Sea Otters in Marin

by Parker Pringle

In recent years, river otters and coyotes have recolonized much of southern Marin. Bald eagles are also making inroads into our area: two juveniles spent some of this past winter eating coots in Richardson Bay. Now, a recent study has raised the tantalizing possibility that sea otters could be the next predator species to return to the Corte Madera Creek watershed.

Up until the 1830s sea otters were abundant in San Francisco Bay and the Corte Madera Creek estuary. Miwoks of the Larkspur area hunted otters in the estuary and San Quentin Bay. Sea otter bones (along with those of grizzly bear and condor) were found in the shell mound at the site of the Rose Lane development. Author Adele Ogden, in her California Sea Otter Trade, 1784–1848, writes that Aleut hunters, operating as part of Russian expeditions out of Fort Ross, made illegal visits to Marin’s sea otter fields in the early 1800s by landing at Point Bonita and portaging around the Golden Gate to avoid Spanish lookouts at the Presidio. They would relaunch their kayaks in Sausalito and work up the Marin coast. In 1830 a hunting party from the San Jose mission found 100 sea otters hauled out at Point San Quentin and “lassoed” 30 of them.

Sea otters are larger than river otters, and often float on their back while feasting on shellfish.

Sea otters are larger than river otters, and often float on their back while feasting on shellfish.

Sea otter pelts were exported to China where they were highly prized. In the days of Spanish and Mexican ownership of California, this fur trade was big business. But the 1830s saw the introduction of the gun to sea otter hunting—which until then had been conducted mainly with spears and arrows—and the populations declined precipitously. In 1840, the grantee of the San Quentin Ran-cho received a license to hunt sea otters, but there probably weren’t too many left to shoot. When an international treaty in 1911 banned the killing of sea otters, the California population was estimated to number only 50 otters. Soon after, the sea otter was thought to have been extirpated from California. Then a relict population was found near Big Sur in 1938. All the sea otters in California today are descendants of this small group.

The possibility of sea otters re-colonizing San Francisco Bay stems from the fact that this year the sea otter population has climbed to its highest number since the 1800s. The historical population is estimated to have been 16,000. This year’s population survey, conducted by the USGS, found 3,272 sea otters in California.

While this is good news, the range of the sea otter range is not expanding, largely due to shark at-tacks killing any otter that takes up residence in the Año Nuevo area. Range expansion is crucial to the long-term survival of the species, but it occurs only in small steps as female otters generally do not migrate very far from their birthplaces. With the population having filled the currently available habitat, and sharks killing off females venturing into the Año Nuevo area, resource managers might attempt to move a colony of sea otters around the shark road-block at Año Nuevo to some suitable habitat to the north.

A visiting sea otter was oblivious of the attention he attracted near Richardson Bay bridge in Mill Valley, in 2015. Photos by Parker Pringle

A visiting sea otter was oblivious of the attention he attracted near Richardson Bay bridge in Mill Valley, in 2015. Photos by Parker Pringle

Transplantation of sea otters has been done successfully once before, at San Nicolas Island in Southern California. According to Dr. Tim Tinker, head of the USGS sea otter research program, San Francisco Bay could be a candidate for a sea otter transplant colony. If a breeding sea otter population is established in San Francisco Bay, these hungry predators would transform the Bay ecosystem. For example, one of their favorite foods is crab. Crabs like to eat the slugs that eat algae on eel grass. A decrease in crab populations due to sea otter predation would lead to an increase in these algae-eating slugs, in turn promoting growth of eel grass which is an important habitat for herring. This phenomenon has been documented in Elkhorn Slough, an estuary which is similar to parts of San Francisco Bay.

Male sea otters do occasionally appear in our waters. In June of 2015 a male sea otter took up residence in Richardson Bay, upstream of the Hwy 101 bridge. He could be seen gorging on mussels, clams and crabs along the Sausalito to Mill Val-ley path. Sadly, this otter ultimately died from a combination of domoic acid poisoning (the same toxin which kept crab out of the super-market in 2015) and a parasite, spread by opossums, that causes an illness similar to toxoplasmosis. The domoic acid poisoning was found to have occurred while the otter was in the bay. But had this sea otter not died, he would have soon left the Bay anyway and headed back to the Central Coast region where female sea otters are exclusively located.

There will be much study and consideration before anything hap-pens on this front. But the return of sea otters to San Francisco Bay, one way or another, seems to be getting closer to a reality.

