[Note added by SaveChatfield.org: The following letter about Chatfield Water Reallocation was shared with us by the Colorado Wildlife Federation. It has been reformatted for presentation on the web.]

CWF logo

September 5, 2012

Colonel Robert J. Ruch
Commander, Department of the Army Corps of Engineers
Omaha District CENWO-PN-AA1616
Capitol Avenue
Omaha, Nebraska 68102-4901

Attn: Chatfield Storage Reservoir Reallocation FR/DEIS

Dear Colonel Ruch:

The following comments are submitted on behalf of the Colorado Wildlife Federation (CWF). CWF is Colorado’s oldest statewide wildlife conservation organization, a 501(c)(3) nonprofit whose members consist of hunters, anglers, bird watchers, and other wildlife enthusiasts. Thank you for the opportunity to comment on the subject feasibility report and draft environmental impact statement.

We have reviewed, analyzed, and provided comments on many proposed water projects since our inception in 1953. In our opinion, Alternative 3 (current preferred alternative) and Alternative 4 would cause very large unacceptable and unnecessary impacts to valuable fish and wildlife resources, and the proposed mitigation is far from adequate. Language on pages 4-84 notes that Alternative 3 would produce the largest impact on a variety of wildlife species and migratory birds, which is inconsistent with the Migratory Bird Treaty Act.

We question whether the proposed project is in compliance with the Clean Water Act. For example, Alternative 3 would destroy an estimated 157.2 acres of wetlands, and Alternative 4 would destroy somewhat less. The proposed mitigation for these losses is substantially less than what the U.S. Army Corps of Engineers (Corps) typically requires when issuing Section 404 permits under the Clean Water Act (CWA) in compliance with the Section 404(b)(1) Guidelines for Specification of Disposal Sites for Dredged or Fill Material (45 CFR 85344). The Corps usually requires at least a 1:1 ratio for replacement of wetland acreage with in-kind habitat when wetland creation is used for mitigation. The proposed mitigation does not reach this basic level, which is critical because wetland creation often is difficult to achieve and maintain.

Furthermore, Alternatives 3 and 4 include dredging in waters of the United States. That activity is not “incidental” as described in Appendix W. The Corps regulations in 33CFR§335.2 states “… the Corps does not issue itself a CWA permit to authorize Corps discharges of dredged material or fill material into U.S. waters, but does apply the 404(b)(1) guidelines and other substantive requirements of the CWA and other environmental laws.” Provisions of the guidelines apply to this activity and have not been addressed as such in the document. We think the Corps should conduct a Clean Water Act Section 404 analysis for the preferred alternative and include it in a Supplemental DEIS.

In addition, the preferred alternative would inundate 454 acres of Preble’s Jumping Mouse habitat. The mouse is listed as a threatened species under the Endangered Species Act (ESA). Approximately 155 acres of the mouse habitat has been designated as critical habitat. The Guidelines prohibit an activity if it “…jeopardizes the continued existence of species listed as endangered or threatened under the Endangered Species Act of 1973, as amended, or results in likelihood of the destruction or adverse modification of a habitat which is determined by the Secretary of Interior or Commerce, as appropriate, to be a critical habitat under the Endangered Species Act of 1973, as amended. If an exemption has been granted by the Endangered Species Committee, the terms of such exemption shall apply in lieu of this subparagraph.” To the best of our knowledge, the proposed project has not been granted such an exemption. When the U.S. Fish and Wildlife Service provides the Corps with a biological opinion in accordance with the ESA, it should be circulated to the public and subsequently appended to a supplemental DEIS and filed in the Record of Decision.

The standard metric for identifying how much water the reallocation would provide is either “safe yield” or “firm yield.” The document does not include this important information. Instead, within Appendix BB under “Project Waivers,” the Corps adds confusion by discussing “dependable yield.” It is unclear if the term dependable yield is intended to mean “safe yield” or “firm yield.” In any event, the Corps states there are several “common measures of dependable yield,” and then concludes, “At Chatfield, all of those measures of dependable yield are 0.” Further, the document fails to disclose the nature of the water rights of the providers that would benefit from this project. We understand they are very junior and the providers would not be able to store water in more than 50 percent of the years during the life of the project. In view of these serious omissions, the Corps needs to explain fully why the preferred alternative is proposed in light of the extensive environmental impact it would have while gaining questionable water supply.

