Thursday, September 30, 2021

Mauʻumae Nature Park

Switching gears again, next up we're visiting Honolulu's Mauʻumae Nature Park, uphill from the Kaimuki business district & the Kahala Mall, and below the Mauʻumae/Lanipō Trail we checked out a few months ago. This was supposed to be another hiking post; I saw "Nature Park" on a map, and a few scattered references to a loop trail. But not a lot of references, so it was probably uncrowded. So I figured I'd go check it out. The park totals 33 acres, separated by Koko Drive into a 4 acre lower section, partly developed as a regular neighborhood park, and a 29 acre undeveloped section where the loop trail is supposed to be. I say "supposed to be" because I completely failed to find it. There wasn't a sign with arrows pointing at it, and I walked back and forth along Koko Dr. a couple of times without seeing anything that looked like the start of a trail. So I ended up settling for some photos of the view from Koko Drive, which looks out at Kaimuki and the back side of Diamond Head. It's undeniably a nice view but not really why I was there, so I chalked this up as a loss. Still, I had photos of the place, so I created a draft blog post about the place but didn't feel especially motivated to do anything with it. I also never quite deleted the thing, because I kept wondering why there was a nature park here, specifically, and what the deal was with the missing trail.

Couple of caveats first: One, I don't currently have an Oʻahu library card, so there are some gaps in what I've been able to figure out that would likely be filled by old newspaper stories if only I could get to them. Two, these photos are from 2016, and your mileage may vary if you go there right now. (I remember being especially annoyed at not finding the trail since I was trying to take my mind off the horrifying Republican national convention that was happening that week.) So with that in mind, I have reason to believe the trail really does exist, and it's not just a scheme to milk City Hall for grant money or whatever. First, there's a GPS track of it on Alltrails, which actually predates me visiting by several years. Second, plugging those trailhead coordinates into Street View shows what looks like a couple of rough stone steps leading to, well, shorter grass than the surrounding grass and brush, which might be the start of a trail if you squint at it just right. And that imagery is from 2019. So my unsuccessful visit is bracketed by the evidence, unless maybe the trail phases in and out of existence according to the season or the phase of the moon. Or, more likely, you can find it if (and only if) you already know exactly where to look, and a motivated neighborhood volunteer who owns a weed trimmer has been there recently. If you do manage to find the trail, there's a geocache hidden somewhere along the trail, for extra credit. The description on that geocache explains "When I was a kid living about 130 yards from where this cache is, we knew this area as the gulch and was left undeveloped because it was needed as a watershed area. It later became the Mauʻumae Nature Park." Which turns out to be a key clue.

And sure enough, in the lower section of the park, right next to the landscaped play area, there's a fenced-off area with the usual imperious "Government Property - Keep Out" signs. These signs never explain which part of the government owns it or why, but the county GIS system says this area belongs to the Honolulu Board of Water Supply, and is home to that agency's Waialae West Well. This well opened in 1998 on the site of an older well named "Waialae Shaft" that operated from 1937 to around 1984. A 1938 book explains that it began construction in 1935 and was built at a 30 degree angle into the hillside for some reason. The book includes a couple of photos of sketchy-looking pump equipment at the bottom of the well, which I suppose must have been state-of-the-art back then. As for the present-day well, here's the federal Environmental Assessment back from when it was proposed, if you like reading that sort of thing as much as I do. (And no, I'm not being facetious about that.) One weird detail about it is that the 225' well is actually drawing in fresh water from below sea level. I am probably not the only person who finds this a bit surprising, even alarming, as the doc explains the science [1] behind this (and the linked footnote goes into more depth if you're really curious):

The Waialaie West Aquifer system provides the most common type of groundwater available on Oahu, consisting of a layer of infiltrated rainfall floating as a lens-shaped body over salt water. Fresh water floats on the heavier salt water, both of which permeate the subsurface rock. The density ration between fresh water and salt water is such that theoretically, for each foot that the fresh water lens stands above sea level, the lens extends 40 feet below sea level to a midpoint where salinity is half sea water. A transition zone of mixture grades upward to fresh water and downward to sea water. The presence of the fresh water head is due to relatively impermeable caprock, located along the coastline, which retards outward flow to the ocean.

It seems that right around the same time the original well was built, developers were planning to build a subdivision called "Kahala Heights" here, covering the entire hillside where the park is now. Somehow the state ended up owning the center of the proposed subdivision instead, though I don't know whether that was a straight business deal, or the Depression or WWII also figured into it. In any case, the state held the land as a buffer around the well, but I gather they did nothing else with the place during the decades they owned it, much to the frustration of the surrounding neighborhood. I don't know whether the whole park was actually fenced off or not, but it very well could have been.