If you are interested in reading more about sea otters, there are two excellent articles at regarding the sea otter that visited Richardson’s Bay in 2015.


Some Progress on the Ross Valley Watershed Program

by Sandy Guldman

 Detention Basins

Although detention basins are essential to providing protection from large floods, they remain controversial and are bogged down by protests. A lawsuit challenging the County’s purchase of the former Sunnyside Nursery growing ground in Fairfax was settled and feasibility studies are in progress to evaluate its use as a detention basin. Preliminary feasibility studies have also been completed for Lefty Gomez Field.

No reports on the results of feasibility studies of the Phoenix Lake Dual Use Facility have been released, although based on the feasibility study being prepared by AECOM, a full dam replacement alternative for the Phoenix Lake dam appears to be the preferred alternative compared with two dam retrofit alternatives. From environmental and constructability standpoints, Marin Municipal Water District and the Marin County Flood Control District agree that full dam replacement will be a significant challenge. The District is working with MMWD for an interim Phase 1 construction project and operations procedure and delaying the full dam replacement.

Temporarily holding back overflow from Phoenix Lake would reduce flooding in Ross. Photo by Charles Kennard

Temporarily holding back overflow from Phoenix Lake would reduce flooding in Ross. Photo by Charles Kennard

Three alternative groups of projects that could be used as a substitute for the Memorial Park Dual-Use Facility have been identified. This project, called the San Anselmo Flood Protection Project, includes no work at Memorial Park or anywhere else in the Sorich Creek sub-watershed. To be acceptable to the Department of Water Resources (the funder) the San Anselmo Flood Protection Project must provide the same benefits that the Memorial Park facility would have provided, cost about the same, and be completed by the end of 2020.

That will be challenging, but is considered feasible. The alternatives are:

Alternative 1: Detention basin at the nursery site and creek capacity improvements in the Morningside neighborhood.

These measures are removal of the Mountain View Avenue Bridge, and 3,500 feet of flood barriers, such as low walls or berms, reaching from Sir Francis Drake to Brookmead Court. Although many residents of the Morningside neighborhood have been supportive of this project, it would require the approval of the owners of 59 parcels to construct the barriers. This will be challenging to accomplish in the limited time available.

Alternative 2: Detention basin at the nursery site, removal of Building Bridge 2 in downtown San Anselmo, and installation of 375 linear feet of flood barriers.

This project would require the approval of the owners of 13 parcels, which might make it easier to finish on time. All of the in-stream capacity measures would occur in downtown San Anselmo. It would be necessary to protect two structures down-stream of the work from higher water surface elevations resulting from the increased flow in the channel.

Alternative 3: Removal of Building Bridge 2, modification of two buildings that overhang the creek and obstruct flow, and the installation of 375 linear feet of flood barriers.

This project would require the approval of the owners of 31 parcels. It would be necessary to protect four structures downstream of the work from higher water sur-face elevations resulting from the increased flow in the channel.

Current plans are to begin preparation of the Environmental Impact Report (EIR), required by the California Environmental Protection Act, for the San Anselmo Flood Protection Project early in 2017. The

Project-level EIR provides a greater level of site-specific detail than the Programmatic EIR (PEIR). The Project EIR can be visualized as a small circle inside the larger PEIR; however, it can also be taken out of the PEIR and function on its own in the event the PEIR is not completed in time for construction to be finished by December 31, 2020.

In-stream Measures

This broad category includes replacing bridges or modifying buildings that limit creek capacity, changing the channel by widening or deepening it, and reclaiming parts of the floodplain. Replacements for several bridges are in a design phase, but the process has slowed because if there are no upstream detention basins, the bridges must be made wider and higher to accommodate the higher flows expected without basins. Plans to increase the channel capacity in downtown San Anselmo are being developed; these plans include modifying structures that intrude on the channel and removing rubble and bedrock that reduce capacity (see Alternatives 2 and 3 above).

US Army Corps of Engineers Project, Corte Madera Creek

Design work is underway. To its credit, the USACE is meeting regularly with regulatory agencies, like the Regional Water Quality Control Board and NOAA Fisheries, to obtain input on proposed designs to facilitate permitting. Fish passage and riparian habitat are major issues.

Alternatives include top-of-bank flood barriers, set back flood barriers, and deepening or widening sections of the earthen and concrete channels. Removal of the existing fish ladder behind the Ross post office is also included. A full alternatives analysis will be released when the draft Environmental Impact Statement/EIR is issued, scheduled for fall 2017.