In addition, selection of this preferred alternative is inconsistent with the Corps’ regulations that state, “The first step of mitigation planning is to seek to avoid or minimize harm.” (40CFR§1508.2) This objective was restated in the Department of the Army NEPA regulations that were appended to the guidance on mitigation and monitoring released by the Council on Environmental Quality on January 14, 2011.

The DEIS claims extensive coordination was conducted with all affected parties and that their input was seriously considered. Our discussion with wildlife biologists from Colorado Parks and Wildlife indicated that for the most part they were not active planning participants. They did provide input to the mitigation planning for the mouse, but otherwise mainly provided basic biological information on fisheries and wildlife. In addition, several members of the Audubon Society of Greater Denver who actively participated in the cooperators meetings, asserted that their input and comments on the preliminary DEIS were not fully considered (e.g., mitigation needs) although their concerns were presented clearly in their comments on the preliminary DEIS. As an example, although project planning has been going on for many years, the Corps rejected requests from Audubon to gather more site data on bird use to ensure estimates of habitat richness were accurate. Furthermore, the Ecological Functional Values for bird sensitive species did not match the Rating Criteria Chart or the values established by the Ecological Functions Technical Committee in its final meeting. Also, the values for upland bird species richness and abundance were lowered without the permission of this committee.

Therefore, we request the Corps work with the project proponents to develop a new proposed alternative composed of some of the many other options available, including aquifer storage and use of the existing Rueter-Hess Reservoir, which has storage capacity available. The preferred alternative must be much less damaging to the affected natural resources and the recreation they provide at Chatfield State Park. Further, this new alternative must be described in a supplemental DEIS that is circulated for public review before a final decision is made regarding the preferred alternative.

Options, such as additional use of gravel pits for water storage, have been implemented successfully in several locations, including north of the dam, and should be reconsidered as a preferred alternative for this project. We understand that the providers have been considering conjunctive water use and trading of water rights. Why is this option not disclosed in the alternatives section?


Chatfield State Park is one of the crown jewels of the state park system and it must be protected. Chatfield State Park and Cherry Creek State Park are the two most heavily used parks in the state. Chatfield State Park supports more than 1.5 million visitor days annually.

We applaud the Denver Water Department’s past efforts to try to maintain water levels in the reservoir with the least amount of fluctuation. In combination with excellent management by Colorado Parks and Wildlife, this Park supports hundreds of acres of prime riparian woodland and wetlands, as well as one of the best reservoir fisheries in the state. As noted on pages 3-21, the reservoir is a primary walleye brood fish and egg collection source for Colorado Parks and Wildlife because approximately 25 million wild eggs are secured annually for hatchery production and subsequent statewide stocking. There are currently no viable substitute sources for that many eggs.

There are more than one hundred very old and very large cottonwood trees that are unique, essentially irreplaceable during the life of the project, and considered rare by the Colorado Heritage Program that would be cut down and removed under the preferred Alternative. These trees existed before the dam was built and should be left alone. The relatively stable pool has enabled the development of beaches, picnic areas, shore fishing, boat ramps and a marina that provide very important recreational opportunities close to home for the Denver metro area population. The recreational value of this reservoir and surrounding lands cannot be taken lightly. This asset provides important opportunities to engage young people in outdoor activities, including biking, hiking, fishing access, and observing wildlife. The DEIS assures lost revenue during the 50-year period of study. The total projected dollars in lost revenue should be added to the water users. The Record of Decision must include a legally binding agreement to make those annual payments in a timely manner. In our experience, nonbinding commitments and expensive mitigation measures tend to decrease in priority or become lost over time.

Additional Comments on Alternatives

The Executive Summary is the only portion of the document many people will read. It must be accurate and transparent. As written, it understates the impacts of the project while assuring the reader that all impacts will be fully mitigated. The lengthy document reveals instead that all impacts will not be adequately mitigated. The Executive Summary must be rewritten to include more specifics on the impacts and the mitigation steps that will be taken, coupled with alternative comparison charts with related costs.

