Mahanoy Township Authority

Lofty Dam Rehabilitation – Wetlands

Mahanoy Township, PA

Background: Benesch performed wetland determinations and delineations in accordance with the United States Army Corp of Engineers (USACE) Wetland Delineation Manual, Technical Report Y-87-1. The review identified wetlands at the toe of the Lofty Dam that would be impacted with the placement of fill for slope flattening.

Scope: Benesch completed a mitigation plan for the project. There were three potential jurisdictional features, two streams and one wetland. Based on the proposed Limit of Disturbance, it was estimated that there would be 0.493 acres of potential wetland impacts (0.356 acres potential permanent and 0.137 acres of potential temporary wetland impacts) associated with the project. The impacts to the potentially jurisdictional wetlands required compensatory mitigation by USACE. The mitigation report was completed as part of permit applications for authorizations under Sections 401 and 404 of the Federal Clean Water Act (CWA) of 1977.

A mitigation design was completed and construction completed prior to the Lofty Dam rehabilitation project impacts. Since the wetland installation and development, Benesch has completed annual Wetland Monitoring Reports. The purpose of the report is to provide documentation of the vegetative and hydrologic status of the wetland mitigation area. As part of the mitigation plan, monitoring includes establishing a sample of six plots that are approximately 1×1 meters in size within the mitigation area. The percent coverage of vegetation in each plot shall be recorded and utilized to determine: species composition of recruited, desirable plant species; species composition and coverage of nuisance/non-native plant species; wildlife utilization and depredation; hydrologic conditions; current site conditions using photographs at each plot point.

Following 3 years of monitoring, USACE and PADEP released the client from submittal of a formal annual monitoring report for the site, saving annual monitoring and reporting costs for the Authority. This was attributed to sound design and subsequent maintenance and monitoring of the site. The overall dam rehabiliation project was funded through a $3.8 million PennVEST Loan and a $1.7 million DCED CFA H2O Water/Sewer Grant.

 

Project highlights

  • Wetland mitigation required per Section 401 and 4040 of the federal Clean Water Act
  • Site released from monitoring by USACE and PADEP after three years of monitoring (permit required five years)
  • Monitoring release saved the client $7,500 annually