Creek Cleanup

With financial support from the Ross Valley Stormwater Fee, crews from Conservation Corps North Bay worked with public works staff to identify problems and clean creeks in Larkspur, Ross, San Anselmo, and Fairfax as well as in unincorporated Marin County. The work was done in September and October 2016. Concrete rubble was removed from a section of the creek in San Anselmo near Sir Francis Drake Boulevard in September 2016

Public Meetings

A community workshop was held on November 30, 2016 to receive public input on the San Anselmo Flood Protection Projects, three of which are described above. A Flood Zone 9 Advisory Board meeting was held December 20, 2016 as this was being prepared.

A presentation to the San Anselmo Town council is scheduled for January 10 on the San Anselmo Flood Protection project. A scoping meeting for the PEIR for the Ross Valley Watershed Program will be held January 18, 2017 from to 9:30 p.m. at the Ross School Library.

More Water in the Marsh at Hal Brown Park

by Sandy Guldman

The southeastern corner of Creekside Marsh at Hal Brown Park in Kentfield had deficient tidal ex-change because the single culvert connecting it to Corte Madera Creek was too small. When the potential for funding from the Regional Water Quality Control Board’s Supplemental Environmental Program came up, Friends proposed replacing the culvert with a much larger one; the proposal was accepted and we signed contracts with Ross Valley Sanitary District, who provided the cash, and the Regional Board. At that point, we hired engineers to design the project.

It was a complicated project because the Kentfield Force Main—two high-pressure sewers—are under the multi-use path along the creek and above the culvert. The initial design of a single box culvert was too expensive and presented some logistical challenges, so the project was delayed and redesigned to incorporate three parallel plastic pipes with the same capacity as the single box culvert.

Thanks to significant logistical and financial support from Marin County Parks, the culvert was successfully installed this fall, just meeting the October 31 construction deadline. Kudos to Chris Bramham and Craig Richardson! We look forward to increased flow and better habitat in the marsh now that water can freely move in and out.

Three new culverts have replaced the single one leading into Hal Brown Park, passing under the creekside multi-use path, and increase the tidal circulation in the marsh. Photo by Sandy Guldman

Three new culverts have replaced the single one leading into Hal Brown Park, passing under the creekside multi-use path, and increase the tidal circulation in the marsh. Photo by Sandy Guldman

What’s Green About Green Infrastructure?

by Gerhard Epke and Sandy Guldman

Small, local flood management solutions, commonly described as Green Infrastructure, have received strong support during public meetings in the Ross Valley.

What Problems Does Green Infrastructure Address?

Stormwater runoff is a major cause of water pollution in urban areas. When rain falls on roofs, streets, and parking lots, the water cannot soak into the ground. Instead, it drains quickly through engineered collection systems (think gutters and storm drains) and is discharged into nearby creeks loaded with trash, bacteria, heavy metals, and other pollutants. High flows resulting from heavy rains also can cause erosion and flooding, damaging habitat, property, and infrastructure.

Green infrastructure can help clean runoff and slow it down. In addition, vegetation in Green Infrastructure projects sequesters carbon, can reduce temperatures in urban areas during hot summer weather, sometimes provides recreational benefits, and improves air quality. When rain falls in natural, undeveloped areas, the water is absorbed and filtered by soil and plants, and any stormwater runoff is cleaner. Even better, if floodplains can be restored, they accommodate water that would otherwise be flowing in low paved areas near creeks.

What is Green Infrastructure?

Green Infrastructure uses vegetation, soils, and other methods to restore some of the natural processes required to manage water and create healthier developed environments. While single-purpose stormwater infrastructure—conventional piped drainage—is designed to move urban stormwater quickly away from the built environment and into creeks, Green Infrastructure reduces and treats stormwater at its source while delivering environmental, social, and economic benefits. Here are some types of Green Infrastructure: downspout disconnection, rain gardens, bioswales, permeable pavements, green roofs, and trees. Open spaces incorporated in infrastructure can address water quality and flooding impacts while providing recreational opportunities.

A Filterra storm drain inlet is located at the southeast corner of Rose Lane and Orchid Drive, in Larkspur. Photos by Sandy Guldman

A Filterra storm drain inlet is located at the southeast corner of Rose Lane and Orchid Drive, in Larkspur. Photos by Sandy Guldman

This close-up of the planted section of the Filterra unit shows accumulated trash, often discarded by students.

