Last updated: 05.07.04 Nadav_Carmel@Brown.edu

First, the study area was narrowed down to the former industrial corridor along the Woonasquatucket River. Next, Sanborn Fire Insurance maps were used to identify potentially polluting industries along the River. Likely pollutants resulting from each industrial site were then determined. Finally, analysis and research into the history of many of the sites was conducted, and the results were compared to records of known contamination along the River. Information on the present-day status of industry along the Woonasquatucket in the form of geographic information systems (GIS) data layers was unfortunately unavailable at the time this project was undertaken.

Narrowing Down the Study Area

It was unfeasible that there would be time to apply the methodology to the entire city of Providence, so a more limited study area had to be selected. The other options at the beginning of this project in addition to the former industrial corridor along the Woonasquatucket River in Providence included the India Point area of the Fox Point neighborhood and the area along Allens Avenue in the neighborhoods of South Providence. Ultimately, the former industrial corridor along the Woonasquatucket was chosen due to the amount of revitalization work occurring there (more than in the other two areas under consideration), and the fact that the area along the Woonasquatucket contained a varied mix of industries that would be conducive to applying the methodology. Additionally, many of the former mills along the Woonasquatucket are now being used or will potentially be used for other purposes. In contrast, the Allens Avenue area contains mostly heavy industry- much of it still active- and the Fox Point area contained mostly small industry. This would not have been conducive to applying the methodology because these small industries likely would not have left much lasting environmental harms. The study area encompassed roughly 500 feet in any direction from the River within Providence.

Manually Transferring Data From the Sanborn Maps Into GIS

Using Sanborn Fire Insurance maps from the years 1889, 1990, 1921, 1951 and 1956 as references, the name of an industrial property and other pertinent notes (manufacturing processes, goods produced, etc.) in a given year were manually entered into the attribute table for the 1999 Providence parcel map in ESRI ArcView 3.2 GIS in a column corresponding to the date of the map. Many of the mill buildings and other industrial structures along the River are still standing (or else the present-day parcels often still bear the same shape as the footprint of whatever facilities had previously been located on them, even if the structures themselves are no longer present) so few glaring geographic discrepancies exist between the Sanborn maps and the 1999 parcel map regarding industrial sites along the River. For the most part, the street layout of Providence since 1889 appears visually to have changed very little as well.

SIC Codes

To the attribute table of the 1999 Providence parcel map, then, were added fields for each parcel in which to enter a description of that parcel in 1889, 1900, 1921, 1951 and 1956. Next, corresponding fields were added in which to enter the type of facility as classified by the four-digit Standard Industrial Classification (SIC) codes published by the US Occupational Safety and Health Administration (OSHA). Because some parcels contained more than one type of industry or industries employing more than one type of industrial process (either in separate buildings on the same property or on separate floors in the same building), multiple SIC columns for each year were used, and as many different SIC codes as applicable were recorded.

The SIC codes were determined using OSHA's 1987 SIC System Search website, which allows a user to search for the SIC code associated with a particular industry by entering pertinent keywords. For instance, if one entered the keyword "wool" into the prompt, all of the SIC codes pertaining to the production and distribution of woolen goods would be returned (in this case, makers of woolen fabrics, makers of wool finishing machines, wholesalers of woolen goods, makers of steel wool, etc.). If the property of interest happened to be a woolen mill, one would select "2231 Broadwoven Fabric Mills, Wool (Including Dyeing and Finishing)," the entry for which includes dozens of descriptions of woolen industries that fall under this category. Some judgment was required In assigning SIC codes, and if there was insufficient information from the Sanborn maps to decide between two similar SIC codes, both were used. However, this kind of ambiguity was infrequent.

From SIC Codes to Hazard Rankings

Though OSHA is currently replacing its SIC system with the newer, more flexible North American Industry Classification System (NAICS), the references involved in the step of associating particular industries with records of past contamination all use SIC codes. (Forthcoming GIS data layers on present-day industry in Providence will likely use NAICS codes, however.) Specific chemicals and pollutants associated with historical incidences of spills and cleanups for different types of industries were obtained via the Agency for Toxic Substances and Disease Registry's Internet HazDat-Site Activity Query website, the Accidental Release Inventory Program's Search website, the US Environmental Protection Agency's Toxic Release Inventory Explorer website and a lookup table graciously provided by the Boston Industrial Archaeology Mapping Project.

Once specific chemicals were assigned by SIC code to each parcel in each year, a hazard ranking methodology was employed. First, each facility was assigned a hazard ranking in each year based upon the following rubric:

The higher the hazard ranking, the more persistent the pollutant is in the soil with regards to biological availability. This allowed the observation of the state of industry along the Woonasquatucket River in each year as it was in that year, irrespective of past industrial activity.

Cumulative Hazard Rankings

Next, the passage of time was incorporated into the hazard ranking scheme, so that a composite map of potential contamination could be arrived at by aggregating the hazard rankings from each year. Since Sanborn maps were available for no later than 1956, it was assumed for this project that VOC's posed a negligible threat in terms of present-day contamination and that hydrophobic organic and soluble metal compounds would not persist in the soil for more than five decades or so. As evidenced by the chronic presence of lead and arsenic in the soils of Providence, heavy metals were assumed to persist from even 1889, the earliest date for which data were available.

A parcel with a hazard ranking of one in any date received a cumulative hazard ranking of zero; a parcel with a hazard ranking of two received a cumulative hazard ranking of zero from 1889 to 1921 and a cumulative hazard ranking of one in 1951 and 1956; and a parcel with a hazard ranking of three in any year received a cumulative hazard ranking of one. That is, the cumulative hazard ranking scores were assigned based upon the following rubric:

Under this rubric, a hazard ranking of zero signified that a contaminant was likely no longer relevant to present determinations of contamination for the purposes of this project; a hazard ranking of one signified that a contaminant was potentially still present and active in the soil. These cumulative hazard ranking scores were then summed to arrive at cumulative hazard rankings for each parcel in the study area.

Summing up the raw hazard scores themselves was also tried (before the application of the above method) in order to determine cumulative contamination, but this method had a tendency to capture contamination where there probably was none. For instance, a parcel with a hazard ranking of 1 in the years 1900, 1921 and 1951 would have the same value as a property with a hazard ranking of 3 in the year 1956 that would be more likely to be contaminated. It was for this reason that the cumulative hazard scoring system explained above was used.

The resulting cumulative hazard map provided a landscape of risk that was then compared to records of known environmental hazards along the River in the form of Rhode Island Department of Environmental Management Environmental Site Assessments.