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Structural Design and Approval Frequently Asked Questions

Q. When is a permit for an overweight truck required to cross a County bridge?
A. All vehicles that are over the Maryland legal load limits or are heavier than the posted load restrictions across a County bridge require an Overload permit from the Department of Public Works, Bureau of Engineering and Construction.

Q. How do I get an Overload Permit to cross County owned bridges with weight restrictions?
A.
  Write to:
      Bureau of Engineering and Construction
      111 West Chesapeake Avenue, Room 219 
      Towson, Maryland  21204

Include the address, the number of axles, and gross axle loads, and the distance between axles. Overload Permits may be issued to the owner of the truck only and may or may not be granted depending on axle loads, spacing, etc.  For further information, you may call Mr. Keith Duerling at 410-887-3764 or email kduerling@baltimorecountymd.gov. Permits may take two weeks, so allow plenty of time.

Q. How do I find out the status of bridge projects before construction starts?
A.  Call the Structural Design and Approval Section at 410-887-3737. After construction starts call Construction Contracts Administration  at 410-887-3461.

Q. How many bridge structures does the Baltimore County Department of Public Works own and maintain?
A. There are approximately 537 structures in Baltimore County's inventory. 

Q. How does the County maintain their bridges?
A. All bridges with span lengths over 20 feet are required to be inspected every two years by Federal law. These inspections must comply with the Federal Highway Administration's National Bridge Inspection Standards. The costs for these inspections are covered 100 percent by Federal funds. Baltimore County follows the same procedures for their minor bridge structures, those between 8 and 20 feet. The inspections for the minor bridges are funded by the County, and when available, State aid. The County also maintains an on-call maintenance contractor for repairs and minor replacement projects.

Q. How does the County determine when a bridge needs to be replaced?
A. The decision to replace a bridge is based on the findings of the biennial inspection reports. County engineers prioritize replacement candidates based on structural condition, ability to repair effectively and economically and availability of funding.

Q. How is the Bridge Replacement Program funded?
A
. Bridges over 20 feet in length and meeting certain criteria qualify for Federal Bridge Replacement funds. These Federal funds pay for 80 percent of the design and construction costs associated with a project. Occasionally a bridge over 30 feet long will be replaced using 100 percent County funds, however Baltimore County is committed to using Federal funding whenever possible. Bridges under 20 feet in length are 100 percent funded by the County.

Q. Are there any differences when Federal Funds versus all County funds are used on a project?
A. The same design criteria, right of way acquisition process and environmental review regulations and permitting process are followed regardless of the funding source. When Federal funds are used, projects must be reviewed by the Maryland State Highway Administration. There is also some additional environmental review documentation required on Federal aid projects.

Q. What are the bridge design criteria used for County bridges?
A.
The American Association of State Highway and Transportation Officials (AASHTO) maintain the building codes for both roadway and bridge construction in the United States. For roadway bridges, we refer to the AASHTO Standard Specifications for Highway Bridges manual and it's successor the AASHTO Load Resistance Factor Design Bridge Design Specifications. These documents for the most part provided criteria governing the structural engineering and geotechnical aspects relating to bridge design. For roadway widths over bridges, both these manuals refer to the AASHTO Policy on Geometric Design of Highway and Streets. This document governs road design. These criteria were incorporated into the Baltimore County Design Standards and Policies for Rural Baltimore County roads.

Q. How are bridge widths determined?
A. Bridge widths are determined by six factors:

  • Functional classification, average daily traffic volumes, percent trucks, design speed, geometric conditions and community input. Functional classification defines roads according to the character of service they are intended to provide. Most County roads are classified as local, collector or arterial roads.
  • Average daily traffic volume data of vehicles per day is maintained and provided by the Bureau of Traffic Engineering and Transportation Planning. Twenty year predicted counts are also developed and incorporated into the bridge design.
  • The percentage of trucks is provided by the Bureau of Traffic Engineering.
  • Design speed is determined by the provided guidance of AASHTO for different types of roadways.
  • Geometric Conditions relates to the existing alignment of the roadway across the structure. For bridge replacement projects, we look to do the least amount of approach roadway work possible to meet the minimum design criteria. Occasionally a bridge needs to be slightly wider to accommodate the curved roadway or for safety reasons relating to line of sight requirements.
  • Community input provides us with information relating to local conditions and concerns of citizens impacted by the replacement of an existing bridge.

Q. How are bridge lengths determined?
A. Bridge length is based on the needs of the feature crossed. Bridges over streams are sized on hydraulic characteristics of the stream passing through the crossing. Most replacement bridges are sized hydraulically in-kind such that the flood characteristics of the new match those of the existing structure. Some replacement bridges and all new structures on new roadways are sized to pass certain design storm based on the design of the roadway. Bridges over railroads are sized by the clearance enveloped required by the railroad.

Q. How are bridge replacement projects developed?
A. Once County engineers determine a structure needs to be replaced preliminary design begins. This initial engineering stage consists of data collection (traffic volumes, location of existing right of way and adjacent property lines, wetland delineations, field surveys etc.). From this data a preliminary design, from a preliminary investigation of type, size and location plans, is developed. These documents represent about 30 percent of the engineering phase of the project. It is during this preliminary design phase that the full extent of the project is developed and community input is solicited. Once a consensus is achieved a final design is undertaken to complete the construction documents for bid.

Q. How can one find out more about Baltimore County bridges and bridge projects?
A. Additional information can be obtained from the County Department of Public Works, Bureau of Engineering and Construction. Once a year they conduct an open work shop to receive public input on all projects location outside the County's Urban Rural Demarcation Line. Public meetings may also be conducted for individual projects. Bureau of Engineering personnel are available to speak at civic groups by appointment.

 

Revised July 11, 2016        

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