This close-up of the planted section of the Filterra unit shows accumulated trash, often discarded by students.

Green Infrastructure and Flood Management

The relative sizes of floods can be described by how frequently a particular flow is expected to occur. A flood with a 1% chance of occurring in any particular year is traditionally referred to as the 100-year flood. These large floods occur when intense rain falls on ground that is already saturated from recent rains. The soil has no capacity for water to infiltrate and it runs off, overwhelming the stormwater infrastructure. In those situations, smallscale Green Infrastructure cannot stop the flooding because cisterns, swales, and small flood plains are also at capacity. However, in floods that occur more frequently, small-scale Green Infrastructure can make a big difference. These smaller floods are often quite damaging in local areas, so this is a major benefit of small-scale projects. (Friends is gathering quantitative information about ability of these facilities to accommodate storm flows. An article describing what we find will be in a future issue of Creek Chronicles.)

It is worth observing that many flood managers consider detention basins to be Green Infrastructure. However, in discussions of measures to reduce flood damage in the Ross Valley, the public has clearly demonstrated that it does not agree with that assessment. Some communities that have implemented Green Infrastructure describe some components as “floodable spaces” including detention basins, flood plains, and swales regardless of size.

The swale, about 550 feet long, is located at the east end of the Rose Lane development, parallel to Larkspur Creek. The swale filled after a big December storm, and is seen from Doherty Drive. Photo by Sandy Guldman

The swale, about 550 feet long, is located at the east end of the Rose Lane development, parallel to Larkspur Creek. The swale filled after a big December storm, and is seen from Doherty Drive. Photo by Sandy Guldman

Ross Valley Examples of Small Scale Green Infrastructure

Here are three examples of Green Infrastructure, two in Larkspur and one in San Anselmo:

Rose Lane Green Infrastructure

The Rose Lane neighborhood, located in the City of Larkspur and adjacent to Larkspur Creek includes a Filterra system. Stormwater runoff enters a drain and then flows through a filtering mixture in a landscaped container. Pollutants are removed from the stormwater, which then flows through underground drains into a swale about 550 feet long near Larkspur Creek, where the water slowly infiltrates. If the water in the swale gets very deep, it overflows into the creek.

City of Larkspur Magnolia Avenue Green Infrastructure

The City of Larkspur has proposed a project to compensate for the increased impervious surface of the new Bon Air Bridge. This project would provide some relief from local flooding, would increase the number of trees and shrubs, and improve water quality. The project includes:

  • Eliminating the second through travel lane in both directions on Magnolia Avenue for one block between Bon Air Road and Dartmouth Avenue and replacing the asphalt with landscaping,
  • Providing curb cuts to direct street drainage into swales, and
  • Installing an underground infiltration system.

Magnolia Avenue south of Bon Air Road and north of Dartmouth Avenue would have only one lane of through traffic in each direction, but the reconfigured intersections would retain two queuing lanes and left and right turn lanes at the Magnolia Avenue/Dartmouth Avenue intersection. Traffic experts do not expect significant worsening of traffic from the change. The City of Larkspur is studying alternatives to the Magnolia Avenue project, but some residents of Larkspur will almost certainly experience a loss of parking and/or travel lanes whatever alternative is selected.

San Anselmo Magnolia Avenue Green Infrastructure

The Town of San Anselmo is finishing designs for three municipal Green Infrastructure projects: bioretention at the Town corporation yard, bioretention in a street median at Greenfield Avenue and Lincoln Park, and reconstruction of the public parking lot at Magnolia Avenue. The parking lot is about 13,000 square feet, accommodates 30 cars, and the pavement has deteriorated. The original design for converting the lot to Green Infrastructure included a combination of permeable pavement and small rain gardens or tree wells wherein one parking stall would be lost. Local merchants have made it clear, however, that the loss of a single parking spot is unacceptable because of the associated losses in revenue. Constraining the final design to not lose any parking should be possible but will likely come at the cost of the rain gardens and trees.


The environmental benefits of Green Infrastructure are not greater than undeveloped areas, but compared to traditional engineering, this approach has several advantages, including reduced local flooding during small, high frequency events; better water quality in streams; and better air quality and more carbon sequestration from the trees and other vegetation that frequently replace pavement.

Right now, it appears that residents of the Ross Valley are all in favor of Green Infrastructure, unless it is located where it might inconvenience them. As advocates of Green Infrastructure, we need to do a better job of demonstrating the benefits of individual projects so that the support for Green Infrastructure changes from an abstract concept to support for real projects


Vegetation Management Plan Delays

by Ann Thomas

A lengthy planning effort to establish guidelines for managing vegetation on county open space is in recess after contentious public hearings this fall which concluded with the acceptance of a plan to be used as a guidance document, its original intent. Environmental review will be conducted for specific projects that need it.

The vegetation management plan for the 18,900 watershed acres owned by the Marin Municipal Water District, stalled in mid-2015 but is restarting with environmental review of the district’s new draft plan.

The ongoing controversy over herbicide use is the cause of the de-lay, even though some very limited herbicide use is necessary to control a few of the invasive plants that are harmful to Marin’s native ecosystem, increase fire danger, and can add to flood risk. Friends of Corte Madera Creek Watershed supports using the Integrated Pest Management (IPM) process to establish strategies to ad-dress invasive infestations. IPM is a science-based, decision-making process allowing herbicide use when all other methods would be ineffective.

Mount Tamalpais, viewed from Loma Alta. Photo by Charles Kennard

Mount Tamalpais, viewed from Loma Alta. Photo by Charles Kennard

Open Space Preserves
Marin County Open Space District began work on their Vegetation and Biodiversity Management Plan (Plan) in 2009. The Plan includes years of data collection on plant re-sources and vegetation science, and describes district goals of balancing public access, fire fuel reduction, and natural resources protection.

An Environmental Impact Re-port (EIR), with a price tag of more than $400,000, was prepared and the dual package came to the County Parks and Open Space Commission, then to the Board of Supervisors, sitting as the Open Space District Board of Directors, in October. Both groups received numerous letters and verbal comments asking decision-makers to not accept the EIR or the Plan but instead support a total ban on herbicide use.

The advisory citizen commission, recommended certification of the EIR and adoption of the Plan. On October 18, the Open Space District Board of Directors/Board of Super-visors, bowing to anti-herbicide activism, did not certify the EIR, and accepted but did not adopt the Plan. As a result of not certifying the EIR, environmental review will now have to be done annually on a project-by-project basis, although many projects do not need environmental review.

Opposition has focused on glyphosate, one of the least toxic of effective herbicides available. Glyphosate is one of hundreds of substances identified by one monitoring agency as a probable carcinogen. It is in the same category as alcoholic beverages, emissions from high-temperature frying, sunlight, chemo-therapy drugs, and red meat: sub-stances for which consumption or exposure should be limited. The assessment of carcinogen-causing potential is not based on an assessment of risk or dose, so its validity is questioned by many experts.

Use of herbicides by open space professionals is carefully targeted to the harmful plant, and rigorous protocols are followed to protect applicators and to post advanced notices of applications at public access points to the area treated. Herbicides use in county parks is strictly confined to areas with natural habitats; no herbicides are used on play-grounds, picnic areas, or other areas of heavy public use. Herbicide use on county open space is estimated to be one percent or less of the county total, with personal and commercial use of chemicals contributing the bulk of use.

The open space district, operated separately from county parks, comprises 34 preserves. Those in the Corte Madera Creek watershed include the following: Baltimore Canyon at the headwaters of Larkspur Creek, Cascade Canyon above Fairfax, King Mountain, Loma Alta, Ring Mountain in Corte Madera, and the White Hill and Bald Hill preserves overlooking Fairfax and San Anselmo.

Unlike the county’s park system, which invites recreational use, the open space areas are set aside primarily to protect their natural habitat in addition to providing recreation. County open space preserves are adjacent to the back yards of about 3,300 residential properties and any uncontrolled vegetation on district lands adds to residents’ wildfire risk.

Water District Watershed
The water district, serving most of Marin County, had not used herbicides for a decade, which has resulted in the explosive spread of broom and other problem plants that cannot effectively be controlled without herbicides. The district, over several years, prepared a new management plan to update its 1995 version and it included a full range of IPM options.

In July 2015 the district’s Board of Directors, who were consistently lobbied by anti-herbicide groups, abruptly stopped review of this plan and directed consultants to prepare a new version that does not include consideration of herbicides in the portfolio of strategies. This revised ‘Biodiversity, Fire, and Fuels Integrated Plan’ was issued in September and is expected to soon begin undergoing environmental review at the end of January, although this could be changed, and the comment period for members of the public will run for 30 calendar days.

Friends is part of a coalition of organizations supporting use of IPM to protect our natural habitat. Information is on the group’s website: