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Air Rail Highway Bike/Ped Public Transit

Project Process

Engineers reviewing plans

Project Process

Now that the project has been approved following the Public Hearing and the issuance of the Record of Decision, the project development process advances into Final Design. The New Hampshire Department of Transportation (NHDOT) has selected a consultant design team to perform the Final Design of the project with review and support provided by the NHDOT. The Final Design process is split between a Preliminary Design Phase and a Final Design Phase. These two design phases are utilized to continue the design development of the approved layout for the project prior to the construction phase. In addition to the design phases, the environmental permitting documentation, research and investigations are also completed in support of the design efforts prior to construction of the project.

The following sections provide a more detailed explanation of these two design phases and the environmental process.

Preliminary Design

Highway Design
The preliminary highway design is developed in two distinct submissions, with the first submission being the Pre-Preliminary Submission and the second being the Preliminary Submission. The Pre-Preliminary Submission utilizes the selected alternative highway layout and applies greater design accuracy and precision to replicate the layout. In addition to this advanced design of the selected alternative, refinements and modifications to the selected alternative are identified and developed for further consideration. The design is developed to provide the best balanced highway layout with respect to the following:

Projected Traffic Analysis          Construction Costs
Drainage     Geotechnical Concerns
Right-of-Way Impacts    Utility Impacts
Environmental Resources    Construction Contracts 

The Preliminary Submission advances the Pre-Preliminary Submission to further develop the details of the design for a more in depth review of the design elements carried forward from the Pre-Preliminary Submission. This design advancement leads to the acceptance of the horizontal and vertical geometries into Final Design.

Bridge Design
The preliminary bridge design begins with the Type, Span and Location (TS&L) Study.  This study is defined as follows:

Type - What bridge types are to be considered for a particular location? (e.g.; concrete, steel, truss, box culvert, etc.)

Span - How many spans are there for each bridge and what are the lengths of these spans?    (e.g.; 1 span has no piers, 2 or more spans do have piers)

Location - Where is this bridge located in relation to the overall project and what is the bridge crossing over? (e.g.;  river, roadway, railroad, etc.)

This study evaluates and compares options based on limited highway and geotechnical information. The TS&L Study develops various alternatives with respect to foundation types, bridge type, number of spans, construction cost, construction staging and the highway geometrics across the bridge.

Final Design

Highway Design
Upon completion of the preliminary highway design, the final design phase is started and consists of three primary submissions. These three submissions consist of:

  • Slope and Drainage
  • Preliminary Plans, Specifications and Estimate (PPSE)
  • Plans, Specifications and Estimate (PSE)

The Slope and Drainage Submission identifies the specific drainage and water quality treatment needs for the project along with additional refinements to the slope work adjacent to the roadways. Geotechnical information and recommendations that establish the pavement depths, underdrain requirements and the structural sub base beneath the pavement are provided as part of this submission.  Project specific traffic control, maintenance of traffic and construction sequencing are also developed during this phase so that the construction limits can be established for each contract.

The PPSE Submission develops a draft of the entire plan set while incorporating the direction provided by the NHDOT review of the Slope and Drainage Submission.  This plan set includes the development of plans for the following:

Traffic Signals Signing Pavement Markings
Landscaping Traffic Control General Plans
Profiles Cross Sections Water Quality Structures

The construction specifications and construction cost estimate are prepared in detail for this submission. During the development of this submission any unavoidable utility conflicts are identified and coordination efforts with the utility companies is undertaken to mitigate these conflicts. The Right-of-Way and property impacts are also finalized during the time that the PPSE Submission is developed so that they can be utilized in the acquisition of property rights required for the construction of the project.

The PSE Submission finalizes all of the plans, specifications and construction cost estimate associated with the project following the PPSE Submission. At the completion of the PSE Submission the project is ready to be advertised for construction and bidding by contractors.

Bridge Design
Upon completion of the TS&L Study phase, the final design phase is started and consists of three primary submissions. These three submissions are:

  • Preliminary
  • Preliminary Plans, Specifications and Estimate (PPSE)
  • Plans Specifications and Estimate (PSE)

The Preliminary Submission for the bridges is considered a final design submission because it is completed concurrently with the highway Slope and Drainage Submission after horizontal and vertical geometry has been established. The Preliminary Submission advances the design based on the TS&L Study. The plan, elevation, profile and the typical cross section of the proposed bridge and the roadway approaches are developed based on the highway and preliminary geotechnical information available.

The PPSE Submission develops a draft of the entire plan set following the Preliminary Submission. The geotechnical information is provided for the development of the foundation designs. The designs developed provide the information to be incorporated into the following plans:

Foundations Abutments Piers
Appurtenances Deck      Railings

The construction specifications and the construction cost estimate are prepared in detail for this submission.

The PSE Submission finalizes all of the plans, specifications and construction cost estimate associated with the project following the PPSE Submission. At the completion of the PSE Submission the project is ready to be advertised for bidding by construction contractors.

Environmental Process
During the completion of the Final Environmental Impact Statement (FEIS) phase of the project the NHDOT applied for many environmental permits that are required to complete the design and construction of the project. These permits provide the NHDOT with design and construction conditions to be utilized for elements such as:

Wetland Impacts  Water Quality Treatment Requirements
Construction Limitations      Temporary Erosion Control Requirements
Shoreland Protection      Invasive Species Control
Hazardous Material Controls  Coastal Zone Management

In addition to addressing the elements associated with the permitting of the project, there are research and documentation efforts required for other environmental elements of the project. The following elements are researched and documented prior to construction:

Wetlands Historical Resources Archaeological Resources
Invasive Species Hazardous Materials Noise Analysis

The approval of the FEIS required a mitigation package that includes the stream restoration of Railway Brook in the Town of Newington. In addition to the stream restoration, there are multiple locations where the NHDOT will be seeking to obtain properties to place into conservation easements.

 






New Hampshire Department of Transportation
PO Box 483 | 7 Hazen Drive | Concord, NH | 03302-0483
Tel: 603.271-3734 | Fax: 603.271.3914
copyright 2009. State of New Hampshire