Despite all these important resource values, the preferred alternative (No.3) would create the most damage to these resources (Table 2-9), which we believe is inconsistent with the intent of the National Environmental Policy Act and the Standards and Principles promulgated by the Water Resources Council. As stated above, a new preferred alternative is necessary. It should focus on minimizing pool fluctuations, impacts to the riparian and wetland habitats, and degradation of water quality and the sport fishery both in the reservoir and downstream. Such revised alternative should be circulated in a Supplemental DEIS. When formulating such new alternative, much more emphasis must be given to water conservation practices, and the project sponsors must commit to them in the document. Before more valuable riparian resources are destroyed, providers must impose additional water conservation practices. (Eventually, they must do so anyway.)

On page ES-7 and elsewhere in the document, Alternative 1 (Penley Reservoir combined with Gravel Pit Storage) has been identified as the “no action” alternative. It should be made clear to the reader that the term “no action” does not mean that it could not be a viable construction alternative to the preferred alternative. That term just indicates that no federal funding or facilities would be required. If it is not a realistic alternative, the Corps should not have included it in the DEIS. However, we understand there is significant public opposition to construction of that reservoir, and the county commission voted against it unanimously. Therefore, we question whether this is an unrealistic alternative, which if included in the DEIS would be inconsistent with CEQ NEPA Guidelines.

Alternative 2 (the least costly alternative to Chatfield Reservoir storage reallocation) would combine continued use of non-tributary ground water (NTGW) with storage in gravel pits. Unfortunately, the DEIS states, “However, the water providers participating in the Chatfield Reservoir reallocation study are opposed to long-term use of NTGW due to water supply management strategies of becoming less dependent on non-renewable water supplies.” It must be noted that despite this statement, some entities continue to permit new housing developments on the basis that there is sufficient ground water supply. Therefore, is this also an unrealistic alternative, or is it one the Corps will seriously consider in view of the much greater environmentally damaging Alternatives 3 and 4?

Another alternative that must be given serious attention an in alternatives analysis would be the possibility of not permitting new housing developments in the suburbs without very strict water conservation requirements for landscaping and interior use (e.g., showers and appliances). Such an analysis should also include the possibility of the water providers paying existing home owners $1 per square foot to replace Kentucky blue grass with xeriscaping as has been done very successfully in Las Vegas. The large amount of money it will cost to build this project, particularly if the mitigation is done right, could conserve a very large amount of water and perhaps preclude the need for this and other projects for a long time into the future. The City of Denver population has increased in recent years, but the per capita use of water has remained stable. It can be done.


We are very concerned that much of the success of the mitigation measures will rely on Adaptive Management. Each of the nine affected resources described in Table 4-1 (e.g., water quality, fisheries, wildlife, recreation) depends heavily upon Adaptive Management for addressing uncertainties that are key to meeting mitigation goals. This management tool is valuable for has value for tackling truly unknown circumstances. However, every effort should be made to identify all possible problems and to plan and implement measures to resolve them. When an alternative is selected, the Corps and water providers must develop specific management plans for each of the nine resources in coordination and with the approval of Colorado Parks and Wildlife. Further, these plans should be made available for public review and comment before they are presented to the Parks and Wildlife Commission.

We were pleased that the company formed by the water providers would maintain an escrow account for the purpose of ensuring the proposed mitigation is fully funded, which is consistent with the guidance on mitigation and monitoring released by the Council on Environmental Quality on January 14, 2011. However, because so much mitigation hinges on Adaptive Management, the Corps must clearly explain what will happen if this escrow account becomes exhausted before all mitigation needs have been addressed. This issue must be addressed in the next document the Corps releases on this project.

In addition, the DEIS commits that mitigation will be implemented concurrently with project construction. We normally recommend that mitigation be implemented before or concurrent with construction. CWF recommends that the cottonwood forest, particularly that in the riparian areas, not be cut until absolutely necessary. That is, the cottonwoods should be removed in stages. Because there is no guaranteed firm yield, we are hopeful that the inundation area ultimately will not reach as far upstream as currently predicted.

