York Haven Dam

Conewago Falls in Lancaster County, Pennsylvania was a historic river barrier 12 miles (19 km) below and south of Harrisburg at a wide spot (8,000 feet (2,400 m)), where the river drops 19 feet (5.8 m) in 1⁄4 mile (0.40 km) along the lower Susquehanna River along either side of Three Mile Island. The falls between the west bank and the west side of the island were inundated-by-design years ago by construction of the York Haven Dam which, when it was completed in 1904, for a time became the third largest in the world. Today the Falls hides inside the Frederic Lake reservoir along the west side of the island. The falls would often be portaged around by Native Americans with their elm bark canoes transiting between Susquehannock (and later, Iroquois and Lenape) Amerindian towns at points upriver to the Oyster beds in Chesapeake Bay or vice versa. The Falls blocked riverine navigation on the Susquehanna River, and were one of the factors preventing barge or ship water transport from Baltimore and the Chesapeake Bay.

The Conewago Canal, on the west bank of the Susquehanna River below York Haven, Pennsylvania, 11 miles (18 km) south of Harrisburg in York County, enabled late 18th and early 19th century rivercraft to safely bypass rapids at Conewago Falls. Work on the canal of less than 1 mile (1.6 km) began in 1793 and was completed in 1797. Robert Morris, a Philadelphia financier, organized the project, which was carried out by chief engineer James Brindley, the nephew of a well-known British engineer of the same name. Two lift locks overcame 19 feet (6 m) of elevation between the ends of the canal, and a guard lock blocked unwanted water, particularly during floods. Cargo could go upstream as well as down. A boat going upriver could navigate the canal in 37 minutes compared to the whole day it would take 30 or 40 men to pull it upriver along the bank. York Haven is at 40°06′39″N 76°42′57″W.Despite the canal, flow variations limited the use of the river for shipping to a few months each year. In addition, river boat captains disliked paying the toll required to use the privately owned canal. River arks, a kind of boat less susceptible to damage from rocks in the rapids, made it possible to run the rapids and avoid the toll. The Eastern Division of the Pennsylvania Canal, which ran between Columbia and the mouth of the Juniata River, later bypassed this same section of the river.

York Haven is a borough in York County, Pennsylvania, United States. The population was 691 at the 2020 census. The borough is the home of the Brunner Island coal-fired electrical generation plant, located on the Susquehanna River on Wago Road and operated by PPL Corporation.

Falmouth is an unincorporated community and census-designated place (CDP) in Conoy Township, Lancaster County, Pennsylvania, United States. As of the 2010 census the population was 420.

Cly is an unincorporated community in Newberry Township, York County, Pennsylvania, United States. Cly is located on Cly Road Route 262, between York Haven and Goldsboro on the Susquehanna River.

Governor Stable is a notable geologic formation in northern Lancaster County, Pennsylvania. Scattered along the northern bank of a small drainage are a high number of large diabase boulders. Governor Stable is privately owned. Friends of Governor Stable administers a recreational lease on the property, allowing organization members access to the property for bouldering.

Brunner Island Steam Electric Station is a coal-fired, alternatively natural gas-powered electrical generation facility in York County, Pennsylvania. It occupies most of the area of the eponymous island on Susquehanna River. The power plant has three major units, which came online in 1961, 1965, and 1969, with respective generating capacities of 334 MW, 390 MW, and 759 MW (in winter conditions). In addition, three internal combustion generators (2.8 MWe each) were installed in 1967. Talen Energy will stop coal use at the plant in 2028.

Conoy Township is a township in northwestern Lancaster County, Pennsylvania, United States. At the 2010 census the population was 3,194.

Bridge between East Manchester and Newberry Townships is a historic Pennsylvania (Petit) truss bridge spanning Conewago Creek East Manchester Township and Newberry Township, York County, Pennsylvania. The bridge was built in 1889 by the Wrought Iron Bridge Company and measures 299 feet (91 m) in overall length. The bridge was taken out of service about 1985, and is located alongside the new bridge. It was added to the National Register of Historic Places in 1988.

The Three Mile Island accident was a partial nuclear meltdown of the Unit 2 reactor (TMI-2) of the Three Mile Island Nuclear Generating Station on the Susquehanna River in Londonderry Township, near the capital city of Harrisburg, Pennsylvania. The reactor accident began at 4:00 a.m. on March 28, 1979, and released radioactive gases and radioactive iodine into the environment. It is the worst accident in U.S. commercial nuclear power plant history. On the seven-point logarithmic International Nuclear Event Scale, the TMI-2 reactor accident is rated Level 5, an "Accident with Wider Consequences".The accident began with failures in the non-nuclear secondary system followed by a stuck-open pilot-operated relief valve (PORV) in the primary system that allowed large amounts of water to escape from the pressurized isolated coolant loop. The mechanical failures were compounded by the initial failure of plant operators to recognize the situation as a loss-of-coolant accident (LOCA). TMI training and operating procedures left operators and management ill-prepared for the deteriorating situation caused by the LOCA. During the accident, those inadequacies were compounded by design flaws, such as poor control design, the use of multiple, similar alarms, and a failure of the equipment to clearly indicate either the coolant-inventory level or the position of the stuck-open PORV.The accident crystallized anti-nuclear safety concerns among activists and the general public, and led to new regulations for the nuclear industry. It accelerated the decline of efforts to build new reactors.Anti-nuclear movement activists expressed worries about regional health effects from the accident. Some epidemiological studies analyzing the rate of cancer in and around the area since the accident did determine that there was a statistically significant increase in the rate of cancer, while other studies did not. Due to the nature of such studies, a causal connection linking the accident with cancer is difficult to prove.Cleanup at TMI-2 started in August 1979 and officially ended in December 1993, with a total cost of about $1 billion (equivalent to $2 billion in 2022). TMI-1 was restarted in 1985, then retired in 2019 due to operating losses. Its decommissioning is expected to be complete in 2079 at an estimated cost of $1.2 billion.

Three Mile Island Nuclear Generating Station (commonly abbreviated as TMI) is a closed nuclear power plant on Three Mile Island in Londonderry Township, Dauphin County, Pennsylvania on Lake Frederic, a reservoir in the Susquehanna River just south of Harrisburg. It has two separate units, TMI-1 (owned by Constellation Energy) and TMI-2 (owned by EnergySolutions).The plant was the site of the most significant accident in United States commercial nuclear energy when, on March 28, 1979, TMI-2 suffered a partial meltdown. According to the Nuclear Regulatory Commission (NRC) report, the accident resulted in no deaths or injuries to plant workers or in nearby communities. Follow-up epidemiology studies did not find causality between the accident and any increase in cancers. One work-related death has occurred on-site during decommissioning.The reactor core of TMI-2 has since been removed from the site, but the site has not been fully decommissioned. In July 1998, Amergen Energy (now Exelon Generation) agreed to purchase TMI-1 from General Public Utilities for $100 million.The plant was originally built by General Public Utilities Corporation, later renamed GPU Incorporated. The plant was operated by Metropolitan Edison Company (Met-Ed), a subsidiary of the GPU Energy division. In 2001, GPU Inc. merged with FirstEnergy Corporation. On December 18, 2020 - FirstEnergy transferred Unit 2's license over to EnergySolutions' subsidiary TMI-2 Solutions after receiving approval from the NRC.Exelon was operating Unit 1 at a financial loss since 2015. In 2017 the company said it would consider ceasing operations at Unit 1 because of high costs unless there was action from the Pennsylvania government. Unit 1 officially shut down at noon on September 20, 2019.Unit 1 decommissioning is expected to be completed in 2079 and will cost $1.2 billion. Unit 2, which has been dormant since the accident in 1979, is expected to close in 2052.

Conewago Township is a township in York County, Pennsylvania, United States. The township encompasses the land between the Conewago Creek and the Little Conewago Creek, west of their conjunction. The township was formed in 1818 from the northeastern portion of Dover Township and the southeastern portion of Newberry Township and consists of approximately 11,000 acres. The population was 8,527 at the 2020 census.