|
This chapter discusses potential mitigation options for the environmental impacts identified in Chapter 5.0, Environmental Consequences, for both the Preferred Alternative and the Other Alternative. The final mitigation measures will be presented as part of the Selected Alternative that will be developed in the Record of Decision (ROD). No neighborhood impacts are anticipated as a result of the Preferred Alternative or the Other Alternative; therefore, mitigation is not required. No environmental justice impacts are anticipated as a result of the Preferred Alternative or the Other Alternative; therefore, mitigation is not required. Relocations will be conducted in accordance with the Uniform Relocation Assistance and Real Property Acquisition Policies Act of 1970, as amended (1989). Relocation brochures are available without discrimination to all residents and businesses that are required to relocate. The Act includes assistance to re-establish a business operation and to secure comparable replacement housing. It also provides for "housing of last resort" in the event that comparable housing cannot be secured at the time that the project is scheduled to proceed. Both residential and business relocations will be completed on a case-by-case basis, taking into consideration the circumstances of the displaced resident or property and the status of the project. The process includes initial property appraisal, determination of just compensation, negotiations, payment, relocation, and rights under eminent domain. Benefits under the Act, to which each eligible owner or tenant may be entitled (including early [or hardship] acquisition), will be determined on an individual basis and explained to them in detail, in addition to information regarding their financial options. No relocations are anticipated as a result of the Preferred Alternative or the Other Alternative along the I-25 Corridor. Nine relocations are required along US 85 based on the conceptual design of the Preferred Alternative and the Other Alternative; six sites are commercial, and three are residential. The conceptual design will be refined in developing the Selected Alternative for US 85. Once the Selected Alternative is defined, it will be presented in the ROD, scheduled to be signed in the spring of 2001. Once the ROD is signed, design and construction may begin. Based on the design of the Selected Alternative, these ten relocations may or may not be required. Also, under the current funding scenario, improvements to the entire corridor may take up to 20 years to construct. Due to these two factors, property acquisition will not likely start until immediately prior to construction. 7.2.4 Right-of-Way Acquisition The right-of-way (ROW) acquisition process follows the Uniform Relocation Assistance and Real Property Acquisition Policies Act of 1970, as amended (1989). The process provides for fair and equitable treatment of those properties that will be acquired. The process includes initial property appraisal, determination of just compensation, negotiations, payment, and rights under eminent domain. The ROW acquisition process, which involves authorization of final ROW plans, parcel appraisal, and acquisition of the needed parcels to construct the project, begins during final design. In many cases, the ROW acquisition process continues just prior to the start of construction. The Federal Highway Administration (FHWA); however, will not release construction funds until the Colorado Department of Transportation (CDOT) demonstrates they are nearly complete with the ROW acquisition process. Completion of the ROW process lasts 1-2 years for projects involving many acquisitions and approximately 6 months for projects with few acquisitions. No mitigation measures for recreational resources are associated with the Preferred Alternative and Other Alternative along the I-25 Corridor. A more friendly bicycle environment is created in conjunction with the Preferred Alternative and the Other Alternative along the US 85 Corridor. Currently no sidewalk or bikeway exists along US 85. The shoulders are between 0.6 meters (2 feet) and 2.4 meters (8 feet) wide, thus making it difficult to bike on the current configuration. Improvement alternatives include a grade-separated crossing for pedestrians and bicycles at the High Line Canal Trail and an improved crossing for the Centennial Trail. The current crossing of the Centennial Trail at the C-470 Interchange has been improved by extending the trail south to Blakeland where bicycles and pedestrians can cross at the traffic signal. An analysis was completed to determine the opportunities available for a detached bicycle/pedestrian facility. In some areas, a detached bicycle/pedestrian facility does not fit due to the environmental impacts the facility causes. The Preferred Alternative and the Other Alternative include:
CDOT will maintain the bikeway/shoulder with regular sweeping. Land acquired by CDOT will be used as a transportation corridor. This acquisition will be minimal; therefore, mitigation is not required. No substantial air quality impacts are projected as a result of the Preferred Alternative or the Other Alternative; therefore, mitigation is not required. 7.3.2 Water Quality and Quantity CDOT is concerned with erosion, sedimentation, and stormwater runoff impacts to both water resources and water quality resulting from highway construction activities. CDOT recognizes that the best approach for avoiding impacts is to ensure sufficient distance between the road alignment and Waters of the US, follow terrain contours to avoid headcutting and other erosion/slope stability issues, and locate the transportation corridor away from high erosion hazard areas. It is not always possible to completely avoid impacts to wetlands and Other Waters of the US. These potential impacts are considered during planning and design phases of CDOT projects and mitigated through the use of best management practices (BMPs), which are implemented as temporary or permanent project features. The following paragraphs identify mitigation measures that will be implemented for both the I-25 Corridor and the US 85 Corridor to mitigate direct, secondary, and cumulative water quality impacts to an acceptable level during construction and operation and maintenance (O&M) of the Selected Alternative presented in the ROD. CDOT will comply with appropriate federal (e.g., Clean Water Act sections 401, 402, and 404) and state legislation (e.g., Colorado Water Quality Control Act, Title 25, Article 8, CRS) to ensure that project-related impacts do not result in additional water quality degradation over current conditions. CDOT will also take reasonable steps to comply with local regulations or special requirements. Examples of local requirements include Douglas County Erosion Control Criteria and the Chatfield Reservoir and Cherry Creek Reservoir Control Regulations. Douglas County’s erosion control criteria limit the release of sediment to historic levels plus 15 percent during construction activities, and sediment discharges must return to historic levels after construction. The Chatfield Reservoir and Cherry Creek Reservoir Control Regulations require the implementation of erosion and sediment control BMPs to prevent nonpoint source pollution (i.e., phosphorus loading) of Cherry Creek and Chatfield Reservoirs. Potential construction-related impacts to water resources and water quality will be further reduced by adherence to conditions included in any United States Army Corps of Engineers (USACE) Section 404 permit and the Colorado Discharge Permit System (CDPS) general permit that will be issued to cover construction-related stormwater discharges (Construction Stormwater Discharge Permit). CDOT will obtain a Construction Stormwater Discharge Permit(s) for the Selected Alternative presented in the ROD. This permit is currently required for construction activities that disturb more than 2 hectares (5 acres). After 2002, the permit will be required for disturbing more than 0.405 hectare (1 acre). The Construction Stormwater Discharge Permit requires preparation of a Stormwater Management Plan (SWMP), site inspections every 14 days, and specific erosion control and pollution prevention requirements. The SWMP is project-specific and will be prepared during the design phase. The SWMP will specify and describe BMPs needed to mitigate any potential adverse impacts to surface water quality resulting from construction activities in the I-25 Corridor and US 85 Corridor. The use of BMPs is crucial during the construction phase to prevent the transport of phosphorus into the Chatfield Reservoir and Cherry Creek Reservoir and to prevent adverse water quality impacts to rare aquatic species or habitat in Plum Creek and East Plum Creek. Erosion and sedimentation BMPs can be used to control phosphorus loading to surface waters. During construction, CDOT will use the following BMPs to prevent the transport of sediment and other contaminants in stormwater runoff:
Additional project development specific BMPs will be detailed in the SWMP created for the Selected Alternative. In addition to adhering to the SWMP, the construction contractor will also adhere to CDOT water quality and erosion control management specifications. As the project progresses, the Colorado Division of Wildlife (CDOW) will be consulted on specific water quality mitigation to avoid impacts to rare fish species inhabiting, or with habitat, in Plum Creek and East Plum Creek. Construction-related impacts to water quality will be mitigated by minimizing the number of piers placed in Waters of the US. Bridges will be anchored outside the bed and banks of East Plum Creek and other project area tributaries, whenever possible. Drainage systems are expected to be the primary means for mitigating potential impacts to water resources and water quality from operation and maintenance of the selected alternatives. Final design of the selected alternatives will include appropriately sized drainage structures and stormwater quality management BMPs to minimize any project related water quantity or quality impacts (i.e., phosphorus loading) to downstream surface waters. The Chatfield and Cherry Creek Reservoir Control Regulations set goals of 50 percent reductions in nonpoint source phosphorus loading from upstream watersheds. BMPs that control sedimentation and erosion, such as those previously described, can be used to reduce phosphorus in stormwater. In addition, Douglas County Storm Drainage Design and Technical Criteria recommend the use of detention basins followed by filtration or rapid infiltration to meet phosphorus reduction goals, where prudent. CDOT will use a combination of stormwater quality management BMPs, including detention and infiltration basins, to protect downstream water quality, channel stability, and property owners from adverse stormwater impacts. Selection of stormwater