Santa Cruz County History - Making a Living



The Laguna Limekilns: Bonny Doon
by Robert W. Piwarzyk

[This article is excerpted from a manuscript titled, "The Laguna Limekilns: Bonny Doon," pp. 44-45. The maps, drawings, and photos of the manuscript are not included on this site. The manuscript is copyrighted 1996 by the author. It is used here with permission.]

Quarries, Tramways, Pulley & A-Frames

On the east side of Laguna Creek, downstream of Ice Cream Grade, are two side-by-side hillside pot kilns. Their floor elevation is at approximately 1450'.The creeksides and hillsides are vegetated with second-growth mixed-evergreen forest, which disguises the fact that this was once a bustling canyon with several quarries providing ore to the limekilns. It is not possible to see the quarries from the kiln site. The floors of the large quarries to the south (downstream) are 30' and 80' above the kiln floors. Quarry tailings were dumped on the west-facing slope on Laguna Creek below these two large pits. Five smaller quarry pits are located up the ridgeline above the large quarries. There are also five pits upstream of the site on the unnamed creek to the east; two on the north side and three on the south side. The north-side pits are below the narrow one-lane section of Ice Cream Grade. Reference should be made to the site plan presented in appendix B and the photographs in appendix C. [Not included on this site.]

Several other limestone quarry sites in the Santa Cruz mountains have evidence of drilling and blasting. Either drill holes are evident and/or powder magazines have been found nearby. Neither has been found at the Laguna quarries, except for one hole in a kiln lintel stone. Since the deposit is so fractured, it is presumed that ore was removed by the use of pry bars, wedges, and sledges, and if black blasting powder was used it was packed into the existing fractures.

The upper quarry has a section of two-foot gauge rails protruding from the limestone rubble. This is a prefabricated section that used metal ties and narrow-gauge sized rails (2" base x 2 ½" height). It could be readily moved and was therefore used in many quarries where the desired location would change as the ore was blasted off the face and removed. The track appears to align with a ridge connecting the upper quarry with the lower. There may be a depression in the ridge where track was laid or a chute built, but there is no evidence of either and erosion of this slope makes it difficult to interpret. However, if there was a chute, that would mean that the ore had to be reloaded and then carted to the kiln from the lower quarry floor. This would not be very efficient. Of course a chute could be made to dump directly into a car, but there is no evidence of any such structure. If track was laid such that an ore car could be lowered to the lower quarry and then moved to the kiln, that might be more efficient. But that method would require a brake drum and a cable to restrain the loaded car as it was lowered down the grade of 50' vertical drop in approximately 100' horizontal distance. Since there is no evidence of a brake drum, it may remain a mystery as to how this work was actually done.

There are two small pits on the ridgeline above these large quarries which appear to have had outcropping boulders removed. These may have been probes made to determine the extent of the deposits. The upper quarry extends into the mountain to the southeast. There is not any limestone quarry face in that direction. Either the outcropping was removed and ran out, or a probe in that direction to find more was unsuccessful. The extant face is not that high or wide to look encouraging to an operator hoping that the whole mountain was limestone!

Much the same can be said of the lower quarry. The vein seems to have sloped up the hillside and the quarry "floor" sloped upward with it. There is a rock wall built to provide a flat work area at the base of the face. The vertical veins are mixed limestone, quartzite, and metamorphic sandstone with some deep red schist. Flowstone coats some of the fracture surfaces (see "Geology").

The lower quarry has a grade cut for a tramway and a creek crossing to the kilns. Several ties with spike holes from two-foot gauge rails were found on this grade and on the lower quarry floor. None showed wear due to animal use. When animals (horses, mules, or oxen) were used, either to brake the load or pull the empty car back up the grade, the ties became "scalloped" between the rails. There are some structural remains (a beam and a 10' plank) in the creekbed, but not enough to ascertain whether the tracks crossed a bridge. This would seem desirable, as the span and the slope of this structure would not be conducive to using a gravity chute to transport the ore across the creek. However, there is not any ramp built up on the kiln side of the creek for tracks to transition onto the flat. The questions regarding this detail may never be answered.

