SAN LORENZO VALLEY WATER DISTRICT CAMPUS CENTER PROJECT WETLAND MITIGATION AND MONITORING PLAN. San Lorenzo Valley Water District

Transcription

1 SAN LORENZO VALLEY WATER DISTRICT CAMPUS CENTER PROJECT WETLAND MITIGATION AND MONITORING PLAN Prepared For: San Lorenzo Valley Water District Prepared By: Denise Duffy & Associates, Inc. 947 Cass St. Suite 5 Monterey, California Contact: Matt Johnson Phone: October, 2010

2 San Lorenzo Valley Water District Campus Center Project Wetland Mitigation and Monitoring Plan Contents 1.0 INTRODUCTION Summary Mitigation Site Description... 8 Vegetation... 8 Soils... 8 Hydrology MITIGATION APPROACH AND RATIOS Wetland Mitigation MITIGATION GOALS, OBJECTIVES, AND SUCCESS CRITERIA RATIONAL FOR EXPECTING IMPLEMENTATION SUCCESS ENGINEERING COMPONENTS MAINTENANCE Weed Control IMPLEMENTATION SCHEDULE MONITORING PROTOCOLS Monitor Reporting Protocols CONTINGENCY AND ADAPTIVE MANAGEMENT MEASURES FUNDING REFERENCES Page 2 of 23

3 San Lorenzo Valley Water District Campus Center Project Wetland Mitigation and Monitoring Plan List of Figures Figure 1 Project Location Map... 5 Figure 2 Assessor Parcel Map... 6 Figure 3 Mitigation Area Location Map... 7 Figure 4 Olympia Mitigation Site and Hydrologic Connection... 9 Figure 5 Site Photos Figure 6 Site Photos Appendices Appendix A San Lorenzo Valley Water District Operations Facilities Project Delineation of Jurisdictional Wetlands and Waters Under Section 404 of the Clean Water Act Appendix B San Lorenzo Valley Water District Operations Facilities Project Olympia Mitigation Site Wetland Assessment Appendix C Geotechnical Feasibility Investigation for Proposed Olympia Wetland East Zayante Road Santa Cruz, California APN Appendix D Storm Water Runoff Evaluation for Wetlands Mitigation Assessment Appendix E Sandhills Habitat Assessment and Endangered Species Surveys for the San Lorenzo Valley Water District s Olympia Wellfield Potential Wetlands Mitigation Site Felton, CA (Apn: ) Appendix F Planting Pallet and Map Page 3 of 23

4 San Lorenzo Valley Water District Campus Center Project Wetland Mitigation and Monitoring Plan 1.0 INTRODUCTION 1.1 Summary The purpose of the preparation of this Wetland Mitigation and Monitoring Plan (plan) is to provide sufficient content and information to facilitate agency review and approval for the implementation of mitigation measures necessary to mitigate impacts to wetland resources as a result of the San Lorenzo Valley Water District Campus Center (Project). This plan provides for mitigation of permanent impacts to the following wetland resources: 0.36 Acre of Wetland Habitat (seasonal wet meadow) This plan includes: success criteria, monitoring protocols to determine if the success criteria have been met, adaptive management protocols in the case that the success criteria are not met, and funding assurances. The Project is located on an approximately 1.7 acre site on the east side of Highway 9 between Mountain Street and Flat Street, in the community of Boulder Creek in north Santa Cruz County (Figure 1). The site lies on five parcels identified as APNs , -03, -04, -06, and -07 (Figure 2). The project site and adjacent areas were evaluated for the presence of jurisdictional wetlands (Wetland Delineation, Appendix A). Wetlands were observed and documented within the limits of the project site through the Corps process of wetland delineation as described in The Field Guide for Wetland Delineation: 1987 Corps of Engineers Manual (Wetland Training Institute, 2002) and Interim Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Western Mountains, Valleys, and Coast Region (U.S. Army Corps of Engineers, 2006). A number of natural springs occur on the project site resulting in ground saturation and some inundation with shallow water in flat areas during the wet season and into late spring in most years. A number of linear ditches have been excavated over time by previous occupants to drain water from the site. These ditches connect to additional off-site drainage and road-side ditches, which ultimately enter the San Lorenzo River. Four wetland polygons were mapped on the project site, ranging in size from 0.01 acre to 0.26 acre (Appendix A). The total wetland area on the project site is determined to be approximately 0.36 acre (Appendix A). Construction of the Project will result in permanent impacts to the approximately 0.36 acre of wetland habitat within the Project boundaries and does not allow for on-site mitigation of any permanent impacts. To mitigate for permanent impacts to this wetland habitat the San Lorenzo Valley Water District (District) is proposing wetland creation southeast of the Project site (Figure 3). This site will be referred to as the Olympia mitigation site for the remainder of this document (Wetland Assessment, Appendix B). The Olympia mitigation site is located within a historic sand wash basin which has a hydrologic connection to the Zayante Creek, a tributary of the San Lorenzo River, through Box Gulch. Page 4 of 23

