U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2011–3101

August 2011 Printed on recycled paper

Trace Metals Related to Historical Iron Smelting at Hopewell 

Furnace National Historic Site, Berks and Chester Counties, 

Pennsylvania

Iron ore containing elevated concentrations of toxic trace metals was smelted at Hopewell Furnace during its 113 years of operation. 

Iron ore, cast iron furnace products, slag, soil, groundwater, streamwater, and streambed sediment were sampled to determine the distribution 

and concentrations of trace metals released into the environment during historical iron-smelting operations. In addition, benthic-macroinvertebrate samples were collected, and habitat surveys were completed at five stream sites to assess possible effects of past smelting operations 

on aquatic life. Toxic metals were not present at concentrations of concern in water, soil, or stream sediments, despite being elevated in ore, 

slag, and cast iron furnace products. 

Introduction

Iron ore containing elevated concentrations of trace metals 

was smelted at Hopewell Furnace during its 113 years of operation 

(1771–1883). The ore used at Hopewell Furnace was obtained from 

iron mines within 5 miles of the furnace. The iron-ore deposits 

were formed about 200 million years ago and contain abundant 

magnetite, the primary iron mineral, and accessory minerals 

enriched in arsenic, cobalt, copper, lead, and other metals. 

Hopewell Furnace (fig. 1), built by Mark Bird during 1770–

71, was one of the last of the charcoal-burning, cold-blast iron 

furnaces operated in Pennsylvania. The most productive years for 

Hopewell Furnace were from 1830 to 1837. Castings were the most 

profitable product, especially the popular Hopewell Stove. More 

than 80,000 stoves were cast at Hopewell, which produced as many 

as 23 types and sizes of cooking and heating stoves. Beginning in 

the 1840s, the iron industry shifted to large-scale, steam-driven 

coke and anthracite furnaces. Independent rural enterprises like 

Hopewell could no longer compete when the iron and steel industries consolidated in urban manufacturing centers. The furnace 

ceased operation in 1883 (Kurjack, 1954). 

The U.S. Geological Survey (USGS), in cooperation with 

the National Park Service, completed a study at Hopewell Furnace National Historic Site (NHS) in Berks and Chester Counties, 

Pennsylvania, to determine the fate of toxic trace metals, such as 

arsenic, cobalt, and lead, released into the environment during historical iron-smelting operations. The results of the study, conducted 

during 2008–10, are presented in this fact sheet. 

What Was Sampled 

Iron ore, slag, soil, groundwater, streamwater, streambed 

sediment, and benthic macroinvertebrates were sampled at and 

near Hopewell Furnace during 2008–10 (fig. 2) and analyzed using 

standard techniques. Cast iron furnace products in the Hopewell 

museum were analyzed in partnership with West Chester University 

using a portable X-ray fluorescence spectrometer, which allowed 

on-site, nondestructive, real-time analysis. Complete analytical 

results and details of the USGS study at Hopewell are presented in 

the technical report by Sloto and Reif (2011).

Results of Sampling 

Iron-ore samples from two of the mines that supplied ore to 

Hopewell Furnace were analyzed for trace metals. Most of the ore 

samples contained concentrations of arsenic, cobalt, copper, iron, 

lead, manganese, nickel, vanadium, and zinc that are typical of 

local iron ore but higher than the average concentrations found in 

most rocks.

Slag, a glass-like waste material produced during the ironsmelting process, was discarded near the furnace. Laboratory 

analyses of samples from three slag piles near the furnace showed 

manganese, iron, nickel, and zinc were concentrated in slag. 

Soil was sampled at eight locations. Seven sites were near the 

furnace, and one site about 0.6 mile away from the furnace was 

sampled for comparison (background conditions). The soil near 

the furnace had elevated concentrations of chromium, copper, iron, 

lead, and zinc compared to the background soil samples. However, 

the concentrations of trace metals met Pennsylvania Department of 

Environmental Protection standards for non-residential use. 

Figure 1. The cast house at Hopewell Furnace National Historic 

Site, Pennsylvania. The cast house encloses the furnace. The stone 

stack of the furnace is visible on the left side of the cast house. In 

the foreground, part of the furnace slag pile is exposed and makes 

up the left bank of French Creek.
Ten cast iron artifacts on display in the Hopewell Furnace 

visitor center museum, including eight stoves, a footed pot, and a 

kettle, were analyzed for trace-metal content. Results of the analyses indicate that arsenic, chromium, copper, lead, and zinc were 

incorporated into the cast iron through the smelting process during 

production at Hopewell Furnace. 

Hopewell Furnace NHS uses groundwater to supply drinking water to park visitors and employees. A groundwater sample 

collected from the park well for field and laboratory analysis met all applicable U.S. Environmental Protection Agency 

drinking-water standards. 

