Of the thousands of visitors who will immerse themselves in the rich heritage of Alexandria, Va., this summer, only one will have the job of helping the city just south of Washington, D.C., make some history of its own.

The new arrival is a 380-ton tunnel boring machine (TBM) that will play a key role in Alexandria’s largest infrastructure project to date—the $665-million RiverRenew initiative to remediate longstanding combined sewer overflow (CSO) issues and improve the quality of city waterways.

美国环境保护局表示，Riverrenew将CSO频率从每年的70次活动减少到不到4个，也将水路溢流的平均溢流量从1.4亿加仑减少到不到1600万加仑。

14英尺，8英寸。高大的TBM将在完全组装时延伸465英尺，将挖一条两英里，12英尺宽的隧道，旨在在大雨期间从四个组合的下水道排放中收集约1.2亿加仑的污水。存储在隧道中的污水将逐渐被释放到该市的水资源回收设施，以进行治疗，并随后释放到波托马克河。该机器是由德国Schwanau的Herrenknecht设计和制造的。

TBM的切割速度为每分钟4.5旋转，以每小时20英尺的速度爬行，当时其长达一年的旅程在今年夏天晚些时候开始了100英尺。该过程的目的是完成，不会破坏现有的污水收集和治疗操作，这些污水收集和治疗操作为亚历山大县和费尔法克斯县邻近地区提供服务。

设计建造合资企业

Traylor Bros Inc.和J.F. Shea Co.的设计建设合资企业在Jacobs和Corman Kokosing Construction Co.的支持下开发了隧道项目，布朗和考德威尔（Brown and Caldwell）担任Alexandria Renew Enterprises的所有者代表，该城市的废水处理公用事业。

Other elements of the $454.4-million tunnel project include 75-ft and 40-ft deep TBM launch and recovery shafts that subsequently will be converted into high-capacity pump stations to empty both the tunnel and a new mile-long, six-ft-wide interceptor line.

亚历山大RiverRenew 2017 sta下实现的te mandate to fix overflows from the city’s 240-mile combined sewer network, parts of which have been in place since the 1800s. Due for completion by July 2025, the program is funded by state and federal sources, including a $321-million EPA loan. Pump station capacity upgrades and treatment facility improvements were completed last year in preparation for the tunnel work.

Named For Environmental Justice Pioneer

这只痣被命名为Hazel，以表彰环境法官先锋Hazel Johnson，后者于2011年去世。亚历山大人选择了她在线民意调查中的命名，其中包括其他五个人为城市，环境，工程或建筑领域做出了杰出贡献。

Johnson worked to improve living conditions in Chicago's public housing system, including organizing a grassroots effort to address landfill-related environmental and public health impacts. She also played a key role in efforts that led to President Bill Clinton's 1994 executive order解决环境正义影响少数群体和低收入人群的差异。