5 9 Mountain Street Project Boundaries Flat Street Boulder Creek Ben Lomond 9 Felton 17 Scotts Valley 1 Santa Cruz 1 Soquel Km Mi Monterey bay Feet Meters N Figure Project Location Map 1 DENISE DUFFY & ASSOCIATES, INC.

6 M o u n t a i n S t r e e t N S t a t e H i g h w a y F l a t S t r e e t E a s t S t r e e t Project Parcels Feet Figure Assessor s Parcel Map 2 DENISE DUFFY & ASSOCIATES, INC.

7 West Zayante Road East Zayante Road Zayante Fire Station Basin Proposed Mitigation Area Boulder Creek Ben Lomond 9 Felton 17 Scotts Valley 1 Santa Cruz 1 Soquel Km Mi Monterey bay Feet Meters Figure N Mitigation Area Location Map 3 DENISE DUFFY & ASSOCIATES, INC.

8 San Lorenzo Valley Water District Campus Center Project Wetland Mitigation and Monitoring Plan 1.2 Mitigation Site Description One mitigation site has been identified that is appropriate for off-site mitigation for impacts as a result of the Project (Figure 4). The wetland mitigation site is located southeast of the project site in a historic sand wash basin near the Zayante Fire Station in Felton, CA. This site was chosen because it was the closest location to the project site that the District owns that is not currently wetland, but has the constituent elements necessary to successfully create jurisdictional wetlands. Specifically, with modification of an existing stand pipe the mitigation site has the potential to pond water sufficient to create wetland hydrology. The mitigation site has a hydrologic connection through a large standpipe to Box Gulch, which then connects, through 2 more culverts, to Zayante Creek which is a tributary of the San Lorenzo River (Figure 4). The San Lorenzo River is a Navigable Water. As a result, it is expected that a sustainable jurisdictional wetland can be created on the Olympia mitigation site that would require no ongoing manipulation. Vegetation The proposed mitigation area is mostly open upland and consists of grass and forb species with scattered shrubs. Dominant species are a mix of upland and facultative species including French broom, tarweed (Madia sp., NL), velvet grass (Holcus lanatus, FAC), and coyote bush (Baccharis pilularis, NL).Other non-dominant species observed within the Olympia mitigation site include Italian thistle (Carduus pycnocephalus, NL), leafy bent-grass (Agrostis pallens, UPL), hairy cat s ear (Hypochaeris radicata, NL), tall cyperus (Cyperus eragrostis, FACW), and sedge (Carex sp., FAC). The vegetation of the basin surrounding the Olympia mitigation area forms a closed canopy. Dominant vegetation includes riparian species such as black cottonwood (Populus balsamifera, FACW), willow (Salix sp., FACW), California blackberry (Rubus ursinus, FAC), velvet grass, and sedge. Soils The SSURGO Database (USDA-NRCS, 2003) identifies one map unit within the Olympia mitigation site, Zayante Coarse Sand 30-50% Slopes. The soil description for this mapping unit is presented below; however, due to the historic use and manipulation of the mitigation site for the purpose of sand mining and washing, the soils are not consistent with the description. As a result, the rare plant associations and unique habitat often found on Zayante soils are not present within or directly adjacent to the mitigation site. Zayante Coarse Sand is somewhat excessively drained soil unit that is found on mountains. The parent material is consolidated marine deposits and/or residuum weathered from sandstone. Zayante sands are composed of approximately 92% sand with the remaining percentage composed of a mixture of silt and clay. In a representative profile of this soil, the surface layer is approximately 10 inches of dark gray to very dark brown, strongly acidic, loose, coarse sand. Below that is approximately ten inches of dark to very dark grayish brown, moderately acidic, soft, very friable, coarse sand. This soil unit is not classified as a hydric soil (USDA-NRCS, 2007). Within the Olympia mitigation site soils consisted of the native Zayante sand with clay and silt fines that were likely deposited as a result of the historical use of the site as a detention basin. Three horizons were Page 8 of 23