In addition to the body of the document, we also reviewed all of its many appendices, including Appendix K, the Draft Compensation Mitigation Plan (DCMP). Page 14 of this Plan contains the statement, “The first priority is on-site mitigation.” This aspirational statement is important, but unfortunately the current plans do not reflect this goal. Another section of the report with regard to wetlands recommends that mitigation banks be used to the maximum degree possible. The first proposition is in conflict with the second. We much prefer the maximum implementation of on-site mitigation, and CWF recommends that the mitigation banking language be deleted in the final EIS.

Chapter 3 of the DEIS (e.g., pages 3-47 to 3-52) describes the very high value of the riparian and wetland habitats to birds. It also specifically describes some of the important wildlife values of the “over 50 acres of mature cottonwood forest along the South Platte River.” The term “mature cottonwood” understates its ecological value. The tree management plan in Appendix Z states that at least 243.5 acres of cottonwood trees and 52.8 acres of willows will need to be removed below 5439 ft. msl because if inundated they would pose a hazard for boating and dam operation. A few trees in select spots could remain for fish and wildlife, at the advice of Colorado Parks and Wildlife, and if approved by the Corps. However, the DEIS also notes that an additional 61.1 acres of trees might need to be cut down between 5439 and 5444 ft. msl if adaptive management does not work. Table 4-8 indicates 185.7 acres of cottonwoods and 16.7 acres of sandbar willow would be lost due to inundation under Alternative 3. There is a large discrepancy in the numbers between Appendix Z and this Table. We assume that Appendix Z contains the correct numbers upon which mitigation should be based.

The lists of species that use the habitats on-site are incomplete and must be updated, including a list of “sensitive species.” Such inaccuracies may have contributed to lower estimates of wildlife values and underestimated mitigation needs. There are numerous birding records that can be reviewed, and the Audubon Society of Greater Denver and Colorado Parks and Wildlife should be consulted to ensure all such lists that are used are accurate. The document erroneously states that great horned owls and red-tailed hawks “can be sensitive to human disturbance so nests may be uncommon.” In fact they are common and tolerate people quite well. That claim cannot be used to lessen the mitigation needs for the old growth cottonwoods.

If Alternative 3 or 4 is selected, CWF would support “implementation of an inundation alternative” as discussed on pages 4-58 where “a step-wise” approach would be allow “maximum water levels to be achieved only after mitigation for partial inundation was achieved or at least underway.” However, actually fully implanting the mitigation measures first is highly recommended to ensure they accomplish their intended purpose. The term “underway” is too general and unacceptable because it could be misconstrued as having satisfied a mitigation requirement even if the measures have just begun to be implemented or planned.

Table 4-8 should be expanded to include losses of different species of wetland plants because every reasonable effort should be made to replicate those diverse ecosystems with the created wetlands.

We do not support the statement on pages 5-58 that current vegetation on the reservoir margins may be replicated over the long term if adequate weed control is maintained. To achieve this goal we believe weed control must accompanied by minimum fluctuation of pool levels. However, we agree that “these successional changes are dependent on the many variables discussed in the preceding paragraph and long-term successional increases in riparian or wetland communities should not be used to temper the estimates of vegetation losses described in Table 4-8.

Table 4.9 estimates that 65 new acres of plains cottonwood would become developed within the 0-6 foot band above the proposed maximum level of inundation for Alternative 3. This was based upon spatial analysis and soil moisture related to presumed hydrology. It is optimistic at best. Further, we did not see a discussion about how many decades are required for that vegetation to become established and mature.

We generally agree with the statement on pages 4-64 that “the assumptions described in Table 4-9 are hypotheses of vegetation community changes above the alternate pool levels” and should not “affect the estimated impact figures from inundation provided in Table 8.” Also, “the figures provided in Table 4-9 do not represent promises of mitigation.” However, we believe that stating they should not be the “sole basis of mitigation proposals” is too generous. Such estimates of natural recruitment should be given little or no credit for mitigation in advance of actually documenting success on the ground, particularly if not accompanied by significant planting of 2” to 3” saplings, a detailed management plan, and dedicated funding for management, maintenance, and replacement when needed.

