5 Colo. Code Regs. § 1002-38.61
The provisions of C.R.S. 25-8-202(1)(a), (b) and (2); 25-8-203; 25-8-204; and 25-8-402; 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
Some renumbering and/or creation of new segments was made in the basin due to information which showed that:
The description of Clear Creek segment 10 was clarified to exclude specific listings in Clear Creek segment 19.
The description of Clear Creek segment 18a was modified to remove Leyden Creek and Van Bibber Creek and extend the segment to the confluence with Clear Creek in recognition of recreational uses. Leyden Creek and Van Bibber Creek were moved to Clear Creek segment 18b.
Little Dry Creek was moved from Clear Creek segment 16b to Clear Creek segment 18b to reflect its uses.
Boulder Creek segment 12 was deleted (Boulder Reservoir) as it was determined this waterbody is in the St. Vrain Creek basin.
St. Vrain Creek segment 7 was created (Boulder Reservoir, Coot Lake, and Left Hand Valley Reservoir).
Middle South Platte River segment 1 was broken into 1a and 1b to accommodate the site-specific dissolved oxygen standard applied on the South Platte River from the confluence with Big Dry Creek to the confluence with St. Vrain Creek.
Middle South Platte River segment 4 was amended to add Milton Reservoir.
Certain tributaries in the vicinity of Denver International Airport were placed into separate segments to accommodate site-specific standards:
Upper South Platte segments | 16d: Second Creek 16e: Third Creek 16f: Barr Lake Tributary |
Middle South Platte segments | 3b: Hayesmount Tributaries 5b: Boxelder Creek |
A separate segment, Upper South Platte segment 16g, was established for Marcy Gulch to accommodate site-specific standards.
A new Clear Creek segment 9b was established to accommodate site-specific standards for Trail Creek.
Based on the information received that showed Recreation Class 1a uses are in place or are presumed to be present in at least a portion of the segment, the Commission changed the following segments from Recreation Class 2 to Recreation Class 1a with a 200/100 ml fecal coliform and 126/100 ml E. coli standard:
Clear Creek segment 18a
The Commission also changed the existing Recreation Class 2 classification to Class 1b for the following segments, with corresponding fecal coliform and E. coli standards:
Big Dry Creek segment 1
ache La Poudre 13b (seasonal)
The following segment retained its Recreation Class 2 classification, however the Commission changed the standard to 200/100 ml fecal coliform and 126/100 ml E. coli standard.
Clear Creek segment 17a
The following segments retained their Recreation Class 2 classification with 2,000/100mL fecal coliform and 630/100 ml E. coli standard after sufficient evidence was received that a Recreation Class 1a or 1b use was not attainable.
Clear Creek segment 7
Big Dry Creek segment 3
Big Dry Creek segment 4b
Big Dry Creek segment 5a and 5b
Big Dry Creek segment 6
Middle South Platte River segment 5
Lower South Platte River segment 6
Lower South Platte River segment 7
The following segments retained their seasonal Recreation Class 1a/Recreation Class 2 classification.
Big Thompson River segment 4a
Big Thompson River segment 4b
Big Thompson River segment 4c
The following segments retained their seasonal Recreation Class 1b/Recreation Class 2 classification.
Big Thompson River segment 5
The Commission reviewed information regarding Aquatic Life Class 2 segments where the full set of inorganic aquatic life protection standards have not been applied. Generally, these are dry segments with only rudimentary aquatic life. There were no changes adopted by the Commission.
The Commission reviewed information regarding existing aquatic communities. There were no Aquatic Life Use Classifications changes adopted by the Commission.
There are several segments in the South Platte, Laramie, Republican, and Smoky Hill River Basins that are assigned ambient standards. Ambient standards are adopted where natural or irreversible man-induced conditions result in exceedances of table value standards. EPA had requested that the Commission review the information that is the basis for these standards as well as any new information that would indicate whether they are still appropriate, need to be modified, or should be dropped.
The Commission did not adopt any changes to the ambient quality-based standards.
