facilities renewal master plan - National Zoo - Smithsonian Institution

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FACILITIES MASTER PLAN ENVIRONMENTAL ASSESSMENT At the end of each section when applicable, SI provides information on mitigation measures that would be employed to help avoid, minimize, or mitigate an adverse impact on a given resource. A. Natural and Biological Resources A.1 Soils, Geology, and Topography The soils of the National Zoo are classified as urban land soils, which are soils that have been previously excavated and filled with other soil materials. Some of the site soils have been historically disturbed for construction, and covered with impervious materials such as asphalt, concrete, and building materials. In steeply sloped areas of the site, soils may be mixed with bluestone for stabilization. In other areas, extensive fill may have been used to create level surface areas for construction of structures. Therefore, the depth to undisturbed soils on the site varies; the natural soils overlie bedrock at depths of 12 to 15 feet below the natural soil surface. The source of historical fill material has not been documented in most instances; however, previous excavations in fill materials at the National Zoo have not detected any signs of contamination. The National Zoo lies within the physiographic province of the Eastern Piedmont Region. The underlying rocks in this province consist primarily of granite, gneiess and schist. The depth to bedrock on the site is approximately 12 to 15 feet below the natural soil surface (USGS, 2008). The topography of the National Zoo consists of a moderate to steeply sloping basin descending eastward from the Connecticut Avenue entrance, at approximately 210 feet in elevation to mean sea level, to the eastern boundary at Rock Creek, at approximately 55 feet in elevation. The natural topography of the site has been modified over time by the introduction of fill material to create level surfaces areas for built structures. One unique aspect of the topography on site is that Olmsted’s design utilized the natural ridge line affecting the placement of many of the exhibits and circulation. Impacts to Soils, Topography, and Geology No-Action Alternative Additional exhibit planning outside of the on-going Elephant Trails project would continue on a site-by-site basis without the availability of large land tracts, preferable for new exhibits. Other small scale site improvements would continue for site improvements, building rehabilitation, and facilities updates related to safety, health, and maintenance. The impacts to soils, topography, and geology from exhibit renewal and other improvements would be localized to small areas. With erosion and sediment control measures to minimize soil runoff and loss, impacts to soils would be minor and shortterm. There would be no impact to topography or geology because construction activities such as surface grading, drilling, pile driving, etc. would not occur; therefore, there would be no change to existing topography or geology. SMITHSONIAN INSTITUTION – NATIONAL ZOOLOGICAL PARK 40 | P a g e
FACILITIES MASTER PLAN ENVIRONMENTAL ASSESSMENT Alternative A Under Alternative A, facilities improvements would result in construction activities requiring land disturbance that would alter topography and disturb soils, including the construction or renovation of facilities and exhibit areas. Construction would occur mostly within previously disturbed and developed areas of the National Zoo. Impacts associated with each activity would include minor and localized soil loss during construction. Some activities would require fill or excavation that would have minor changes to the topography. Negligible impacts to geology are anticipated, however further investigation would be needed prior to constructing the proposed underground parking structure. Activities effecting soils, topography, and geology under Alternative A include: Reclamation of Parking Lots A, B and the Bus Lot for the creation of new large multi-species exhibit areas and ; New Beaver Valley exhibits and walkways; Revitalization/expansion of visitor entrances at Connecticut Avenue, Midpoint entry, and Harvard Street Bridge/Beach Drive; New above ground parking structure at current Parking Lot C site, Two-story underground parking structure near the Connecticut Avenue entry; Addition of two new traffic circles on North Road; Construction of an aerial tram system; The construction of a new administrative, support and operations hub near the Parking Lot C site; and Additions to research buildings near the hospital, and a new greenhouse. Parking Lots A, B and the Bus Lot would be reclaimed and older exhibits and flat land areas would be revitalized. Land clearing and grading would be required to construct five new large multi-species habitat and exhibit areas throughout the park to enhance animal exhibits and visitor experience. It should be noted that collection planning for animal exhibits at the National Zoo is a separate process from the master planning process. In order to provide flexibility for exhibit renewal to keep pace with the latest knowledge of animal health and well-being, the exact designs and uses of these new exhibits is unknown at this time. The reclamation of Parking Lots A, B and the Bus Lot, and revitalization of older exhibits and flat land areas would cause land disturbance, minor soil erosion, and alteration of existing topography. The new Beaver Valley exhibits and walkways would be designed to separate park service from visitor circulation through a series of bridges, structures, lifts, and ramps. Minor soil loss would occur due to land disturbance activities. The Beaver Valley walkways would be designed to work within the existing landscape contours, and therefore would have negligible impacts to topography and geology. Although construction would occur within previously disturbed areas, the creation of new animal exhibits would also have minor adverse impacts to soils, geology, or topography due to activities such as site clearing, excavation, grading, and fill. SMITHSONIAN INSTITUTION – NATIONAL ZOOLOGICAL PARK 41 | P a g e
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