The majority of all the trees that will be lost are “mature,” not only those located on the 50-acre parcel focused upon in the document. The 50 acres referenced contain more than 100 trees that are very old and very large (e.g., 2 foot diameters or greater), and described on pages 4-83 as “rather unique within the Denver Metro area and possibly along the South Platte River.” We agree with the statement, “Loss of this habitat for songbirds would cause long-term adverse impacts that are not easily mitigated.” We would go further and assume they are practically irreplaceable during our lifetime. There is also language on pages 4-83 noting that they are a special feature of the Park.

The cavities of these old trees provide important habitat for great horned owls, raccoon, woodpeckers, and wood duck. Yet the proposed mitigation for this loss is only 13 acres of on-site mitigation for recruitment of new cottonwood growth (section, protecting up to 22.5 acres of existing mature cottonwood habitat in offsite areas, and designating up to 10 acres of off-site areas for recruitment. We are dumbfounded that the Corps believes this is adequate mitigation for the essentially irreplaceable old growth trees. Further, we are unaware of any plans to replace the forest values of the other cottonwoods and willows, which also have very high wildlife value for many species in addition to the state record number of birds that rely on the habitats in the Park. The extensive loss of forest habitat also would cause permanent reductions in local populations of deer, raccoon, small mammals, and songbirds. They cannot relocate somewhere else if the habitat is already occupied. Therefore, reservoir levels must be managed to minimize adverse effects to the old cottonwood forest.

The majority of mitigation depends on protecting existing habitat through fee title or permanent easement. CWF objects to this approach. This approach may be part of a mitigation plan if the acquired habitat is very valuable and documented as being danger of being lost in the near foreseeable future and/or important for sustaining threatened and endangered species by precluding undesirable human activities and providing buffer. Otherwise, it is just protecting something that already exists and replaces no lost values. That is why the Corps has required as much as a 10:1 ratio when using protection of existing habitat to mitigate for wetland losses as a condition to issuing a Section 404 permits under the Clean Water Act.

The assumption that planting cottonwood seeds is adequate mitigation for loss of these huge trees is untenable. It is essential that all of the acreage of cottonwood trees and willows that is lost be replaced with varying ages of saplings in addition to seeding in moisture managed plots.

The Corps assumes that the bird values not fulfilled by the proposed “mature cottonwood” mitigation described above would be addressed using the Ecological Functional Approach model and the bird values existing, created, or enhanced in the habitat replacements/protected areas for wetlands and the Preble’s mouse. As stated on pages 3-51, “Each habitat type supports a different community of bird species…” “The most dramatic difference is between wetlands and woody vegetation, such as woodlands and shrubs. Wetlands support a distinct group of birds including shorebirds …” On pages 3-52, the Corps states, “Woody vegetation supports a variety of passerines, woodpeckers, and owls not found in wetlands.” These and other statements in the document reaffirm the need to mitigate habitat losses in-kind to the degree possible, including all losses of forest acreage, not only bird Ecological Functional Units (EFUs).

We agree with the statement on pages 4-7 that the analysis of impacts on wetlands should be based upon the maximum level of inundation or worst case scenario. Table 4-11 shows that implementation of Alternative 3 would result in the loss of 157.2 acres of wetlands. However, stating that the exact new condition for each alternative is unknown due to the high fluctuation of water levels associated with certain alternatives sweeps reality under the rug. Those future conditions must be projected to the degree practicable in accordance with CEQ Guidelines and adequately mitigated.

Pages 4-78 state that potential impacts that transform or reduce wetlands would be minimized as much as possible through adaptive management. That is not specific enough. Specific wetland management plans must be completed and circulated to the public and to the Colorado Parks and Wildlife Commission. We agree that compensatory mitigation should be maximized to the extent practicable within or adjacent to the Park. However, only 30 EFUs of 123 wetland EFUs impacted would be mitigated on-site, which hardly meets the definition of “maximized.” Furthermore, no EFUs should be credited for preservation; only creation should be credited and partial credits given for enhancement.

