Mending a Toxic Mountain; Lehigh Gap Nature Center

Project type: Revegetation, Bioremediation 
Location: Lehigh Gap Nature Center, Slatington/Palmerton PA [open Google map]
Status: Revegetation efforts complete, research ongoing, open to public

A while back I emailed Tom Whitlow, professor of restoration ecology at Cornell, asking him where to find some restoration sites in the northeast.  He graciously responded with a long and helpful list, at the top of which was Lehigh Gap Nature Center.  "It's an EPA Superfund site and is impressive in all of its aspects.  Truly Impressive, both for its successes and failures."

It didn't take long to convince me.  At very first glance, driving across the flatlands of eastern PA, a massive mountain chain seemed to suddenly spring up in the distance—a great green wall—except at one point where a river split the chain in two, where sides were rockier and less green than elsewhere.  This was the Lehigh Gap.  On one side towers Blue Mountain, home of a ski resort and toxic slag piles; on the other, Lehigh Gap Nature Center (LGNC), a restoration site and subject of this article.

Both sides are part of a ridgeline known as Kittatinny.  To its early inhabitants, the Lenape, the name meant "endless mountain."  Unfortunately, later inhabitants nearly did put an end to it, polluting its soil, destroying its vegetation and eroding its slopes.  Fortunately these conditions are being reversed through restoration ecology. 

Zinc Production, Mountain Destruction

  • Arrival of the  New Jersey Zinc Company (1898).  Inexpensive real estate, the availability of coal from nearby coalmines, canal and railway access, and close proximity to NJ made this area ideal.   Led by president Stephen Palmer, the company constructed two smelters and founded the settlement of Palmerton. [1]
  • Zinc production averaged 300 tons daily (1912-1979).  This zinc contributed to early alkaline batteries, cables in the Brooklyn Bridge, shell casings for WWII ammunition, and commodities such as cosmetics, tires and paint.
  • During that period, sulfuric acid output averaged 500 tons daily.  While 99.5% of this byproduct was harvested, the remaining 0.5% (2.5 tons per day) entered the atmosphere.
  • Also during that time, 33 million tons of waste containing cadmium, iron and other heavy metals, was dumped into a 2.5 mile long, 100-foot high, 500 to 1000-foot wide slag pile along Blue Mountain.
  • Nearly eight decades of these toxic practices led to a total defoliation, loss of wildlife, erosion of soil, and contamination of water in the region.  The mountain was left a desolate, rocky moonscape.
Photo courtesy of Lehigh Gap Nature Center website.

In 1983, the Environment Protection Agency (EPA) declared Palmerton a Superfund Site. [2]  This designates contaminated areas to be remediated under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) of 1980, and to be researched and advised under the Agency for Toxic Substances and Disease Registry. [3]

In 2002, the LGNC purchased the mountain.  The nearly $1 million acquisition was assisted by Viacom (who had a stake in the land following mergers and acquisitions) and the PA DCNR (who provided a $250,000 grant). [4]

Display @ LGNC Visitors Center

In 2003, a private consultant oversaw the planting of 56 test plots, each with combinations of mostly warm-season grasses (see below), as well as some cool-season grasses and amendments.  Tractors with spreaders sowed most areas, while volunteers on foot sowed the steeper slopes.  The tests were successful, encouraging larger scale sowing of warm-season grasses.

In 2004, LGNC hired a biplane to experiment with aerial seeding.  Following some delays, full-scale aerial seeding took place in 2006.

Ecosystem types

Display @ LGNC Visitors Center

Grassland can be found throughout the LGNC's higher slopes, where harsher conditions prevent the establishment of larger species.  

 Warm season grasses were central to the restoration strategy due to the following advantages:
  •   Deep roots - drought tolerant, able to draw moisture from far down.  Also able to draw nutrients from deep in the subsoil, making them available on the surface. 
  •   Slow growth - suited to such an environment with little competition.
  •   Clumping growth - spaces between clumps allow for wildlife habitat and establishment of other plants.
  •   Soil building  - root system dies back by 1/3 annually, adding organic matter to the soil.  The grasses also die back, adding a mulch layer to the surface.
  •   Toxin tolerance - crucial for such an environment contaminated with zinc and lead.   
During my visit in July of 2015, most plots seemed overgrown with Birch trees, representing increased fertility and succession to the next ecosystem stage.

Display @ LGNC Visitors Center

Scrublands are home to woody vegetation, such as staghorn sumac, clethra, silky dogwood, spicebush, viburnum, elderberry and American hazelnut.  This ecosystem type is spreading naturally on the upper slopes.  It is also maintained deliberately in a strip of land near the Visitor Center.  Here, the Pennsylvania Power and Light Company (PPL) owns lines and requires tree-cutting to protect them.  Breaking from standard PPL protocol of spraying herbicides, LGNC cuts by hand and forms brush piles for wildlife habitat.

Display @ LGNC Visitors Center

Forests can be found in various forms throughout the LGNC.  Older red oak, chestnut oak and pitch pine persist on the southwestern slopes, farthest from the former zinc smelter.  Fast-growing red maples, sassafras and sweet birch have also established in many areas more recently.  In any case the largest trees can be found in the gulleys, where increased moisture and greater protection from extreme weather probably helped.   Ferns proliferate in most understories.

LGNC manages its Oak savannas with prescribed burns.

In September of 2014, the EPA issued an Excellence in Site Reuse Award to LGNC for achieving the "ultimate environmental goal of turning a formerly contaminated site back to nature." [5]

Check out more forest restoration sites:
 - Conococheague Creek, PA
 - Gene Rush WMA, AR
 - Ouachita NF, AR
 - Warren Prairie, AR
 - Longleaf Pines in Louisiana and Texas

[1] Cajetan Berger, "Ex-zinc Company Official Speaks at Nature Center." Times News. April 12th, 2013. [link]
[2] "Mid-Atlantic Superfund: Palmerton Zinc." Environmental Protection Agency. [link]
[3] "Public Health Assessment: Palmerton Zinc Pile." Agency for Toxic Substances and Disease Registry. [link]
[4] Robert Hoopes, "Five Years Ago and Back to the Future," Wildlife Activist: #58, Spring 2007. [link]
[5] "EPA Announces Excellence in Site Reuse Award for Pa. Lehigh Gap Nature Center." Environmental Protection Agency (Sept. 26, 2014). [link]

LGNC Website [link]


  1. Does that list of restoration projects have others in eastern PA or in NJ? Send me an e-mail at the lmtree address.

  2. In the meantime, the EPA link needs an update, possibly with the announcement of an award: EPA Announces Excellence in Site Reuse Award for Pa. Lehigh Gap Nature Center.

    1. Link fixed and suggestion added. Thanks Dad... err I mean anonymous person.