There were several segments where temporary modifications that reflect current ambient conditions were adopted or retained. Temporary modifications were generally set to expire on February 28, 2010 to coincide with the next triennial review except as otherwise noted. The segments and the constituents are:
Upper South Platte River segment 4; Cu(ch), Zn(ch)
Upper South Platte River segment 5b, Zn(ch)
Upper South Platte River segment 15; E. Coli, F. Coli
Upper South Platte River segment 16a; Se(ch), Se(ac)=no standard
Upper South Platte River segment 16c; Se(ch), Se(ac)=no standard
Clear Creek segment 2; Cu(ch), Mn(ch), Zn(ch)
Clear Creek segment 3a; Zn(ch)
Clear Creek segment 3b; Pb(ch), Zn(ch)
Clear Creek segment 6; Zn(ch)
Clear Creek segment 9a; Cu(ch)
Clear Creek segment 9b, Cd(ch), Cu(ch), Mn(ch), Pb(ch), Zn(ch)
Clear Creek segment 11; Mn(ch), Zn(ch)
Clear Creek segment 13b; Cd(ch), Mn(ch), Zn(ch)
Clear Creek segment 15; E. Coli
Big Dry Creek segment 1; E. Coli, Se(ch), F. Coli
Big Dry Creek segment 5: NO3, NO2, 6 organic chemicals
Boulder Creek segment 2; E. Coli for the portion below Broadway Street in Boulder
Boulder Creek segment 7b; E. Coli
Boulder Creek segment 10; E. Coli
St. Vrain Creek segment 4b; Cu(ch), Pb(ch)
St. Vrain Creek segment 6; Se(ch)
Middle South Platte River segment 1b; NH3 (ch)
Middle South Platte River segment 5a; NH3 (ch)
Middle South Platte River segment 5b; D.O.
Big Thompson River segment 4b; Se(ch)
Big Thompson River segment 5; Se(ch)
Big Thompson River segment 9; Se(ch), E. Coli
Big Thompson River segment 10; Se(ch)
Cache La Poudre River segments 11 and 12; NO2 as a 30-day average
Cache La Poudre River segment 12; E. Coli for the portion below Eaton Draw in Greeley
Lower South Platte River segment 1; Se(ch), NO3 (ch)
Lower South Platte River segment 2b; Se(ch) for Springdale Creek, Se(ch) and E. Coli for Beaver Creek
The following segments had temporary modifications which are being removed because current ambient conditions are meeting the underlying standards:
Upper South Platte segment 2c; Fe (dis)
Upper South Platte River segment 15; Se (dis)
Clear Creek segment 13b; Fe (dis)
Big Dry Creek segment 4a and 4b; NO3, NO2
Big Thompson segment 4c; F. Coli, E. Coli
These segments had the Water Supply classification added to them. The associated water supply standards will now apply to segments:
Upper South Platte River segment 5b
Clear Creek segment 18b
Middle South Platte River segment 1a
Middle South Platte River segment 1b
Middle South Platte River segment 4
Lower South Platte River segment 1
Numeric Standards to protect Agricultural Uses were adopted for the following segments:
Lower South Platte River segment 2a
Republican River segments 6 and 7.
Use Protected Designation was added to Upper South Platte River segment 16a. The Use Protected Designation was adopted by the Commission in 2000 but was inadvertently omitted in the regulation.
The Commission made the following changes to Segment 2b, Mosquito Creek and Segment 2c, South Mosquito Creek.
Segmentation: South Mosquito Creek from the source to the confluence with No Name Creek was removed from Segment 2c and put in Segment 2a.
Water Quality Standards: The Commission adopted type iii temporary modifications based on uncertainty for Mosquito Creek of Zn (ch) = 283 µg/L and South Mosquito Creek of Zn (ch) = 400 µg/L and Cd (ch) = 3.3 µg/L; and underlying standards for Mosquito Creek of Zn (ch) = 220 µg/L and South Mosquito Creek Zn (ch) = 280 µg/L.
There are two significant sources of zinc in the Mosquito Creek Basin, the London Mine Water Tunnel and the Extension Tunnel. The Water Tunnel flow is about ten times the flow of the Extension Tunnel and the Extension Tunnel zinc concentrations is about one hundred times the Water Tunnel. The zinc load from the Extension Tunnel greatly exceeds the load from the Water Tunnel. Based on the evidence presented, the Commission found that it is economically infeasible to treat the Water Tunnel flows with currently available treatment technology. However, it is feasible to treat the Extension Tunnel flows. Under current limited operations, the Extension Tunnel Treatment Plant produces water with an estimated 85th percentile zinc concentration of 5,000 µg/L. The Commission heard evidence that the existing Extension Tunnel treatment plant can be upgraded to improve its reliability and will likely be able to achieve water with a 30-day average concentration of 500 µg/L.
