Tasks
Field Investigation
The Field Investigation will be done briefly, in order to observe any challenges. In addition, the Field Investigation will provide the design team with a better understanding of the boundaries of the design area.
Physical Encumbrances
The initial design proposed by the client has a typical cross-sectional width of 106 feet and some areas along the roadway are smaller than the proposed width. A visual assessment will be conducted to help determine physical encumbrances. The property encumbrances will be determined during the research task.
Drainage Challenges
A Field investigation is also needed to determine if there are any channels that rainwater runoff flows into. This will determine if open channel flow analysis is required. The design team can also use this opportunity to map out any existing drainage structures along Route 66. Also, the team needs to determine where Clay Wash crosses the existing roadway to locate the culvert that needs to be extended.
Researching Existing Conditions
Research of the segment of Route 66 to be widened and the local area must be conducted to understand the current conditions. Such as current roadway geometry, traffic studies, property encumbrances, and topographic features of the local area.
Pre-Design Traffic Analysis
Level of Service (LOS)
The Route 66 expansion must improve the quality of travel for various modes of transportation such as bicyclists, pedestrians, automobiles, and forms of public transit. This roadway expansion will allow vehicles to travel with more ease as the capacity of the roadway will be increased. Vehicles need to be able to turn onto other roadways from the expanded roadway as well. The design vehicle will be either WB50 (semi-truck) or a normal consumer vehicle towing a trailer. This design vehicle will be used to determine that space needed to make U-turn along the roadway.
Capacity Analysis
A capacity analysis will be performed in order to determine how the roadway expansion will assist in maximizing the capacity after the design and implementation of the roadway. The expansion must either increase or maintain the current LOS of the existing road.
As-Builts
The as-builts for the roadway will be provided by ADOT. The design team will go through the as-builts to determine which one is most adequate to current condition of the roadway and obtain the geotechnical report from ADOT based on the project as-builts [1]. This will assist the team in conducting the geotechnical analysis, roadway alignment and grading of the roadway.
Geotechnical Data
In order to design the pavement for the roadway expansion, proper research must be done on the soil characteristics in the design area. Geotechnical reports will provide needed information that is critical for the pavement design, as the pavement design demands on the soil type classification of ASTM.
Property Encumbrances
After conducting the task, Physical Encumbrances, property research must be conducted to determine the property boundary lines along Route 66. This will provide a visualization of the right of way for widening and assist in determining if additional right of way is required for the proposed design.
Traffic Data
Research on existing traffic data is necessary to find crash data, traffic counts, signal warrants, and traffic impact analyses which are done when new developments are considered in the general area. These will allow the design team to obtain an idea of current and future traffic conditions along the segment of Route 66 that is to be widened.
Topographic Data
The existing survey data will be obtained from GIS and USGS. These programs will provide the topography of the surrounding area.
Pre-Design Hydrologic Analysis
Hydrologic analysis is necessary to help determine the rainwater runoff for the design storms that will be used in the aid of designing the hydraulic features of the roadway. The design storms that will be used in the hydrologic analysis are 1-year, 2-year, 5-year, 10-year, 25-year, 50-year, 100-year, and 500-year storm events [4]. Along with the design storms, ADOT has specific duration for each storm event for different intensities. These will result in greater rainwater runoff volumes and flows. These analyses will be conducted to determine the behavior based on the existing roadway. They will help with the design of the new drainage feature locations.
Watershed Delineation
The design team needs to delineate the watershed to determine the area that contributes rainwater to this area of Route 66 expansion. To delineate the watershed, StreamStats by United States Geological Survey (USGS) will be used [5]. StreamStats is a program that determines the watershed(s) that may contribute to the project location.
Time of Concentration
Time of concentration is the time it takes for rainwater to travel from the furthest point, to the watershed outlet. Determining the time of concentration will assist in predicting flow rates for the design storms. Using this, the peak flow can be determined and can be accounted for in the design.
Discharge Calculations
The rational method will be used to determine the runoff values for the design storms. This will assist the design team in the hydraulic design for drainage capabilities and locations. The runoff values will change once the design is complete and must be calculated again to determine if the new drainage infrastructures are adequate for the higher discharge values. In determining the discharge values, the runoff coefficient (C) will be weighted as the terrain of the watershed is a combination of forest and roadway surfaces. The runoff coefficient is the variable that will change from the existing to the proposed, as there will be an increase in impermeable area.