9 DENISE DUFFY & ASSOCIATES, INC. Zayante Creek Meters Feet Map Detail Miles Box Gulch Culverts Hydrologic Connection to Zayante Creek Proposed Mitigation Area N Olympia Mitigation Site and Hydrologic Connection 4 Figure

10 San Lorenzo Valley Water District Campus Center Project Wetland Mitigation and Monitoring Plan present at Sampling Point 1, consisting of a thin (approximately three inch) silt layer (10YR 4/3) underlain by two layers of fine sand, the upper with large inclusions of clay ((10YR 4/4) and the lower with only a few small inclusions of clay (2.5 Y 4/4) (Appendix B, Figure 2). The soil at Sampling Point 2 consisted of only two horizons (Appendix B, Figure 2). The upper horizon (approximately eight inches thick) consisted of sandy silt (10YR 3/2), while the underlying horizon was fine sand (2.5Y 5/3) with some small silt layers, but lacking any clay. No indicators were identified for hydric soils. Additionally, the SLVWD conducted a geotechnical feasibility report to explore the soil profile throughout the Olympia mitigation site (Appendix C). The soil profile indicated roughly 7.5 to 10 feet of quarry wash deposit consisting predominantly of clay with interbedded lenses of sand. The borings indicated that the sand lenses were localized and discontinuous within the Olympia mitigation site. The geotechnical feasibility report also included a double-ring infiltrometer test which resulted in a vertical infiltration rate of 0.40 in/hr. This rate is typical of soil with a significant clay content. Hydrology The mitigation site is located in the San Lorenzo watershed. A large standpipe drain is located within the mitigation area, which indicates that water likely pools within the mitigation area during periods of high rainfall; however, the height of the outlet likely prevents long-term ponding (Figure 5, Photo 1). No hydrologic indicators were identified. All soils smelled earthy and all root pores were black or brown, lacking any signs of oxidized rhizospheres. Bed and bank features connected with road runoff from disturbed trails were observed upstream from the mitigation area, indicating the mitigation area is influenced by more rainfall than what is found within the immediate basin area (Figure 5, Photo 2). Water that collects at the standpipe is then transferred through the dam structure within a culvert to Box Gulch (Figure 5, Photo 3). Box Gulch crosses the railroad tracks (Figure 5, Photo 4) and East Zayante Road (Figure 6, Photo 5) through two more culverts before connecting with Zayante Creek (Figure 6, Photo 6). Zayante Creek is a tributary of the San Lorenzo River, Navigable Water. 2.0 MITIGATION APPROACH AND RATIOS DD&A considered the type, acreage, and quality of the impacted wetland habitat in an effort to determine the appropriate habitat type and acreage that would be required to mitigate for project impacts and satisfy regulatory agency permitting standards. The impact to mitigation ratios specified below are expected to ensure no net loss of acreage or quality of habitats lost due to permanent impacts. The ratios reflect the availability of practical mitigation sites, feasibility of creating mitigation habitat within the watershed, and the quality of the impacted habitat. 2.1 Wetland Mitigation The project is scheduled to remove approximately 0.36 acre of wetland habitat. Wetlands permanently impacted as a result of the project shall be mitigated by creating wetlands at the location shown in Figure 4 at a 1:1 ratio. After evaluating the wetland habitat impacted by the Project this ratio was determined to be appropriate to mitigate for the permanent impacts. Although the wetland mitigation is not occurring on-site, which is preferred to off-site mitigation by typical regulatory agency practices, the quality of the impacted wetlands, which have been historically disturbed and degraded, resulted in a lower mitigation ratio. The wetland shall be created by grading a depression in the lowest portion of the basin adjacent to the Page 10 of 23

11 Photo 1. Standpipe located at the bottom of basin at the Olympia mitigation site. Photo 2. Evidence of bed and bank features upstream from Olympia mitigation site. Photo 3. Culvert connection from Olympia mitigation site to Box Gulch Photo 4. View from culvert under railroad tracks on Box Gulch. N Olympia Mitigation Site Photos Figure 5 DENISE DUFFY & ASSOCIATES, INC.

