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Maxwell Pond Dam Removal

 

DuBois & King planned and designed the removal of the Maxwell Pond Dam, which necessitated the restoration of Black Brook through the 5.4-acre Maxwell Pond. The pond, once used for purposes such as ice harvesting and recreation, was impounded by a 1900-era dam located immediately upstream of Front Street in Manchester. Development in the watershed resulted in declining pond quality, ecological value, and aesthetics. A storm event caused significant flood damage at and around the dam and prompted the decision to remove the dam and restore the affected area of Black Brook to minimize the potential for future flooding and to reduce future maintenance requirements. Services included:

Site inspection and evaluation
Data collection and review
Preliminary and final designs
Plans and specifications
Hydrologic and hydraulic evaluation
Wetland delineation
Utility coordination
Construction cost estimates
Sediment Analysis Plan
Permitting
Quality Assurance Project Plan
Construction and post dam removal monitoring

Marshfield No. 6 Hydroelectric Dam Inspection

 

D&K engineers performed an independent consultant dam safety inspection at Green Mountain Power’s Marshfield No. 6 hydroelectric facility located on Mollys Brook. The inspection and associated report were prepared in accordance with the Public Service Board of Vermont, Rule 4.500 with the purpose of identifying and evaluating potential deficiencies that might endanger public safety.

The dam structures consists of a 1,100-ft-long, 48-ft-high earthen embankment with a 260-ft-long concrete chute-type spillway structure at the left abutment; a concrete control structure that serves as an emergency spillway; and an intake structure with a 6-ft diameter penstock. The dam impounds a 4,000-acre flood control/hydroelectric/recreation reservoir. The facility is classified as a high hazard dam.

D&K performed the following tasks associated with the dam safety inspection: collection and review of documentation, field investigation, evaluation of project works, and preparation of the Sixth Safety Inspection Report. As part of the field investigation, two areas of downstream sloughing were observed and profiled for analysis. Based on this analysis, recommendations for remedial work were provided in the report.

Manufacturing Campus and Addition

 

Program management, permitting, and multi-disciplined engineering design (civil/site, structural, geotechnical, mechanical, plumbing, electrical) services for site development and design of a 224,000-sf manufacturing and office facility on a 242-acre parcel. Project was delivered as a fast-track design-build. An extensive wetland area encompassed 190 acres of the site. Detailed delineation was performed as part of the base mapping for the project. Project was designed to avoid any direct wetland impacts and potential for indirect impacts were mitigated through the stormwater management system.

Site design included 200 parking spaces, water and sewer service lines, a 24-ft-wide paved fire-loop road, and buried utilities. Separate services were provided for domestic water, process water, and fire flow. Process and domestic wastewater were combined outside the building into a 12 inch gravity sewer line and connected to municipal sewer.

A comprehensive traffic impact study was performed to develop required improvements to Route 108, the access road leading to the facility. Improvements included the addition of a left turn lane and deceleration/acceleration lanes. The alignment of the original roadway was also modified to meet current NHDOT standards.

Electrical design included site power distribution, parking lot lighting, and building interior lighting and power. Mechanical design included building HVAC systems, all plumbing and process piping, and consideration for special environmental requirements for process operations. Structural design included a perimeter foundation wall, a soil-boring program, and design of a site retaining wall.

Subsequent to the original campus construction, D&K engineers provided multidiscipline engineering and permitting services for a 195,000-sf addition to the manufacturing facility. The addition was also delivered as a fast-track design-build project.

Lyndon State College Stonehenge Parking Lot and Recreational Facilities

 

DuBois & King provided civil/site, electrical, and environmental engineering, and landscape architecture services to redesign and expand the main parking area of the College. Project included sustainable stormwater management improvements that incorporated a 1,800-sf rain garden and 0.25-acre channel rain garden/bioswale; energy saving LED area lights; expanded recreational facilities, including an enlarged basketball court, with modifications added for winter hockey use, and a 6,000-sf skatepark with connecting walkways; a waterline extension to serve the athletic fields; and design of interpretative signs for the rain garden sites. Project was designed and implemented to accommodate a rapid construction schedule during the summer break. Services include:

Topographic survey
Design of parking lot reconstruction and expansion
Design of pedestrian pathways
Supervision of boring subcontractor
Regular meetings with ad-hoc campus project team
Stormwater control and treatment measures
Design of two rain gardens
Permitting including Act 250
Design of basketball area with concrete curb for winter hockey
Erosion control measures
LED lighting design for recreation areas, pathways, and parking
Bid phase services
Construction administration and observation

Lefferts Pond Dam Reconstruction

 

The Lefferts Pond Dam Rehabilitation project involved the renovation of a 130-year-old earthen, concrete spillway dam owned by the USDA Forest Service. The dam is located at a popular recreational destination. The goal was to rehabilitate the East and West Dams to meet modern dam safety standards and maintain the historic look of the structures. The constructed project consists of a low-maintenance earthen and concrete dam, concrete spillway, pedestrian bridge, and rehabilitated step-pool structure.

Unexpected deterioration of existing structural components was encountered during construction. A solution was designed while construction was under way, keeping the project on budget. Regulatory bodies required construction activities to take place without lowering the level of the 75-acre pond. The contractor constructed a temporary bladder dam of maximum size (11 ft high) to safely retain water.

The design for replacing the stone walls, which made up the downstream abutments, involved building a new concrete wall behind the original abutments and using anchors to mechanically connect cobblestone facing to the new concrete walls. To maintain the historic character of the dam and contain costs, existing cobblestones were reused on the facing of the piers and pedestrian bridge.

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