Water Quality: Planning Targets and Preliminary Effluent Limitations (PELs)

The engineering design review processes are described in Regulation 22 and related policies. The permitting processes are described in Regulation 61 and related policies. In general terms, the engineering review process can be considered as leading to an approval to construct (i.e., following design approval and design engineer self-certification of final design), and the permitting process can be considered as leading to an approval to discharge.

These procedural steps include

1. Site Location Application, a Regulation 22 step.
   1. The Engineering Section does not determine the applicability of standards or effluent limits. To conduct the site location and design review steps and evaluate if a facility can minimize the potential adverse impacts on water quality, the Engineering Section needs to understand what treatment goals are needed for a particular facility, so the Engineering Section initially checks what existing WQPTs are available during a review.
2. Design Review, a Regulation 22 step.
   1. Once the design review is completed and approved, a facility can be constructed. 
3. Discharge Permit, a Regulation 61 step. 
   1. Any condition set forth in the approval of the site location may become a condition of the permit, if identified specifically in the permit. This provides a parallel process for developing the discharge permit while site approval, design review and construction occur.

WQPTs are most effective when based upon a current (not administratively continued) permit or general permit certification.

WQPTs can include an existing or newly (re)issued individual permit, general permit, general permit certification, reclaimed water notice of authorization, water quality assessment, Preliminary Effluent Limitations document (PEL), or a combination thereof, depending on the proposed change. A WQPT is a document issued by the Division Permits Section. Applicant-prepared PELs are not WQPTs — though there is potential for applicant-prepared PELs to be used as an entity's identified treatment goals by the Engineering Section.

Permitting process recommendations

  For new facilities

For a new facility, the permittee can apply for a discharge permit, obtain an effective permit, and be eligible to discharge whenever the facility is completed. Facilities < 1 MGD, please apply for coverage under a general permit. Facilities equal to or greater than 1 MGD must apply for an individual permit.

  For facilities without surface water discharge permits

See the new facility section

  For existing facilities with surface water discharge permits

We recommend that as part of facility planning for current discharge facilities, you confirm that the renewal application is updated with complete information. This can be done by submitting a new renewal application or submitting an Application Supplement form — typically to include data collected outside of discharge monitoring reports (DMRs), Regulation 85 reporting, or to provide complete chemical evaluation forms for coverage in the renewal permit. You can provide the proposed change (e.g., design flow change) in the renewal application or application supplement, and the renewal permit can contain the proposed change.

For an existing facility with a current permit or certification (i.e., the individual or master general permit is not administratively continued), the permittee can submit a permit modification and apply to incorporate proposed site application changes into the permit or certification.

  Permit documents and applications for domestic discharges to surface water

Other permittee planning

Permittees can also review existing permitting resources when developing future treatment plant plans. Permittees may use this information for initial planning before plans for the facility are certain. The permittee can contact the permits section for resources to help with facility planning. Common resources that may help a facility to plan are the following:

•  A renewed permit or certification  - To facilitate a renewal permit, update the renewal application 
• The Surface water General Permits COG590000 and COG591000
• Reviewing the applicable water quality standards, technology-based limits, and applicable control regulations
• For parameters subject to antidegradation, calculating 15% of the water quality standard will provide the permittee with a conservative estimate.
• Contact the permits section for additional resources that may be useful in your scenario.

The following concepts are recommendations to assist domestic wastewater permittees in facility planning and if the permittee seeks to develop applicant prepared PELs - which have the potential to be used as an entity’s identified treatment goals by the Engineering Section. 

Generally applicable recommendations

1. Identify all pollutants of concern for the facility’s discharge (effluent) by evaluating the service area and potential industrial and non domestic contributors, including pollutants added to the collection system and treatment facility.
2. Collect at least three (3) representative effluent samples for the surface water quality standards parameters listed in the applicable Segment ID table in the basin Regulations 32-38 or listed in the groundwater quality standards, if these parameters have not been reported in DMRs or otherwise required (e.g., Reg 85 required monitoring). For example surface water segment COUCBL01 in Regulation 33:

1. For surface water discharges
   1. Identify the antidegradation protection applicable to the receiving segment(s). This is one of the designations in the basin table, top right, and can be use protected, reviewable, or outstanding. For more on antidegradation requirements, see Regulation 31.8.
   2. Conduct a whole effluent toxicity (WET) test (acute or chronic depending on the instream waste concentration (IWC)) to check whether there are any existing toxicity concerns that need to be addressed. If present, identify the cause(s). See Part V in the division’s WET policy linked above (Automatic Compliance Response for WET Testing Failures)
   3. Review Regulation 93 for impairment status parameters. Impairment status is an indication that there is no assimilative capacity in the receiving segment(s) for those parameters.   
   4. Review for any total maximum daily loads (TMDLs) applicable to the receiving segment(s) and the loading or other restrictions that would apply to the discharge
2. Review other applicable regulations (e.g., Reg 31, Reg 61, Reg 62, control regs (Regs 71-74), Reg 39, etc.), policies, and guidance

Conservative Approach and/or for New Discharges

Plan to meet water quality standards at the end of the discharge pipe. For antidegradation, plan to meet 15% of the standard for antidegradation based average concentrations (ADBACs).

For a Permit Renewal of an Existing Discharge

If there are no changes in water quality standards, TMDLs, etc., no changes in the facility's operation as disclosed during the prior permit renewal, etc., then those the previous WQBELs and ADBACs would be the anticipated values. 

Note: During the renewal permit, staff may identify other changes, and some examples include regulatory framework changes since the previous renewal, flow changes in the receiving segment(s), incorrect discharge location or receiving segment(s), and correcting previous mistakes.

For Increased Discharge Capacity

• The prior WQBELs and ADBACs would be the starting points; however, the WQBELs and ADBACs would become more stringent because of the increased discharge capacity. As an approximation to illustrate this concept, if capacity doubled then the values would be halved.
• Review other existing facilities in proximity and model assimilative capacity for combined discharge capacity to the receiving segment(s). Often there is not much assimilative capacity when multiple discharges exist, so the division recommends permittees use the approach for “Conservative Approach and/or for New Discharges” to ensure that current water quality standards will not be exceeded, as required by Regulation 61.

A PEL is optional for industrial wastewater dischargers since the Regulation 22 site application process does not apply. The division has limited resources for industrial discharge PELs and may not be able to complete these PELs in a timely manner. Please reach out to the division’s industrial discharge permitting Unit Manager (erin.scott@state.co.us) before applying for an industrial PEL. The division no longer accepts third-party PELs for industrial discharges for review and approval.

A Water Quality Planning Target will be needed for site approval of a reclaimed water facility and may be derived from a reclaimed water notices of authorization. Visit the water quality reclaimed water (reuse) permits web page for further instructions.