The temporary modifications for Segments 2b and 2c were based on the 85th percentile of the predicted zinc concentrations with treatment at the Extension Tunnel (5,000 µg/L) and the underlying standards for Segments 2b and 2c were based on the assumption that the Extension Tunnel treatment can achieve levels of 500 µg/L. No treatment of the Water Tunnel discharge was assumed in developing the temporary modifications or underlying standards for either segment. Monthly design flows were those included in the 2001 TMDL developed by the Division for the Extension Tunnel and actual flows for the Water Tunnel. The duration of the temporary modifications is through February 28, 2007.
The Commission's action establishing a technology-based standard and temporary modifications in this case is based on the unique facts and assumptions associated with the London Mine and Mosquito Creek Basin site, including the willingness of THF Prairie Center Development to undertake improvement and operation of the Extension Tunnel Treatment Plant. The Commission does not intend this action to establish a precedent for any other site-specific water quality standards. It is the Commission's intent that these standards should be reviewed and updated as appropriate based on the stream monitoring data collected after the completion of improvements and full operation of the Extension Tunnel Treatment Plant. Finally, the Commission notes that there is a need to continue to review in the future the feasibility of reducing zinc levels in these waters by means other than treatment of the extension tunnel discharge.
The Chatfield Watershed Authority submitted two alternative proposals for a temporary modification of water quality standards for total phosphorus and selected metals in Segments 6a and 6b of the South Platte River Basin. The temporary modifications were requested in response to concerns over the potential effects of runoff from the Hayman Wildlands Fire. The runoff may contain increased levels of total phosphorus and metals, which impede attainment of water quality standards in the South Platte River system and Chatfield Reservoir.
The Authority and the Division have concluded that additional monitoring data is required to establish whether there is a basis for temporary modifications and, if any, the appropriate numeric values to adopt. The Authority therefore withdrew its proposal for a temporary modification of standards. The Authority, in cooperation and coordination with the Division and other interested parties has committed to the development and implementation of a monitoring plan designed to collect needed data on both metals and nutrients within Chatfield Watershed, including Chatfield Reservoir. Additional monitoring data will help the Chatfield Authority and the Division determine what, if any, long-term modifications may be necessary to the uses and water quality standards for Chatfield Reservoir
The point source and storm water discharge permit holders in the Chatfield Watershed, which contribute a small percentage of the total phosphorus load to the Reservoir, discharge regulated constituents, including phosphorus. These dischargers will continue treatment and best management practices so as to minimize nutrient and metal loads in the Chatfield Watershed. The Authority and the Division have agreed that point source discharge permit holders and stormwater permittees who are in compliance with their permit limits and terms for a constituent will not have those limits or terms modified prior to any future adjustment of classifications or standards by the Commission to the extent any observed water quality standards exceedances are attributable to other factors such as the Hayman Fire. However, the Authority has agreed to cooperate with the Division in the identification and promotion of enhanced stormwater control BMPs which could be implemented on a voluntary basis prior to any such adjustment if warranted by monitored conditions in the watershed.
The South Platte Coalition for Urban River Evaluation, Metro Wastewater Reclamation District, and the Plum Creek Wastewater Authority cooperated on a study to develop adjustments to the acute and chronic numeric standards for copper using a water effect ratio (WER). The segments in question are the mainstem segments of the Upper and Middle South Platte Rivers from the confluence with Marcy Gulch to the confluence with the St. Vrain River (USP River Segments 6c (downstream of Marcy Gulch), 14, 15 and new Middle South Platte Segment 1a (commencing at the confluence with Big Dry Creek and continuing to a point just upstream of the confluence with the St. Vrain River), Plum Creek Segment 10a (below Plum Creek Wastewater Authority discharge), Marcy Gulch (new USP Segment 16g) and Sand Creek (USP Segment 16a).
