Solar Array Design at the Ballenger-McKinney Wastewater Treatment Plant

Client:                  Northeast Maryland Waste Disposal Authority

Location:             Frederick County, Maryland

EA provided engineering support to the Northeast Maryland Waste Disposal Authority and Frederick County for the installation of an approximately 1.3-megawatt DC photovoltaic (PV) solar array and battery energy storage system at the Ballenger-McKinney Wastewater Treatment Plant (WWTP). Specific services provided included feasibility studies and analysis, drafting of Request for Proposal language and technical specifications, bid analysis, oversight of the design-build process including permitting, and system commissioning. EA served as the County and Authority’s engineer for advisory services, as well as review and approvals throughout the design-build process.

With a design capacity of 15 million gallons per day, the Ballenger-McKinney WWTP serves more than 25,000 residences and businesses and is the County’s largest wastewater facility. It had historically experienced unplanned outages from the power utility.

Situated on 5 acres, the fixed-tilt PV panels offset approximately 17% of the plant’s power requirements and, in the event of a complete power outage, eight 130-kilowatt lithium-ion batteries utilize a programmable logic controller for optimized load shedding to ensure operations of critical equipment and systems to prevent sewer overflows for up to 4 hours.

During the planning stage of the PV solar and battery energy storage, EA provided advisory services for the County and managed feasibility studies conducted by a subcontractor. Glare/glint, shading, and viewshed analyses were completed. EA then worked with the Authority/County to determine relevant considerations for project management such as permitting timelines and order of magnitude system sizing based on awarded grant funding for the project and site constraints. Our team performed a review of existing electricity usage and demand at the WWTP, an evaluation of the critical equipment and loads in need of power during unplanned outages, budgetary level cost estimation to determine potential sizing, and potential tie-in locations of the PV system at the WWTP based on existing electrical equipment. These services allowed for the Authority/County to determine a scope of work for the Request for Proposal that met the County’s needs, but also stayed within budgetary and site constraints. Notably, the original scope of work included only a PV system for solar generation at the site; however, based on the preliminary analysis performed by EA, it was determined that a battery energy storage system would be added to the project scope in order to provide the WWTP a dependable backup energy source during times of power utility unplanned outages. To date, less than a year from commissioning, the battery energy storage system has already successfully come online in 2021 during an unplanned outage from the power utility, allowing critical equipment to continue operating and preventing a potential sewage backup at the plant headworks.

Based on the conceptual analysis and feasibility studies, EA prepared technical specifications for the Solar PV and Battery Design-Build Request for Proposal. Our team prepared ranking criteria and evaluated the technical completeness of the received bids for the Authority/County to use in bid selection. Upon award of the project, EA continued to provide support by reviewing and approving submittals, design drawings, change orders, and payment applications submitted by the contractor. All analyses, reviews, and deliverables were completed in a fast-turnaround schedule to successfully use Maryland Department of the Environment’s Energy Water Infrastructure Program grant funding.

Our team also provided limited on-site oversight and quality assurance during construction including permitting assistance, change-order/claims negotiations, submittal review, and construction oversight as needed. An on-site inspector oversaw critical construction activities, reviewed delivered materials against approved construction drawings, and provided technical engineering support and guidance as needed.