5 Colo. Code Regs. § 1002-72.26
The provisions of 25-8-202(1)(c), and (2) and 25-8-205, C.R.S. provide the specific statutory authority for adoption of these regulatory amendments. The Commission also adopted, in compliance with 24-4-103(4) C.R.S., the following statement of basis and purpose.
BASIS AND PURPOSE
"Individual sewage disposal system" has been amended to include wastewater, not just sewage. Commercial or industrial systems or facilities producing less than two thousand gallons per day would be included under this definition. Systems or facilities producing two thousand gallons or more per day are considered wastewater facilities and required to have a Colorado Discharge Permit System permit.
"Industrial process wastewater sources" previously described construction dewatering as an industrial process wastewater source, and later in the paragraph it was specifically excluded as an industrial process wastewater source. It was the Commission's intent under this definition that construction dewatering be regulated as an industrial process wastewater source.
"Land disposal" was refined to make it more clear that no treatment is intended for pollutant-containing waters that are applied to land for disposal.
"Phosphorus Bank." The language was amended to reflect that trade credits could be voluntarily assigned to the Phosphorus Bank. Also, it clarifies that the project proponent retains control over the transfer or use of their credits held in that Phosphorus Bank.
"Reserve Pool" now specifically defines that this "pool" consists of those phosphorus pounds available from historic Authority nonpoint source projects.
The 2000 version of this regulation included an allocation of 216 pounds of phosphorus in the Phosphorus Bank that was accounted for in the "Wastewater Facility Sources" allocation. That 216 pounds was intended to be available as credits in the Trading Program described at 72.5(3).
Since the last rulemaking hearing, the Authority proposed that the 216 pounds allocated in the Phosphorus Bank for trading limited the success of the Trading Program and that the Trading Program should not be limited to this allocation. The primary goal of the Trading Program is to encourage construction of phosphorus reduction projects. The incentive to the creators of the projects is the receipt of trade credits to use, transfer to an allocatee, or retire. Therefore, the 216 pound cap on the Trading Program trade credits accounted for in the Phosphorus Bank severely limited the efficacy of the Trading Program. EPA's Trading Policy (2003) does not suggest that the amount of trades should be so limited. Because trading reduces total loading within the Cherry Creek Watershed, trading should not be restricted. Because trading will always be within, and actually result in loads less than the TMAL of 14,270, no modifications to the TMAL are necessary.
All parties agreed with this concept, and the Commission revised the provisions in the Phosphorus Bank to eliminate this limit. The 216 pounds of phosphorus are now accounted for in the Nonpoint and Regulated Stormwater Sources allocation.
Language here, and in subsequent sections, has been changed to make it clear that the Trading Program as described in 72.5(3), and Temporary Transfers as described in 72.4(3) are processes to authorize awards of phosphorus pounds and that the Reserve Pool and the Phosphorus Bank are places where phosphorus pounds do, or could reside.
Language has been added that describes how phosphorus pounds are accounted for in the various allocations as transfers of these pounds occur. For example, as trading credits are awarded for projects reducing nonpoint source pounds, the point sources that purchase or trade for those credits will receive increased wasteload allocations, an amount dependent on the approved trade ratio. The minimum trade ratio for a nonpoint source/point source trade is 2:1. Therefore, for every two pound decrease in the nonpoint source / stormwater loads, a maximum of a one pound of increase in a phosphorus wasteload allocation can be made.
The list of activities to provide reasonable progress in attaining water quality standards and support revisions to the TMAL identified in the 2000 version of this regulation has been amended to eliminate the association of an activity with a particular year. The list is now comprised of activities that are complete, are in progress, and that are future activities. Language has been added that requires the Authority to submit an updated list of activities and their priorities annually in their annual report to the Division. These changes allow more flexibility in planning and conducting activities according to new information that is gathered in understanding the needs of meeting water quality standards for the reservoir.
