7.3 Site Planning Conditions

7.4.1 Natural Conditions

7.4.1.1 Topography

accomodate natural conditions

The natural terrain is a major determinant of the layout and form of the installation. The following guidelines should be used to maintain the natural topography of the installation. Fort Carson is located in relatively flat, semi-arid country on the eastern slope of the Rocky Mountains. Immediately to the west, the Front Range rises abruptly - providing a sharp contrast to the gently undulating high plains to the east. Because of this transitional location, the landform character is a mix of high plains and foothills terrain, broken by broad, gently sloping valleys.

Immediately east of the Cantonment Area are a series of low hills, which screen the post from view by motorists on Interstate Highway 25. There are a number of other areas that take advantage of the screening and visual variety provided by the gently rolling terrain.
Pinon Canyon Maneuver Site supports a diverse ecosystem with large numbers of big and small game, fisheries, non-game wildlife, forest, rangeland, and mineral resources. It is bounded on the east by the dramatic topography of the Purgatoire River Canyon, a 100-meter (328 foot) deep scenic red canyon with flowing streams, sandstone formations, and exposed geologic processes.

7.4.1.2 Preservation and Existing Topography

preserve natural topography

The following is a list of site planning design criteria pertaining to the development and preservation of the existing topography and natural conditions at Fort Carson.

Maintain natural ground slopes and elevations. The main Cantonment Area occupies a valley running from the northern boundary of the installation stretching for four miles, terminating near Fountain Creek on the east. This main developed area, the "banana belt" in particular, was directly influenced by the landform.

Align roadways and buildings along topographic lines. The curvilinear layout of the street grid "banana belt" was developed to fit within the natural flat area of the valley. This variable topography encourages lower density development and takes advantage of natural subdivisions provided by the foothills.

Locate facilities that have expansive ground coverage on relatively flat terrain.

Use moderately sloping areas for buildings with less ground coverage area.

Avoid development on steep slopes.

Avoid development in natural drainage ways and flood plains.

Provide a reasonable balance of cut and fill.

7.4.1.3 Hydrology and Stormwater Management

Fort Carson is faced with the responsibility of managing and protecting the natural resources of large parcels of land reserved for many different functions. Land uses can be intensive and can pose a variety of challenges for managing stormwater runoff. Additionally, the Clean Water Act (CWA) prohibits the discharge of any pollutant to waters of the United States from point sources, unless the discharge is authorized by a National Pollutant Discharge Elimination System (NPDES) permit. Facilities that discharge stormwater from certain activities (including industrial activities, construction activities, and municipal stormwater collection systems) require NPDES permits. These facilities must implement commonly accepted stormwater discharge management controls, often referred to as best management practices (BMPs), to effectively reduce or prevent the discharge of pollutants into receiving waters.

Historically, conventional stormwater conveyance systems were designed to collect, convey, and discharge runoff as efficiently as possible. The intent is to create a highly efficient drainage system, which will prevent on lot flooding, promote good drainage, and quickly convey runoff to a BMP or stream. This runoff control system decreases groundwater recharge, increases runoff volume, and changes the timing, frequency, and rate of discharge. These changes can cause flooding, water quality degradation, stream erosion, and the need to construct end of pipe BMPs. This approach only controls the rate of runoff allowing significant increases in runoff volume, frequency, and duration of runoff from the predevelopment conditions and provides the mechanisms for further degradation of receiving waters, (EPA 2000).

Conventional stormwater management practices also focus on providing an efficient site drainage system that rapidly conveys runoff away from buildings and off pavement, and may attenuate the peak runoff rate at a large stormwater management facility (e.g., detention pond) downstream. In contrast, an alternative, sustainable approach, Low Impact Development (LID), provides runoff management as far upstream as possible – where it originates – and if necessary, also at multiple points along each flow path. The LID methods for storm water management at Fort Carson are documents in Unified Facilities Criteria 3-210-10.

Stormwater management efforts at Fort Carson will have a higher value when the design objectives involve, not only the control of runoff at the drainage area outlet, but also on-site water conservation, strategic conveyance of runoff, pollution prevention, stormwater treatment, and habitat preservation. However, installation staff and designers will face several significant challenges when pursuing these objectives while simultaneously considering mission, environmental, facility, and budgetary goals. In many instances, strategies such as LID will benefit several of these goals at the same time.

Retrofitting existing sites should also include consideration and evaluation of LID techniques. The source control or micro-scale approach of LID methods will generally require less site disturbance. Locating sites to install small devices will generally be easier than finding larger sites for conventional stormwater management facilities. LID retrofits can also be customized to pollutant loads, allowing more control over pollutant removal.

