南波托马克供应改进项目
Temple Hills, Md.
Best Project
Owner:Washington Suburban Sanitary Commission
Lead Design Firm:Black & Veatch Corp.
General Contractor:Garney Cos.
Subcontractors:Eureka Concrete Construction Inc.; Kroeger Electric Co.
To combat failing prestressed concrete cylinder pipe (PCCP) in its system, the Washington Suburban Sanitary Commission has placed a high priority on replacing sections of existing PCCP with ductile iron or steel pipe. The $14.7-million South Potomac Supply Improvement Project addressed a critical WSSC water-supply line that affects about 180,000 customers in Prince George’s County, Md. The main serves as a primary feed to the National Harbor hotel-retail-casino development.
该团队安装了大约10,000个线性英尺42英寸。CL-56 ductile iron pipe with PRITEC coating along Henson Creek, portions of which disturbed and disrupted an existing hiking and bike trail through a park. Crews also removed and disposed of approximately 5,000 linear ft of existing 42-in. PCCP water main pipe. The project also included installing 10 precast concrete entry-port/air-release vaults; demolishing an existing flow-control vault; and constructing a new cast-in-place, flow-control vault structure, featuring remote flow adjustment using SCADA technology.
Construction of four 60-in.-dia jack-and-bore crossings, totaling 725 linear ft, presented some of the project’s greatest challenges, says Garney Cos., the general contractor. During construction of jack-and-bore sections below Henson Creek, Garney’s jack-and-bore subcontractor encountered an extremely hard layer of what turned out to be an ancient ocean floor oyster bed.
When traditional auger boring to get through that hard layer proved futile, the team implemented pipe ramming. That method—known to cause vibration—was marginally successful and the resulting vibration ultimately led to the collapse of Henson Creek and flooding of the tunnel and tunnel shaft. After immediately notifying the appropriate parties and stabilizing the situation by damming the creek and installing bypass pumping, the team received expeditious approval from environmental regulatory agencies to install the remaining portion of the trenchless crossing by open cut across Henson Creek. Quickly mitigating the emergency over one weekend avoided a negative impact to the project’s overall schedule and budget.
在道路下方建造千斤顶和孔区域之前，机组人员在无处不在的穿越地点确定了联邦政府的光纤通信线。多次尝试后，无法找到光纤实用程序。在确定光纤线不在杰克和钻孔的路径上之后，加尼指示杰克和钻孔分包商进行隧道。但是，在安装了40英寸60英寸的二号套管后，分包商遇到了被废弃的42英寸。PCCP Water Main与范围直接冲突。受现有的光纤实用程序和通行权约束的限制，加尼被迫放弃无沟口并安装42英寸。延性铁水主通过开挖。
在六个月的时间里，项目团队在批准开放计划之前，在乔治王子县进行了多次计划准备，审查和评论。Garney实施了一项实质性的临时交通管制计划，并按计划在两天内执行了开放切口。
Related Article:地区最好的工作遇到了重大挑战