quality management BMPs will depend on local topography, drainage area size, available land, proximity to Waters of the US, and the final designs for the selected alternatives. CDOT may be required to purchase additional right-of-way to accommodate permanent mitigation measures (e.g., detention and infiltration facilities). Lastly, good road maintenance and cleaning and stabilization of roadside ditches will reduce pollutant loadings from these sources. Impacts to native vegetation have been minimized where possible. For example, along US 85 ROW take has been minimized along the entire alignment. Sideslope grades were adjusted, and guardrails and retaining walls were incorporated into the design. Construction BMPs in accordance with CDOT’s Erosion Control and Stormwater Quality Guide, 1995, and as directed by CDOT, will be implemented to minimize unavoidable impacts to native vegetation. These BMPs will include, but are not limited to, the following:
Shrubland, woodland, and riparian areas will be denoted on the construction plans. Impacted shrubs and trees will be replaced contingent upon water availability and ROW maintenance. In accordance with Clean Water Act Section 404 (b)(1) Guidelines, wetland mitigation is identified as avoidance, minimization, and compensatory mitigation. These guidelines stress the avoidance of adverse impacts to wetlands with the goal of no overall net loss of wetland functions. Consideration for avoidance and minimization of impact to wetlands will be given throughout the design and construction process. However, because avoidance is not possible across an entire alignment, mitigation includes minimizing or compensating unavoidable impacts. Design features such as alignment shifts and construction alternatives (e.g., retaining walls and steeper side slopes) were considered to avoid or minimize impacts to wetlands and Other Waters of the US. For example, impacts to wetlands may be minimized by using a steeper catch slope. Currently, the catch slope is at 4:1 (4 horizontal, 1 vertical). Where possible, this slope may be adjusted to a 2:1 with the addition of a guardrail. The avoidance of many of the non-jurisdictional wetlands in ditches is not possible due to their location adjacent to the roadways. Similarly, the avoidance of Other Waters of the US is not possible due to their crossing of the highways. Implementation of BMPs discussed in the Erosion Control and Stormwater Quality Guide, 1995, minimizes impacts to wetlands and Other Waters of the US. Specific measures to reduce erosion and maintain water quality will be identified by CDOT and include the following:
Impacts to Other Waters of the US will be mitigated through the restoration of the original topography. Compensatory wetland mitigation will occur at a ratio of 1:1 as close to the site of impact as possible. Water rights issues will be considered during the final selection of mitigation sites. Two methods of compensatory wetland mitigation are restoration of existing degraded wetlands and wetland creation. Wetland mitigation will occur within the riparian area adjacent to East Plum Creek in Castle Rock. Two potential additional wetland mitigation areas are Newlin Gulch located on I-25, and Spring Gulch located on US 85. These areas were chosen for their proximity to sites of impact and their favorable hydrological conditions for wetland creation. Due to channel incision along East Plum Creek, the water table is no longer connected to the adjacent floodplain. Wetland mitigation is complicated along East Plum Creek by the presence of the federally threatened Preble’s Meadow Jumping Mouse (PMJM). Wetland mitigation in this area will consist of a series of three 1.2-meter (4-foot) tall check dams. Currently, CDOT has committed to these three check dams. Additional dams may be constructed by CDOT in the future. These dams are designed to raise water levels in the surrounding floodplain thereby reconnecting hydrophytic vegetation with the water table. The check dams will be constructed of sheet piling and will extend into the adjacent floodplain terraces at, or just below, the ground surface to prevent failure of the check dams during flood events. Design features of the check dams include a low-flow notch and plunge pools just below each check dam, which are expected to improve aquatic habitat diversity along this reach of East Plum Creek. The three check dams will be located at the newly constructed 5th Street Bridge, just below where the Town of Castle Rock sewer line crosses the stream, and another at a midpoint between these two fixed points. In addition to wetland restoration, the check dam at the Town of Castle Rock sewer line will help to protect the pipe from breakage during high-flow events. The total amount of wetland mitigation area achieved will be determined through the monitoring of 18 shallow groundwater wells. Wetland restoration in this area will be accomplished through the re-establishment of wetland hydrology and will consist of soil saturation within the top 0.3 meter (12 inches) of the soil surface for 18 consecutive days during the growing season (12.5 percent of the growing season). Compensatory wetland mitigation may also occur at Newlin Gulch on I-25 and at Spring Gulch on US 85. Newlin Gulch was used for wetland mitigation for the Climbing Lanes Phase II Early-Action project. Opportunities for additional wetland mitigation exist there through the re-grading and expansion of existing