Evaluating a Large Number of Station and Alignment Alternatives
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TRANSPORTATION RESEARCH RECORD 1266 229 Evaluating a Large Number of Station and Alignment Alternatives SALLYE E. PERRIN AND GREGORY P. BENZ A novel three-step evaluation process was used to select the final modern utilities (including a conduit built in 1910 that carries alignment t<dion loca1ions. and construction method for the the Jones Falls stream), and potential archaeological features. 'Maryland Mass Transit Administnuion·s mil trnnsit ex t nsi n inro The extension, consisting of twin circular tunnel trackways northea t Bahimore. During preliminary engineering of this sub driven partially with compressed air, is now in construction. way line , known as Section C, several station box locations for two stations, numerous route ali gnments, and two tunnel con The stations will both be built by cut-and-cover methods, i.e., s1ruc1ion techniques resulted in 24 alternative designs for the open excavation from the surface. extension. Over a dozen eva luation categories, many with mul At the end of the UMTA Alternatives Analysis/Draft Envi lipl ' criteria had to be addres. cd including cost patron access. ronmental Impact Statement (AA/DEIS) process for the rail consuuctability, environment al and community impacts. and joint transit project, the alternative extending from the present devel pment potential. A conventional evaluation matrix was not metro terminus at the Charles Center Station under Baltimore a pm tica l n r appropriate means to select th • best option . T he eva lu ation procedure u. ed had three see ps-the first of which Street, continuing eastward below Fayette Street, and sub \ a· a con 1ruc1ion method I gy valu ation conducted wi thin a sequently northward under Broadway to a new terminus at capital cost threshold established by a financing cap. Then. indi Johns Hopkins Hospital, was selected as the preferred alter vidual component · that made up the alternatives such <is a ration native (see Figure 1). Several variations of the preferred alter location, were evaluated to detern1ine 1he be t-to-wou ranking native merited further investigation during the preliminary against the relevant crit eria. The alternative· that inclnded che engineering/final environmental impact statement (PE/FEIS) most top-rnnked components we r then ·valu ated using a focused display matrix that included only those crite ria clmt distingui ·hed phase of the project. Design options that were to be evaluated the rem ~1 ining alt erna1 iv . Thi procedu re, which was ucccssful and refined during PE/FEIS included alignments below either in identifying the plan ror 1hc extension now under con truction Baltimore Street or Fayette Street; shallow or deep profiles; pro,1i le · a practical means enabling engineers, 11 rchitcct., plan'. cut-and-cover construction instead of shield-driven, soft-ground, ners. operators, and policy rnakers to manage a kirge number of and rock tunneling; variations in the location of stations and alternatives and evaluation criteria. station entrances; rail-bus transfer facilities; and other pos sible changes in the then-defined characteristics of the When the number of alternatives and evaluation criteria preferred alternative. exceeded the practicability of a conventional evaluation matrix, The initial phase of the PE/FEIS consisted of an evaluation an innovative three-step evaluation procedure was developed of alternatives leading to a recommendation for the design and successfully applied. The procedure demonstrates that a alternative to be chosen for advancement into preliminary de complex set of alternatives can be evaluated by disaggregating sign. The process was used to evaluate alternative alignment the alternatives into components and focusing on the distin and station options and construction methodologies. guishing features among the alternatives rather than the abso lute measures. The procedure reduces the number of alter natives and criteria to a manageable number that can be handled by more conventional evaluation techniques. BASIC BUILDING BLOCKS Section C of the Baltimore Metro will extend service from downtown at Charles Center into the northeast section of The set of alte rnatives for the Metro Extension resulted from the city to the Johns Hopkins Hospital medical center. The the combination of various station locations, crossovers, align extension will be about 1.5 mi in length and will include ments, and different methods of construction. A total of 24 two stations-one called Shot Tower/Market Place on the possible alternatives were defined. A traditio nal evaluation eastern side of Baltimore's central business district, and one process that would compare thi ~ e t of 24 alte rnatives was at Johns Hopkins Hospital, a major employment center. All dete rmined to be 100 cumber ·ome, and, more important the facilities for the extension to Johns Hopkins Hospital are individual differentiating factors relative to station locations underground, through an area that was part of the early set and construction methodology tended to be