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Project At A Glance:
Project Name: Hayfield Road Pipe Conveyance System
Project Owner: Fairfax County Department of Public Works And Environmental Services Stormwater Planning Division
Location: Alexandria, VA
Construction Time Period: October 2019 to July 2020
Contractor: Garney Construction
Trenchless Subcontractor: Midwest Mole
The Hayfield Farm Community subdivision was built in 1960s with approximately 670 houses. An existing 36-in. reinforced concrete pipe (RCP) adjacent to Hayfield Road collected stormwater runoff from commercial businesses and subdivision and discharged into Dogue Creek which eventually discharged into Potomac River.
Due to urban growth over the years, the existing stormwater collect system failed in a considerable rain event such as 100-year rain event, which left the residents of the subdivision with grave flooding issues. Hayfield Farm had experienced three 100-year storms in the past 5 years.
A new stormwater conveyance system was designed by Bowman Consulting for Fairfax County for the subdivision, which consisted of installing a new network of 1,200 lf of 7-ft x 4-ft box culvert and 2,000 lf of 48-in. RCP with numerous interconnections with the existing stormwater system through new 8-in. stormwater manholes.
This new system was installed on Hayfield Road from Telegraph Road to Huntley Meadows Park until it discharged into Dogue Creek. The new stormwater system also prompted various utility relocations including the installation of a new 8-in. sanitary sewer system for residents on the southside of Hayfield Road due to conflicts with existing sanitary sewer laterals. The stormwater discharge area also included extensive tree planting around the new plunge pool and new circular concrete weirs.
The safety of the community and residents were a paramount concern for everyone since the new stormwater conveyance system was installed in a densely populated residential neighborhood. The construction was sequenced into numerous phases with one side of Hayfield Road being closed at all times and traffic being diverted on the opposite side, thus requiring an extensive maintenance of traffic setup. The work area was always guarded with safety fence and all open excavations were covered as an added safety measure.
Another emerging challenge in the latter part of the construction was COVID-19 pandemic. Due to lock downs of public schools and businesses, pedestrian traffic increased in the subdivision, requiring an even greater effort of keeping everyone safe around moving construction traffic. The proactive safety efforts undertaken by Garney and its subcontractors and vendors were appreciated and recognized multiple times by the local community and homeowner association.
Since the subdivision was built in the 1960s, some of the public utilities such as power and communication lines were installed above ground. The installation of the new stormwater conveyance system required relocation of some of the existing utilities The existing high pressure 12-in. gas main on Hayfield Road was relocated on the opposite side and gas services to residents were also raised underground to allow enough clearance for stormwater box culverts. At some locations, the existing power lines on poles were raised to allow constructability of the new stormwater conveyance system. Several electrical conduits were also raised to allow enough underground clearance.
The most important utility relocation was the installation of new 8-in. PVC sanitary sewer line approximately 2,000 lf with 9 new sanitary sewer manholes, 22 new 6-in. sanitary sewer laterals with cleanouts installed parallel to new stormwater system to service residents on south of Hayfield Road. Since the excavation for the new 8-in. sanitary sewer was in close proximity to power and communication poles, a support system called Ver-t-Pole was installed to support these poles as the construction progressed.
Due to heavy traffic volume on Telegraph Road intersection with Hayfield Road and nearby public schools, the project owner only allowed the construction of 48-in. RCP in the intersection with a challenging time-restrained period of May 2019 to July 2019, which included approximately 150 lf of 48-in. RCP installation via traditional jack-and-bore method. The new 48-in. RCP was jacked approximately 16 ft underneath the intersection. An extensive maintenance of traffic system including relocation of signal heads on Hayfield Road was in place to divert traffic away from the open excavation.
Garney’s jack-and-bore subcontractor, Midwest Mole, completed the trenchless installation in under a month. All major utilities at the intersection were test pitted and visually verified before trenchless installation could took place.
The construction started October 2019 and finished in July 2020, approximately 4 months ahead of schedule The project restoration efforts included installation of new concrete header curb approximately 6,000 lf including new concrete driveway aprons and sidewalks measuring over 8,000 sq ft. Over 1 mile of roadway was also freshly paved with asphalt as part of restoration.
Overall, the community and public feedback was very positive and very much appreciated throughout the construction timeframe and of the end-product, which was put in place just in time for the arrival of Hurricane Isaias in August 2020.