wetland areas. Similarly, wetlands at Spring Gulch may be expanded by regrading existing sideslopes to permit saturation/inundation of adjacent areas. Although not required by USACE, non-jurisdictional wetlands (temporary impacts) will be mitigated in the newly created ditches when possible, adjacent to the site of impact, by broadcast seeding these areas with a wetland seed mix specified by CDOT. No geological impacts are anticipated as a result of the Preferred Alternative or the Other Alternative; therefore, mitigation is not required. Habitat fragmentation and barriers to connectivity among areas of high quality wildlife habitat (i.e., conservation areas) are the primary wildlife concern. Because I-25 already poses a substantial barrier to wildlife movement, and several conservation areas exist on both sides of the US 85 Corridor (see Chapter 4.0, Affected Environment), wildlife habitat along US 85 is a higher priority than it is along I-25. Therefore, compensatory mitigation for habitat conversion will be most effective, and should occur, within the US 85 Corridor. Mitigation for lost habitat and permeability among habitats will be coordinated with the CDOW and will include:
CDOT will coordinate with the CDOW, Douglas County Open Space, and the Chatfield Basin Conservation Network during the design phase of the wildlife crossing enhancements at Tracking Stations 1 and 3 (MP 195.2 and MP 189.7) in order to determine if any additional wildlife crossing enhancements are needed. Installing noise walls, retaining walls, jersey barriers, and curbs could create additional barriers to wildlife permeability. CDOT will consult with the CDOW, Douglas County Open Space, and the Chatfield Basin Conservation Network during design in areas of known wildlife movement. No wild and scenic rivers are within the I-25 Corridor and US 85 Corridor study area; therefore, mitigation is not required. All practical measures to minimize harm to floodplains are incorporated in the Preferred Alternative and the Other Alternative for both the I-25 Corridor and the US 85 Corridor. Little to no change to historic drainage patterns is expected within, or downgradient from, the area of potential effect (APE). Impacts to the floodplain are minimized by following standard stream crossing design criteria, avoiding direct impacts on stream channels, and adjusting the alignment where possible. Bridge and roadway designs seek to minimize impacts to floodplains in compliance with Federal Highway Administration (FHWA) requirements, including efforts to span 100-year floodplains. Final designs will adhere to CDOT drainage criteria for both minor and major hydraulic structures, as well as following all Federal Emergency Management Agency (FEMA) requirements. The Selected Alternative, which will be defined in the ROD, will also avoid the longitudinal and significant encroachment in the floodplains. Under the direction of CDOT, the implementation of BMPs identified in the Erosion Control and Stormwater Quality Guide, 1995, minimizes impacts to floodplains. Specific measures include the following:
7.3.9 Threatened, Endangered, and Other Special-Status Species Threatened, endangered, and other special-status species are especially sensitive to impacts due to their low population densities, or minimal amounts of suitable habitat remaining to them. The PMJM and black-tailed prairie dogs are two special-status species with habitat within the APE that will be directly impacted by the Preferred Alternative or Other Alternative. Mitigation of secondary impacts to aquatic habitat is described in Section 7.3.2, Water Quality. Impact to PMJM habitat has been avoided or minimized where possible. The I-25 Corridor is realigned 14 meters (46 feet) to the east between Ligget Road and Wolfensberger Road to avoid impacts to PMJM habitat. Impacts to PMJM habitat are also minimized by widening I-25 to the inside, adjusting sideslopes to 3:1 and 2:1 grades instead of the typical 4:1 grades used on transportation projects, by minimizing construction zones and access roads, by scheduling construction in these areas during the hibernation period (October 15 to April 30), and by not permitting night-time work. Compensatory mitigation for the PMJM habitat will include:
Due to channel incision along East Plum Creek, the water table in the adjacent floodplain has dropped dramatically over the past few years. PMJM habitat mitigation in this area will consist of a series of three 1.2-meter (4-foot) tall check dams. Currently, CDOT has committed to these three check dams. Additional dams may be constructed by CDOT in the future. The check dams are designed to reconnect the water table to the surrounding floodplain and riparian vegetation. The check dams will be constructed of sheet piling and will extend into the adjacent floodplain terraces at or just below the ground surface to prevent failure of the check dams during flood events. Design features of the check dams include a low flow notch and plunge pools just below each check dam, which are expected to improve aquatic habitat diversity along this reach of East Plum Creek. The three check dams will be located at the newly constructed 5th Street Bridge, just below where the Town of Castle Rock sewer line crosses the stream, and another at midpoint between these two fixed points. In addition to PMJM habitat enhancement, the check dam at the Town of Castle Rock sewer line will help protect the pipe from breakage during high-flow events. The Preble’s Meadow Jumping Mouse Biological Assessment for the South I-25 Corridor and US 85 Corridor Environmental Impact Statement, October 2000, contains more detailed information on PMJM mitigation. Impacts to black-tailed prairie dog colonies were reduced along US 85 by minimizing ROW take along the entire alignment; this involved adjusting sideslopes and incorporating guardrails and retaining walls into the design. Compensatory mitigation for black-tailed prairie dog habitat conversion might include:
