Hydraulics & Drainage

GM2 employs a hydraulic team that possesses more than 20 years of work experience with the Connecticut Department of Transportation. The staff is certified in WMS (hydrological and Flood Plain mapping software) and SMS (2D-Unsteady Flow Analysis). GM2 has strong capabilities in hydrology, hydraulic modeling, scour analysis, flood plain mapping, and regulatory permitting.

Our regulatory experience includes: Flood Management Certification, Stream Channel Encroachment Permits, Stormwater Discharge General Permits, Coastal Consistency Reviews, and Inland Wetland and Watercourses Permits (both State and Local permits).

Recent Examples of Work Include:

Moses Wheeler Bridge – Milford/Stratford, CT
GM2 prepared a hydrologic, hydraulic, and scour susceptibility study relating to the reconstruction of the Moses Wheeler Bridge, carrying I-95 over the Housatonic River between Stratford and Milford in the state of Connecticut. Due to the close proximity of the Moses Wheeler Bridge and the Metro-North Railroad Bridge ("Devon Bridge"), plus the existing scour susceptibility of the Devon Bridge, a detailed hydraulic analysis of this reach of the river was required. This analysis involved the use of the ACOE computer program HEC-RAS to evaluate and compare water surface profiles and velocities for the existing, proposed, and temporary (during construction) conditions. The unsteady flow component was used to perform a basic one-dimensional tidal hydraulic analysis of the daily tide cycle and the associated possible storm surges. In order to perform the required detailed hydraulic analysis in the vicinity of the two bridges, a two-dimensional tidal hydraulic analysis needed to be employed. This was possible with the Surface Water Modeling System (SMS Platform) running Finite Element Surface Water Modeling Software (FESWMS). The boundary conditions for this two-dimensional hydraulic analysis were developed with unsteady flow analysis with the HEC-RAS program. Scour evaluations for both bridges were prepared with recommendations for foundation design for the Moses Wheeler Bridge. The scour evaluation was completed in accordance with HEC-18 "Evaluating Scour at Bridges" and followed the mechanics of evaluating scour for complex piers in relation to the pier stem (single or multiple), pile cap or foundation and the pile group. Based on the results of the study, a determination of the impacts of the proposed Moses Wheeler Bridge on the existing Devon Bridge with regards to the stage, velocities and predicted scour depths (with a discussion of scour countermeasures) was presented in a detailed technical report. Click here for photos.

Pearl Harbor Memorial Bridge (Q-Bridge) Floodplain Analysis – New Haven, CT
GM2 prepared a floodplain analysis for the purposes of Department of Environmental Protection Floodplain Management Permitting. This analysis required the recreation of original FEMA Floodplain data with the use of the ACOE computer program HEC-RAS. GM2 evaluated and compared water surface profiles and velocities in order to determine if there would be significant changes to the FEMA regulated A-zones (regarding base flood elevations) or the regulated V-zones (regarding the velocities of the base flood) following the replacement of the proposed Q-Bridge. Click here for photos.

Wolford Hill Road Bridge – Colebrook, CT
This project involved preparation of a hydraulic analysis of Wolford Hill Road over Sandy Brook in Colebrook, CT. This required the completion of a general location survey and creation of a survey base map to be used for roadway, structural, and hydraulic engineering. This hydraulic analysis involved the use of the ACOE computer program HEC-RAS to evaluate and compare water surface profiles and velocities for the existing, proposed and temporary (during construction) conditions. The hydraulic analysis was then used for Floodplain Management Permits.

Mountain Road Bridge – Norfolk, CT
GM2 prepared a hydraulic study of the Mountain Road Bridge over Norfolk Brook in the Town of Norfolk, CT. This analysis required the completion of a general location survey and creation of a survey base map to be used for roadway, structural and hydraulic engineering. This hydraulic analysis involved the use of the ACOE computer program HEC-RAS to evaluate and compare water surface profiles and velocities for the existing, proposed and temporary (during construction) conditions.

Stone Mill Road Bridge – Mansfield, CT
GM2 completed a hydraulic study of the Stone Mill Road Bridge over the Fenton River in Mansfield, CT. This analysis required the completion of a general location survey and creation of a survey base map to be used for roadway, structural and hydraulic engineering. This hydraulic analysis involved the use of the ACOE computer program HEC-RAS to evaluate and compare water surface profiles and velocities for the existing, proposed and temporary (during construction) conditions.

Valley Road Bridge over the Branford River – North Branford, CT
This project involved a hydraulic analysis of the Valley Road Bridge over the Branford River in North Branford, CT. This hydraulic analysis involved the use of an existing survey base map and the ACOE computer program HEC-RAS to evaluate and compare water surface profiles and velocities for the existing, proposed and temporary (during construction) conditions. The hydraulic analysis was then used for Floodplain Management Permits.

Route 130 Fairfield Avenue – Bridgeport, CT
GM2 developed the drainage design for the roadway reconstruction associated with the replacement of Metro-North Railroad Bridge over Route 130, (Fairfield Avenue) in the City of Bridgeport. This included designing the storm sewer system outletting to a pumping station currently under construction under the CDOT I-95 project.

James H. Naylor Elementary School – Hartford, CT
GM2 developed a drainage design and computations in conjunction with the lead architect of this project. The design involved a major addition of impervious areas. The constraints of this project, as set by MDC, included pipe detention in order to match or reduce runoff in comparison with the existing conditions. This hydraulic design and associated computations were then used to prepare a DEP Stormwater Management Permit.

Hydrologic Analysis as part of the Realignment of CT Rte. 31 – Coventry, CT
GM2 gathered, created and compiled all hydrologic values for the creation of a TR-20 model for hydrologic analysis of a drainage basin with 5 sub-basins. Total basin size was 3.25 sq. mi. This job included hydrograph routing through a gate outlet from a 363-acre lake. The project included five design points for hydrograph generation. GM2 is fully versed in Connecticut regulations for hydraulics and drainage, and we have experience with nationally accepted industry standards, as well as various Federal Highway Administration publications involving hydraulics, hydrology and scour. Click here for photos.

Addison Mill Pond – Glastonbury, CT
GM2 conducted a hydrologic assessment regarding streamflow at the Mill site for a feasibility study for implementation of micro-hydroelectric power generation through techniques of instantaneous area-velocity measurements over a period of time. Measurements were collected for different meteorological conditions, including extended periods of dry weather and times of peak flows following rainfall events.

Cyril Johnson Dam – Stafford Springs, CT
GM2 performed a flow analysis as part of a feasibility study for implementation of small-hydropower generation at an active textile mill in Stafford Springs, Connecticut. Methods of analysis included installation of a water level logger recording the stream stage every 15 minutes. This data was then used with the channel geometry to determine velocity and thus flow rates for application in determining the amount of power that can be generated on a monthly average basis.

Real-time streamflow measurement and monitoring capabilities for ungaged streams
GM2 employs a number of streamflow monitoring techniques for flow gaging of rural and ungaged streams including weir and flume structures, flow velocity gages, pressure transducers, and water level loggers. Analysis techniques include instantaneous as well as real-time data logging, and approach is determined on a project need and economic basis.

Following is a list of applicable software programs that our team has experience with and that is readily available to us: MicroStation, HEC-RAS up to Version 3.1 with HEC-DSS extension, TR-20, TR-55, SMS (Surface Water Modeling System) with FESWMS (Finite Element Surface Water Modeling Software) Interface, WMS (Watershed Modeling System), The Hydrain Package (with HY8) produced by the FHWA, HEC-HMS and StormCAD by Haestad Methods.