Irish Hills HP P1K
Mine Hill

Jul 6, 2015
Story Photos / Slideshow Maps: 1 2 GPXs: 1 2 Profiles: 1 2

The Irish Hills are a moderately-sized collection of hills in coastal San Luis Obispo County, framed by US101, Los Osos Valley Rd and the Pacific Ocean. At the west end is Montana de Oro State Park along the coast and to the east is the Irish Hills Natural Reserve, leaving most of the remaining hills in private hands. On the southwest side of the hills is the Diablo Canyon Nuclear Power Plant whose access is strictly limited (I tried the gate at Avila Beach once, but got turned back). The highpoint of the region is unnamed, and though it has a very modest elevation of barely 1,800ft, it boasts a surprising prominence in excess of 1,600ft. Access seems remote and difficult at first glance but it has some positive attributes working for it. The mostly paved Prefumo Canyon / See Canyon Rd goes within 1.5mi of the highpoint. A good dirt road forking off this goes within half a mile of the top. In looking at the land management layer on, it appears much of this dirt road is on state lands. The only real problem I could see, and it's a good one, is that last half mile - it appears the summit is covered by very dense chaparral. The satellite view shows what looks like might be the remains of an old fireroad or trail (though nothing is shown on the 7.5' topo) - would it be enough to help?

I was in Pismo Beach on a short holiday with the family which usually means relaxing for everyone else while Dad goes out hiking or biking somewhere. Today I decided to head out to explore the Irish Hills. I found the start of the dirt road off Prefumo/See Canyon Rd by 9:30a, finding a gate barring vehicle access. No problem, I had come prepared to hike it anyway. It appears that foot and motorcycle traffic have regularly skirted the gate and without any No Trespassing signs anywhere, I was feeling pretty good about it as I started up. The road goes through the understory of an oak forest in the lower reaches, poison oak lining the road edges everywhere. Higher up where the road follows closer to the ridgelines, large manzanitas grow well, oaks and poison oak less so. While I had started out in a thin fog layer, it had burned off almost completely by the time I had reached the ridgelines with open views of the surrounding hillsides. I had no ocean views at this time but hoped they might be available from the summit. 45min and a few miles hiking later I came to a property boundary with a dilapidated gate that hasn't been closed in decades. just past this is the start of the connecting ridgeline to the highpoint. To my surprise, my GPSr showed a side road leading to the highpoint. Is this what I had seen on the satellite view? I looked for a junction a short distance down the road where the GPS indicated it should be, but found nothing but brush and forest. I went back up to the saddle to see if the old road started there, but was met by a wall of brush. What to do? How much bushwhacking would it take to cover the last 1/2mi? I decided to give it a try though I didn't hold out much hope - even a modest amount of poison oak would get me to turn back. I dropped down on the southeast side of the ridge and began traversing under the steep, oak-covered slope. There was much loose forest duff here on very steep terrain, but at least no poison oak. I worked my way across for about 100yds before moving up to the ridge proper. Here I had a stroke of luck and found an old path right along the ridge. It looked like either an old fireroad or abandoned trail, possibly decades since it was last maintained - just the sort of thing I was hoping to find. The chaparral is slow to reclaim it, overgrowing parts but leaving most of the trail still navigable. I had to hunch over for much of it, crawl through a few tight spots, and even some all-out bushwhack for a short stretch or two. Old cuts can be seen on the manzanita along the route, evidence it was maintained at one time. What might otherwise have taken more than an hour was done in little more than ten minutes. The trail goes over the highpoint which is devoid of views amidst the tall brush well over head level, but if you continue another 1/10th mile or so you reach the end of the trail at a small clearing with really fine views overlooking San Luis Obispo Bay to the south. The Avila pier can be seen in the center of the view. In other directions one is surrounded by the chaparral-covered Irish Hills. The nuclear plant at Diablo Canyon is out of view to the west. A very neat little find, this trail.