The Environmental Protection Agency (EPA) is the regulatory agency with primacy for permitting stormwater discharges from federal facilities in Colorado. Discharge of stormwater at Fort Carson is authorized by the EPA under three separate National Pollution Discharge Elimination System (NPDES) permits 1) a Municipal Separate Storm Sewer System Permit (MS4) that functions as the overarching permit for stormwater discharge to surface waters and which includes requirements for post construction stormwater management, 2) a Multi-Sector General Permit (MSGP) for runoff associated with specific industrial operations, and 3) a Construction General Permit (CGP) for stormwater discharges from construction and redevelopment sites. The respective regulatory bases for the three permits are: 40 CFR 122.26, Federal Register, volume 65, No. 210, Monday, October 30, 2000 (new Region 8 regulations pending publications), and 40 CFR 122.26(b)(14)(x), 40 CFR 122.26(b)(15). Installation staff, tenants, activities, contracting officers, and contractors are responsible for compliance with the requirements specified in these regulations and Fort Carson’s Stormwater Management permits, as iterated through the Fort Carson Garrison Command Policy #XXX. See Appendix B 5.17 Water Quality Management Program for Permit information.

Additionally, to meet requirements under both the MS4 and CGP, a Post-Construction Stormwater Management Outline must be prepared for any construction projects that are covered under the CGP. This outline will need to incorporate permanent best management practices (PBMPs) that address stormwater runoff after the construction project is complete. The main objective of the plan is to minimize post-construction water quality damage and damage to public and private lands. PBMPs will need to be designed for a 2-year 24-hour storm in order to significantly maintain the predevelopment runoff volume and flow rate. The Urban Drainage Criteria Manual by the Urban Drainage and Flood Control District (UDFCD), the Colorado Springs Drainage Criteria Manual (Version 2) and the Low Impact Development (LID) manual by Unified Facilities Criteria should be consulted for additional guidance as needed. All of these documents are located on the above referenced SEMS website. Consideration of water quality and use of LID structures is recommended during this screening process. All outlines will need to be coordinated with and approved by Fort Carson prior to implementation. The Fort Carson Stormwater Program will assist with modeling capabilities, as needed.

7.4.1.4 Climate

sun angles

Fort Carson is located in a temperate, mid-latitude, semi-arid climate. Design and site development to balance the effects of seasonal thermal variations promoting both winter warming and summer cooling in terms of seasonal solar orientation and prevailing winds. The following list of design considerations should be considered when developing the site layout in response to the climate.

Entries should not be located on the northern façade of the building. Entries should be located so that they are protected from the prevailing winds and weather.

Buildings should be sited with the longest façade oriented north/south to increase potential daylighting and solar load control.

Sun shading devices should be utilized on southeast and west facing windows. Sun shading shall be appropriately sized, shaped, and located to control unwanted direct sunlight.

Locate outdoor living and plaza areas on south and west facing sides of buildings. The buildings will protect these areas from winds and weather. Shading on the south windows can be accomplished with overhangs. Minimize the number of east and west windows if possible.

Deciduous trees can be utilized to block unwanted summer sun while letting the sun in during the winter months.

See Appendix D for further discussion on sustainable building design and its relationship to the climate.

7.4.1.5 Views and Vistas

take advantage of views and vistas

Care must be taken, with further development and construction on the installation, to preserve and enhance scenic views and vistas, and to screen those that are less desirable. Because of Fort Carson’s unique location at the foot of the Rocky Mountains, the installation has wonderful opportunities for optimizing the views and vistas toward the mountains, specifically Cheyenne Mountain. The naturally open landscape allows unobstructed panoramic views, sometimes providing vistas for several miles from prominent high points. The open grasslands also act as a visual unifier, an expression of openness, and a counterpoint to the dramatic impact of the mountains to the west. Visual extensions through open spaces provide a sense of orientation, relief, and enjoyment. Consider the layout and design of future buildings to maximize these views for those using the facility. The uninterrupted view towards the mountains from the plaza outside the entrance to the Headquarters Building is a great example of what can be achieved through proper site design.

7.4.1.6 Vegetation

Further development on the installation will be designed to protect and preserve existing native vegetation. This preservation reduces maintenance and enhances sustainability. A preferred plant matrix (Plant Matrix) is included in this Installation Design Guide. (Also see Section 10 – Landscape Design Component).

Proper plant selection is key to the success of the visual landscape at Fort Carson. Plants should be selected for their ability to grow in the region under the current site conditions.

Landscaping has been used effectively as an overall visual unifier across the installation, particularly through the consistent use of turf grasses, rock mulches, and evergreen trees. The one area of improvement around existing facilities that can make the most visible impact is the enhancement of the landscaping.

7.4.1.7 Floodplains

Floodplains perform important natural functions, including temporary storage of floodwaters, moderation of peak flows, maintenance of water quality, groundwater recharge, and prevention of erosion. Floodplains also provide habitat for wildlife, recreational and training opportunities, and aesthetic benefits. These characteristics of floodplains and associated wetlands should be preserved and enhanced.

Avoiding development in floodplains will help retain the natural functions of the floodplain and associated wetlands. Retaining natural floodplain functions will allow creeks and streams to flood without threatening health and safety and will reduce damage to facilities and training resources. In all cases, disconnection of a creek or stream from its natural floodplain should be avoided and, if needed, the connection restored to ensure the floodplain’s natural function. Restoration and protection efforts should focus on those floodplains or portions of floodplains identified as having the greatest flood risks and significant natural and beneficial functions. Encourage natural, non-structural solutions to reducing flood damages.