12 Photo 5. Culvert on Box Gulch under East Zayante Road. Photo 6. Box Gulch connection to Zayante Creek. N Olympia Mitigation Site Photos Figure 6 DENISE DUFFY & ASSOCIATES, INC.

13 San Lorenzo Valley Water District Campus Center Project Wetland Mitigation and Monitoring Plan existing standpipe. The depth and extent of the depression will be determined based on watershed hydrologic modeling and geotechnical evaluation to reflect the necessary depth and duration of inundation to support wetland conditions. The constructed wetlands shall be planted with sedge, rush, and wetland grass species contract grown in a local greenhouse from local seed stock. 3.0 MITIGATION GOALS, OBJECTIVES, AND SUCCESS CRITERIA Data shall be collected and reported as described in Section 8.0. The results of the monitoring data shall be used to evaluate project conditions in regard to the specific success criteria outlined in this section. The success criteria have been chosen to directly reflect the mitigation goals and objectives as described in Section 2.0. The goals and objectives of this plan are as follows: Goal 1: Mitigate for the permanent loss of 0.36 acre of wetland habitat at a 1:1 ratio. Objective 1: Construct and install 0.36 acre of wetland located at the Olympia mitigation site. Success Criteria 1: Confirm, via monitoring, that construction and installation are conducted according to the final plans and Special Provisions prepared for the mitigation. Objective 2: Document 0.36 acre of self sustaining, persistent wetland habitat. Success Criteria 2: Wetland conditions must satisfy the criteria provided in the 1987 Army Corps of Engineers Wetland Delineation Manual for wetland hydrology and vegetation within 0.36 acre of the mitigation area by the end of the five year monitoring period. Success Criteria 3: The wetland mitigation area must be dominated (greater than 50%) by native, locally-occurring plant species by the end of the five year monitoring period. Success Criteria 4: The wetland mitigation area cannot have greater than 10% cover of any plant listed in the California Plant Pest Council s 2006 Inventory or the most recent update to that inventory at the end of the five year monitoring period. Success Criteria 5: The overall percent aerial coverage of vegetation is greater than 20% in year one, 50% in years two through four, and greater than 70% at year five. 4.0 RATIONAL FOR EXPECTING IMPLEMENTATION SUCCESS Existing conditions of the Olympia mitigation site will allow the creation of jurisdictional wetlands with slight modifications in elevation, vegetation suite and hydrologic infrastructure to create at least 0.36 acre of sustainable wetland conditions. Weber, Hayes and Associates completed a storm water runoff evaluation for the Olympia mitigation site to determine the size of the watershed contributing runoff to the mitigation site and the estimated amount of runoff in an average rain year (Appendix D). According to the storm water runoff evaluation the mean Page 13 of 23

