5 Colo. Code Regs. § 1002-41.14
The provisions of sections 25-8-202(1)(a), (b), and (2); 25-8-203; and 25-8-204; C.R.S., provide the specific statutory authority for adoption of the attached regulatory amendments. The Commission also adopted, in compliance with section 24-4-103(4) C.R.S., the following Statement of Basis and Purpose.
The Commission has revised section 3.11.6 to eliminate the previous requirement that the Commission establish a point of compliance at the time of each ground water classification proceeding. The Commission determined that the former approach will often be inappropriate, where classifications are not being established to address a specific contamination source. At the time of a classification proceeding, the Commission may not be aware of all contamination sources within the specified area. In addition, the Commission has determined that establishment of points of compliance by the Division in the first instance is more consistent with the new framework established by Senate Bill 181, adopted in 1989. In this regulation the Commission is now establishing criteria to be taken into account by the Division in establishing such points of compliance. This structure is then parallel to that for other SB181 implementing agencies, who establish points of compliance in accordance with criteria adopted through rulemaking.
A definition of the term "point of compliance" has also been added by the regulatory amendments. The definition reflects the Commission's view that it generally will be more practical to determine compliance with the standards at a vertical surface downgradient from the regulated activity (as opposed to a point directly below the activity). However, the Commission retains authority to designate a point of compliance other than a vertical surface on a case-by-case basis when a site-specific point of compliance is adopted under section 3.11.6 (E).
IMPLEMENTING AGENCY COORDINATION
In response to SB181, the Commission has amended the Basic Standards for Ground Water to clarify that a point of compliance for activities that are regulated by implementing agencies identified in that statute is not a part of this regulation. Consistent with the spirit of SB181, these other implementing agencies will have the first opportunity to assure that adequate water quality protection is provided by the facilities in question. The Commission anticipates that Memoranda of Agreement entered into between the Water Quality Control Commission and Division and appropriate other agencies will provide a mechanism to assure that the other agencies' programs provide protection that is comparable to that provided by this regulation. Pursuant to SB181, the ultimate authority of the Commission is retained to apply additional regulation to such facilities if necessary to ensure a consistent statewide water quality control program. The Commission intends to monitor the implementation of SB181 closely to assure that an acceptable overall water quality control program is maintained.
A question was raised during the hearing as to whether Commission oversight pursuant to SB 181 of other agencies' activities would be only programmatic, or might also address individual, site-specific actions by such agencies. The Commission anticipates that its oversight generally will be programmatic. However, the Commission has authority to act with respect to individual situations, if it believes its intervention is necessary to assure compliance with the intent of the Water Quality Control Act. Of course, even if the Commission did choose to act in such circumstances, it would be limited to acting through the adoption of control regulations or permit regulations.
WATER QUALITY CONTROL DIVISION IMPLEMENTATION
Section 3.11.6 creates authority for the Water Quality Control Division to establish points of compliance whenever it has authority to do so pursuant to discharge permit regulations or control regulations. The Commission has scheduled a rulemaking hearing later this year to consider revisions to the discharge permit regulations, 6.1.0 (5 CCR 1002-2) to address discharges to ground water. At this time there are no control regulations governing ground water impacts, and no specific regulations of this type have been scheduled for consideration by the Commission. However, the Commission believes that it is advisable to have the point of compliance process in place, so that it should not be necessary to revise this regulation when new control regulations are adopted or the permit regulations are revised.
The Commission intends that determinations of a point of compliance within classified areas, as well as for statewide standards, by the Division will be appealable. The exact process for such appeals would be set forth in amendments to the permit regulations or any new control regulation.
WHERE THE STANDARD IS APPLIED
After standards, the most important issue regarding ground water protection is the physical point at which the standard should be applied. At what point in the aquifer does contamination constitute noncompliance? Among the points considered were the site boundary, the limit of existing contamination, or some specified distance from the contamination source.
It was determined that the site boundary should set the outer limit for a point of compliance (except for surface water discharges, as discussed below) because it distinguished areas that a responsible party controls from areas where the general public may be affected. For the inner limit we chose the edge of the activity or contamination source boundary to minimize the area affected. These limits are consistent with previous Commission rulings on the statewide standards.
For existing activities contamination may have, to some extent, merged with the immediate surroundings, making the contamination source boundary difficult and expensive to define. Where the standards might be exceeded only in the immediate vicinity of a source, the cost of remediation to avoid the exceedence might be unjustified in relation to the benefits of remediation. Therefore, for existing activities the regulation allows the Division to establish the point of compliance at a specified distance from the contamination source, taking into account site-specific facts in accordance with criteria spelled out in the regulation. Application of the standards at the specific activity boundary might not serve the intended purpose of avoiding large expenditures for very little gain, and yet setting some large arbitrary distance would be insufficiently protective. For those facilities who have conducted prior investigations to discover and map the extent of existing contamination, the option exists to set the point of compliance at the leading edge of the plume.