A June 2000 Star-Bulletin article explains that the state had handed the land over to the city in 1991 -- several years after the original well had gone out of service -- and residents had big plans for the place. Volunteers had already built the elusive loop trail by the time of the article, and had been planting native plants starting around 1994. A couple of years later the city approved an official master plan for the park, finalized in July 2002 (see also a 2003 environmental assessment for the plan). That doesn't tell us very much about the nature area unfortunately, since the master plan for that part was to just leave it alone other than the existing nature trail. While the lower part of the park was slated to get some neighborhood park-type improvements, only some of which have actually happened so far. Among the things dropped from the finalized plan was a proposed Zen archery range, which would have replaced an existing one somewhere in Kapiolani Park. Strictly speaking it wasn't completely dropped, just moved to a timetable-less "Phase IV" of the comprehensive park plan, which is much more polite and non-confrontational than a simple 'no' would have been. Volunteer enthusiasm naturally ebbs and flows over time, and after that initial burst of urban planning excitement, there's a decade gap in easily-found news items until 2013, when residents were campaigning to close the park at night as it -- specifically the viewpoint part -- had become a late-night party spot. The park closes at 10pm now, so the campaigners may have gotten their rule change. Whether the city actually enforces the closure is, as always, anyone's guess.

For a little alternate history, here's the undated overall map for the proposed Kahala Heights subdivision. When I said this was roughly contemporary to the well, I was going by the earliest date stamps on some plat maps for various pieces of the development. These maps were updated and re-stamped every time anything about the map changed up into the mid-1980s or so when presumably everything was digitized. The future "natural area" portion of the park is shown filled with houses and crossed by a couple of never-built roads labeled simply "Road F" and "Road I", with a bunch of proposed and then canceled parcel numbers X'ed out. The maps also contain a bunch of hyphenated numbers that look like dates, specifically March 3rd of consecutive years from 3-3-13 thru 3-3-22. Those are actually "TMK numbers [2]", part of the state's unique property ID system, and I have to say I'm quite glad I figured that out before posting a whole paragraph trying to guess what was so special about March 3rd, which is something I had in an early draft of this post. The docs show the park as owned by the state, which was true past the point where the county stopped relying on paper maps. I suppose that after statehood in 1959, some poor junior surveyor must have drawn the short straw and had to go through every single map in the office with a pen and a jug of whiteout, manually updating anything that said "Territory of Hawaii" on it.

I did find a handful of random historical items by searching for "Kahala Heights", as that name was once used for the general neighborhood but largely fell out of use several decades ago, at least going by the stuff I can find on the internet easily. As a result, search results are (unusually) not completely swamped by real estate listings. In the present day the neighborhood generally goes by "Wilhelmina Rise", and becomes "Maunalani Heights" a short distance further uphill, per a 2017 Honolulu Magazine piece that explains the difference and drops in a little history of both. Anyway, I can't come up with much of a storyline linking these random historical items together, so I'm going to go with an oldest-to-newest bullet point list and call it even:

  • The neighborhood is mentioned briefly in a biography of John Henry Wilson, whose Wikipedia bio describes him as "a civil engineer, insurgent, co-founder of the Democratic Party of Hawaii, and Mayor of Honolulu, Hawaii three times: from 1920 to 1927, from 1929 to 1931, and from 1946 to 1954." It seems the neighborhood had a small cameo role in the 1928 mayoral election. I don't know the whole story, because it's not included in the free Google Books excerpt of the book, but I gather there was an ongoing controversy about a stone crushing operation somewhere vaguely near Kahala Heights, and local Republicans were trying to make an election issue of it, arguing Wilson wasn't protecting neighborhood children and the local school properly. It turned out that the rock crushing operation was over half a mile from the school, and the people pulling the strings behind this astroturf campaign were snobby rich people in the beachfront Kahala neighborhood, because some things never change, and Wilson ended up regaining the mayor's office that year.
  • Skipping forward to December 7th 1941, a 2016 Star-Advertiser story related a reminiscence from a longtime resident who was 11 when it happened. Confusing news reports were saying that something bad was happening across town at the navy base, so he and some friends hiked uphill somewhere in the the Kahala Heights area to get a better view, and just then a Japanese Zero flew by at about eye level. Not understanding what was going on, the kids waved at the pilot, and he saw them and waved back. A 2013 Orange County Register story related another Zero pilot story from someone else who was from Kahala Heights but saw the plane over in Aiea, much closer to the attack.
  • Brief reference to a 1961 study on doing some urban renewal in the Kaimuki, Maunalani, and Kahala Heights neighborhoods. In a 1962 issue of "Housing and Planning References", a sort of quarterly bibliography of recent studies and publications relating to urban renewal topics nationwide and around the world. This might be what eventually led to the large public housing projects in Palolo Valley next door, which have about the same reputation as midcentury public housing does everywhere else.