With regard to wetland creation, we have seen instances where it has been effective, including Cherry Creek State Park. However, our experience has been that wetland creation usually does not work as planned, including wetland mitigation banks. The ability to adequately control the needed hydrology is often problematic and will become worse with ongoing climate change. Also, it is common for cattails to take over when the plans called for developing and maintaining a variety of plant species to replace the lost ecological diversity. Therefore, all wetland projects must be monitored and actively managed continuously for at least 5 -10 years to ensure sustainability and adequate water supply. Where those costs taken into account? Further, because the created wetlands are unlikely to be as productive and diverse as those created by nature, replacement acreage should exceed lost acreage by a ratio of 2:1.

Some of the proposed wetland mitigation would take place on the 18½ acres of wetlands that were constructed on the Chatfield Arboretum to mitigate for wetlands impacted by the construction of the C-470 freeway. These constructed wetlands were never fully functional because of unreliable hydrology, which reflects the concern mentioned above about the unreliability of created wetlands. The Colorado Department of Transportation (CDOT) is responsible for fixing the problem. Using these wetlands for mitigation for the Chatfield project is unacceptable. The Corps intends to assume CDOT’s existing responsibility to satisfy its own mitigation obligation and then also count it as mitigation acres for this project! If this project uses these wetlands for mitigation, it should not claim an acre for acre credit. Enhancing these wetlands would have some value, if it really can be accomplished in view of the long history of marginal hydrology, but they should only be credited on a high ratio of acres of enhancement for each acre of compensation for lost wetlands in Plum Creek and the South Platte River. Also, the Corps should first document the adequacy of hydrology to maintain the wetlands in sound ecological condition.

Page 68 of the Draft Compensation Mitigation Plan (DCMP) states that a Project Coordination Team will be comprised of representatives from the Corps and Colorado Department of Natural Resources. The team will be responsible for general oversight of the design, construction, and implementation of the project. We approve that approach, and it also is consistent with the aforementioned CEQ guidance on mitigation and monitoring. However, on page 69 the DEIS states that the water providers will form the “Chatfield Reservoir Mitigation Company”, and that the Company would have exclusive control of the implementation activities. We disagree with this approach. The Army policy attached to the CEQ memo makes it clear that the Corps retains overall responsibility to ensure proper mitigation implementation and monitoring and that monitoring results should be provided to the public. The DEIS should describe that responsibility, and the Corps must commit the fiscal resources necessary for travel and staff time to fulfill it.

As proposed on page 69, this Company would only have to “consider” comments and recommendations from the advisory committees. We disagree with that approach and request that it be changed. Otherwise, it amounts to putting the fox in charge of the hen house. This decision making structure is crucial because the money set aside for mitigation likely will not prove sufficient. The recommendations of these committees should be adopted unless the Corps, rather than the water providers, determines them to be unreasonable. Third party oversight is crucial because much of the mitigation depends on adaptive management.

It is stated in the DEIS that the water providers are not responsible for dealing with “Acts of God” that adversely affect mitigation areas. Flooding and drought could be examples of such Acts. The option to avoid repairing and restoring damaged habitats because they are so- called “Acts of God” gives the providers far too much leeway and must be deleted. The DCMP should note that the project sponsors are responsible for managing the habitat as identified in the site management plan for perpetuity. The recommended contents of the management plans described on pages 58 and 59 are good, and we urge that they remain requirements in the final mitigation plan.

Table 2-9 states Alternative 3 could result in 21 feet of pool fluctuations, and that the target pool elevation will only be reached in 18 percent of years. It also states there may be more mud flats. We agree that weed control will be very important for re-establishment of desirable plant species after construction and support the species identified for control on pages 4-57. Cocklebur should be included on the list. Based upon experience at Glendo and other reservoirs with greatly fluctuating levels, invasion of cockleburs and Canada thistle can become very problematic. We request the Corps ensure that the magnitude of the potential weed problem and the resultant annual management costs to the providers are fully evaluated and clearly identified. Those costs usually will be much higher for chemicals and labor than anticipated. Too often the weeds become established and the land managers give up on maintaining weed control on extensive mud flats.

Some of the wetland mitigation would occur below the flood pool line. The providers must commit to cleaning out those wetlands if they become silted in during high water, as well as replanting and construction repairs if needed, just like responding to “Acts of God.”