For new activities, new opportunities for site selection and preparation become available. For new sites we propose to apply the standards at the specific activity boundary. In effect, this is as protective as applying them at the specific contamination source (e.g., the point at the bottom of an impoundment at which a leak occurs), while allowing some benefit from sorption and dilution in immediately adjacent ground, in case small leaks occur.
HOW THE STANDARD IS APPLIED
The Commission recognized the difficulty of complying with a concentration limit standard at a fixed point in space, when operating within the temporal and spatial variations inherent in ground water flow.
The intent of any permit or control regulation should be to permit sampling frequency and interpretation that adequately reflects groundwater quality variation over time. Owners and operators should have latitude in this regard provided that an acceptable minimum number of samples are taken from each well annually. At the discretion of the owner/operator a shorter sampling interval may be employed to demonstrate that an exceedence of standards is due to temporal effects. This interval should be determined after evaluating the aquifer's effective porosity, hydraulic conductivity, and hydraulic gradient (which would govern rates of flow), and the fate and transport characteristics of the potential contaminants. This additional effort should help identify seasonal trends in the data and permit evaluation of the effects of seasonal variation or slugs of contamination if present in the samples. To better characterize spatial variability, an owner/operator may wish to install and sample from multiple background and compliance wells. If sufficient data is made available through these additional efforts, the owner/operator may employ statistical procedures such as moving averages and trend analysis to reduce seasonal and temporal effects. Utilization of site-specific characterizations to statistically evaluate an exceedence of standards requires detailed knowledge of the site. For owners/operators to use these methods they should be able to identify the uppermost aquifer, and aquifers hydraulically interconnected beneath the facility property, including groundwater flow direction and rate, and the basis for that identification.
In many situations it may benefit the owner/operator to install intermediate monitoring points. These monitoring points could be closer to the source or activity, or within the unsaturated zone. The monitoring points could function to alert the owner/operator to a potential contamination problem before it reaches the point of compliance.
"CONTAMINATION" DEFINITION
Because it is used several times in the point of compliance provisions, a definition of the term "contamination" has been added to the definitions section. This term is defined broadly, to provide a threshold determination of when non-naturally occurring pollution is present, and to help identify the appropriate locations for points of compliance. This definition does not determine who is responsible for cleaning up any specific contamination. It is not the Commission's intention by this broad definition to make individuals responsible for contamination caused by others. Nor is it the Commission's intention to adopt an antidegradation standard for ground water. The regulation does not state that all "contamination" must be avoided or cleaned up; rather, any adopted ground water standards remain the target for regulatory activities.
HYDROLOGICALLY DOWNGRADIENT LIMIT
Concern was expressed during the hearing regarding the use of the term "hydrologically downgradient limit." This phrase is commonly used in the industry. Generally, it refers to the "downstream" edge of the ground water in question. For example, "the hydrologically downgradient limit of the area below the activity potentially impacting ground water quality" is located by a vertical plane at the immediate edge of the surface activity in question, on the side of the activity toward which the ground water is flowing.
SURFACE WATER DISCHARGES
The Commission has included in section 3.11.6 language to address points of compliance for surface water discharges that may adversely impact ground water. Specifically, the Commission has added a cross-reference to the Discharge Permits System Regulations, where such points of compliance will be addressed. The Commission also added language to section 3.11.6 (2)(b)(iii) to add the quality of water discharged to the factors to be considered by the Division in setting points of compliance.
Other changes to the Basic Standards, first pointed out at the triennial review, involve corrections to table 1 and table A. In table 1 duplicative standards that are already established in the statewide standards for radioactive materials and organic pollutants have been deleted. In table A the detection level for the pesticides chlordane, DDT, and dieldrin were incorrectly listed in the GC/MS column. The corrected detection level of 0.1 ug/l is now under the GC column heading. These pesticides are part of a chemical group known as chlorinated organics and therefore should be tested by the GC method only. Concern was expressed at the hearing as to whether a second column confirmation would be conducted to achieve these practical quantitation limits. Dr. Sexton of the Health Department Laboratory testified that they routinely use such confirmations in accordance with the EPA methods.
The Commission has agreed in response to a proposal by AMAX, Inc. to delete the previous molybdenum standard from Table 3, Agricultural Standards. The Commission has taken this action because it does not believe that the information submitted in the hearing was adequate to support any specific numerical standard at this time. The Commission has not made a determination that molybdenum poses no risk to potential beneficial uses of ground water, If better information is submitted at a later date regarding an appropriate numerical protection level for molybdenum, the Commission will reconsider the potential need for a standard at that time.
PARTIES TO THE PROCEEDINGS OF THE PUBLIC RULEMAKING HEARING FOR THE BASIC STANDARDS FOR GROUND WATER
5 CCR 1002-41.14