So yeah. In summary Mauʻumae Nature Park is a land of contrasts. Still wish I could find that dumb trail, though.

Ghyben-Herzberg Theory
The science behind this aquifer stuff is something called "Ghyben-Herzberg theory", dating back to work by a couple of German engineers in the late 19th Century, building on ancient Greek discoveries about density and buoyancy from thousands of years ago, just swapping out the bathtub and gold crown with fresh water and salt water inside semi-porous solid rock. And a bit of assuming one of those legendary spherical cows physicists keep going on about, as this 19th century model just gives you a general idea of what the state of your aquifer is at a given point in time and how much fresh and fresh-ish water there is. It doesn't tell you how much water it's safe to remove from the system without drawing saltwater in from the ocean and ruining your aquifer. For that you need to understand how much freshwater is naturally entering and exiting the system and how quickly saltwater can move in if the equilibrium shifts. I gather the aquifer here is a relatively simple example of this kind of system, as there were computer simulations of it as early as 1985. This 1985 paper explains that the Waialae West aquifer is separated from adjacent aquifers by dense, non-permeable volcanic dikes underground, and separated from the ocean by dense coastal marine sediments, so the above-sea-level groundwater doesn't just leak out to sea immediately (which makes it a good place to dig a well), and it isn't flowing sideways deep underground to a significant degree, which makes it easier to model. In fact it's a literal textbook example, in Seawater Intrusion in Coastal Aquifers: Concepts, Methods and Practices (1999, pp. 234-237), which looks at how closely a couple of models (the original Ghyben-Herzberg one, and a newer one called SHARP) model the actual behavior of the well, going by a nearly four decade dataset (1937-1975) from the well, and rainfall data from the same period. If I understand correctly, the classic model doesn't fit exactly because rainfall varies a lot between years and by season, and then the rainwater takes a while to make its way down into the aquifer.

A weird data point on how long it takes for rain to become aquifer water here comes from a 1973 study measuring tritium levels in water around Oahu. Tritium being a radioactive isotope of hydrogen with a half-life of about 12 years. It occurs naturally in very low levels, but at the time of the study the bulk of it in the environment was residue from above-ground nuclear tests. Among other things, this provided a unique way to date the groundwater, or in this case set a lower bound on it, since they found essentially zero tritium in well water from here, which they took to mean that tritium-enriched water had not yet filtered down into the aquifer in significant quantities since 1954, when the stuff would have begun entering the environment in detectable quantities. (They don't explain the 1954 date, but I imagine it relates to hydrogen bomb tests, or maybe ordinary non-fusion nuclear tests conducted in the open ocean.) I imagine this study would be unusually difficult to replicate in 2021, as you'd probably have to develop your own nukes first to supply the needed tritium, and most university IRBs tend to frown on that sort of thing these days.

Of course the hardest part of all is that even if you're figured out the natural rates of inflow and outflow and such down to all the decimal places you'll ever need, that rarely stops people from getting greedy and trying to push the envelope even further. There's the classic tragedy of the commons with everyone overdraws the aquifer a little and nobody feels responsible, and the modern plague of professional contrarian experts who will happily tell you you can draw 27% more water than you're doing now and it'll be fine according to these PowerPoint slides, just do it and be legends, etc. Or developers come to town touting a multi-billion-dollar scheme that unfortunately involves cutting through those coastal sediments and pulling the cork out of the bottom of the local groundwater supply, and (this being Hawaii) it gets approved quietly by an anonymous city bureaucrat in exchange for a suitcase of cash, steady no-attendance jobs for various no-good relatives, VIP trips to Vegas, and the other usual inducements.

TMK Numbers
TMK ("tax map key") numbers, which Hawaii uses instead of the township-range-section-lot arrangement used across much of the mainland. Here's a local realtor's blog post explaining this unusual system, as he explains it better than I can. A number like "3-3-15" says this is zone 3, section 3, plats 15, and that combined with the parcel numbers on an individual lot gives you the TMK. The full TMK for these lots would all have a leading '1', which is the island number for everything on Oʻahu, but in common use those are typically left off as implied. Linked from that post, here's a map of Oahu showing the zone & section layout of the island. The striking thing about that is that those boundaries correspond very closely to traditional moku and ahupua'a boundaries, which date back to many centuries before the first European visitors showed up, and in turn are largely based on natural watershed boundaries. Lots of other things follow the same lines to varying degrees, despite having nothing to do with watersheds or land tenure, like city, state, & federal legeslative districts, zip code boundaries, zones of the city park system, and so on.