The standards are adjusted to include the mean final water-effect ratio calculated for each segment. These WERs were developed using Streamlined Water-Effect Ratio Procedures for the Discharges of Copper USEPA-2001 (USEPA-822-R-01-005), based on toxicity testing and The Biotic Ligand Model: Technical Support Document for its Application to the Evaluation of Water Quality Criteria for Copper USEPA 2003 (USEPA-822-R-03-027), which predicts copper toxicity to four common freshwater species using site water quality data. Specifically, EPA's 2003 draft Copper Criteria that relies on the BLM was used to confirm the results of the Streamlined Water-Effect Ratio (SWER) Procedure.
The proponents submitted evidence that indicated that simply relying on EPA's Streamlined Water Effect Ratio Procedure would have resulted in a larger adjustment to the acute and chronic table values for copper. Application of the BLM resulted in a more conservative adjustment to the table value standards. The results of the BLM are specifically sensitive to changes in alkalinity and dissolved organic carbon (DOC) in the site water. In this instance, the site water quality data did not indicate a seasonal variation in DOC or alkalinity, to a degree that resulted in any significant seasonal variation in the BLM results. The parties acknowledge that this lack of seasonality may not be present in all waters and future application of the BLM method should include an analysis of seasonal variability. The parties also acknowledge that should additional species be added to the BLM that they would be considered in future BLM model runs.
The Commission extended the temporary modifications for fecal coliform and E.coli = existing quality because the standards are not being met because of human-induced conditions deemed correctable within a twenty-year period. The Commission recognizes that the Metro District has voluntarily operated its facilities to meet the underlying TVS and that the District is in the process of upgrading its treatment facility at a cost of $7.8 million to reliably meet TVS.
The Commission adopted site-specific dissolved oxygen (D.O.) standards for Segment 15 in 1995. However, since these site-specific standards were adopted portions of the text were inadvertently deleted from the Colorado Code of Regulations. The Commission re-adopted the 1995 standards to ensure that a complete and accurate text of the site-specific D.O. standards is included in the regulations.
The City of Aurora, Suncor Energy, and Valero Energy (Selenium Stakeholders) requested the Colorado Water Quality Control Commission (Commission) extend the temporary modification pursuant to section 31.7 of the Basic Standards for selenium on Upper South Platte River Basin Segment 16a (Sand Creek). More time is needed to determine the appropriate selenium standard for Segment 16a.
The Selenium Stakeholders developed a study plan in March 2001 to identify sources of elevated selenium in Sand Creek and determine if they are man-made or natural sources, and to determine the appropriate selenium standard for Segments 15 and 16a. Studies included collecting water quality, sediment quality, habitat, fish population and density, fish tissue, and macroinvertebrate samples for Sand Creek. Technical memoranda summarized data, and were critiqued and discussed with the Water Quality Control Division, EPA Region 8, Colorado Division of Wildlife, and US Fish and Wildlife Service (collectively the "Agencies"). The refineries also examined treatment and alternative discharge options. The data collection efforts outlined in the Study Plan were completed in October 2003; however, the Selenium Stakeholders and Agencies agreed that there is not enough information on the sources of elevated selenium concentrations in Sand Creek to come forward to the Commission with a recommendation at this time. Furthermore, the US EPA is in the process of developing an update to the selenium criteria document that may help to better define appropriate selenium standards for Segment 16a. Additional time is necessary to determine the source of the selenium, its impact on aquatic life, and determine an appropriate standard.
The Commission adopted resegmentation and corresponding site-specific dissolved oxygen standards for segments in the vicinity of Denver International Airport (DIA). These changes were proposed by DIA following a site-specific study that included an extensive stakeholder process. Ambient-quality-based numerical dissolved oxygen standards were adopted for Second Creek, Third Creek and Box Elder Creek. Narrative dissolved oxygen standards were adopted for Barr Lake and Hayesmount Tributaries.
The adoption of these site-specific, ambient quality-based dissolved oxygen standards is based upon the cumulative information provided by three separate, credible lines of evidence provided during this rulemaking. The Commission's action is dependent on the unique, site-specific nature of this cumulative evidence and should not be interpreted as precedent for the revision of dissolved oxygen standards for other Colorado surface waters.
First, the evidence resulting from the Receiving Water Study demonstrates that the previously effective table value standards for dissolved oxygen are exceeded by natural conditions in Second Creek. It further showed that there is not a substantial difference in the dissolved oxygen levels attained naturally in Second Creek and those attained in Third Creek, taking into account the influence of DIA.