I returned to the road, finding the start of the old trail at the saddle I had investigated near the gate. Had I walked around the initial "wall" of brush I'd have easily found it. Back through the gate, I descended the road a short distance to a sharp turn at a second saddle with another peak called Saddle Peak on the topo (Mt. Buchon on Google Maps). The topo and my GPSr show an old road leading to its summit from this sharp turn. I found such a trail and started along it, but soon realized it was descending into Irish Canyon and not towards Saddle Peak. Whether I missed a fork or the depicted trail no longer exists I didn't discover as I decided to head back since I was already pressed for time. I had told the family I'd be back around noon and it was already past 11:30a. Another summit, Davis BM, is found along the return route less than half a mile off the road. This one has some communication towers at its summit and a separate access road leading up from See Canyon through obviously private property. It may also have a connecting trail from the road I traveled but I left this also as a future exercise. A few minutes before my return the quiet was disturbed by a truck coming my way down the road. The occupant simply waved to me with a smile and continued down to the gate - he didn't seem to be concerned in the least with my being there.

Back at the van I returned to San Luis Obispo along Los Osos Rd and contacted the family. They didn't seem to be in need of me or the van so I was free for a second hike. I drove to the south end of Madonna Rd where I found an entrance to the Irish Hills Natural Reserve. My target was the park highpoint located at Mine Hill. At the TH kiosk one learns that the name derives from the Irish miners that took a stab at prospecting in the hills. Chromite was found and mined some, but the low-grade ore never amounted to much and the efforts were eventually abandoned. The reserve trails are based on some of the old prospector trails. There is evidence of the prospects with tailings in a number of places but not enough to significantly mar the landscape. I used a combination of the King, Froom Creek and Ocean View trails to hike around the north and east sides of the preserve before climbing to higher elevations on the Wednesday Trail. This last trail, designed primarily to allow bikers easier gradients up the hillside has a whole series of annoying (for hiking, anyway) switchbacks that seem to stretch out the trail to ridiculous length. A great deal of time and energy went into its construction and I'm sure the designer thought themself a pretty smart cookie, but I thought it one of the worst trails I've been on. In hindsight, I think the Ocean View Trail (basically a powerline road) or the Old Prospector Trail (perhaps the best choice, not open to bikes) would have been better. Most of these trails cut through slopes covered in dense chaparral. Initially rising above the San Luis Obispo neighborhoods and shopping areas, views soon open to the group of volcanic plugs known as the Sisters, and north and east across the larger community. There are more trails than are shown on the official park maps, one of these going within about 100yds of the summit, across a saddle to the south. It was necessary to do some modest bushwhacking to reach the highpoint. The brush wasn't particularly thick here, but it was very stiff and scratchy, adding some new rips and holes into my already beleaguered hiking pants. The views from the summit are decent but not particularly noteworthy. Aside from a very distant view to Morro Rock, I had no ocean views but primarily the surrounding Irish Hills and across to the Santa Lucia Range. On my way back down I found that there is an older version of the Wednesday Trail that was replaced by the switchbacked version. Though rockier and not conducive to cycling, the older trail seemed perfectly servicable for hiking but has been blocked by boulders and piled with brush in an effort to erase it. It seems it might have been fine to leave it be, but who knows what terribly evil things have been prevented by its obliteration. I was back to the TH just after 2:30p - time to drive back to Pismo and enjoy the rest of the afternoon with the family...


Powen Ru comments on 11/09/22:
Why you consider Peak 1800+ as the HP of Irish Hills? Saddle Peak has clear elevation 1819 and BM. On ArcGIS World Topo, Saddle has 1821 and Peak 1800+ has 1814; and both Peakbagger and give p1k to Saddle. Only OpenTopo shows Peak 1800+ has 540+m that is taller than Saddle Peak's highest contour; yet it still shows Saddle Peak 540m.
My database is based on LoJ which uses average prominence (in this case, 1820ft) rather than clean prominence used by PB (in this case, 1800ft). Average prominence is more accurate than clean, but still has uncertainty, so we may have to wait for Lidar analysis to be more definitive.
Submit online comments or corrections about the story.

More of Bob's Trip Reports

This page last updated: Mon Nov 14 15:04:34 2022
For corrections or comments, please send feedback to: