Bold Creativity / Twinbrook Station Phase 1A

“ Those are real 10s! The Harkins pre-construction team was a huge asset and an invaluable resource throughout the process. ”

Creative Site Management Pays Huge Schedule Dividends

The Challenge

The site was the challenge. Surrounded by a WMATA parking facility, an Exxon gas station, and a residential neighborhood, the site was very tight, with very little room for staging. Before vertical construction could begin, a large amount of sitework had to be completed. Active sewer lines and existing utilities had to be moved and rerouted. Because of the very wet spring in 2008, the soil had a high level of moisture, which resulted in more haul-off than expected.

Most importantly, the site was located between a very large Metro parking area and the storm system discharge point. Therefore, a tremendous amount of run-off would have to be handled through the site – both during and after construction. It was the handling of this run-off during construction that represented a major opportunity for the Harkins team.

The Solution

All site activities were coordinated with a WMATA representative, and access and power to the gas station were maintained. To mitigate the high moisture content found onsite, soil modification techniques, using lime and soil cement, were used to expedite work where possible at minimal expense to the owner.

The permanent engineering solution for stormwater management was a 120’ x 200’ x 25’-deep storage vault under the parking structure and a large concrete culvert running under Higgins Street between the two buildings.

As for handling the runoff during construction, the original sediment and erosion control design required use of multiple sediment traps and dewatering devices across the site. Some of these traps were located in the footprint of Building A, and of Building B, which was on the critical path. Our team, with the help of civil engineer Johnson Bernat Associates and leadership from JBG, offered an interim solution that included an elaborate temporary five ft.-diameter corrugated culvert system diverting the Metro lot run-off past our site. In support of this engineering creativity, the project management team coordinated numerous permits and approvals from the City of Rockville, WMATA, PEPCO, WSSC, and Montgomery County.

The Results

Throughout construction on this very tight site, the Harkins team had the confidence and trust of all of our neighbors, meeting their needs and requirements, and minimizing the project’s impact on their operations and daily lives.

By devising this creative solution to the management of water through the site, and through close coordination and supervision with city inspectors, the Harkins team was able to modify the original sequence of construction for the permanent vault installation and sediment traps. This significant contribution to a major project challenge enabled an earlier start on the vertical construction of Buildings A and B, and accelerated the construction schedule by five months.

This was Harkins’ first project with The JBG Companies. The sense of teamwork, partnership, and trust that had been developed during preconstruction, continued throughout the life of the project and we met these challenges together as a team.