An earlier grade from the lower quarry went up the side-canyon to the east (see site plan) and gets lost in the rubble of the intermittent creek bed and the floor of the quarry located there. It must have been used prior to the bridging structure as that cut is lower in elevation and cuts through the original grade. It is likely that it crossed the creek. Perhaps a spur and switch, or a turntable, was necessary as the space available was too narrow to allow use of a hairpin curve.

A three-foot gauge tramway was uncovered at the top of the kilns. It was buried beneath the hard pack surface of the loop road. It ran parallel to and 4 ½' from the back wall of the kilns. One 24' section of narrow gauge rail curves to the east towards the quarries that are up the side-canyon (see drawing in appendix B [not included on this site]). It is possible that larger cars were used to bring the limestone blocks, used to construct the kilns, down from these quarries. They may have continued using this tramway to transport ore, or they abandoned it. More work needs to be done with metal detectors to locate other rail sections or spikes.

A large cast iron 6 ½' diameter pulley is located 85' above the top of the kilns to the east of the lower quarry. This sits on an earthen platform, retained with a 6' stone wall, overlooking a cut on the hillside which was made to provide clearance for the hanging ore cars. Mortar is not evident in the wall. The pulley was most likely brought down to the site from upper Ice Cream Grade. The structure that the wheel was mounted on is missing, or may have never been completed. Although there are two wooden footings, nominally 8" x 5" x 7 foot redwood, there are no other beams or any obvious evidence of fire. The bolts, nuts, and washers on the axle bearing mounts do not have any wood attached. These bearings are cast and have babbit metal bearing surfaces. One is 8" long and is cast with raised letters identifying the manufacturer as "Vulcan Iron Works SF Cal" and "2 ¾" designating the diameter of the pulley shaft. The shaft is 11" long on this end. The pulley hub is 7" wide and the shaft is stepped to 3" diameter and is 25" long on that end. The bearing there is 8 ½" long and is a thrust bearing, indicating that the wheel may have been mounted horizontally, with the shaft vertical or at an angle from vertical. The six-spoked pulley has a 4" rim, 2 ½" thick with a 3 ¾" flange, and a 6" diameter hub. The base of the flange opening has a ¾" diameter woven fabric material which may have absorbed a lubricant for the cable and is still intact after many years of exposure. No seam can be detected in this material, and it is not known how it was installed. Although no aerial cable (called "wire rope" at the time) has been found, it was most likely 1 to 1 ½" diameter.

Galvanized, 1" diameter anchor cables and a small quarry pit are uphill of the pulley. These cables have six strands of seven strand wire sub-cables wrapped around a three strand rope core. The four anchor cables were each cut through, apparently with a hacksaw, at the loop made by the extant cast cable clamps (see photograph [not included on this site]). There is also a U-clamp on each assembly. Continuity tests were made using a volt-ohmeter to see if the cable sets could be determined. It is felt that either the left and right cables are one, or the inner and outer cables are one. Due to the damp conditions, continuity existed across all legs of the cables and across the earth from one side to the other, and the configuration could not be determined. These cables are most likely wrapped around a log which was buried under a pile of rocks to make a "dead man" to counter the weight of a loaded ore car. They have a spread of 5 ½' compared to the shaft length of 43". The cut cables indicate that there was some other load bearing device (perhaps another cable loop, or a metal strap) which had been in place but was removed. The inside surfaces of the loops seem to be flattened from loads applied during use of the aerial tramway. It seems likely that the cables would not have been cut if the wheel was being removed by the company at the end of operations. In that case they probably would have disassembled the anchor pile and deadman, and unbolted the cable clamps. The fact that the cables were cut may be evidence that an attempt was made scavenge the wheel. Scrap metal drives during the Second World War stripped many of the industrial sites in the Santa Cruz mountains. Many artifacts were also lost in the 1960s when a frenzy of nostalgia hit this country.

The metal parts found near the wheel are the 2" wide brake band from the 43" diameter brake (cast into the wheel) used to control the descent of the ore car. It is probable that the loaded car, descending by gravity, pulled an empty car back up. The exact configuration of this installation is not known since the pulley mounting structure is missing. It is possible that there were other smaller pulleys used to control the runoff of the cable (similar to ski-lifts seen today), but that these are missing also. Gravity-powered aerial tramways were considered a very economical means of transport.

