Great research tools !

Below are some additional checklist questions for community forensic geographers and CSI agents (Creek Scene Investigators)

Sites with these land use characteristics may often have contamination and other environmental issues:

- is your site  low lying - eg where surface water would naturally flow to ? Historically valleys, stream beds and ponds acted as garbage dumps for first settlers. Even if valley site itself was filled with clean soil (eg. a chopped down local hill) the buried stream bed may still carry contaminants from, for example, the upstream now landfilled pond behind the demolished chemical factory.

- is your site within 1 block of a rail line? (which may no longer exist..) Check old maps like the Library of Congress online map library (https://www.loc.gov/collections/) and the David Rumsey map archives (https://www.davidrumsey.com/) for excellent libraries of historical maps. Historically, sites near rail were prone to all the industrial products and contaminant (spills) carried by rail.

- Is the site within 3 or 4 blocks of a shoreline ? To facilitate docking, natural edges were land filled with a wide range of materials. Shorelines include now gone canals (think Love Canal) and now invisible piped rivers.

- where are the oldest roads in your neighborhood ? The more history, the more potential issues for the lots adjacent to those roads.

- is your site crooked - or not square, or near an angled road ? Non gridded sites tend to  pre colonial, with the longest history of human use (and pollution)

- Does your street have an unusual name ? Like Railroad, Depot, Pearl, Spring, Mill, Kill, or Fly (vlei) street for example .. often the land use history of a site is in plain sight on the street sign.

- How BIG are the buildings around your study area? Try color coding them by their square footage area, and you will often get the ghost of the underlying ecosystem.  It turns out (in New York City) that buildings over 2000 square feet are typically built on landfilled marsh sites. This is is because when developers would split up newly acquired farm land, the well drained hillside areas became the smaller (typically less than a 1000 ft2) easy to sell residential lots. Farmer Brown's old mill pond (expensive to drain) would be where construction waste ended up. Such "waste land" would get inherited by industrial developers or the city who would make it a playground, school or public housing. 

An example of forensic geography mapping for the Gowanus Canal Superfund Brouwers Mill Pond site in Brooklyn New York. Mapping is based on the 1766 Ratzer Survey Map and NYC DOITT building footprints. The stream mapping was refined using balloon vegetation mapping techniques with the Gowanus Canal Conservancy and the Dredgers Canoe Club.

Small buildings are at the edge of the marsh. Larger buildings are on the landfilled tide marsh. The actual pond and stream bed became city parks and parking lots.

By mapping the stream flows through the "Map of Nothing" empty spaces, we can better understand the flow directions of buried coal tar pollutants.

- Is there Nothing on the historical map ? You go through the old maps at the library, and you are disappointed that there are just blanks for your study area. Do not despair - get excited. Lack of data in this case is also information. Take a piece of tracing paper and start using a green marker to fill in all the white "vacant" spaces on the old map showing first buildings appearing in your study area.  Sanborn maps are a good reference for this. (https://en.wikipedia.org/wiki/Sanborn_Maps)

You may start seeing appear patterns of the old marshes and stream beds .. these were often considered too unimportant to map. Start comparing your "Map of Nothing" to even earlier maps to see if there was actually a river or shoreline indentation there. Indentations are clues to stream outflows. Did the road take a weird bend or split right at the area you are interested in ? Why ? What were the "Nothing Spaces" subsequently filled with ? Where there contaminants in the landfill ?

- Are there the dead end roads on your Map of Nothing? Highlight them. Now look at the topography or contour lines near those road ends. United States Geological Survey 1:24000 maps are good for this. (https://en.wikipedia.org/wiki/Quadrangle_(geography))) Are there unusual piles of stuff where you wouldn't expect them to be in the normally flat former marshland area ? Unusual dirt piles in you backyard are often a clue to something funny going on.

Blame the dog - or the absence of the dog.

Gregory (Scotland Yard detective): "Is there any other point to which you would wish to draw my attention?"

Holmes: "To the curious incident of the dog in the night-time."

Gregory: "The dog did nothing in the night-time."

Holmes: "That was the curious incident."

 (from The Adventures of Silver Blaze, Arthur Conan Doyle, 1892) 

 Sherlock Holmes on The dog that didn't bark - because it knew the murderer.

Absence is Presence. And the Invisible can be made Visible.

Happy forensic geography mapping !

Eymund