A hole in Los Altos (continued)

The city clerk got back to me this morning. (Thanks much for the prompt response!) The hole in the map is also a hole in the ground — a reservoir belonging to the City of Mountain View.

We happened to be in the area after checking out Tom’s Depot Cafe yesterday so I snapped a couple photos:

Poking around on the City of Mountain View site leads to docs giving the name for the site, like this one talking about cutting down a tree — “Miramonte Reservoir”. And that led me to some articles about the site:

• “Miramonte Reservoir troubles [Los Altos] neighbors” (2003): “Miramonte Reservoir, constructed in 1945, is located on Miramonte Avenue in Mountain View, but sits adjacent to a handful of houses on Stanley Avenue in Los Altos.”
• “Los Altos mulls options over Mtn. View Miramonte reservoir plans” (2003): “The city of Los Altos has options for thwarting a reservoir expansion project set for Mountain View land on Miramonte Avenue that is surrounded by Los Altos residences.”
• “Reservoir construction disrupts neighborhood” (2005): “As far as the community at large is concerned, the controversy surrounding Mountain View’s Miramonte Reservoir Expansion Project has gone away as the project has gone forward… Since last summer, residents along Stanley, Russell and Berry avenues, and Diamond Court have been enduring noise, traffic congestion and dirty air from construction of a new reservoir designed to hold 3.2 million gallons. This in addition to an existing 700,000-gallon reservoir on the 3-acre site for nearly 60 years.”

How many other cities have holes? I think this may do what we want. Once again using the data from https://lab.data.ca.gov/dataset/california-city-boundaries-and-identifiers:

> library(sf)

> cities <- read_sf("~/Downloads/California_Cities_and_Identifiers_Blue_Version_view_-6943741225906831761.gpkg")

# What CRS should we use? 4326 seemed to good a job getting
# the reported area for Whittier so I use it here too.
> cities <- st_transform(cities, 4326)

> exteriors <- st_exterior_ring(cities)
> holeAreas <- st_area(exteriors) - st_area(cities)

# Check: everything >= 0?
> all(as.numeric(holeAreas) >= 0)
[1] TRUE

> mean(as.numeric(holeAreas) > 0)
[1] 0.2484472

> units(holeAreas) <- "mi2"

> holeSizeOrdering <- order(holeAreas, decreasing=TRUE)
> cities$CDTFA_CITY[head(holeSizeOrdering, 3)]
[1] "Palmdale"    "Los Angeles" "Fremont" 

> head(sort(holeAreas, decreasing=TRUE), 3)
Units: [mi^2]
[1] 26.74540 23.36606 14.04076

So, around 25% of incorporated California cities (120 in total) have a hole and the top three in terms of absolute area are Palmdale (around 27 mi^2 of hole), Los Angeles (around 23 mi^2), and Fremont (around 14 mi^2).

Here’s what those cities look like:

> library(ggplot2)
> ggplot(subset(cities, CDTFA_CITY == "Palmdale")) + geom_sf()
> ggplot(subset(cities, CDTFA_CITY == "Los Angeles")) + geom_sf()
> ggplot(subset(cities, CDTFA_CITY == "Fremont")) + geom_sf()

Fremont’s the closest of these to me, and its hole stands out the most visually so I’m a little curious about it:

> fremont <- subset(cities, CDTFA_CITY == "Fremont")
> (fremontHoleCentroid <- st_geometry(st_centroid(st_difference(st_exterior_ring(fremont), fremont))))
Geometry set for 1 feature 
Geometry type: POINT
Dimension:     XY
Bounding box:  xmin: -122.0309 ymin: 37.51999 xmax: -122.0309 ymax: 37.51999
Geodetic CRS:  WGS 84
> cities$CDTFA_CITY[whichContains(cities, fremontHoleCentroid)]
[1] "Newark"

So, the hole in Fremont, CA, is Newark, CA.