Second, the biological evidence provided demonstrates that there are more biota present in the streams impacted by DIA's operations than would be present without the presence of DIA. The evidence indicates that habitat and flow are the primary stressors limiting the aquatic life use for these segments. It is not apparent that increased controls of fugitive releases of deicing fluid from DIA would result in increases in aquatic life in the affected segments.
Third, the evidence demonstrates that DIA is currently implementing a state-of-the-art system for the control of aircraft deicing fluids. These controls are implemented pursuant to a stormwater discharge permit. In addition, DIA will remain a predominant land use in this area for the foreseeable future and will continue to be required to utilize aircraft deicing fluid for air travel safety. Therefore, remaining fugitive releases of such fluids can reasonably be viewed as irreversible at this time. This conclusion can and should be revisited in the future if available control technologies continue to evolve and improve.
The ambient standards adopted for Second Creek, Third Creek and Box Elder Creek were calculated based on extensive field data. Daytime only data (6:30 a.m. to 6:30 p.m.) were used in the calculation of the ambient standards because it is anticipated that in the future, field data will be collected during those hours. In addition, a review of available data from downstream waters demonstrates that the table value dissolved oxygen standard is attained.
A site-specific narrative dissolved oxygen standard was adopted for Hayesmount and Barr Lake tributaries. These water bodies are ephemeral with flow only occurring in response to precipitation events. No dissolved oxygen data are available for these surface waters to calculate an ambient quality based standard. The aquatic habitat associated with these waters is greatly limited and any residual water following a stormwater runoff event will be present only for very short periods of time. Accordingly, the narrative dissolved oxygen requirements to protect Class 2 Warm Water Aquatic Life and Agriculture uses are appropriate.
The Colorado Division of Wildlife (CDOW) participated in the stakeholder process and stated that it was in general agreement with DIA's proposal, but had a few reservations. CDOW remains interested in conducting additional chemical and biological monitoring on the segments subject to DIA's proposal, and will contemplate incorporating sampling on the subject segments into their annual biological monitoring program. CDOW intends to prepare proposed sampling plans for discussion with DIA. DIA may participate in the collection of additional chemical and biological data on the relevant segments on a voluntary basis.
FRICO also participated in the stakeholder process, but opposed the DIA proposal. In its Responsive Prehearing Statement, FRICO offered alternative proposals for re-segmentation and dissolved oxygen standards relating to Recreation 1a, Agricultural, and Water Supply use classifications. It also raised other concerns related to the proposal and/or DIA's industrial stormwater discharge. Based on the written material and oral testimony provided for this hearing, the Commission concludes that FRICO's concerns have been effectively rebutted and that adoption of the proposal is appropriate. The alternative resegmentation proposed by FRICO is inconsistent with the Commission's general approach to segmentation, which is based upon natural drainages, not transbasin water diversions. FRICO has not demonstrated that the proposed dissolved oxygen standards are inadequate to protect aquatic life, or that additional dissolved oxygen standards are necessary to protect other uses of downstream waters. The Commission supports the efforts of the Division's stormwater program to seek agreement on notification of FRICO of events at DIA that could affect downstream water quality.
The Commission created a new segment 16g for Marcy Gulch, which was previously included in the segment 16c "all tributaries" segment. In addition to the site-specific copper water effects ratio adopted for this segment as noted above, the Commission found that the "fish ingestion" standards for organic chemicals should not apply to this segment. Specifically, the Commission found that Marcy Gulch does not contain fish of a catchable size and that fishing does not take place on a recurring basis. Because Centennial withdrew its request for site-specific ammonia standards for this segment, the Commission determined that it was inappropriate to revise the Marcy Gulch ammonia standard in this hearing.
Type iii temporary modifications were adopted for selected trace metals in Clear Creek segments 2, 9a and 9b, 11 and 13b. These temporary modifications are based on ambient water quality levels, using the 85th percentile values calculated by the Water Quality Control Division from the period of record 1999-2003 for a systematic and consistent database developed and maintained by various stakeholders.
Clear Creek segment 13b currently has temporary modifications in place for cadmium, copper, iron, manganese, and zinc. The temporary modifications for cadmium, manganese, and zinc were recalculated based on the most recent 5 years of record, and adopted as described above. The previous temporary modifications for copper and iron are no longer needed (ambient data shows the current underlying standards are being met) and were therefore deleted.
