Merkel & Associates, Inc Ruffin Road, San Diego, CA Tel: 858/ Fax: 858/

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1 Merkel & Associates, Inc Ruffin Road, San Diego, CA Tel: 858/ Fax: 858/ February 23, 2009 M&A # Ms. Staci Merriman Metropolitan Wastewater Department 9192 Topaz Way San Diego, CA Dear Ms. Merriman, Re: Assessment Letter Report for the Chollas Parkway Mitigation Project Pursuant to your request, Merkel & Associates Inc. (M&A) assessed the potential for wetland and upland mitigation within Option A and B sites located along Chollas Creek in the City of San Diego, as identified by the Metropolitan Wastewater Department (MWWD) for the Canyon Sewer Cleaning Program and Long-Term Canyon Sewer Maintenance Program. Each of the Option sites were evaluated based on 5 site characteristics as identified by M&A: 1. Wetland Creation and Enhancement Potential - A sites potential for creating wetland habitat (also known as restoration) is based upon the potential for expanding an existing wetland into an adjacent disturbed upland habitat. Additionally, enhancement opportunities by replacing non-native wetland species with native wetland species or supplementing existing wetlands with additional native wetland plant species was also assessed. Site characteristics reviewed on site included assessment of wetland hydrology, soils, and existing hydrophytic vegetation. 2. Upland Creation and Enhancement Potential A sites potential for creating upland habitat (also known as restoration) is based on upon the potential for converting existing disturbed habitat into a native upland community. For example, isolated non-native grasslands can be converted to coastal sage scrub or native grassland habitat by removing non-native species from these areas and replacing them with native species. In many instances, native upland habitats can also be created on cut or fill slopes associated with wetland creation projects. Additionally, enhancement opportunities are evaluated based on the opportunity to enhance an already existing native upland community. 3. Grading Requirements - Costs of restoration projects are highly dependent upon the amount of grading required at a potential site. Visual assessments of probable cut required to achieve wetland hydrology were therefore estimated. 4. Existing Easement Restrictions Existing or presumed utility and property easements were assessed to determine if wetland creation would be precluded in these areas. 5. Native Habitat Restrictions - Creating one native habitat at the expense of another native habitat is typically not an accepted practice. Desirable wetland creation sites were selected based on the presence of a dominance of non-native vegetation in areas where suitable wetland habitat could be created.

2 6. Access to Irrigation - Wetland restoration using a temporary irrigation system has proven to be beneficial in expediting wetland creation goals. Access to a point of connection however, can be difficult in remote areas. Areas surveyed for this project occur within urban areas where water sources are likely available for irrigation purposes. EXISTING CONDITIONS Location The Chollas Parkway mitigation site is located within unsectioned lands, Township 16 South, Range 2 West of the San Bernardino Base and Meridian; U.S. Geological Survey 7.5 National City, California Quadrangle (Figure 1). Specifically, Option A and B sites are contiguous right-of-way of land that occur just east (Option A) and west (Option B) of 54 th Street in the community of Oak Park. Option A is partially owned by the City of San Diego s (City) Parks and Recreation Department (Parks) and a portion is owned by the City s Street Division (Streets), while all of the Option B site is owned by Parks Department. Biological Resources Storm water is conveyed from Option A to Option B through a box culvert that traverses beneath 54 th Street. As such, both Options A and B have similar existing conditions. Vegetation communities that occur within these areas are summarized in Table 1 and Figure 2 and discussed in detail below. While a jurisdictional wetland delineation was not performed along the Creek, the below table and attached figure provide presumed jurisdictions for wetland communities under Army Corps of Engineers (ACOE) and California Department of Fish and Game (CDFG) based on field observations. The City of San Diego also regulates jurisdictional wetlands and thus would be consistent with ACOE and CDFG regulated habitats. Overall, Options A and B are located within the upper most reach of Chollas Creek (i.e., first order stream), and convey urban runoff within a relatively narrow and moderate velocity drainage system with moderately steep slopes. An open concrete drainage channel collects urban water and conveys the flow into Option A. Riparian habitat along Chollas Creek mostly consists of hydrophytic, nonnative vegetation. Species directly associated with the drainage and/or drainage banks were mapped as either exotic riparian woodland or a native wetland community. Floral species outside of the drainage banks were generally associated with upland habitats. Typical species found within and on the banks of the streambed include invasive trees such as Brazilian pepper tree (Schinus teribinthifolius), Mexican fan palm (Washingtonia robusta), Canary Island date palm (Phoenix canariensis), Eucalyptus (Eucalyptus spp.), and shamel ash (Fraxinus uhdei). Patches of native habitat including southern willow scrub and coastal freshwater marsh are sporadic along the channel bottom and lower banks of the streambed. Willow scrub is mostly comprised of individual arroyo willow (Salix lasiolepis) and Goodding s black willow (Salix gooddingii) with understory shrubs of mule fat (Baccharis salicifolia) and blue elderberry (Sambucus mexicana). Wetland native and non-native forbs such as western ragweed (Ambrosia psilostachya) and common celery (Apium graveolens) are found beneath the shrub layer. Patches of freshwater marsh vegetation consisting of California bulrush (Schoenoplectus californicus) and southern cattail (Typha domingensis) are patchily distributed beneath the non-native vegetation and willow scrub canopy where silt has accumulated.