Five stream sites were sampled during fall low-flow conditions. Four sites were on French Creek, and one background site 

was on Baptism Creek (fig. 2). Streamwater, streambed sediment, 

and macroinvertebrates were sampled, and a habitat evaluation 

was conducted at each site. Results of chemical analyses of the 

streamwater indicated good overall water quality. The background 

site on Baptism Creek generally had the lowest concentrations of 

constituents. Concentrations of metals in the streamwater samples 

met U.S. Environmental Protection Agency criteria for protection 

of aquatic organisms. 

Streambed-sediment sampling results indicated higher concentrations of all metals, except nickel, at sites on French Creek 

than at the background site on Baptism Creek. Concentrations 

of aluminum, cadmium, and nickel were highest in sediment at 

the most upstream site on French Creek and generally decreased 

in concentration downstream, indicating that the source of these 

metals is upstream from Hopewell Furnace and that the metals are 

possibly related to discharge from Hopewell Lake. The highest 

concentrations of arsenic, boron, cobalt, copper, iron, lead, manganese, mercury, and zinc were measured in sediment at sites on 

French Creek below Hopewell Furnace, indicating that the source 

of these metals may be related to Hopewell Furnace operations. 

Concentrations of metals, except copper, in sediment at the five 

stream sites met guideline concentrations for protection of aquatic 

organisms. The concentration of copper at one site exceeded the 

guideline concentrations.

Sampling of benthic macroinvertebrates (bottom-dwelling 

organisms, such as insect larvae, worms, and clams) showed that 

all four sites sampled on French Creek had disturbed communities 

and degraded stream conditions for aquatic life when compared 

to the background site on Baptism Creek. Habitat evaluations 

were performed to assess the surrounding physical habitat that 

affects the condition of the benthic-macroinvertebrate community. 

Habitat conditions at the background site on Baptism Creek and the 

upstream site on French Creek were good, but degraded conditions 

were found at downstream sites on French Creek that appear to be 

related to a lack of stable substrate, erosion, and deposition. 

Summary and Conclusions

A study was done by the U.S. Geological Survey, in cooperation with the National Park Service, to determine the distribution 

and concentrations of trace metals in Hopewell Furnace NHS 

related to historical iron-smelting operations. Iron ore, slag, cast 

iron furnace products, soil, groundwater, streamwater, and streambed sediment were sampled and analyzed for trace-element concentrations. In addition, benthic macroinvertebrates were analyzed 

in samples from the five stream sites where the streamflow and 

streambed-sediment samples were collected. 

Some trace metals were present in elevated concentrations 

in the iron ore smelted at Hopewell. Arsenic, chromium, copper, 

lead, and zinc were incorporated into the cast iron produced by 

Hopewell Furnace. Manganese was concentrated in slag along 

with iron, nickel, and zinc. The soil near the furnace had elevated 

concentrations of chromium, copper, iron, lead, and zinc compared 

to background soil concentrations. 

Arsenic, cobalt, lead, and other toxic metals, which could 

pose a significant health risk to visitors and park employees, were 

not released to soil, slag, groundwater, or streamwater. Soil samples 

collected from the Hopewell Furnace NHS met Pennsylvania 

Department of Environmental Protection standards for non-residential use. Groundwater samples from the park supply well met 

U.S. Environmental Protection Agency drinking-water standards. 

Concentrations of metals in streamwater at the five stream sampling sites met criteria for protection of aquatic organisms. Concentrations of metals in sediment from the five stream sampling sites 

met guidelines for the protection of aquatic organisms, with the 

exception of copper at one site.

—Ronald A. Sloto

References Cited

Kurjack, D.C., 1954, Hopewell Village National Historic Site 

Pennsylvania (now Hopewell Furnace): National Park Service 

Historical Handbook Series No. 8, accessed on February 25, 

2011, at http://www.nps.gov/history/history/online_books/hh/8/

hh8toc.htm.

Sloto, R.A., and Reif, A.G., 2011, Distribution of trace metals at 

Hopewell Furnace National Historic Site, Berks and Chester 

Counties, Pennsylvania: U.S. Geological Survey Scientific 

Investigations Report 2011–5014, 79 p.

Figure 2. Locations of slag, soil, and stream sampling sites in 

Hopewell Furnace National Historical Site, Pennsylvania.

For additional information, contact:

Director, U.S. Geological Survey

Pennsylvania Water Science Center

215 Limekiln Road

New Cumberland, PA 17070

http://pa.water.usgs.gov

B aptism

Creek

French

Creek

Hopewell

Lake

345

Visitor

center

Furnace

HOPEWELL FURNACE

NATIONAL HISTORIC SITE

BERKS COUNTY

CHESTER COUNTY

Stream sampling site

Soil sampling site

Stream sampling site

(background)

Soil sampling site

(background)

Slag sampling site

EXPLANATION

75°46'30" 75°45'30"

40°

12'

40°

12'

30"

0 0.1 0.2 MILE

0 0.1 0.2 KILOMETER