The Commission created a new segment 9b, encompassing Trail Creek, and adopted standards reflecting ambient water quality. Trail Creek has water quality not representative of either segment 2, of which it was formerly part, or the rest of segment 9.
Underlying standards for segments 2, 9a, 11 and 13b remain unchanged; they will be reviewed after the completion of the efforts to resolve uncertainty, as described below.
Numerous efforts are underway to clean up sources of metals pollution in this heavily mining impacted area, including Superfund projects. There remains considerable uncertainty concerning what level of water quality can ultimately be achieved. Examples of recent remediation projects include Argo Tunnel water treatment, Little 6, Big 5 and Minnesota Mine tailings pile removal. EPA and CDPHE have investigated many additional sites for remediation. A primary effort is nearing completion involving Superfund Operable Unit 4 (OU4), principally involving conditions in the North Fork (segments 13a and b), but including a few areas along the mainstem. This RI/FS and the ROD are due to be completed in 2004. A CDPHE remediation project in Virginia Canyon is due to begin this year. The Upper Clear Creek Watershed Association ("UCCWA") anticipates receipt of a Section 319 grant in 2004 to identify additional non-point source projects, potential funding sources and implementation issues to be resolved prior to cleanups. UCCWA submitted a Plan to Resolve Uncertainty for Clear Creek segments 2, 9a, 11 and 13b. The information generated under the plan is expected to permit the Commission to determine the extent to which existing quality is the result of natural or irreversible human-induced conditions, and to adopt an appropriate standard.
Ambient quality-based temporary modifications are adopted until the above studies are completed and the uncertainty regarding the underlying standards is resolved. These are adopted as type iii temporary modifications pursuant to §31.7 of the Basic Standards. As provided in §31.7 of the Basic Standards, the Commission intends that the temporary modifications be used in establishing any applicable control requirements while they are in effect, due to the uncertainty that warranted the adoption of the temporary modifications. The evidence supports the following findings by the Commission with respect to Clear Creek segments 2, 9a, 11 and 13b:
Segment 5, Mainstem of West Clear Creek from the confluence with Woods Creek to the confluence with Clear Creek.
The Commission adopted site-specific zinc standards based on the protection of cold water biota, resulting in a new acute equation, e0.8404(ln(hard))+1.8810, and a new chronic equation, e0.8404(ln(hard))+1.5127, for this segment. These equations were derived using the recalculation procedure removing warm water biota from an updated version of the U.S. EPA zinc toxicity database (expanded from the "1995 updates"). To develop the site-specific standards for Segment 5, a new acute database was created consisting of only those species expected to represent the biota typical of cold water, high elevation stream systems. Non-resident amphipods and isopods were included as surrogates for mayflies which are resident species but for which no toxicity data exist at this time. The four most sensitive genera from this database were identified and a new final acute value (FAV) and acute equation were determined. The final chronic value (FCV) and resultant chronic equation were calculated using an updated acute-to-chronic ratio (2.891). The Commission believes that acute and chronic zinc criteria based on coldwater biota (i.e., trout and benthic macroinvertebrates) are more representative of the conditions present in this segment than TVS. The Commission recognizes that if mayfly toxicity data become available in the future that such data would be considered in the zinc recalculation process.
The Water Quality Control Division proposed that the classification of Big Dry Creek Segment 1 be changed from Recreation Class 2 to Recreation Class 1a. Broomfield opposed this change based on a 2000 Use Attainability Analysis and a 2003 Student Survey of Recreational Uses. To resolve the issue, Broomfield proposed that the segment be classified Recreation Class 1b. The Commission adopted this revised proposal.
Broomfield proposed a narrative temporary modification for selenium of existing quality based on uncertainty. The Division proposed a numeric temporary modification of 7 µg/L. Based on additional selenium data submitted by Broomfield, the Division revised its proposal to 11 µg/L. Broomfield agreed with this revised proposal and it was adopted by the Commission.