overshadowed by tlement area of Baltimore. Subsurface features include wa ter alignme nt issues. saturated soils, areas where the harbor was filled, old and Because the alternatives were defined by stations and cross over locations, alignments, and construction methods, a basic building block approach was applied for comparing the com S. E. Perrin, Parsons, Brinckerhoff, Quade, and Douglas, Inc., 301 ponents. The individual compone nts that make up each alter N. Charles Street, Baltimore, Md. 21201. G. P. Benz, Parsons, Brinckerhoff, Quade, and Douglas, Inc., One Penn Plaza, New York, native were as essed individuall y to arrive at the preferred N.Y. 10119. option. The components were termed 230 TRANSPORTA T/ON RESEARCH RECORD 1266 ' ! .. - I > Mariut(' \ PJG , .'Eas~ . S taJ;loo'"' FIGURE 1 Preferred alignment-AA/DEIS. • Conditions. Refers to station locations and related cross •Johns Hopkins Ho. pita/ Station (all under Broadway with over variations. There are nine conditions, five at Shot Tower/ tailtrack immediately north of 1latform) Market Place and four at John · Hopkins Ho pita!. Some sta -Condition 6: North oriented with direct connection to ti on locations, especially a l ho t Tower/Market Place, are the north bus transfer facility. No. 10 crossover immediately only pos ·ible with certain alignment options. south of platform. • Alig11111e11ts. There are four alignment variations, one on -Condition 7: More southerly oriented than Condition Fayette Slreet, one on Baltimore Street, and two alternatives 6, indirect connection to north bus transfer facility. No. 15 that transition from Baltimore Street to Fayette Street at crossover located on Fayette Street west of curve. different locations. -Condition 8: Same platform location as Condition 7, • Construction Methodology. Refers to the mix and extent with direct connection to north bus tran fer facility and of cut-and-cover construction and tunneling. hospital developmem. No cro s ver immedia tely south of p'latform. The nine station conditions are as follows: -Coudition 9: Mo t outherly oriented i> tati n locati n with direct connection to south bus transfer faci li ty and •Shot Tower/Market Place hospital development. N . 10 cross ver immediate ly outh -Condition 1: West of the Jones Falls Boulevard under of platform. Baltimore Street. -Conditiou 2: Straddling the Jones Falls Boulevard under The four alignment variations all start under Baltimore Street Baltimore Street. at the existing Charles Center Station. They are summarized -Condition 3: East of the Jones Falls Boulevard under below: Baltimore Street. -Condition 4: East of the Jones Falls Boulevard under • Alignment I. A Fayette Street alignment that transitions private property, diagonally between Baltimore and from Baltimore Street to Fayette Street near Gay Street. and Fayette Streets. then curves over to Broadway, north of Orleans Stre t . A -Condition 5: Underground station east of the Jones refined version of the Fayette Street alignment shown in the Falls Boulevard, in Fayette Street. AA/DEIS. Perrin and Benz 231 • Alignment JI. A Baltimore Street and Fayette Street the 24 design options are designated as shown in the matrix alignment that transitions to Fayette Street at about Eden of Figure 2. Street, and then curves over to Broadway, north of Orleans Street (same as Alignment I). This alignment is a refined version of the Baltimore Street alignment shown in the AA/ OUTLINE OF THE PROCESS DEIS. • Alignment Ill. A Baltimore Street alignment, continues The evaluation was conducted in three steps. In the first step, under Baltimore Street all the way to a block east of Caroline comparative costs for each alternative were reviewed to deter Street where it curves over to Broadway at a point just south mine if a significant cost saving could be realized by cut-and of Fayette Street. (Does not follow Fayette Street at all.) cover construction versus tunneling for the alignments. The • Alignment IV. A variation of Alignment II that stays evaluation was performed within the context of a capital under Baltimore Street only as far as the Jones Falls Boule financing cap established by the amount of funds available vard where it curves up to Fayette Street, and then curves from an Interstate transfer. over to Broadway north of Orleans Street (same in this section In the second step, the components that make up the alter as in Alignments I and II). natives (conditions and alignments) were assessed against measures that reflect the key factors and issues at each station The combination of variations in conditions, alignments, and area and along the alignment. The information was presented construction methodologies resulted in 24 alternatives that in a simple matrix with a relative rating given to the condi were evaluated by this process. These alternatives, perhaps tion or alignment for each evaluation measure. The measures better designated as "design options," are really design var fell under seven major headings that best distinguished sig iations of the recommended scheme that are out of the AA/ nificant differences among the station conditions and align DEIS process.