Due to the geology of the anthracite region in Scranton the room and pillar method was used. First a gangway would be driven into the bed, or vein of anthracite. Off of the gangway, rooms of anthracite would be mined. Separating the rooms, were pillars or solid blocks of coal left behind to support the roof, and overlying surface. Much of which had been built upon. Schools, churches, homes, etc. Once mining was completed at the boundary of the individual mine. Third or retreat mining would be conducted working back through the mine to the area where mining had begun. The pillars left to support the surface were reduced in size by 85 percent, or removed entirely. The roof and surface could be disrupted and cave immediately, or 100 years after mining had ceased. Causing great damage to the surface. The purpose of this was to mine or remove as much of the anthracite as possible. And although great damage was caused on the surface, the mining companies were protected by the laws in place at the time. When purchasing a property in Pennsylvania you do not purchase the ground below your house. This is called mineral rights. Rather you purchase just the surface. With large individuals purchasing the mineral rights, who in turn sold them to small mining companies. Ultimately being absorbed and consolidated into larger companies.
On November 1st, 1960 the pumps in Lackawanna county were shut down permanently. It was these pumps that kept the groundwater from seeping into the mines and flooding the coal measures. As it was the lower veins or beds were allowed to fill with water years before as pumps were pulled, and abandoned. By 1962 the water had reached equilibrium at 609 ft. above sea level. The only mining that continued were small operations that lay above the water pool that formed under Lackawanna county. Finally in 1966 the last mine shut down and was abandoned. Sections of Scranton that had not already been exposed to mine subsidence’s or “caves” began to settle. Huge holes began to open up unexpectedly . Whole neighborhoods became victims of large subsidence’s. Scranton, once the capital of anthracite, was now just a battered wasteland. Even gaining the reputation of “being built on toothpicks” as quoted in a Wall Street journal article. Unemployment was in double digits, factories, and stores sat abandoned. Only three out of seven railroads remained solvent. Huge cracks and holes were everywhere, and a permanent haze hung over the city from the huge culm bank fires that burned. Even a whole neighborhood was relocated and torn down so that an underground mine fire could be dug out, and extinguished.
As a result of these conditions, both federal and state money began to pour into the region. One visible action was “flushing” projects that began. The purpose of these flushing , or backfilling projects was two fold.. First it would stabilize the surface above. Second the large culm banks that dotted the region could be used as the material to fill the mine voids below. Before a flushing project was begun, a needs analysis was conducted. Taking into consideration the value of properties in the area to be flushed, a review of mining maps to determine the conditions below, and third the history of subsidence . As stated previously both state and federal funds were used. State projects were called PH&S, Public Health & Safety projects. Federal projects were ASP, or Appalachia Subsidence Projects. The process of flushing began with the location of a culm bank for raw material. Next, boreholes would be drilled into the ground to the mines below. Usually being 6 to 9 inches in diameter, and then lined with cast iron pipe. Back at the culm bank a crushing plant would be assembled to crush the raw culm material into minus a half inch diameter material. Then trucked to the borehole being used. At this point flushing could be conducted using two methods.
The first method being “blind flushing”. In this method a vast quantity of boreholes would be drilled. A central mixing site would be operated, where the crushed culm would be mixed with water and forced under pressure through a series of pipes that would meander through the area. Finally reaching the borehole being used. A top that borehole a gauge measuring the back pressure would be monitored. When the pressure reached a determined point, it would indicate that the underground void was filled to capacity. And flushing would be stopped. The flush material would then be directed through pipes to the next borehole to be flushed. Blind flushing was in later years the preferred method of backfilling the mine voids below. Liability was limited, and the greater pressure used, forced the material into areas that could not be accessed using the second method of flushing. When drilling a borehole air was injected into the borehole to clear it of drill cuttings. When air was lost going through an opening, it was determined that the flush material could be forced into the area even if broken or badly caved material was encountered in the mined vein indicating the roof in the mine had collapsed. Later when the newly formed bureau of surface mining assumed leadership over the flushing projects, they would be funded by labeling them as “demonstration” projects. Testing new methods of flushing.
