Even prior to the start of construction, the Park Service and PRNSA had to contend with an accidental breach of the levees in early July 2008 after months of carefully drying out of the site. Repairing the Levees Necessary Before Removal
Phase II of the project has included the following components:
Restoration Components under Phase II:
Removal of the remainder of the levees in the East and West Pastures of the Giacomini Ranch, except for areas where sections will be retained as high tide refugia for rails. In 1946, the Giacominis built an elaborate levee system on either side of Lagunitas Creek to improve pasture conditions in a marsh at the headwaters of Tomales Bay and thereby established the Waldo Giacomini Ranch.
One of the most important actions taken to restore this former dairy ranch back to wetland was to remove this levee system. Approximately 5,940 linear feet of levee in the East Pasture and 5,240 linear feet of levee in the West Pasture adjacent to Lagunitas Creek were excavated to the adjacent pasture elevations.
While the levee was completely removed during construction in the southern portions of the Project Area, in the northern portions, the levee system was excavated in stages. During the first stage, most of the levee material was removed such that a 1- to 3-foot high berm was left at the 7.5-foot NAVD88 elevation to ensure that the pasture interior did not become tidal during higher high tides.
A shallow trench ranging in size depending on the berm height was excavated on the inboard side of the berm in the area where the levee was formerly located. During the final breaching of the levees in October 2008, material was pushed into this trench and smoothed to match adjacent grades during a low tide cycle.
East Pasture levee excavation generated approximately 22,300 cubic yards (CY) of material, with the West Pasture (except for the northern portion) generating another 18,533 bulk CY. In the East Pasture, most of the levee material excavated was used to fill ditches, create high tide refugias for rails or berms, or restore natural topographic conditions at the Dairy Mesa. Conversely, in the West Pasture, all of the material from the levee removed along Lagunitas Creek was hauled off-site to one of the quarries on the Tomales Point slated for restoration (see Where Did Excavated Soils from Phase I and Phase II Go?).
Further lowering of the levee in the southern portion of the East Pasture that was removed last year. The southernmost section of East Pasture levee was originally removed in 2007, but excavation left a wedge of earthen materials that reduced the frequency of flood overtopping slightly and, therefore, affected the value of the restoration project to reducing vertical flood elevations in this reach, which adjoins several private and state-owned properties and roads. In 2008, another 1 to 2 vertical feet of soil was removed from the 2,200 lineal feet of levee on the southern perimeter. This material was not off-hauled, but was used for final grading of the Dairy Mesa.
Grading in the southern portion of the East Pasture to improve floodplain processes. During some of the flooding events in the winter of 2007—2008, it became apparent that flood flows were being conveyed irregularly across the southernmost portions of the East Pasture floodplain adjacent to Lagunitas Creek. As part of Phase II, additional grading was included in this area to create a very broad and shallow swale or depressional 4.1-acre basin to capture, consolidate, and direct overbank floodwaters from Lagunitas Creek that accumulate in the area west of the Mesa. These flood flows will now be directed through this swale toward the former Manure Disposal Pasture in the center of the East Pasture, where sediments transported in floodwaters can continue to deposit on the former manure slurry disposal area as they did in 2007 and, over time, create a clean surface soil "cap" over the deeper layers of manure-laden soils that could not be fully excavated.
Creek bank stabilization activities such as removal of riprap, laying back of vertical creek banks, and creation of floodplain terraces along the southern portion of the East Pasture Lagunitas Creek Bank.
Approximately 1.74 acres of bank along Lagunitas Creek in the southwestern portion of the East Pasture was graded to convert the current moderately steep slope (3:1) into a terraced floodplain bench to expand the active floodplain within this reach of Lagunitas Creek. Approximately 2.3 acres of additional grading was conducted in adjacent uplands to lower floodplain terrace elevations. Once grading was completed, revegetation was conducted through native riparian plant species grown from locally collected material and seeding of native grass species.
To the east of this, an approximately 300-foot section of the East Pasture Lagunitas Creek bank was riprapped following the 1982 flood, which involved use of large rock or boulders on creek banks to minimize erosion or loss of levee. This riprap area was frequently impacted by high energy flood flows, with upstream and downstream areas often eroding in response. In addition, the riprap area remained largely unvegetated, creating a break in the riparian corridor or zone of unfragmented, continuous riparian tree and shrub canopy along Lagunitas Creek. Unfragmented riparian corridors provide important habitat for many terrestrial and aquatic species, including federally threatened and endangered salmon and freshwater shrimp species.