3 Chollas Parkway Mitigation Project Assessment Letter February 23, 2009 Diegan coastal sage scrub occurs on the relatively steep hillside to the south of the creek within Option A site. This north-facing slope is dominated by a heavy phase of sage scrub comprised mostly of lemonadeberry (Rhus integrifolia). Laurel sumac and blue elderberry occur in fewer numbers. Areas of this community that have a high inclusion of non-native grasses and forbs and generally disturbed in nature have been identified as a disturbed sage scrub community. Non-native grassland including wild oat (Avena barbata), purple false brome (Brachypodium distachyon), African fountain grass (Penesetum setaceum) and smilo grass (Piptatherum miliaceum) are the primary constituents that occur in areas mapped as non-native grassland adjacent to Chollas Creek. Non-native forbs such as white stem filaree (Erodium moschatum), smooth cat s-ears (Hypochaeris glabra), and wild radish (Raphanus sativus) also occur within the grasslands. Areas identified as disturbed habitat support the above species but to a much lesser degree and a greater inclusion of bare ground and compacted soils. Overall, Option A and B sites are expected to support a low diversity of fauna. Those present are expected to be common, urban tolerant species found throughout San Diego County, the majority of which are highly associated with Chollas Creek. While on site, species detection was limited. The western pygmy-blue (Brephidium exila), a commonly encountered butterfly in association with alkaline areas was the only butterfly observed flying along the non-native grassland within Option A. In addition, the Pacific treefrog (Pseudacris regilla) was the only amphibian detected (audio) within the Creek. Although no reptiles were observed on site, common species such as the western fence lizard (Sceloporus occidentalis) and southern alligator lizard (Elgaria multicarinata) are expected. Avian diversity is expected to be limited to species typical of those found throughout San Diego County, many of which are considered habitat generalists and year-around residents. Species observed within the Creek include the song sparrow (Melospiza melodia), western scrub-jay (Aphelocoma californica), and Nuttall s woodpecker (Picoides nuttallii). Additional species detected include Anna s hummingbird (Calypte anna) and western kingbird (Tyrannus verticalis). On-site nesting within the Creek by commonly encountered passerines such as the song sparrow are expected. The song sparrow is expected to build cup like nests in or under dense low vegetation such as that within portions of the exotic riparian woodland. While no raptor nests were observed on site, the barn owl (Tyto alba), San Diego County s most urban owl, is known to nest at the skirts of fan palms and the crevices among the leaf bases (Unitt 2004). Canary Island date palms, a species found on site, are specifically known to attract many barn owls. Merkel & Associates, Inc. #

4 Chollas Parkway Mitigation Project Assessment Letter February 23, 2009 Table 1. Summary of Habitats/Vegetation Communities within the Study Area 1 Vegetation Community MSCP Tier Habitat Type Holland/ Oberbauer Code ACOE/ CDFG Option A Site 2 (acreage) Option B Site (acreage) Parks Streets Parks CDFG ACOE/ CDFG ACOE/ CDFG Total Total Only CDFG Only CDFG Only Exotic Riparian Woodland Wetland NA Southern Willow Scrub Wetland sq. ft Disturbed Southern Willow Scrub Wetland Mule Fat Scrub Wetland Coastal and Valley Freshwater Marsh Wetland sq. ft Total Presumed Jurisdictional Habitat: Diegan Coastal Sage Scrub Tier II Disturbed Diegan Coastal Sage Scrub Tier II Non-native Grassland Tier III B Disturbed Habitat Tier IV Eucalyptus Woodland Tier IV Non-native Vegetation Tier IV Total Upland Habitat: Total Study Area: A jurisdictional wetland delineation was not performed along the Creek, the acreages are presumed jurisdictions for wetland communities under ACOE and CDFG based on field observations. The City of San Diego also regulates jurisdictional wetlands and thus would be consistent with ACOE and CDFG regulated habitats. 2 Option Site A is owned by the City of San Diego s Parks and Recreation Department (Parks) and a portion is owned by the City of San Diego s Street Division (Streets), while all of the Option B site is owned by Parks. Total Merkel & Associates, Inc. #