Prior to construction, the USFWS and the CDOW will review the final mitigation measures for species under their respective jurisdictions. Final mitigation measures may include additional information on timing of construction activities, steeper sideslopes, or other means of reducing impacts. This section considers mitigation for Historic Resources impacted by the Preferred Alternative and the Other Alternative along the I-25 Corridor and the US 85 Corridor. D&RG Railroad (5DA921.1) The segment of the D&RG Railroad impacted by the project will be recorded prior to the beginning of construction on the I-25 Corridor, and prior to the demolition of the property so that there will be a permanent record of its present appearance in history. Recordation shall consist of Level II documentation as determined in consultation with the State Historic Preservation Officer (SHPO). All documentation must be accepted by the SHPO prior to the start of construction. Copies of documentation will be provided to the SHPO and to a local archive designated by the SHPO. Information will include historic research and documentation and archivally stable photographs of the property. Cherokee Ranch Historic District (5DA708) The historic gate and segment of Rattlesnake Road impacted by the project will be recorded prior to the beginning of construction on the US 85 Corridor, and prior to the demolition or displacement of the properties so that there will be a permanent historic record of their present appearance. Recordation shall consist of Level II documentation as determined in consultation with the SHPO. All documentation must be accepted by the SHPO prior to the start of construction. Copies of the documentation will be provided to the SHPO, the Cherokee Ranch and Castle Foundation, and to a local archive designated by the SHPO. Information will include historic research and documentation and archivally stable photographs of the property. Once the above-mentioned documentation is complete, the original Main Gate to Cherokee Ranch will be moved to a new location on Rattlesnake Road. The final location of the gate will be determined through consultation with the Cherokee Ranch and Castle Foundation Board of Directors, and the SHPO. 7.3.11 Section 4(f) Properties A discussion of mitigation measures for impacts to Section 4(f) properties is included in Chapter 6.0, Section 4(f) Properties Evaluation. These measures will be adopted by the FHWA with the completion of the South I-25 Corridor and US 85 Corridor ROD. 7.3.12 Archaeological Resources When a Selected Alternative alignment for the South I-25 Corridor and US 85 Corridor ROD is developed, the CDOT staff archaeologist will compare it to previously studied alternative alignments. If any inconsistencies occur between the previous alternative alignment and the Selected Alternative alignment to be constructed, on-the-ground reconnaissance will be conducted as necessary to document that the Selected Alternative alignment has been adequately evaluated and that no archaeological resources determined to be significant by the SHPO will be adversely affected. Should any evidence of archaeological resources be discovered during construction, work in that vicinity will be stopped until the CDOT staff archaeologist can completely evaluate the significance of the finding according to criteria established for the National Register of Historic Places. 7.3.13 Paleontological Resources Construction of the Preferred Alternative or Other Alternative may adversely affect, by burial, the presently known areal extent of fossil locality DMNS 1200, but all reasonable and prudent efforts will be made to avoid such adverse effects. Construction of the Preferred Alternative or Other Alternative will adversely affect, by construction excavation, previously unexamined, but potentially fossiliferous areas immediately lateral to and stratigraphically above the known areal extent of the locality. Prior to construction of the Preferred Alternative or Other Alternative, test excavation(s) will be conducted to determine, as accurately as possible, the horizontal and vertical extent of DMNS 1200 within the boundaries of the Preferred Alternative or Other Alternative. Test excavation(s) will also be conducted in CDOT rights-of-way in areas adjacent to the known lateral extent of DMNS 1200, but outside of the proposed impact area of the Preferred Alternative and Other Alternative, in an effort to designate an alternate location(s) for continued future scientific study of the DMNS 1200 paleoflora. Adverse effects to those portions of the site that will be destroyed by construction excavation proposed as part of the Preferred Alternative and Other Alternative will be mitigated by salvage excavation prior to construction of the Preferred Alternative or Other Alternative. Construction of the Preferred Alternative and Other Alternative will adversely affect fossil locality UCM 