In 2008, more than an estimated 800 cubic yards of riprap above the Mean High Water (MHW) mark was removed, with 35 percent of this hauled off-site to a storage area for the Seashore. The remainder was used to stabilize an approximately eroded 100-foot section of creek bank just upstream through excavation of a trench just below MHW. The approximately 0.18 acre of creek bank exposed by removal of riprap and an approximately 100-foot section of non-rip rapped, highly eroded creek bank just upstream was regraded above MHW to a more stable topographic profile and then stabilized by installation of erosion control blanket and revegetation. The lower section was planted with willow sprigs, while the upper slopes were planted with native riparian plant species grown from locally collected material.
Realignment of Tomasini Creek into one of its historic alignments in the East Pasture, converting its current leveed channel into a muted tidal backwater slough.
In the 1960s, the Giacominis leveed one of the smaller creeks that flowed into the East Pasture to run along the eastern perimeter of the ranch directly adjacent to the Point Reyes Mesa and constructed a tidegate and flashboard dam structure at the creek’s northern end near Railroad Point. Despite being leveed, Tomasini Creek has still continued to support some threatened and endangered species, including the federally endangered tidewater goby (Eucyclogobius newberryi), the federally endangered coho salmon (Oncorhynchus kisutch), and the federally threatened steelhead salmon (Oncorhynchus mykiss).
As part of Phase II, the downstream portion of Tomasini Creek was entirely realigned into one of its historic channel alignments prior to being leveed. Just downstream of the Worker Housing, which is west of Mesa Road, an approximately 0.2-acre section of levee that separates Tomasini Creek from the East Pasture was removed, and the approximately 200 CY of excavated materials were used to construct a new berm measuring approximately 0.2 acre in the existing, leveed Tomasini Creek channel that would allow flood overflow into the old channel during storm events exceeding a 2-year return interval. The old channel and its tidegates and flashboard dam system were retained to function as a backwater slough feature for the tidewater goby, which prefers muted tidal, impounded conditions. Approximately 1.0 acre of new creek channel was then created through the Tomasini Triangle to the north of the new freshwater marsh and linked to the enhanced tidal creek network in the East Pasture (see below). In upstream portions of the realignment, adjacent creek banks have been revegetated with native riparian plant and marsh species.
Creation and enhancement of tidal channels in the East Pastures.
Tidal channel creation efforts were focused in the East Pasture, because the underlying substrate in the East Pasture—dense, clay muds deposited when the site was tidal—were considered more likely to preclude natural channel development than the more alluvial or sandy soils underlying the West Pasture.
Approximately 10,280 linear feet of new tidal channel was excavated in the northeastern, central, and western portions of the restored East Pasture. This tidal channel network represents the downstream portion of the newly realigned Tomasini Creek or Tomasini Slough, which now flows through the East Pasture rather than being leveed to run along its eastern perimeter. In certain areas, Tomasini Slough flows into remnant portions of the historic slough system that were not eliminated by ranching. In most channels, a small berm or weir was created to establish a balance in water residence time such that ponded areas are retained during low tide for aquatic species such as tidewater goby, but flushing occurs regularly enough that water quality and intertidal mudflat conditions are maximized.
Because some of these channels had become overgrown by cattails, existing vegetation and at least 1 to 2 feet of sediment was removed from approximately 2,700 linear feet or 3.0 acres of historic slough in the northern end of the East Pasture to improve tidal circulation in the central portion of the restored East Pasture. This excavation generated approximately 3,000 CY of very wet material, which was allowed to dry out temporarily next to the channel, and, then, later, most of it was hauled to the Dairy Mesa.
Directly northward of the cattail excavation area, the very southern end of the new Tomasini Slough was actually realigned to avoid the East Pasture Old Slough Pond, a bermed portion of the historic channel that may have been used once for duck hunting. This "pond" supported large numbers of tidewater goby, so it was retained as a muted tidal impounded feature by rerouting the tidal channel around the pond and constructing or enhancing a berm around its perimeter. The berm varied in height so that at least a portion of the berm—the portion at 6 feet NAVD88—could be overtopped during extreme high tide or high water events. The higher elevation portion—constructed at 9 feet NAVD88—was built so that, even during extreme high water events, the top would not be inundated and, therefore, would provide high tide refugia for special status bird species such as the state threatened California black rail (Laterallus jamaicensis coturniculus) and the federally endangered California clapper rail (Rallus longirostris obsoletus; see more description of this and similar features below). The new lower Tomasini Slough consisted of creating an approximately 50-foot wide channel with 1:1 side slopes and a flat channel bed elevation of 0-foot NAVD88, similar to the lowest elevations in nearby areas of Lagunitas Creek.
