3.0 Site Information

Transcription

1 3.0 Site Information

2 3.0 SITE INFORMATION 3.1 Local Conditions Market Conditions: In Washington D.C. there is a constant flood of construction making the market for building exceptional. The Concrete International Journal describes Washington DC as recession proof due to the number of businesses with interests related to the government that are located there. Although, not all buildings in Washington DC are concrete, it is the preferred method of construction. In 1899 a height restriction was enacted by Congress stating that no private structure can extend higher than the monument or capital building. Again in 1910 a bill was passed limiting the height of buildings in the business district to 130 ft. These height restrictions make concrete the material of choice in order to optimize floor area. Existing Site Conditions: The site is located on the corner of Massachusetts Avenue and Nebraska Ave. in Northwest Previously, the site was occupied by an indoor swimming pool, a two-story metal building, and one-story masonry block building. At that point in time the existing grades were EL 397 at the south part of the site and EL 385 at the north. The east portion of the site was an access and parking area at EL 396 EL 398. Boring Samples and Soil Classification Subsurface conditions were evaluated by using existing soil information from borings drilled in 1990 for the Washington College of Law on campus. In January of 2002 two additional borings were drilled. Boring locations can be found in Appendix B: Boring Plan. Boring Samples B-16 and B-17 are the two most recent samples. Test borings were completed using a 2-1/4 inch hollow stem auger. Standard penetration test were performed with a split sampling spoon driven with a 140 lb hammer, falling 30 inches. An initial six inches were penetrated to make sure the soil being tested is undisturbed and then the number of blows to get down 12 inches was recorded to determine inplace density of cohesionless soils. After the samples were recovered they were visually classified. Table 1 summarizes the boring sample results. 9

3 Table 1: Boring Sample Results Boring Number Boring Boring Boring Refusal Elevation Refusal Depth Elevation (ft.) (ft.) (ft.) Estimated Elevation where rock excavation methods will be required B N/A B N/A B N/A B-4R N/A B N/A B B-7R B B B B B B B B B B Soils encountered on site during test borings are classified as follows: Stratum A: Brown sandy silt sand FILL, silty sand FILL, clayey sand FILL, will asphalt, concrete, quartz, and gravel Below ground surface and pavement to 2.0 to 12.5 feet depth Stratum B: Brown clayey SAND (SC) and poorly graded SAND with clay and gravel (SC-SC) Below pavement and Stratum A to 6.0 to 20.0 feet depth Stratum C: Brown and reddish brown sandy LEAN CLAY (CL ) and LEAN CLAY (CL), with sand; stiff consistency Below the ground surface and Stratum B to 3.5 to 17.0 feet depth 10

4 Stratum D: Yellowish brown, brown, and grayish white silty SAND (SM) and sandy SILT (ML), with lean clay layer; loose to compact density Below Strata A, B, and C to 13.0 to 34.0 feet depth Stratum E: Brown and gray silty SAND (SM), sandy SILT (ML) and LEAN CLAY (CL), with sand and quartz; loose to very compact density Below ground surface and Strata A, C, and D to 5.0 to 49.5 feet depth Stratum F: Grayish white and yellowish brown DISINTEGRATED ROCK; very compact density Below Strata D and E to 38.1 to 59.7 feet depth Ground water was encountered at EL to EL 378. EL 378 is 28 feet above the lowest floor level at EL Site Layout Planning Construction Site Plan: The construction site plan identifies the location of all temporary facilities that are required on site in order for construction to occur. This includes site trailers, parking, access roads, and fences to name a few. A chain link fence surrounds the building at the construction limits and is locked nightly to prevent people from getting on site outside of working hours. There are three entrances/exits on site that are used for construction traffic. The first is located off Massachusetts Avenue where the future entrance to the parking deck will be. The second is further west on Massachusetts Avenue and the third is off of Nebraska Avenue near Nebraska Hall. Construction traffic utilizes these entrances and a temporary road that was set up around the perimeter of the building footprint; within the limits of construction. The temporary road is extended towards the west side of the site to mimic what will be the buildings loading dock following construction. All Holder Construction staff and both the mechanical and electrical subcontractors park across the street from the construction site on Massachusetts Avenue in an existing parking lot that belongs to the main campus. The mechanical and electrical subcontractors and Holder Construction also have their trailers in this area. The remaining subcontractors park on the other side of Ward Circle in a parking lot that is owned by American University. Construction of the Katzen Arts Center does not hinder normal traffic patterns. All regular traffic patterns exist with the exception of an additional stop due to a new traffic signal at the entrance to the parking deck on Massachusetts Avenue. Pedestrian traffic is closed off along the construction side of Massachusetts Avenue. 11

5 Excavation Site Plan: Excavation began in component C and then went to B, A, and D, respectively. Three excavators and a number of dump trucks were used to remove the 122,000 cubic yards of fill off of the site. Two ramps were constructed within the footprint in order to allow the machinery in/out of the excavation area at ease. The first ramp was located in component B and the second in component D/A as indicated on the site plan. The temporary road, as described above, was used as a loading area for the dump trucks. Once the dump trucks were loaded, they immediately exited the site using the nearest of the three exits. Little fill was required on, so all fill was taken from component D and transferred to the required location. By directly transferring the soil to the backfill location Holder Construction eliminated the need for fill storage on site. Structural Site Plan: Construction began on the structure in the same pattern as excavation; C, B, A, and D respectively. Three cranes were set up along the south side of the building and were positioned such that one of the three could reach within the building footprint, but so none could swing over the nearby residential property. The two cranes to the west have a swing of 143 and the third 200. The cranes were used for picking buckets of concrete off of trucks, hoisting the bucket within the site, and for placing the cast-in place concrete. Concrete trucks entered/exited the site at the nearest of the three gates, depending on where construction was occurring. A portion of the site, near the new location for the loading dock was accumulated for layout of rebar, embeds, etc. Exterior Enclosure Site Plan: Exterior enclosure materials were delivered to the site only shortly before enclosure began. The CMU, limestone veneer and precast were place around the perimeter of the building area that was being worked on at the particular time. Two hoists were used for building exterior locations that could not be reached from the ground. In addition, the cranes remained during the enclosure phase for pieces of precast veneer that were too heavy for a man and hoist. Construction of the exterior enclosure followed the same path as both excavation and structure. Finishes Site Plan: During the finish phase of the project the three cranes were deconstructed. As finishes arrived on site, a storage room was dedicated to a type of material (doors, hardware, etc.) in Parking Level one and the areas were locked to prevent damage/theft. The building finishes were completed from component C, B, A, and D, respectively. To review in further detail, please see Appendix C for figures of the Site Layout Plans. 12