A bearing 90 degrees to the center of the retaining wall sights down to the two A-frame structures found at the top of the left kiln. These are located on the north side of the kilns and are on the uphill side of the loop road. They were set 5' apart at the base and appear to be pushed over by slide material coming down from Ice Cream Grade. There is some remaining structure aligned opposite the frames (and downhill of the loop road) with dimensions similar to the 6' spread of the frame legs, but it is not known if they are part of a single installation. The frames are bolted at the apex of two 13 ½' long redwood poles resulting in about a 27 degree angle. The diameters of the poles facing the pulley are smaller than the others --- 8" and 12" for the right frame, and 5" and 10" for the left. The bolt on the right hand frame is slightly different from that on the left hand frame for reasons unknown. The cross braces are 4' long, ¾" diameter iron rods, each threaded and bolted on each end.

It is not certain that the A-frames actually were the downhill end of the aerial tramway. The alignment may be coincidental. If they were, they would have had to have been anchored someway to take the load of the ore car (or cars, or buckets) hanging from the cable. There is no evidence that this was done --- no cables, no deadmen, and no cable marks on nearby trees. Also, if the pulley was mounted horizontally (which is the best arrangement for handling and loading a two car system) the question arises as to how a pulley would have been mounted on the A-frames. Although no cable or ore cars were found, it seems reasonable that an aerial tramway was used at some point of the operation, and that the A-frames may have been part of the downhill anchor point.

Again, the quarry pit behind the pulley extends into the mountain to the south. There is no large quarry face. Veins of limestone and quartzite appear on the east side of the quarry "gate." The small pit above this quarry may also have been a probe to ascertain the extent of the deposit and may also have given the operator false hope. Perhaps the successful experiences of the Holmes Lime Company in their quarries on the Felton side of Ben Lomond Mountain also helped to mislead them?

There was another small quarry pit reported west of the kiln site off of Ice Cream Grade on what were the lands of Walter Mahan (see oral interview #1 in the bibliography). Ore is said to have been delivered to the Laguna kilns from this pit. Ore brought to the site by wagon could be unloaded into the top of the kiln. Traffic would be clockwise around the kilns as loaded wagons would go up the long ramp, and empties would go down the short ramp.

Judging from the sizes of the kilns and the quarries, not too many loads were burned. Further work could be done to calculate the volume of ore removed for burning. This is the volume of the quarry hole less the volume of the tailings. To estimate the total production of the facility in terms of total number of loads burned, the volume of ore mined can be divided by the volume of ore needed to load a kiln. To calculate this, the total volume of the kiln pots must be adjusted by the volume of the fire chamber inside each arch, and the voids between the chunks of limestone. Unfortunately, the number of years that the kilns may have operated can not be estimated unless more facts are known or more assumptions are made. The loads burned per year might be a function of many variables, including the length of the rain season and whether the kilns operated over consecutive years.

More research is needed to determine when the track section, pulley, anchor cable, and clamps were manufactured. Most likely both were "off-the-shelf" items that were advertised in the industrial or mining equipment catalogs of the day. Such catalogs are available to researchers. However, like with bricks, this equipment could have been purchased before or after construction of the kilns and knowing when they were manufactured does not necessarily fix that date.

On the ridge line between the two small pits above the upper quarry there is a power pole. Some wire with weathered insulation is dangling, but the insulators that would be on the pole have been removed. The pole is creosote soaked and has a round metal tag attached which says "Osmoplastic Dan Kamp-Ausen Co." around the edge and the number "62"in the center. No other poles have been located, either uphill or across the canyon, so it is not known whether this line brought power to the site or was routed to Bonny Doon. It is possible that the number stands for 1962.

There are at least ten quarry sites where blasting took place on Ben Lomond Mountain, five above Felton and five in Bonny Doon. This mountain has another name whose origins are obscure: "Battle Mountain." In addition to the stories told by Clark, some locals talk of the limestone and sandstone rocks, like "Bald Mountain" on Smith Grade and the "moon rocks" on Martin Road invoking the image of battles waged on these fortresses, while others reflect on unremembered family feuds and road access struggles. The author favors the blasting at so many quarries as being the reason! The battle-like rumble can still be experienced.

>>Continue with: Kiln Construction.

Bibliography

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Bonny Doon, kilns, limestone, quarries

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