In order to meet the requirements of the federal coal combustion residual (CCR) rule, Dominion Virginia Power has undertaken several upgrade projects at their Chesterfield Power Station (CPS).
These upgrades included two ash pond closures, construction of a new landfill, construction of a new low-volume wastewater treatment system (LVWWTS), and conversion from a wet-to-dry ash management system. Geosyntec was asked to provide conceptual design and cost estimation; detailed design; federal, state and local permitting; and contractor bid preparation for the closure of the Lower Ash Pond (LAP) and construction of the LVWWTS.
Geosyntec's Scope of Services
Geosyntec prepared conceptual closure design drawings and a cost estimate for Dominion's planning purposes, resulting in cap-in-place of the CCR as the preferred closure option. We prepared a Class 2 cost estimate prior to issuing a bid package. We conducted a geotechnical field investigation to evaluate properties of the CCR and the underlying foundation soils and conducted a pump test to evaluate options for dewatering the wet sluiced CCR.
Using field investigation results, we prepared a cap-in-place closure design that included incorporating 1.2 million cubic yards of cap subgrade fill from new landfill construction, designing a stormwater control system to manage a full probable maximum precipitation event through a single outfall location, and incorporating a CCR Rule-compliant cap. We also designed a subsurface sheet pile for temporary construction sequencing purposes and geotextile tubes for management of CCR sediments.
As part of evaluation of the LAP embankment, we discovered the need for improvements so we designed a sheet pile wall and riprapped slope, providing construction quality assurance during installation. We prepared a design for the use of geotextile tubes for the purpose of managing soft CCR from the wet pool and stabilizing an area for soil stockpile. Dredging soft CCR from the wet pool and stabilizing in geotextile tubes minimized the need for the contractor to stabilize the soft CCR after dewatering. In addition, the geotextile tubes provided consolidation of underlying sediments with the intent to increase available volume of soil stockpile behind the tube wall.
Due to new state laws, Dominion could not conduct cap-in-place and was required to prepare for closure by removal. Therefore, Geosyntec prepared a temporary closure design that stabilized the ash and prevented contact stormwater runoff while we prepared the designs for closure by removal. We also provided construction assistance for the project.
Throughout the design and permitting process, multiple internal and external stakeholders were engaged in the closure process including federal, state, and local regulatory agencies; legal defense groups; environmental groups; and interested public. Geosyntec provided valuable support as Dominion continued to engage the stakeholders, helping make the entire permitting and public review period run very smoothly and saving them unnecessary delays and associated costs.
- Location: Richmond, Virginia
- Client: Dominion Virginia Power
- Project Practice Areas: Geotechnical
- Type of Facility: Coal-fired power plant
- Services Provided: CCR geotechnical investigations, Water quality assessment, Closure design and contractor bid preparation, Federal, state, and local permitting, Sheet pile, geotextile tube designs
- Type of Work: Coal ash pond closure
- Governing Regulation: Federal and state