In addition to the tidal channels draining to the realigned Tomasini Creek, another channel was constructed in the southern end of the East Pasture that drains directly to Lagunitas Creek. The starter channel is actually located roughly in the same alignment as a historic slough that followed the San Andreas Fault trace, and the mouth of the creek was adjusted slightly to overlap with the area where the levee breached repeatedly in 2008 (see Repairing the Levees Necessary Before Removal). The channel drains the newly excavated marshplain enhancement area in the southern portion of the East Pasture (see below). Length of this channel is approximately 2,000 feet.
Excavation for all tidal channels totaled approximately 8.7 acres, with much of the excavated material being used to fill adjacent ditches, restore the Dairy Mesa, or set aside for off-hauling to quarries slated for restoration in the park.
Lowering topographically elevated areas in the southwestern portion of the East Pasture to increase hydrologic connectivity of the marshplain with a created tidal channel.
Much of the southern portion of the East Pasture has been above elevations that would be subject to regular tidal and floodplain processes due to large amounts of sediment deposited by past flooding and past fill and grading activities. Approximately 16 acres of the southwestern portion of the East Pasture where elevations equaled or exceeded approximately 5 feet NAVD88 were excavated anywhere from up to 0.5 to 2 feet to create mid-marsh, high-marsh, and floodplain elevations ranging from 4.5 to 8 feet NAVD88. An additional 2.3 acres adjacent to the floodplain terrace creation area were excavated where elevations ranged between 10 and 11 feet NAVD88. The areas were graded to mimic natural topography by creating a gradual downward slope from south to north. Excavation of the 16-acre marshplain enhancement area generated approximately 29,760 CY, some of which was disposed of off-site at quarries on the Tomales Point that are slated for restoration (see Where Did Excavated Soils from Phase I and II Go?). Much of this area is expected to revegetate naturally as tides bring in seeds and branch, rhizome, and root fragments into the new tidal basin, although this process was jumpstarted on the higher-elevation edges by manual spreading of fragments of rhizomatous, stoloniferous, or above-ground materials from locally collected native salt marsh plant species.
Removal of the West Pasture North Levee and borrow ditch used to create the levee.
Levees that are oriented perpendicular to the general direction of creek and tide flow can often have the largest impact on natural hydrologic processes. The north levee in the West Pasture, often referred to as "Waldo’s Dike," was really the only levee in the Project Area that was oriented perpendicularly and, therefore, received special consideration during planning and construction design. Material excavated during removal of the approximately 950–foot North Levee was used to fill the 0.5–acre borrow ditch to the north, which was the ditch created by "borrowing" of material for levee creation. The approximately 770–foot borrow ditch was filled with materials from levee removal to adjacent pasture grade or elevations (±0.5 feet).
During construction, an existing natural channel in the undiked marsh was reconnected to the trace of its former channel in the West Pasture to increase hydrologic connectivity in this area. This channel actually appears to lie directly over the San Andreas Fault trace and may have originated or developed further after the 1906 earthquake. Additional material from the north levee removal was used to expand high tide refugia for special status bird species such as California black rail (State Threatened) and California clapper rail (Federally Endangered; see below). The remainder of the material was off-hauled to the quarries.
Enhancement of special status species habitat through retention or creation of topographically elevated berms as high tide refugia for state-listed threatened California black and endangered clapper rails and muted tidal impounded areas for federally listed endangered tidewater goby.
California black rails and California clapper rails are resident species in marshes, so, during extreme high tides and floods, these poorly flying species require high elevation upland areas as refuge. Because rails are vulnerable and exposed during this period, raptors and other predators often lurk nearby. Therefore, refuge areas need to be not only higher in elevation, but have good vegetation cover to screen rails from predators and distant from areas where predators are abundant such as residential or urban areas. Prior to removal of the levees, California black rails—California clapper rails are not commonly observed in this area—would use the levees as refuge during high water conditions. These areas were not always optimal refuge areas, because trampling from both cows and people had decreased vegetation cover needed for protection. With removal of most of the levees, alternative habitat needed to be created for the rails, so some portions of levees were retained and even enhanced through grading and revegetation.