Design Phase
The design phase will consist of analyzing the results from the research phase and existing data to complete a final design that meets all requirements of the client and presents an effective solution for the current issues of the roadway.
Roadway Design
The following elements are the basis of the expansion of Route 66. All of these will be implemented in the final plan set.
Typical Cross-Section Design
Prior to the design of the alignments of the roadway is conducted, a typical cross-section of the roadway is required. This will aid in the implementation of the proposed design. It will also allow for easier alignment, excavation and fill values.
Vertical and Horizontal Alignment
Vertical and horizontal grading will be determined based upon multiple aspects including the ADOT roadway construction standards and the intended route of the storm water. The grading of the side roads that approach route 66 will have to be maintained to ensure the approach fulfills the City of Flagstaff specifications.
Excavation and Fill
Based on the roadway design grades, the cut and fill volumes of the roadway can be determined and held to a minimum to save on costs.
Signage and Pavement Markings
The correct signage and pavement markings must be implemented into the roadway. The MUTCD will assist in determining the correct signage and pavement markings along the roadway.
Temporary Traffic Control
Temporary traffic control duration and cost estimates will be provided by the design team. This will be based off of construction timing and scheduling.
Pavement Design
Pavement design will be determined based upon the specifications and standards of the ADOT road construction manual. The ADOT manual provides materials and types of pavements to be used along with the conditions of the roadway prior to pavement implementation.
Post-Design Hydrologic Analysis
An increase of stormwater runoff will occur due to an increase in the area of impermeability. Since there will be an increase in the runoff, a hydrologic analysis will need to be conducted using the rational method. The rational method will be using a different runoff coefficient (C) due to the roadway expansion. The new runoff coefficient will produce higher discharge value (Q). The new discharge value will be used to evaluate the proposed drainage infrastructure.
Post-Design Hydraulic Design
The new discharge value will be known once the hydrologic analysis is conducted for the proposed design. It will be used to analyze the pipe network used in connecting the catch basins to one another that drain into the existing culvert and Clay Wash. The new discharge value will also be used to analyze the culvert that allows Clay Wash to cross under Route 66.
Drainage Design
The proposed drainage design for the expansion will consist of additional catch basins at each intersection and a pipe network. The pipe network will connect each catch basin and drain into Clay Wash and the culvert.
Pipe Design
Civil 3D will be used for the design of the drainage structures and pipe network. This program will allow for the drainage structures and pipe network to be drawn to elevation and give a representation of what it will look like under the roadway. Civil 3D will display the grades of the pipes and where they will connect to each catch basin along Route 66.
Once the pipe network is finished, an analysis will be conducted to determine if the network is adequate for the runoff volumes and drains efficiently. If it does not, the pipes need to be redesigned and analyzed again. Once the design is up to standards, it will be included in the plan set.
Culvert Design
Along with the drainage structures and pipe networks, the existing culvert under Route 66 must be extended using ADOT standards. The culvert will be extended so that it is wider than the expansion of the roadway. The design of the culvert will be done in Civil 3D to draw it to grade with the other infrastructures that will be implemented.
Analysis of the culvert must be conducted due to the increase in runoff volume. With the increase in runoff volume, the culvert may fail. If the culvert fails, the culvert will be increased to the next size up, or it may become a double box culvert.
Post-Design Traffic Analysis
A post-design traffic analysis will be conducted to evaluate the capacity of the roadway to ensure the capacity increases. This analysis will be provided to the client and the technical advisor to demonstrate that the design meets the original goal of increasing the capacity in the roadway.
Creating Plan set
The plan set for the expansion of Route 66 will be a culmination of the roadway design, pavement design and hydraulic infrastructure. These plans will be drawn in either AutoCAD or Civil 3D and submitted to the client.
Project Impacts
The impacts will be evaluated and provided to the client, technical advisor, and grading instructor within the design process. The project impacts will evaluate social, environmental, and economic impacts that may occur due to the implementation of the roadway design.