Mitigation Model

One of the authors of this letter had experience in using Hydrogeomorphic Classification, Habitat Evaluation Procedures, and Habitat Suitability Indices, during his career in the U.S. Fish and Wildlife Service, for the purpose of evaluating mitigation needs and proposed mitigation measures. We reviewed the appendices to the Draft Compensation Mitigation Plan, including Appendix C – Ecological Functions Approach; Appendix G Assumptions and Calculations for On-Site Mitigation Gains in EFUs and Costs; and Appendix I – Ecological Functions Approach Model Review Report, Chatfield Reallocation Study. We remain unconvinced that existing models in addition to the Functional Assessment of Colorado Wetlands could not have been used successfully with some site specific tweaking. Research should be done to ensure a riparian cottonwood model does not already exist. If not, then this model should be modified to ensure that the forest habitat type receives as much focus as birds in the mitigation planning because those trees in combination with the shrub habitat and wetlands support a very diverse and valuable community of species. When the model was developed, it seems that the Corps was overly concerned with minimizing foreseeable mitigation costs to the developers. We find this troubling.

As this model plays a key role for developing mitigation plans for birds and Preble’s meadow jumping mouse, it should be subjected to peer review by experts outside the Planning Division of the Corps. We do not agree that the agency’s technical review process employed for this project is sufficient. It was technically reviewed only by one Corps biologist and a private consultant, whose expertise is primarily on the biology of the mouse, not modeling per se. Corps experts in its regulatory program and its Natural Resource Research and Development Center in Vicksburg, the Natural Resources Conservation Service, and other agencies should be consulted to ensure the model and the manner in which it is being used is valid ecologically.

If the USFWS and the former Colorado Division of Wildlife (now Colorado Parks and Wildlife) were fully involved in developing the Ecological Functions Approach (EFA) and agree to how it is used, we do not object to its use on a conceptual level. However, we have a problem with some of the weighting factors that were tacked on by the Corps. We sense that they might have been added in an effort to rationalize an overall sound conclusion. We also question why the weighting factors were multiplied times each other instead of adding them after they are multiplied by the number of applicable acres. Whether done inadvertently or intentionally, the many weighting factors greatly reduce the amount of land needed for off-site mitigation, which in turn makes the project and the mitigation significantly less costly. That may be good for the project proponents, but it does harm to the affected resources.

Weighting factors for preservation, connectivity, and buffer are not ecologically supportable in this model, and we request they be eliminated. They should be used only to compare the relative value of and to rank potential acquisition and easement parcels. Why are the weighting factors only employed to provide extra value to the potential off-site habitat? If these weights are used they should be multiplied for the habitats that are being destroyed because they also have values such as buffer and connectivity. Only the enhancement weighting should be considered for bird mitigation and only when specific habitat has been acquired and a management plan precisely lays out how the habitat will be improved and managed.

As previously mentioned, using acquisition and perpetual conservation easements normally should require more acreage than that destroyed because they protect existing habitat values and do not replace lost values unless enhanced and intensively managed with peer reviewed plans. Furthermore, on-site creation/enhancement projects should be given the same degree of credit as off-site mitigation. By giving a credit of 1.25 for on-site mitigation and only 1.0 for off- site, the result is that using on-site mitigation lessens the amount of overall mitigation needed.

We will defer comments on the proposed mitigation for the mouse to the experts at the USFWS and Colorado Parks and Wildlife, and until we have an opportunity to review the USFWS biological opinion on the project. That biological opinion should be attached to the forthcoming document in conjunction with the planning aid letter the USFWS submitted to the Corps in February 2006.

Water Quality and Fisheries

We agree with the comments on pages 4-55 and 4-56 that if “more evenly reservoir releases distributed throughout the year so appropriate pool levels were maintained during fish spawning and embryo development, there could be less impact on reproductive success of warm-water fish species in the reservoir.” Also, “keeping instream flow rates high on the South Platte River below the reservoir during times of low flows and higher temperatures could reduce stressors put on the aquatic community in this reach.” Unfortunately, the paragraph goes on to state that “future water demands would dictate alterations in current flow patterns in the South Platte regardless of increased storage capacity in Chatfield Reservoir.” Therefore, we support development and implementation of a Coordinated Operations Plan that is developed in cooperation with Colorado Parks and Wildlife. We also support stream habitat improvements for the South Platte River upstream and downstream of the reservoir.