The first habitat creation effort started in 2006 with a separate habitat enhancement project that created approximately 0.3–acre of rail refugia by widening the existing West Pasture levee at the very northern portion of the Giacomini Ranch. This feature was not fully constructed due to the fact that unseasonally wet weather made continuation of construction infeasible. Therefore, some of this project was actually completed in 2008.
Two high tide refugia areas have been created since 2006.
As part of Phase II, approximately 0.1 acre of high tide refugia was created north of the 2006 habitat enhancement area and 1.2 acres of refugia was created south of the 2006 habitat enhancement area. The northernmost refugia was built up to the elevation of the adjacent created High Tide Refugia (~10 to at most 11 feet NAVD88) and then gently tapered down at a 30:1 slope to meet and match elevations of the much lower alluvial or natural levee to the north that borders Lagunitas Creek. The 10-foot NAVD88 top elevation is maintained for at least 70 linear feet before the refugia begins to taper down the natural alluvial levee. The width of the 10-foot NAVD88 "top" is at least 35 feet.
The 1.2-acre southern refugia expansion area involved widening of the existing levee just south of the 2006 refugia area. The expansion of the Rail High Tide Refugia extends 440-feet southward, creating a refugia with a 65-foot top width at elevation 11-feet NAVD88.
The second refugia area occurs in the northern portion of the East Pasture just east of the new lower Tomasini Slough and west of Railroad Point. The Rail Refugia consists of a 0.71-acre, 570-foot-long berm with a crest elevation of 9-feet NAVD88.
All of these areas have been actively revegetated with native salt marsh and upland ecotone plant species at the appropriate elevations.
To the north and south, the berm tapers down to an elevation of 6 feet to allow for overtopping of this portion of the berm during extreme high tides and flood flows. This overtopping provides another source of water for the now diked portion of the East Pasture Old Slough Pond, the former terminus of the East Pasture Old Slough. During baseline surveys, the East Pasture Old Slough "Pond"—probably diked at some in the past to create habitat for duck hunting—was found to support relatively large numbers of the federally endangered tidewater goby. The tidewater goby is a small, brackish water resident estuarine species that tends to thrive in muted tidal or impounded conditions and off-channel habitats rather than in areas open to the full flood and ebb of the tide or that frequently scoured by flood flows. Brackish waters are those of intermediate salinity between freshwater (0 ppt) and marine salinity (34 ppt).
To ensure that habitat is maintained for gobies during restoration, several features have been specifically maintained as muted tidal, including the East Pasture Old Slough Pond.
In addition, the following measures have been taken:
The former Tomasini Creek channel—where goby were first documented—has been maintained as a backwater slough feature. That is, the Tomasini Creek tidegate and flashboard dam structure have been retained, but it has malfunctioned so that the channel receives the full flood of the high tides, but the flashboard dam structure prevents full drainage during low tides. Some flood flows will continue to overtop the created realignment berm/new creek bank into the Tomasini backwater slough. In addition, strong groundwater flow from the Point Reyes Mesa will maintain brackish water conditions in the channel during the summer even without Tomasini Creek freshwater inflow. (Tomasini Creek typically dries up in the late summer–early fall, so it has historically had little impact on maintaining brackish conditions in this creek.)
Small "weirs" or berms have been left in the mouth of created tidal creeks to ensure persistent ponding even during low tide.
The Park Service will continue to work on a captive propagation plan for captive breeding of goby for the purpose of releasing fish and creating new sub-populations or occurrences both within the Project Area and in the larger Tomales Bay watershed.
Final grading and restoring natural mesa topography at Dairy Mesa in Point Reyes Station.
The Dairy Facility or Dairy Mesa had been altered by years of ranch maintenance and construction of roads and manure ponds. The natural contours and topography of the Point Reyes Mesa bluff have been recreated at the Dairy Mesa by decreasing the steepness of the slopes outboard of the Dairy Mesa and eliminating the road from the Dairy Facility leading down into the pastures. The softness of the natural topography was enhanced through selective and fill and grading just outboard of the former manure ponds. Roughly 35,000–40,000 CY of material was estimated to be used in this component, and the material all came from on-site sources such as the levee removal, marshplain enhancement in the southwestern corner of the East Pasture, and other excavation activities. Once completed, the regraded area was stabilized using appropriate erosion control measures a weed-free straw and tackifier, coir logs or straw wattles, and revegetated with locally collected native plant species and seed characteristic of the Point Reyes Mesa bluff and other mesic scrub environments. In the future, this area will be used as a viewing area for the public.