14 San Lorenzo Valley Water District Campus Center Project Wetland Mitigation and Monitoring Plan annual rainfall and mean runoff totals for the area (40 inches and 13 inches, respectively), are sufficient to create localized inundation and sustain wetland hydrology if the water is detained (J. Hayes, pers. comm. 2010). The existing standpipe at the Olympia mitigation site empties the basin at ground level. This outlet does not allow for inundation of the Olympia mitigation site. As part of the engineering component of this mitigation plan the outlet of the existing standpipe will be raised to allow for sufficient inundation for duration necessary to create 0.36 acre of wetland habitat. As mentioned above the vegetation surrounding the Olympia mitigation site within the basin has been identified as riparian. To create 0.36 acre of wetland habitat inundation will have to occur within some fringe riparian vegetation. Wetlands and riparian habitat often exist within the same area. The inundation and creation of this wetland habitat is not considered an impact to the existing riparian habitat. 5.0 ENGINEERING COMPONENTS Following approval of this conceptual wetland mitigation plan a final plan sufficient to bid and contract the wetland creation will be prepared for the San Lorenzo Valley Water District. Mitigation components such as the Planting Plan, irrigation, and maintenance protocols will be incorporated. Additionally, the mitigation site will require grading to create an area that will inundate for a sufficient duration for wetland conditions. The grading includes leveling the existing topography to create a consistent elevation over the entire mitigation area. Conditions in the field will ultimately determine the amount of grading necessary. The final plan will include Special Provisions; including equipment access and location of staging areas, to ensure that the sand hills habitat and any special-status species associated with this habitat type will not be impacted as a result of the wetland mitigation installation. A biological assessment of the proposed project has been included with this document to assess the potential impacts and includes measures necessary to eliminate any expected impacts (Appendix E). The final plan will incorporate all of these measures except wetland manipulation to ensure that standing water does not exist after Mount Hermon June beetle flying season (May). USFWS does not believe that this impact will have an adverse effect on the Mount Hermon June beetle population (D. Cooper, pers. comm. 2010). The Planting Plan included as an appendix to this document (Appendix F) is a graphical depiction of the species, size and location of each plant to be installed. The Planting Plan indicates Special Provisions for planting, including soil amendments, exclusionary fencing and caging, staking, fertilizer, maintenance, plant material collection, planting protocol, and weeding schedule. A planting pallet outlining these species and their general placement in relation to the existing outfall location has been included with this document (Appendix F). The species chosen and the distribution and placement of the individual plants planned for installation was a result of a site-specific analysis which included horticultural and research based information for the specific species, as well as, industry standards in regard to installation and maintenance specifications. All of the species included in the planting pallet were identified in the immediate vicinity of the wetland mitigation site during a site visit on October 22, MAINTENANCE Maintenance of the mitigation areas shall take two forms: first, annual maintenance outlined as a Page 14 of 23

15 San Lorenzo Valley Water District Campus Center Project Wetland Mitigation and Monitoring Plan component of the mitigation implementation in this section which includes annual invasive plant removal (weeding); second, weeding and/or replanting that may be applied as indicated by the monitoring and adaptive management protocols detailed in Section 8.0 and Weed Control French broom and other invasive weed species shall be removed from all mitigation areas annually for five years. Control of invasive weeds shall be achieved by hand clearing between individual installed plantings during a dry period between April 15 and May IMPLEMENTATION SCHEDULE Replanting shall be initiated for all wetland mitigation areas in the early part of the wet season, between November 1 and December MONITORING PROTOCOLS A qualified biologist/restoration practitioner shall be contracted prior to the installation of the mitigation and designated as the project monitor 1. The monitor will work with the restoration contractor prior to and during mitigation implementation, perform the required inspections, and prepare the monitoring reports as detailed in this section. Any changes in the mitigation plans or specification will have to be approved by the monitor and the project proponent (District). All mitigation areas shall be monitored subsequent to the installation (within 30 days), and then annually in the month of June for the next five years. A monitoring report shall be submitted to the project proponent subsequent to each monitoring visit (within 30 days). The total duration of monitoring shall be a minimum of five years from initial mitigation implementation monitoring and may be extended if the success criteria detailed in Section 3.0 are not met. The total aerial vegetative coverage, percent native cover, and percent non-native cover of all wetland mitigation areas shall be visually estimated and recorded by the project monitor. 8.1 Monitor Reporting Protocols After each inspection, a report shall be submitted to the project proponent for their approval. The reports shall be based on field observations and measurements as described in this section. The monitoring reports shall include, but not be limited to, the following information: Dates and descriptions of all maintenance activities conducted during the reporting period and the entire monitoring period, including but not limited to weed control, and other activities; Photographic documentation; Description of the general health and vigor of the plants; Description of any pests or circumstances substantially affecting the plants; Description of any changes in the physical environment of the plants since the end of the previous reporting period and since the beginning of the monitoring period; 1 The monitor must poses an education in biology or another related field and demonstrate experience with the management of restoration projects of a similar nature within the region. Page 15 of 23