With regard to water quality, the reservoir historically has had higher than optimal phosphorus levels. While not listed on the 303(d) list by the Colorado Department of Health and Environment (CDPHE), the influent load far exceeds that of the effluent, with both point and non-point sources entering through Plum Creek, the South Platte River and other tributaries, as well as an unknown amount from boaters and other recreational users of the Park. Instead of being a point of remediation and treatment, Chatfield Reservoir has been a source of phosphorus rich flows that waters and municipalities downstream are forced to manage. The preferred alternative would exacerbate this problem.

Aquatic ecologists and fishery biologists know that phosphorus is typically the limiting nutrient for aquatic plant and algae growth. In addition to soluble phosphorus entering the system, every summer when the hypolimnion becomes anoxic, phosphorus previously locked in the sediment is reduced, released, and becomes available for primary production. The layer of seasonal anoxia ranges from one to up to five meters on the bottom of the resource. The exact range was hard to determine as it did not appear that the same point in the reservoir was measured each time.

With increased water storage at the Chatfield site, the seasonal anoxic zone will grow as well. Neither of the alternatives that called for raising the water in Chatfield took into consideration that with increased depth, the thermocline will rise as well, releasing phosphorus previously locked in the sediment. The DEIS needs to be revised to reflect that problem. Furthermore, the inundation of the organic rich area currently occupied by the deciduous forest and the horse corrals will increase the available phosphorus within the resource as well as increase the biological oxygen demand.

Even if correctly stated on pages 4-49 that Alternative 3 would generally positively impact forage fish populations, which we question, the overall effect on the sport fishery will be negative. The sport fishery in Chatfield Reservoir has high public value and must be protected at its current level of productivity.

For example, the fish will be unable to inhabit the increased zone of low oxygen because warm water fish prefer dissolved oxygen levels of greater than 4 ppm. Higher levels of phosphorus and nitrogen in the water column in conjunction with expansive shallow shelves created by the periodic flooding will likely experience increased primary production in the lake. While increases in cellular algae will increase the forage for some lover level fishes, it also will act to reduce the secchi depths (i.e., depth of visible light) within the lake and inhibit species that rely on sight to forage. The inundation of agricultural and organic rich areas will create a number of chemical and biological oxygen demands that can further stress or impair the fishery.

Should the Corps decide to proceed with the increased storage of water at the Chatfield site, aeration or some other type of effective circulation system should be implemented to mitigate the increased phosphorus loading. This system should be designed and operated to keep the aquatic ecosystem in a perpetual state of turnover throughout the summer and fall. There is ample iron and manganese in the resource, and in the presence of oxygen, will oxidize with phosphorus and cause it to particulate out of the water to be stored in the sediment.

If Chatfield Reservoir becomes impaired by nutrient loading in the future to the point of being added to the 303d list by CDPHE, its Water Quality Division would write a total maximum daily load (TMDL) limit at that time. That is where most actions end as neither the CDPHE nor EPA has the capability to mandate action. Therefore, the Corps and the water providers should carefully reconsider building a project that they know will worsen ongoing water quality problems. It they do, they must be held accountable to mitigate these issues. We request that the Record of Decision and FEIS include a detailed management plan and budget for the aforementioned water circulation system and other mitigation needed to protect water quality. A system similar to this was alluded to in conjunction with the preferred alternative. In addition to possibly improving the water quality to levels greater than those being currently experienced in the reservoir, the results might open up the entire water column for fish to inhabit by creating a near uniform oxygen and temperature profile.


Our comments above provide substantial support to our opinion that the DEIS has several major flaws that must be rectified in a Supplemental Draft Environmental Impact Statement. Examples include the following:

If you have any questions, please contact us at the address shown below.


Dennis Buechler
Director Emeritus

1410 Grant Street, Suite C-313, Denver, Colorado 80203 (303) 987-0400 Fax (303) 987-0200
www.coloradowildlife.org cwfed@coloradowildlife.org

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