The table in this section describing point source allocations has had the allocation for Phosphorus Bank removed as described above.
The table also reflects the transfer of phosphorus pounds from the Semi-urban Areas allocation to Plum Creek Wastewater Authority and the City of Aurora pursuant to 72.4(3).
The 2000 version of this regulation limited the ways that dischargers in the basin could determine return flow factors for land application sites. The Commission revised this section such that the regulation is more flexible in how return flow factors are determined. In order to ensure consistency with water rights, this version has been amended to require return flow factors to be determined from a decreed augmentation plan where one exists. For sites with no approved augmentation plan, return flows may be determined from an available study of return flow factors, upon approval of the Division. As a third option, the discharger may use lysimeters to determine a monthly volume discharged at each land application site using a formula described in section 72.4.5(c).
Under the first two options, the phosphorus concentration limitation would be calculated by dividing the 0.05 mg/l limit that applies to surface water discharges by the return flow factor. For example, if an augmentation plan was based on returning 20% of the land applied flow to the ground water system, the concentration limitation for phosphorus for that land application system would be 0.05 mg/l/0.20 = 0.25 mg/l. Where a return flow factor is used, the limitation is applied at a point prior to the effluent being land applied. This point could be at any location after the final treatment unit at the wastewater treatment facility and up to the sprinkler head at the land application site. Measurements of the amount of return flow from lysimeters would not be used by the Division to develop a return flow factor unless it is at the request of the permittee pursuant to an approvable study as required in 72.4.5(b).
Where lysimeters are used to determine the amount of applied flow returned to the ground water, the Commission determined that a limitation of 1 mg/l, to be applied prior to land application, is appropriate. This represents a phosphorus concentration that can be reliably achieved by a treatment facility employing biological nutrient removal. This is seen as a reasonable level of treatment given that it is generally commensurate a minimum concentration that permittees would have to meet in order to remain within their wasteload allocation. In some cases, a higher level of treatment may be required depending upon how much phosphorus is projected to be removed by the plants and the underlying soils at the land application site.
In most cases, removal is more a function of application at agronomic rates than soil conditions and phosphorus that is not driven below the root zone by heavy precipitation or over application should be taken up by the plants.
The previous version of this regulation at 72.5(3)(j) discussed the sale of phosphorus pounds out of the Phosphorus Bank and revenue received by the Authority from such sale. The Authority is only authorized to sell pounds out of the Reserve Pool, and this language has been moved to 75.5(2)(e) which is the section that discusses the Reserve Pool.
The regulation has been amended to eliminate the ceiling on the trading ratio of 3:1 that was in place previously. This was done to provide for more flexibility when approving trading requests. This could allow a trade to be approved at a higher trade ratio, that may not been acceptable with a maximum trade ratio of 3:1 in place.
The title of this section has been modified to include Individual Sewage Disposal because of the paragraph now included discussing limitation on construction of new individual sewage disposal systems, which are considered to be point source discharges.
At the 2003 Triennial Review hearing, the Commission raised concerns about the installation of new individual sewage disposal systems especially in proximity to Cherry Creek and alluvial groundwaters.
A study of ISDS showed that seepage from ISDS within the flood plain/alluvial zone was not attenuated and readily reached Cherry Creek waters.
In order to address this concern, and in order to protect water quality and public health, the Authority and the Division proposed language to prohibit construction of new individual sewage disposal systems within the 100 year flood plain of Cherry Creek watershed in Arapahoe and Douglas counties as designated by Urban Drainage and Flood Control District (UDFCD), or the Federal Emergency Management Agency if no UDFCD designation exists. Arapahoe and Douglas Counties testified that each had zoning regulations which prohibited construction, including ISDSs, within the floodplain. Therefore, this restriction will establish a consistent watershed-wide policy. It is not the intent of the Commission to restrict owners of existing ISDSs within the Cherry Creek flood plain from making improvements to the operation of, or replacing the existing, ISDSs.
