Oldtimers still refer to the area northwest of the present day intersection of Hill Drive and Arbor Dell Road as the "Lemon Grove." A tunnel for irrigation had been drilled there by Benjamin Dreyfus, soon after he was awarded the Eagle Rock area in the Division of Rancho San Rafael in 1870.

The land changed hands twice before being bought by W. H. Stimson, who maintained a 75-acre grove of 800 lemons, 30 avocados, and other choice trees, between 1907 and 1928.

It is uncertain how much the rancher relied on the tunnel to irrigate these 75 acres. What we do know is that the rancher worked hard to increase his water supply. Francis Johnston reports, "[Stimson] ran a second water tunnel into the hills and built a reservoir to catch the run-off from the surrounding slopes. Unfortunately, this latter effort was unsuccessful, and a piping system had to be connected directly with the water tunnels."

Bob Moffitt remembers at least one of the Stimson tunnels still flowed into the late 50s, and was used by Larry Wilson, who acquired the property for the purposes of subdivision. Moffitt described the tunnel as a 4' cave at the foot of the hill, from which a spring arose. Though the Wilson household had regular city water piped in, they used the spring water for drinking. The spring water would have been softer than the city water, which meant better taste, and better suds.

Other Eagle Rock tunnels were located at the top of Argus Drive (alongside an open spring) and at the top of Hermosa Avenue on the Cook property. Cromwell Galpin writes, "many of [the tunnels] yielded water for domestic purposes until the season happened to be rather dry. Not one of the tunnels ever proved of value for irrigating."

A road directly south of the Stimson ranch, was called "Tunnel Road" until neighbors petitioned to have it renamed "Monte Bonito" in the 1920s.