# Merrimack

ISO-NE asset profile · https://askthegrid.com/assets/facilities/merrimack

GSP Merrimack LLC - Merrimack County - ISONE

Merrimack Station is a fossil-fuel electric generating facility at 431 River Road in Bow, New Hampshire, consisting of two bituminous-coal steam generating units (MK1, Babcock & Wilcox RB-337 cyclone boiler, approximately 113.6 MW; MK2, Babcock & Wilcox UP-42 cyclone boiler, approximately 345.6 MW) and two petroleum-liquid combustion turbines (MKCT1 and MKCT2, both Pratt & Whitney FT4A-8LF, 18.6 MW each). MK1 and MK2 were permanently disabled in December 2025. MKCT1 and MKCT2 remained active as of the latest regulatory filings. The facility ceased coal-fired commercial operations on September 12, 2025, several years ahead of the announced June 2028 retirement date. GSP Merrimack LLC, a wholly owned subsidiary of Granite Shore Power LLC (ultimately owned by Atlas Holdings following its acquisition of Castleton's remaining interest in January 2022), owned and operated the station. The operator has announced a planned redevelopment involving a 120 MW combined solar and battery energy storage system.

## Metrics

- **Nameplate capacity:** 150.79999999999998 MW — Canonical EIA plant baseline.
- **Registry anchor:** Plant 2364 — plant-2364

## Facts

- **Technology:** Conventional Steam Coal, Petroleum Liquids
- **Operator:** GSP Merrimack LLC

## Related parties

- **Parent company:** Granite Shore Power LLC — Parent company; Granite Shore Power is the joint venture that acquired the asset and holds GSP Merrimack LLC ([source](https://www.graniteshorepower.com/))
- **Parent company:** Atlas Holdings — Ultimate holding company; Atlas Capital Resources affiliate ACR II acquired Castleton's remaining interest ([source](https://www.atlasholdingsllc.com/))
- **Regulator:** U.S. Environmental Protection Agency, Region 1 — Federal environmental regulator; NPDES permitting authority ([source](https://www.epa.gov/))
- **Regulator:** New Hampshire Department of Environmental Services — State air permitting authority ([source](https://www.des.nh.gov/))

## Sources

- [nepool.com](https://nepool.com/wp-content/uploads/2022/02/Lit_Report_20220201.pdf) — nepool.com · public_source — Source retained for exact-record publication review.

---

Canonical page: https://askthegrid.com/assets/facilities/merrimack
Website: [GSP Merrimack LLC](https://www.graniteshorepower.com/)

Source: Ask the Grid — https://askthegrid.com/