16 San Lorenzo Valley Water District Campus Center Project Wetland Mitigation and Monitoring Plan The number and species of plants that are unhealthy or have died during the reporting period and since the beginning of the monitoring period; The results of the data collection as described above; and Recommendations for further maintenance and management that may be necessary for maintaining the success criteria in this plan. Recommendations made in each monitoring report shall be carried out in a timely manner after approval. Follow-up of this maintenance and management shall be documented by the biological monitor in followup reports and shall be submitted within 30 days of the end of such follow-up maintenance and management activities. Annual reports shall include a cumulative analysis; summary of the data collected throughout the previous year, and shall identify any adaptive management measures necessary for the success of the mitigation effort. A final report shall be submitted at the end of the monitoring period and shall include a cumulative analysis, summary of the data collected throughout the duration of the monitoring period and a definitive statement as to the success of the mitigation based on the success criteria provided in Section 3.0 of this document. If it is determined that the mitigation has not been successful, a supplemental report shall be prepared that identifies the causes of failure and suggests measures that shall achieve success and the monitoring period shall be extended one year. At the end of this extended period, an additional report shall be prepared as described above. This report shall satisfy the same criteria as outlined above for the final report. If at the end of the extended monitoring period, the report indicates the success criteria have not been met, the monitoring shall be extended again and the process repeated until success is achieved. 9.0 CONTINGENCY AND ADAPTIVE MANAGEMENT MEASURES If annual success criteria are not met, an analysis of the cause(s) of failure shall be prepared and, if determined necessary, remedial action shall be proposed for approval. The District shall be responsible for reasonable funding of the contingency procedures necessary for successful completion of the mitigation effort. Contingency measures might include replanting, regrading, the additional soil amendments, and/or rodent and herbivore control. In addition, an adaptive management approach shall be employed which consists of evaluating the monitoring data and modifying the project approach or mitigation Special Provisions as necessary in order to increase the potential to achieve the stated success criteria. This might include, but would not be limited to, planting species not on the final planting pallet, and/or increasing the size or depth of the wetland features FUNDING The off-site mitigation area located at the Olympia mitigation site is currently under the ownership of the District. The District will provide the funding to construct, monitor and maintain the created wetland until all success criteria have been met or it is determined otherwise by the Corps. Page 16 of 23

17 San Lorenzo Valley Water District Campus Center Project Wetland Mitigation and Monitoring Plan REFERENCES Cooper, D Personal Communication with Douglas Cooper, Senior Biologist, US Fish & Wildlife Service - Ventura Fish & Wildlife Office, regarding possible impacts to Mount Hermon June beetles due to standing water. February 8, 2010 Hayes, J Personal communication with Joe Hayes, Senior Hyrdogeologist, Weber, Hayes and Associates, regarding annual runoff at Olympia mitigation site. March 5, U.S. Army Corps of Engineers Interim Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Arid West Region. Ed. J.S. Wakeley, R.W. Lichvar, and C.V. Noble. ERDC/EL TR Vicksburg, MS: U.S. Army Engineer Research and Development Center. 109 pp. U.S. Department of Agriculture (USDA) Natural Resources Conservation Service (NRCS) Hydric Soils of the United States, February Available online at: USDA-NRCS, United States Department of Agriculture Soil Survey Geographic (SSURGO) Database. Wetland Training Institute, Inc Field Guide for Wetland Delineation: 1987 Corps of Engineers Manual. Glenwood, NM. WTI pp. Page 17 of 23

18 Appendix A San Lorenzo Valley Water District Operations Facilities Project Delineation of Jurisdictional Wetlands and Waters Under Section 404 of the Clean Water Act

19 Appendix B San Lorenzo Valley Water District Operations Facilities Project Olympia Mitigation Site Wetland Assessment

20 Appendix C Geotechnical Feasibility Investigation for Proposed Olympia Wetland East Zayante Road Santa Cruz, California APN

21 Appendix D Storm Water Runoff Evaluation for Wetlands Mitigation Assessment

22 Appendix E Sandhills Habitat Assessment and Endangered Species Surveys for the San Lorenzo Valley Water District s Olympia Wellfield Potential Wetlands Mitigation Site Felton, CA (Apn: )

23 Appendix F Planting Pallet and Map