A meeting of stakeholders in the Cherry Creek Basin was held on August 3, 2004 specifically to discuss this restriction on ISDSs. A primary concern that was raised at the meeting was that the regulations on construction of ISDS within the floodplain should be consistent among all agencies. This language creates that consistency.
Land Disturbance activities were restricted to the exposure of 40 acres or more of disturbed land for 30 consecutive days. Under the revision, the MS4 Permittee will now be allowed to authorize an exemption from the 40-acre limit when that limit is demonstrated to be physically or financially impracticable, upon a showing by the Owner that sufficient erosion control BMPs will be incorporated. The Owner must provide detailed plans on earth moving activities, phasing plans, and erosion and sediment control plans, above and beyond what would normally be required, thus providing the kind of protection usually achieved by the phased construction restrictions. This exemption will be utilized for developments where the design and grading requirements make the 40acre/30day disturbed land limitation unfeasible, such as master planned golf course communities and public works projects. The waiver from this requirement may not be applied for the sole purpose of conserving resources (e.g., limiting mobilization days for graders).
The requirement in section 72.7.2 for the submission of inspection and maintenance information for BMPs has been modified to harmonize with the processes of reviewing and accepting land development proposals. The new requirement is that the applicant MUST submit procedures for BMP maintenance and dedication of easements. It is common for land disturbing activities to commence some time between the county's acceptance of an erosion control plan and the final acceptance of the full development proposal. Likewise, easements cannot be properly recorded in accordance with the final site design until the final site improvement plans are completed. The revised language in this section clarifies that the applicant must plan for BMP maintenance and easement dedication early in the development process, but may begin certain preliminary construction activities before the finalization of these plans.
The language in section 72.7.2 has been changed to allow flexibility in the implementation of porous pavement detention and porous landscape detention in combination with a grass swale, instead of requiring the grass swale to precede the other BMPs.
PARTIES TO THE RULEMAKING
The control regulation previously included a section for monitoring of phosphorus from both point sources and nonpoint sources in the Cherry Creek Basin (Section 72.7). The purpose of the monitoring program was to determine phosphorus loadings from point sources, and phosphorus removal efficiencies of nonpoint source controls.
Section 72.8 has now been revised to encompass monitoring of nutrients, rather than only phosphorus. In the past, the main emphasis of watershed studies related to nutrient transport has been on the development of monitoring programs that provide information on total annual transport of phosphorus at various points along the main stem of Cherry Creek, and monitoring of trophic-state variables for Cherry Creek Reservoir. This section also has been expanded to identify the roles of the Authority, the Division, and other agencies in developing monitoring plans. The Commission decided that the monitoring program should continue as expanded, and include an emphasis on nitrogen as well as phosphorus.
Section 72.8 now includes the development and implementation of special studies, in addition to routine monitoring. Monitoring by itself is insufficient as the sole basis for a long-term program whose objectives are to document the validity of mass transport and reservoir trophic state modeling, and to identify environmental mechanisms that have an effect on water quality. The Commission agreed that routine monitoring will be combined with special studies having one or more specific objectives involving information that cannot be obtained from routine monitoring.
This section previously required reporting on control of nonpoint sources and monitoring of phosphorus to the Commission under three separate sections. The revisions have combined all reporting requirements into Section 72.9. The revisions require an annual report with specific information on point and nonpoint source controls, wasteload allocations, trading program, and other activities related to complying with the TMAL and attaining water quality standards. The Division and Commission will use this information in assessing the progress of the Authority.
This section previously required an annual report to demonstrate progress towards control of nonpoint sources. The revisions require a report at each triennial review on the progress of point and nonpoint source controls and effects on the reservoir. Recommendations can be made to the Commission at this time, and the Commission can adjust the TMAL load allocations, the Trading Program, and other requirements to assure that progress is being maintained.
PARTIES TO THE RULEMAKING
5 CCR 1002-72.26