Segment 5 contains a goal qualifier (last column Table 1) and temporary modifications for nitrate, nitrite and several organic parameters (Table 3). The Division proposed that the temporary modifications and goal qualifier expiration dates be moved from 2009 to 2006 to coincide with the accelerated date for cleanup and closure of Rocky Flats set by DOE and Kaiser-Hill. These two parties have provided assurance that "active remediation of groundwater contamination ... will continue past the completion of the contract between DOE and Kaiser-Hill" and that it will be the responsibility of DOE to oversee this work. They also stated that it is their "intent to accelerate the timeframe to meet the underlying standards." Based on these commitments and the fact that this portion of the site cannot be taken off the National Priorities List until the ongoing remediation efforts are completed, the Division withdrew the proposal for the earlier expiration dates.
The Commission added a footnote to Table 2 providing that for the portions of Walnut and Woman Creeks within Segment 5 (where the majority of the surface disturbing cleanup activities are currently occurring) the methodology for determining attainment is changed to allow for a 12-month flow-weighted rolling average (computed monthly) method to measure ambient levels of plutonium and americium. The Commission has determined that this change is appropriate due to the unique circumstances related to the accelerated Rocky Flats clean up.
The Division proposed temporary modifications for fecal coliform and E. Coli, Broomfield agreed with this proposal and it was adopted by the Commission.
In addition, for Big Dry Creek segment 5, secondary drinking water standards were removed that had been incorrectly added to this segment. The Commission determined in its 1996 Regulation No. 38 Rulemaking Hearing that secondary drinking water standards would not be applied for Big Dry Creek segments 4a, 4b and 5.
The Commission adopted a change to the D.O. standards for the upper reach of Middle South Platte Segment 1 (from Big Dry Creek to the St. Vrain Creek) to be consistent with the site-specific standards immediately upstream in Segment 15 of the Upper South Platte River. This change recognizes that the South Platte River is effluent dominated (e.g., effluent makes up a majority of the flow in the River during a majority of the year).
The Metro District undertook extensive studies of DO and the affects of low-DO levels on aquatic life during the 1990's. These studies included toxicology testing of nine different species of fish that are either found or expected in the South Platte River and clearly showed that fish can tolerate short-term DO levels below the current statewide standard for warm water aquatic life of 5.0 mg/L. This work resulted in the site-specific DO standard the Commission adopted for Segment 15 of the South Platte River. That site-specific DO standard includes instantaneous standards for both older life stages (8/1 -3/31) of 2.0 mg/L, and early life stages (4/1 - 7/31) of 3.0 mg/L. Early life stages are further protected by a 7-day average DO standard of 5.0 mg/L, while older life stages have a 30-day average DO standard of 4.5 mg/L. Regular aquatic life sampling events in Segment 15 have demonstrated these site-specific DO standards are protective of the aquatic life in the segment.
Lost Creek is as its name describes a creek that disappears. Two segments are separated by dry land with no visible stream channel for more than one mile. The segment south of US Highway 76 is characterized by unconnected ditches that disappear into fields and pumped wells. This segment is located in the Lost Creek Ground Water Basin. It is a designated over-appropriated ground water basin. Well pumping for irrigated agriculture reduces groundwater tables and result in tail water ditches having no flow for significant time periods. Irrigation ponds regularly are pumped dry and freeze in the winter. Rudimentary benthic matter found in tail water ditches, seasonal stock ponds and isolated wetlands created by irrigation seepage is not tributary to the segment of Lost Creek north of Highway 76 that is tributary to the South Platte River. Further depletion of the Basin ground water by exportation is anticipated in the future. A use attainability analysis was submitted supporting a Recreational Class 2 use. Evidence demonstrated no access to and no recreational use of Don Sloan's two stock ponds that also receive treated effluent for storage and land application.
Numeric standards associated with a water supply classification were deleted from Upper South Platte segment 7, since that classification was previously removed from this segment.
Upper South Platte River segment 5b and Lower South Platte River segment 1, water supply TVS for arsenic and chromium III were applied.
Cherry Creek segment 2, E. Coli = 126/100 ml was applied.
Clear Creek segment 5, the water supply TVS for chromium III was applied.
Boulder Creek segment 4c and 4d, Cowdrey Drainage, had site-specific standards that were changed to table value standards.
The Commission corrected several typographical and spelling errors, and clarified segment descriptions.
PARTIES TO THE RULEMAKING HEARING
5 CCR 1002-38.61