Greenhorne & O’Mara

General Information

Contact Email:

Organizational Narrative:

Greenhorne & O’Mara (G&O) is a full-service, multidisciplinary consulting engineering firm with a culture of personalized client service, innovative solutions, and on-time project delivery. We serve clients in the private and public sectors on projects located throughout the United States and overseas. Founded in 1950, G&O is an employee-owned firm that is consistently ranked by Engineering News Record among the top architectural/engineering design firms in the United States. Our diversified staff of more than 500 knowledgeable and quality-oriented employees offers our clients a broad spectrum of engineering expertise. Our Vision is to bring together the best in integrative consulting and technical talent. We provide our clients with inspired solutions for improving lives through better communities, a healthier environment, and a safer world.

Provider Background

General Services:
  • Watershed Modeling
  • Mapping
  • Education
  • Facilitation Resources
General Services Details:

G&O’s multi-disciplinary team is committed to working closely with clients to achieve project goals, minimize and mitigate impacts, and develop innovative ways to enhance the environment. Our environmental scientists, planners, NEPA specialists, ecologists, water resources engineers, hazardous materials managers, floodplain managers, GIS specialists, cultural resources experts, and public information professionals work consistently to provide innovative approaches to achieve the best possible outcome for both government and private-sector clients.

Our Water Resources and Environmental Sciences Division consists of a core of experienced professionals focused on stream assessment and monitoring; aquatic and habitat studies; watershed assessment and planning; stream stabilization and restoration design; flood control; the protection of watersheds, streams, and wetlands; and a full suite of GIS consulting services for our federal, state, and local government clients. We offer engineers and scientist that are familiar with numerous water quality, hydrologic, and hydraulic related regulations at all levels of government, including the National Pollutant Discharge Elimination System (NPDES) Municipal Separate Storm Sewer System (MS-4) Permit Requirements, Total Maximum Daily Loads (TMDLs) and TMDL Implementation Plans, State Stormwater Management Regulations, Local Government Stormwater Management Regulations, Erosion and Sediment Control Requirements, Maryland Tributary Strategies, and Chesapeake Bay Program Goals.

Our professionals bring the following multi-disciplinary services:

  • Watershed Management, Assessment, and Planning
  • Land Use Planning
  • Stream Physical Habitat Assessment and Monitoring
  • Stream Geomorphic (Rosgen) Characterization
  • Benthic Macroinvertebrate Sampling
  • Water Chemistry Sampling and Analysis
  • Best Management Practices Mapping, Evaluation, and Design
  • Stream Stabilization and Restoration Design
  • Water Quality, Watershed, Hydrologic, and Hydraulic Modeling Experience
  • Public Outreach and Education
  • Information Technology & GIS Services
  • Surveying
  • Statistical Analysis
BMP’s / Tech Implementation:
  • Wetland management
  • Stormwater
  • Onsite wastewater
  • Erosion control
BMP’s / Tech Details:

An example G&O project for stream bank stabilization and restoration included the daylighting of Broad Branch represented a large-scale stream restoration project located on protected National Park Service land. G&O was responsible for the restoration of approximately 1,600 LF of stream, which drained a 170-acre subwatershed.  The stream restoration work involved the use of stormwater infiltration Best Management Practices (BMPs) and streambed protection to simulate a natural watercourse while slowing stormwater flows allowing for more groundwater recharge and restoring the natural stream. Groundwater recharge features, such as bioretention cells and regenerative step pools, were also included in the design.  The design was developed with the intention of preserving and enhancing the existing wooded stream valley corridor. G&O’s work improved the water quality of the Broad Branch Subwatershed.

For Stormwater, an example G&O project involved working with the South Florida Water Management District (SFWMD) to reduce phosphorous loads flowing into Lake Okeechobee from the Lamb Island Tributary as part of the Comprehensive Everglades Restoration Program to mitigate the up to 600 metric tons of nutrients that flow into Lake Okeechobee each year.  G&O used best management practices, develop, design and implement low cost operations and maintenance alternatives to divert stormwater and reduce nutrient runoff.

For Wetland management, a G&O project example involved provided environmental, cultural resources, and engineering services.  G&O conducted wetland delineations and completed a Joint Permit Application for impacts to waters/wetlands regulated under Section 404 of the Clean Water Act. For this assignment, G&O prepared wetland and stream mitigation package and design.

Service Area

  • All – We serve the entire state

Other Services

  • Floodplain Mapping

As a leader in the ongoing FEMA Risk Mapping Assessment and Planning program, G&O’s engineers and GIS experts consistently produce and update high quality and cost-effective flood insurance studies for communities, and contribute to the overall evaluation of the Program.

  • We are the prime service provider for engneering, GIS and DFIRM mapping and database services for FEMA Region VII which consist of the States of Kansas, Iowa, Nebraska, and Missouri. 
  • G&O also provides floodplain mapping services to the State of Georgia and throughout the eastern and central United States as a contractor for FEMA’s Regions III, V, VI, and VIII.
  • Parks and Recreation Design

G&O’s diversity of disciplines provides our planners and landscape architects with the advantage of continuous interaction with all members of a project team — planners, engineers, and scientists — who play a vital role in identifying project constraints, resolving technical issues, and enhancing the project team’s creativity.

We have designed award-winning parks, downtown areas, and streetscapes, and have prepared community master plans, zoning ordinances, and tree preservation regulations for our city and county government clients. For federal and state clients, our work has included site and landscape design, military base planning, facilities analysis, landscape and architectural evaluation, environmental preservation plans, and military housing and neighborhood design and revitalization.

Throughout the planning and design process, our planners and landscape architects translate your goals into economically sound and visually imaginative projects.

  • Hazard Mitigation Planning

Greenhorne & O’Mara (G&O) has provided hazard mitigation services to federal, state, and local agencies for more than 29 years. This experience includes performing hazard identification and risk assessments using geographic information system (GIS) tools (including ESRI’s ArcView), and conducting hazard mitigation planning to meet federal requirements such as the Disaster Mitigation Act 2000 (DMA 2000) and the National Flood Insurance Program’s (NFIP’s) Community Rating System (CRS)

G&O has the depth of staff with planning, mitigation, GIS, and structural assessment experience to complete comprehensive all-hazards mitigation plans tailored to your community. G&O’s project teams comprise American Institute of Certified Planners (AICP)-certified planners, engineers, Certified Floodplain Managers (CFMs), GIS specialists, and many more technical specialists.

The G&O Project Team offers a thorough understanding of the Stafford Act policy changes and the mitigation planning implications of DMA 2000 to help guide communities through the mitigation planning process.

  • Information Technology and GIS

Asset Inventory and Work Order Management

Technology is playing an increasingly significant role in helping government manage stormwater runoff in ways that protect the environment while managing transportation infrastructure. G&O uses mobile devices and GIS to inventory and map drainage features and stormwater control structures as part of maintenance and regulatory compliance efforts.  G&O uses Global Positioning System (GPS) units, field data collectors, and GIS systems, detailed information is precisely located, inventoried, and mapped to provide accurate information of the features associated with each drainage area.

Greenhorne & O’Mara