendation of approval from the county is considered to be a statement that the proposal is consistent with the water quality considerations contained in its local comprehensive plan.
As the 208 planning/management agency, the county is asked to comment as to:
…the consistency of the proposed treatment plant to the water quality management plan….
The Arapahoe County Comprehensive Plan addresses the relationship between water quality and discharges from treatment plants into streams as it affects water quality as stated in the goals and policy as quoted below:
Strategy PFS 3.3(a) - Encourage the Reuse of Water by Water Suppliers and Individual Users Many water suppliers in the County use reclaimed water for irrigation and other appropriate uses. The County supports these efforts and encourages the continued practice. The County supports efforts to expand the reuse of water to individual users.
Rangeview will continue to reuse water from the Sky Ranch WRF to the extent that the water can be used.
Policy PFS 4.2 - Support Provision of New Wastewater Treatment Facilities in Designated Growth Areas
The County will support the approval and construction of new wastewater treatment facilities in Designated Growth Areas only when no other feasible or practicable alternatives are available to provide treatment.
Strategy PFS 4.2(a) - Work with Districts to Plan for New Wastewater Treatment Facilities
The County will cooperate with sanitation or metropolitan districts created in Designated Growth Areas to ensure that they are planning for adequate capacity to meet future growth demands.
The outfall will have the capacity to serve its area and the discharged water will meet its state discharge permit conditions. The site application includes preliminary effluent limits. The Arapahoe County Health Department has commented that the final effluent limits should address phosphorus concentrations. With a four-mile pipeline, Rangeview should install a monitoring system to quickly identify and address any breaks in the system.
Strategy GM 3.3(h) - Locate Critical Facilities to Avoid Floodplains
The County will require that critical facilities avoid locating in 100-year floodplains, including water and wastewater treatment plants, fire and police protection facilities, community facilities, major utility substations or facilities, and other facilities of critical importance in an emergency or disaster.
The outfall by necessity will be in the 100-year floodplain of Box Elder Creek. It is being engineered to withstand the anticipated flood flows. The pipeline also crosses the floodplains of several other drainages including Coyote Run. These crossings should also be designed to withstand flooding. Details for these designs will be reviewed by the County during an amendment to the applicant’s 1041 review. In addition, the Mile High Flood District has requested the opportunity to review the final designs.
In the case of LR24-002, the Board County of Commissioners has the responsibility, as the 208 Planning/Management Agency, to sign the Applicant Certification and Review Agencies Recommendation, Section 22.4 of Regulation 22: New Domestic Wastewater Treatment Facility, on behalf of Arapahoe County.
Based on the information in the site application materials, the staff recommends approval.
Fiscal Impact: None.
Alternatives:
1. Authorize the Chair of the Board of County Commissioners to sign the Applicant Certification and Review Agencies Recommendation form to forward to CDPHE.
2. Do not authorize the Chair of the Board of County Commissioners to sign the Applicant Certification and Review Agencies Recommendation form; the Board may want to identify areas of concern to be addressed.
3. Continue a decision to a future date to receive additional information or to further consider information.
Alignment with Strategic Plan:
☐Be fiscally sustainable
☒Provide essential and mandated service
☒Be community focused
Concurrence: The City of Aurora and the Arapahoe County Health Department concur with approval of the pipeline and new discharge outfall and have provide comments that are attached to this report.