| Permanente Creek | |
| Name Other: | Arroyo Permanente[1] |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | California |
| Subdivision Type3: | Region |
| Subdivision Name3: | Santa Clara County |
| Subdivision Type5: | Cities |
| Subdivision Name5: | Los Altos, Mountain View |
| Source1: | Black Mountain in the Santa Cruz Mountains |
| Source1 Location: | Los Altos |
| Source1 Coordinates: | 37.3222°N -122.1447°W |
| Source1 Elevation: | 2421feet |
| Mouth: | Mountain View Slough in southwest San Francisco Bay |
| Mouth Location: | Mountain View |
| Mouth Coordinates: | 37.4333°N -122.0858°W |
| Mouth Elevation: | 0feet |
| Tributaries Left: | West Fork Permanente Creek and Hale Creek |
Permanente Creek is a 13.3adj=midNaNadj=mid[2] stream originating on Black Mountain in Santa Clara County, California, United States. Named by early Spanish explorers as Arroyo Permanente or Río Permanente because of its perennial flow,[1] the creek descends the east flank of Black Mountain then courses north through Los Altos and Mountain View, discharging into southwest San Francisco Bay historically at the Mountain View Slough but now virtually entirely diverted via the Permanente Creek Diversion Channel to Stevens Creek and Whisman Slough in San Francisco Bay.[3]
The Ohlone Indians lived in the area for over 3,000 years prior to the arrival of the Europeans. A large village, known as Partacsi, was located in this general area. An expedition led by Colonel Juan Bautista de Anza passed through this area in March 1776 as he forged the first overland route from Monterey to San Francisco Bay. Mission Santa Clara de Asis was founded in October of the same year, where many of the local Indians were taken. Governor Alvarado granted Rancho San Antonio de Padua to Juan Prado Mesa in 1839. This 440acres rancho was bounded by Adobe Creek to the north and Stevens Creek to the south, and included Permanente Creek.[4] On a diseño of Rancho San Antonio in 1839 Permanente Creek is shown as Arroyo Permanente.[1] Mesa had been a soldier at the Presidio of San Francisco since 1828, served as a corporal in the Santa Clara Guard, and had won fame as a soldier and Indian fighter. Mesa died in 1845.
Permanente Creek is also the namesake for Kaiser Permanente. Bess Kaiser and her spouse, industrialist Henry J. Kaiser, had a lodge on the creek's headwaters above the large Permanente Quarry and Cement Plant, and, in 1945, Bess felt that the name of their attractive and dependable stream would be a good name for their medical program at the shipyards. That medical program became Kaiser Permanente.[5]
Permanente Creek consists of approximately 13.3miles of channel[2] draining a watershed area of 17.5sqmi.[6] From its origination at 2421feet in headwaters protected by the Midpeninsula Regional Open Space District just north of the peak of Black Mountain (and just east of the Black Mountain Trail), Permanente Creek descends along the Permanente Quarry (currently known as the Lehigh Southwest Cement Plant and Quarry), and continues easterly through unincorporated County land for about five miles (8 km), then turns to the north at the base of the foothills and continues another eight miles (13 km) along the valley floor. It has two major tributaries, the West Fork Permanente Creek and Hale Creek. West Fork Permanente Creek and its Wildcat Canyon tributary were formerly known as Ohlone Creek.[7] West Fork Permanente Creek begins on the east side of 1253feet Ewing Hill, and runs easterly until it reaches the connector from the Chamise and Rogue Valley Trails where an earthen dam forms High Meadow Pond (aka Rogue Valley Pond). Below the pond, the West Fork is joined by 1.7miles long Wildcat Canyon Creek at Deer Hollow Farm, then continues on its run (3.2miles total) to the Permanente Creek mainstem which it joins 0.5miles south of Interstate 280.
Flows are perennial in the upper watershed but seasonal on the valley floor, with two exceptions: the portion of the Permanente Creek mainstem between Foothill Expressway and Interstate 280, and the Hale Creek tributary. The perennial reaches of these creeks share the same perennial nature as a similar reach on nearby Adobe Creek.
Except for sakrete (bagged concrete) banking and several weirs, Permanente Creek's upper mainstem runs about 8miles in a relatively unmodified natural channel until reaching Portland and Miramonte Avenues at the north end of Heritage Oaks Park. Here the creek enters a concrete trapezoidal channel constructed by the Santa Clara Valley Water District (SCVWD). Just before reaching the rear of Blach Intermediate School, it becomes the Permanent Creek Diversion Channel, built by the SCVWD in 1959, and runs a total of 1.3miles,[2] continuing due east until passing in a culvert beneath east under Highway 85 to Stevens Creek. A floodgate is closed every winter that diverts virtually all winter flows east to Stevens Creek, preventing high winter floodwaters from flowing north in the original creek channel through dense residential areas. Only during high floods can a portion of the creek's waters surmount the floodgate and return to the original channel.[8] Therefore, the Diversion Channel effectively reconnects Permanente Creek to the Stevens Creek watershed. This recapitulates the 1862 Allardt Map of the San Francisco & San Jose Railroad which shows Permanente Creek (Arroyo Permanente) as a tributary of Stevens Creek (then Cupertino Creek) (see inset). This is significant ecologically, because Stevens Creek still hosts an anadromous steelhead trout run. Although steep drops in the Diversion Channel are impassable barriers to upstream fish migration, modifications to the Diversion Channel would open up an additional 9miles of upper Permanente Creek watershed to steelhead trout.[2] The Diversion Channel essentially changes the total length of Permanente Creek from 13.3miles to San Francisco Bay to 9.3miles ending at its junction with Stevens Creek just past Highway 85.[2] However, Hale Creek still flows to the channelized lower reaches of Permanente Creek.
The original creek channel below the floodgate in the Diversion Channel, now severely depleted of water, runs north another 1.5miles to its confluence with Hale Creek just upstream from McKelvey Park. Permanente Creek's original channel then goes on to pass under U. S. Highway 101, along the west side of the Google campus, and out to the Bay at the Mountain View Slough just east of Shoreline Park, the latter built on a reclaimed San Francisco garbage dump in 1983. This lowest part of the creek historically disappeared into the marshland before reaching the Bay, and its channel was extended to the Bay in the nineteenth century. The creek must have been hydrologically connected to the Bay at times of high winter flows since steelhead trout were able to access Permanente Creek historically. Saltwater is pumped from Charleston Slough into Shoreline Lake and from there it flows to Permanente Creek and then back into the Bay. The Mountain View Slough carries flows to the Bay between former salt ponds A1 and A2W. The levees around these ponds will be breached and opened to the Bay as part of the South Bay Salt Pond Restoration Project Phase II.[9]
The Santa Clara Valley Water District has been working (2010–2020) to excavate as much as 23feet down to create flood detention basins to protect homes from a 100-year Permanente Creek flood, at Cuesta Park Annex, Blach Intermediate School, McKelvey Park, and Rancho San Antonio County Park.[10] Despite considerable community opposition, the SCVWD Board approved the decision to go ahead on June 17, 2010.[11] The Blach School Board voted against use of school property for a detention basin but construction permits are being sought as of 2016 for the McKelvey Park and Rancho San Antonio Park basins.[12] Construction of the McKelvey Park detention basin and recreational facilities was completed in February 2020.[13] Construction at Rancho San Antonio Park is planned to include a 15-foot deep basin and new park infrastructure.[14]