Removal of remaining agricultural infrastructure and conditions such as drainage ditches, pumphouse, culverts, bridges, irrigation pipes, fencing, and equipment.
One of the largest agricultural condition removal efforts in 2008 was filling in of the 3.4-acre drainage ditch network in the East Pasture. More than 20,000 CY of soil is estimated to have been used to fill the ditch system to at or slightly above adjacent pasture grade elevations. The ditch system ended up taking an estimated 50 percent more soil than expected due to the extremely unconsolidated nature of the substrate materials, which actually ended up being pushed along in front of the fill materials in a mud "wave" that was scraped to the side, dried, and re-used for on-site fill. To enable the ditches to be filled, temporary earthen dams were placed at selected intervals in the ditch system starting in the southern portion of the East Pasture. Water was pumped from these "cells" into adjacent sections of ditch, and once water levels were low enough, fisheries personnel began clearance surveys to remove aquatic species and transfer them to non-construction areas. Several thousand fish species—including the federally endangered tidewater goby (Eucyclogobius newberryi) individuals—were recovered and relocated as part of this large-scale monitoring effort. Once ditch sections or "cells" were cleared, that section was completely filled.
The tidegates and culverts on the northernmost end of the East Pasture Old Slough adjacent to Lagunitas Creek were removed, as well as the tidegates and culverts on Fish Hatchery Creek in the West Pasture. Because of the importance of Tomasini Creek to tidewater goby, a brackish water fish species that favors muted tidal conditions, the tidegates and flashboard dam structure on the old Tomasini Creek channel (see realignment description above) were not removed to retain impounded subtidal or persistent open water habitat for the species. In addition to these structures, approximately 200 linear feet of culverts that channeled irrigation and surface runoff waters through the drainage ditches were also removed. Culverts were either reused in other locations, or the material was disposed of at a municipal landfill.
Other infrastructure such as concrete spillways, Tomasini Creek railroad car-type bridge, electrical lines, transmission poles, and a pumphouse were also dismantled, and the materials totaling approximately 340 CY were either recycled or disposed of at the appropriate facilities. In addition, approximately 0.75 acre of compacted ranch roads were shallowly graded and ripped to remove compaction, and excess soils were used to fill in road ditches or to restore natural topographic conditions at the Dairy Mesa.
As noted earlier, most of the public access components will be constructed at a later date when funding becomes available. The Park Service is currently in the process of trying to raise funds for public access and additional restoration components. In general, more monies are available for government agencies and non-governmental organizations for restoration than for public access. Despite this, some funding was available to construct some portions of the public access component in 2008.
Minor relocation of the Lagunitas Creek spur trail in the southern portion of the East Pasture slightly away from the creek bank to increase the buffer for the creek as mandated by many regulatory agencies and allow for reestablishment of healthy riparian habitat.
Prior to purchase of the Giacomini Ranch by the Park Service, an informal trail occurred on the outboard side of the southern East Pasture levees. This earthen, unimproved trail ranged anywhere from 25 to 45 feet from Lagunitas Creek. As part of general efforts to encourage development outside of riparian or potential riparian habitat areas, several county and state agencies, including the County of Marin, have established streamside conservation areas or buffer zones around creeks in which they try to discourage or prevent development. Buildings, trails, and other manmade features preclude establishment of riparian vegetation and introduce sources of disturbance to habitat areas that already exist alongside the creek. The Streamside Conservation Area in the Local Coastal Plan establishes a 100-foot buffer on either side of creeks in Marin County's Coastal Zone. In keeping with this policy, the Park Service elected to realign the 1,400 linear feet of the Lagunitas Creek spur trail to be approximately 100 feet away from the creek. It also has ripped the former trail alignment to remove compaction and replanted with native riparian plant species. Minimal cable and bollard fencing has been constructed along the trail's perimeter to reinforce that public access should be limited to established trails to continue to promote restoration of other areas in the Giacomini Ranch.
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