The second method of flushing used in the early flushing projects was called “controlled flushing”. In this method a smaller number of boreholes would be drilled. Old mine openings would be reopened so that workers could enter the old mine workings. Or if none were available, a 42 inch borehole would be drilled. And a hoist placed at the top. A capsule would be used to lower or raise the workers into the mine. In the controlled flushing method there was no central mixing plant. Instead a single hopper of various capacities would be placed above a borehole and connected to it. In this hopper the crushed culm material would be mixed with water. At the bottom of the borehole the workers would connect to it, by placing an elbow . Then they would run piping underground to the exact area to be flushed. Gravity would provide the pressure down the borehole and the worker below would manually by hand direct the flush material into the area. Controlled flushing could be time consuming, and labor intensive. As the various mine voids had to be made temporarily safe for the workers. This involved removing large amounts of rock that had fallen, and also timbering the same areas. Also according to state mining laws fresh air had to provided, and a second opening available to be used in an emergency. If natural ventilation was not sufficient, then a second 42 inch borehole would be drilled, and a fan placed a top of it. Fresh air would be forced down the borehole, instead of flush material. The benefits of controlled flushing were visual confirmation that a particular area was completely filled from floor to roof. Also the series of flushing pipes that meandered along city streets was eliminated.
There were several controlled flushing projects within the city, we will focus on a few of them here:
ASP No. 11 – South Scranton – Boreholes #1 & #2, Hemlock Street, Borehole B on Hickory Street, Borehole A on River Street.
ASP No. 12 – Phase 1- Hill section, East Side of Scranton’s Hill Section – Borehole #1 on North Irving.
ASP No. 12 – Phase 2- Hill section, West Side of Scranton’s Hill Section – Clay Ave Access Borehole
SMCRA created an Abandoned Mine Land (AML) fund to pay for the cleanup of mine lands abandoned before the passage of the statute in 1977. The law was amended in 1990 to allow funds to be spent on reclamation of mines abandoned after 1977. The fund is financed by a tax of 35 cents per ton for surface mined coal, 15 cents per ton for coal mined underground, and 10 cents per ton for lignite. Half the AML fees collected in each state with an approved reclamation program (see below) are given to that state to fund its reclamation program. The other half is used by OSM to respond to emergencies such as landslides, land subsidence, and fires, and to carry out high priority cleanups in states without approved programs. States with approved programs can also use AML funds to set up programs to insure homeowners against land subsidence caused by underground mining.
Beginning in 1977 OSM took over responsibilities of major projects from the United States bureau of mines. And over the years undertook the flushing projects in or near Scranton:
Hickory Street –
In 1976 at the request of the City of Scranton an underground inspection was performed. Access boreholes from ASP 11 were reopened. There inspection revealed that the pillars left behind to support the surface and overlying coal beds were “shafing”. When anthracite is exposed to air it tends to deteriorate. Actually chipping away. To aggravate this problem, the pillars were not columnized. Pillars in overlying coal beds did not lie directly over the pillar in the lower beds. This allowed the pillars to get driven into the rock interval between beds, offering no support. A massive subsidence was a great probability.
This project took place from August 12, 1977 to it’s final inspection on July 18,1980. The project area was located in Scranton’s South side, and abutted an area flushed by OSM’s predecessor the United States bureau of mines, Appalachia subsidence project ( ASP) eleven. The unique aspect of this project was that the areas being flushed were accessed through two 42 in. boreholes. Gangways in the New County & Clark veins were repropped, and cleared of any debris. Actual first hand visual confirmation of blind flushing was performed.
The contract for this project was awarded to the No. 1 contracting. A supply of culm was obtained from the Pine Ridge bank near Wilkes-Barre and permission was obtained from Penn Anthracite to flush the actual mine voids. In the area there were four beds. Clark, New County, Dunmore Number 1, and the deepest the Dunmore Number 2. Water for the project was obtained by drilling a borehole into the Dunmore number three, which was completely filled with water.
From its inception OSM had an abundance of money to perform these projects. Thanks to two long standing highly influential members of congress. Daniel Flood and Joseph McDade. These two members would often obtain funding, before there was a need. Mainly through manipulating the projects from a proactive approach, to being demonstration projects. In other words trying new methods, to make flushing more successful.
US Bureau of Mines photos from the flushing projects in Scranton, 1960s and early 1970s.
Our photos of a manway entrance in Olyphant, used for flushing the mines in the area. Now sealed, 2022.