Presented at USSD Conference April 20-24, 2009, Nashville, TN HIDING IN PLAIN SIGHT USING THE NATURAL LANDSCAPE AS A VISUAL BARRIER ABSTRACT

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1 HIDING IN PLAIN SIGHT USING THE NATURAL LANDSCAPE AS A VISUAL BARRIER 1 Andrew Aceves, P.G., Paul C. Rizzo Associates, Inc. 2 Melissa L. Dubinsky, Ph.D, Paul C. Rizzo Associates, Inc. 3 Craig Giesmann, P.E., AmerenUE ABSTRACT This paper presents a demonstration of the use of the visual horizon concept in the planning and execution of a large civil engineering project in a visually sensitive area. The execution of large civil engineering projects are often constrained by environmental factors such as wetlands, forested areas, and areas of pristine visual beauty. For this major dam construction project located on the top of a mountain, the visual impact of construction activities was mitigated using an adapted version of the landscape architecture principal of visual horizon called a shadow-line survey. INTRODUCTION Paul C. Rizzo Associates, Inc. (RIZZO) was contracted to provide design and construction management services for the rebuild of the Taum Sauk Pumped Storage Facility Upper Reservoir. The Upper Reservoir rises 100 feet above the top of Proffit Mountain in Annapolis, Missouri. It covers essentially the entire top of the mountain. At the foot of the mountain s western flank is the historic and unique Johnson Shut-Ins State Park. Following a catastrophic failure of the Upper Reservoir in December 2005 that significantly affected the Park, plans were developed for the reconstruction of both the Upper Reservoir and the Park. In the 45 years since the Upper Reservoir was originally constructed, much has changed in the way of environmental awareness and permitting requirements. Construction plans of federally-permitted hydropower projects are scrutinized by the Federal Energy and Regulatory Commission (FERC) not only for safety and engineering concerns, but also to assess impact on the environment, including aesthetic impacts. Johnson Shut-Ins provides beautiful vistas of the Ozark Mountains, and draws thousands of tourists every year. The area also offers hiking opportunities along the Ozark Trail, which passes within 3 miles of the north end of the Upper Reservoir. 1 Environmental Compliance Manager, Taum Sauk Rebuild Project, Paul C. Rizzo Associates, Inc. Taum Sauk Plant, Route 1, Box 108, Annapolis, MO 63620, andrew.aceves@rizzoassoc.com 2 Managing Principal, Environmental Programs, Paul C. Rizzo Associates, Inc., Expo Mart-Suite 270E, 105 Mall Blvd., Monroeville, PA 15146, melissa.dubinsky@rizzoassoc.com 3 Managing Supervisor, Hydro Engineering, AmerenUE, 3700 South Lindbergh, Sunset Hills, MO , cgiesmann@ameren.com

2 The construction plans called for maximal use of the available level area surrounding the Upper Reservoir for equipment staging and laydown areas. Site preparation required removal of existing forest cover. The possibility of unsightly concrete plants, temporary buildings and heavy equipment intruding on the vista enjoyed by hikers were of such a concern that various agency stakeholders initially opposed development of a critical construction staging area along the west side of the Reservoir. Using a three-dimensional modeling technique called a shadow-line survey, the lines of view from the Shut-Ins towards the construction staging area were calculated and plotted by RIZZO, and a grading plan was developed that preserved the scenic view, undisturbed, and provided for a 13-acre staging area that could accommodate items up to 75 feet high; completely unseen from the Shut Ins or the Ozark Trail. This grading plan was approved by the FERC and implemented in late 2007, and the staging area is currently being used as a critical component of construction without impacting the scenic view from the Shut-Ins. Shadow-line survey techniques developed for this project provided a solution that both served the needs of construction and preserved the scenic beauty of the area for the surrounding community. VISUAL HORIZON In the field of landscape architecture, it is common to assess the visual impact of constructed structures in certain areas. Buildings, roads and clearings are sited such that they cause the least amount of objectionable visual impact. This relationship is reciprocal. The views from both the structure and the landscape must be considered. To the landscape architect, a properly sited project is designed to fit aesthetically into the landscape. In the civil construction field, however, it is often the case that we must build in certain areas. It is our task to design the project in a manner that meets the engineering objectives and protects the physical and aesthetic environment while being constructible within siting constraints. To this end we seek to minimize the visual impact of the project by carefully assessing the visual aspects of the natural environment and to use these aspects as much as possible to our best advantage. It is in this respect that what we are doing is different from classical landscape architecture. Definition Visual Horizon is the apparent or visual junction between the earth and sky as viewed from any specific position. In our use, it is the line from the eye of the viewer that touches tangentially the ground or vegetated surface. In this paper, we use the term True Horizon to refer to the line of sight that is tangential to the ground surface, and Visual Horizon to refer to the line of sight tangent to vegetation. Figure 1 illustrates this relationship.

3 The relationship between the eye of the viewer and the earth/sky junction is important because it is dependent not only on the relative slope between the points, but also the rate of change of the slope. Use of Visual Vs True Horizon Figure 1. Visual vs. True Horizon The decision of which horizon to use depends on the required degree of concealment, the type of vegetation, and seasonal variations in vegetation. The true horizon offers a more conservative approach and negates the additional concealment value of vegetation. If absolute concealment is required or if vegetative cover is seasonal or thin, true horizon is the necessary choice. For most applications, visual horizon is adequate. From a distance, even deciduous trees in winter can provide effective screening. In some instances, visual horizon may be augmented by the selection of natural colors for structures to aid camouflage, or by planting additional vegetation to reinforce the visual barrier. SITE EVALUATION The Shadow-Line Survey technique begins with the careful evaluation of the natural site and the project requirements.