92164. Adverse effects will be mitigated by salvage excavation of a statistically valid representative sample of the preserved paleoflora prior to construction of the Preferred Alternative or Other Alternative. Once design plans for any and all future construction projects permitted by the approval of this EIS are finalized, the CDOT staff paleontologist will examine them to estimate the required scope of construction monitoring work, if any. A special note requiring a paleontological monitor during construction (similar to those attached to the standard specifications for past projects requiring paleontological monitoring during construction) will be attached to the specifications for any future construction project(s) permitted by the approval of this EIS for which final design plans indicate the likelihood of affect to Denver Formation subsurface outcrop. If any paleontological resources are uncovered along the alignment corridor during construction, work in the immediate vicinity will cease. The CDOT staff paleontologist will be notified, and the material will be evaluated by a qualified paleontologist and coordinated with the SHPO. 7.3.14 Prime and Unique Farmland Prime and unique farmland does not exist within the APE. Statewide important farmland soil does exist. By minimizing sideslope grades, impacts to these areas of High Potential Dry Cropland along US 85 have been minimized by the Preferred Alternative and the Other Alternative. Increased farmland fragmentation along US 85 will be avoided by maintaining existing underpasses used by farm machinery. The prevention and elimination of noxious weeds is discussed in Section 7.3.3, Vegetation. Noise abatement in the form of noise walls and earthen berms was evaluated along the I-25 Corridor and US 85 Corridor. Section 5.3.3.14, Noise Impacts presents the mitigation types, locations, and effectiveness for the receivers at or approaching the noise level abatement criteria (66 dBA for residences and 71 dBA for commercial businesses). One noise barrier is recommended and will be re-evaluated during final design. In addition to the effort to minimize roadway width, other measures will be taken to offset potential impacts and potentially enhance the visual quality of the corridor. Landscaping treatments using native grasses and slope flattening will be included in the plans. The roadway is designed to blend with the natural setting, conforming to the line and form of the adjacent terrain and natural setting. Further evaluation of potential hazardous waste sites will continue prior to property acquisition (once a Selected Alternative is selected) and during preliminary highway design. The Selected Alternative will avoid potentially contaminated areas whenever practical. However, where avoidance is not feasible, further site investigation will be required and will be coordinated with the affected property owner. Necessary cleanup plans are coordinated with appropriate agencies and landowners. The inclusion of environmental specifications in the construction bid package will address worker health and safety during construction and contractor requirements. No energy impacts are anticipated as a result of the Preferred Alternative or the Other Alternative; therefore, mitigation is not required. The following measures are recommended to mitigate temporary construction impacts:
The potential indirect disruptive, or quality-of-life, impacts that may occur over the long term have been, or will be, considered during the zoning and comprehensive planning process of the local jurisdictions. As these projects come closer to being finalized, the county and communities will have additional opportunities to address specific quality-of-life concerns in the zoning process and site plan review. Cumulative impacts are impacts on the environment resulting from the incremental impact of a project when added to other past, present, and reasonably foreseeable future actions (regardless of responsible agency or person). Habitat restoration for the PMJM, as a result of non-project actions (other projects or cumulative actions), is mitigated by constructing check dams. The check dams will be installed on East Plum Creek. Other habitat restoration in Sellers Gulch, and a former upland grassland along East Plum Creek, are also under consideration as mitigation sites. It is anticipated that the check dams will promote the riparian vegetation that serves as PMJM habitat that has been degraded due to previous projects and could be further intensified by the proposed improvements. CDOT-implemented mitigation measures will prevent the proposed projects from further contributing to the cumulative degradation of water quality in the Chatfield and Cherry Creek basins, reducing the potential cumulative impact. Proper implementation of construction BMPs and adherence to all applicable regulations will minimize impacts to water quality during the construction phase of the proposed projects. Cross culverts and other drainage structures will be appropriately sized to maintain hydrologic connections across the project corridors. Stormwater detention basins will improve water quality and maintain stormwater runoff to historic levels. Particulates and other contaminants will settle in stormwater detention basins. The state will continue to work with local agencies that can influence growth and promote the benefits of controls that incorporate environmental protection into all planned development. |