4 The first step requires a complete geographic inventory of observation points. The inventory should take into account not only the position of the viewer, but in what season(s) the viewer is likely to be present and what they will be viewing. In some cases the viewscape will be clear and quantifiable. But in many cases, this is a highly subjective step, involving questions of relative beauty and aesthetic worth. Public comments received during the project permitting process or from tourism operators, natural resources and parks agencies, and local conservation clubs are all good resources in determining what views are required to be protected. However, some construction constraints may be present that require a balancing between viewscape protection and constructability. These issues may require negotiation with the authorized permitting agenc(ies). Following the geographic inventory, the next step is to assess the general project requirements. It is important to differentiate between items of the project that are flexible and those that are fixed. For both fixed and flexible items, clearing, grading, and structure height are noted on a plan drawing. These are the items that feed the model in the Shadow-Line Survey Technique. THE SHADOW-LINE SURVEY The Shadow-Line Survey consists of a series of rays, drawn from eye height (about 65 inches above grade) starting at each geographic inventory point to the nearest visual horizon along multiple directions across the site. This set of intersecting and radiating lines forms a ceiling over the project boundaries wherein any object below the ceiling is not visible from the points called out in the geographic inventory. The area between the graded land surface and the ceiling is called the shadow, hence the name, Shadow-Line Survey. It is by careful exploitation of this shadow area to stage construction equipment that the project can be executed with minimal visual impact. Not all visual impact is treated the same. By first using points of view in the geographic inventory to establish the shadow, the planner seeks to protect the most valuable views ahead of general views. This is the essence of the Shadow-Line technique: the preferential protection of desirable aesthetic views while executing a large civil construction project. Overview TAUM SAUK REBUILD The Taum Sauk Pumped Storage Facility, near Annapolis, Missouri, is situated between large sections of the Mark Twain National Forest, and is immediately east of the Johnson Shut-Ins State Park (Park). The original upper reservoir, constructed from rock fill in

5 1963, failed catastrophically on December 14, It is currently being rebuilt as a roller compacted concrete structure. The rebuilding process is equipment intensive. A full aggregate processing facility as well as four concrete batch plants and associated heavy equipment, have been moved onto the site for the duration of the project. To safely and economically construct the reservoir in this constrained area, substantial areas needed to be cleared and graded, including Laydown Area 3, shown in Figure 2. Laydown Area 3 is on a ridge overlooking the Park, and in the initial permitting process, the FERC and the Missouri Department of Natural Resources (MDNR) had concerns regarding the clearing and subsequent use of this area due to the visual impact such action would have on the view from the Shut Ins and the Ozark Trail. To address this concern, RIZZO conducted a Shadow-Line Survey to determine if it would be possible to utilize Laydown Area 3 without impacting the viewscape. Figure 2. Plan View of the Relationship between Geographic Inventory Points and Laydown Area 3. Geographic Inventory The geographic inventory included four points: Point One is the camping area at the Park. Points Two, Three and Four are points along the Ozark Trail where positioning of valleys

6 and ridges allow the best opportunities to view the site. These sites were ground truthed by a geologist equipped with a Global Positioning System (GPS) unit who hiked along the Ozark Trail 14 miles from Taum Sauk State Park in the east to Johnson Shut-Ins State Park. The proposed laydown area was 13.2 acres, with an elevation of 1479 feet above sea level at the plan center. This laydown area is surrounded by a dense mixed forest of oak, pine and hickory trees with an approximate canopy height of 50 feet above ground level. Shadow Line Survey Using Digital Terrain Model (DTM) data from a recent survey fly-over, a topographic map was generated that encompassed the Trail, the Park and the laydown area. From each observation point, a cross section was generated and a line of site was plotted to determine the true horizon. Figure 3 shows the cross-section from Observation Point 1 at the Park. Upon completing this first step, it became apparent that the natural ground contours from the Park provided a significant shadow zone using the more conservative technique of true horizon. Therefore, it was possible to develop the grading plan on true horizon, thus eliminating the need to depend on foliage for visual screening. Figure 3. Cross Section from Observation Point 1 to Laydown Area 3. Observations from the Ozark Trail resulted in similar results. Based on the surveyed true horizon, the laydown area would have been visible from Observation Point 4 on the Ozark Trail. However, field observations from ground truthing demonstrated that the dense vegetation (even during the winter) at Observation Point 4 blocked all line of site to the target. Using these results, a grading plan was developed that allowed the laydown area to be graded to 1465 feet. The result was a shadow zone, based on true horizon, that would conceal any clearing or building activity ranging from a maximum of 30 feet tall at the west end to a maximum of 68 feet at the east end of the laydown area. In the laydown

7 area itself, a land use was pursued such that all structures would fit into the planned shadow zone. CONCLUSIONS The use of the Shadow Line Survey resolved the concerns of the various agency stakeholders, and subsequently, the FERC and the MDNR approved the development and use of Laydown Area 3. At the conclusion of construction, it will be required to implement a reforestation plan for this cleared area. The Laydown Area is now developed and in use, and a second ground truthing obtained during a hike from Taum Sauk State Park to Johnson Shut-Ins State Park demonstrated that the laydown area is indeed invisible from the Trail and the Park. The Shadow Line Survey technique, a modified use of the landscape architecture principle of Visual Horizon, can be useful in civil construction planning as a method of preserving valuable viewscapes. In an increasingly restrictive regulatory environment that values scenic beauty as well as physical assets, Shadow Line Survey will be a useful resource in the planner s tool box.