5 Chollas Parkway Mitigation Project Assessment Letter February 23, 2009 Special Status Species Palmer s sagewort (Artemisia palmeri), a California Native Plant Society (CNPS) List 4 was the only special status floral species found on site. CNPS List 4 species are plants of limited distribution (watch list) per CNPS. No additional floral species are known to occur on site or within the immediate vicinity. Palmer s sagewort was sporadically found on the southern slope of Option B site along the Creek. This species is most often detected along perennial watercourses and thus declining due to loss of wetland habitat. The potential for additional sensitive floral species to be on site is considered to be low due to the disturbed native of the Creek. Two special status faunal species were detected on site. These species are not mapped as the distribution patterns of more mobile animals are generally less well described by mapped observations. One Accipiter species was briefly observed flying over Option B north to the urban development. Based on the features, it is presumed that the species was a sharp-shinned hawk (Accipiter striatus), which is a CDFG species of special concern (for nesting sites only) and California Natural Diversity Database (CNDDB) special animal. The CNDDB identified special animals as a general term that refers to all of the taxa the CNDDB is interested in tracking, regardless of their legal or protection status. The sharp-shinned hawk is a winter resident to San Diego County and thus not expected to nest on site. The Nuttall s woodpecker, a CNDDB special animal (for nesting site only) was also commonly detected throughout the Creek. This species is a common resident of San Diego County and expected to nest on site. This species generally feeds on insects and arthropods and some fruit. Nesting generally occurs via excavation of cavities in dead branches or snags of various trees; primarily natives including Salix, Plantanus, and Quercus species. In addition, non-native flora unknown to support Nuttall s woodpecker nests include Ulmus and Eucalyptus species. The potential for additional sensitive faunal species to be on site is considered to be low due to the disturbed native of the Creek and lack of mature riparian woodland multi-canopy. MITIGATION OPPORTUNITY Option A Site Wetland Enhancement Approximately 0.99 and 1.29-acre of wetland enhancement opportunity occurs within the City Parks and Streets Division right-of-way, respectively. Wetland enhancement would include the replacement of exotic riparian woodland with native wetland species within and along the banks of Chollas Creek (Photo Point 1 and 2). Suitable conditions for successful wetland habitat enhancement are exemplified by the presence of hydrophytic vegetation (i.e., southern willow scrub and coastal freshwater marsh understory) currently existing within the channel. The existence of sporadic freshwater marsh indicates the presence of perennial surface water and the potential for expanding existing native wetland communities, once the competing exotic vegetation has been removed. Wetland Creation Steep slopes and native vegetation on the south side of Chollas Creek limit wetland creation to the north side of the Creek in the City Streets Division right-of-way. Creation would occur via conversion of non-native grassland and eucalyptus woodland adjacent to Chollas Parkway to native wetland habitat (Photo Point 3). This conversion would result in approximately 0.2-acre of wetland Merkel & Associates, Inc. #

6 Chollas Parkway Mitigation Project Assessment Letter February 23, 2009 creation potential within the City Streets Division right-of-way. This would require approximately 10 feet of cut to create floodable conditions. The net acreage of created wetlands is based on a 10- foot offset from Chollas Parkway and a 2:1 slope leading down to the proposed wetlands. This large cut limits the available net acreage of created wetlands given the amount of slope that would be required to meet daylight. Approximately 3,800 cubic yards of cut would be removed and disposed of off-site at an approved location. If wetland creation is not feasible, upland creation of sage scrub and/or native grassland could be achieved (refer to the below discussion). Coastal Sage Scrub Enhancement Disturbed coastal sage scrub is limited to the south side of the Creek within the City Parks right-ofway with a minor amount located within the City Streets right-of-way. Here, non-native species could be removed and replaced native sage scrub associates. Approximately 0.43 and 0.02 acres of native upland habitat could be enhanced within the City Parks and Streets right-of-way, respectively. Coastal Sage Scrub Creation Creation of native upland habitats would involve the conversion of non-native grassland and nonnative vegetation to coastal sage scrub (with inclusions of native grassland). The primary location for upland creation is limited to the south side of the Creek. Here, approximately 0.51 and 0.48 acres of habitat could be utilized for creation of Diegan coastal sage scrub within the City Parks and Streets right-of-way, respectively. As mentioned above, if wetland creation is not feasible within the non-native habitat on the north side of the Creek within the City Streets right-of-way, the land could be converted to native upland habitat; this would result in an additional (approximate) 0.78 acres of additional native upland habitat. Option B Site Wetland Enhancement Approximately 1.41-acre of wetland enhancement opportunity occurs within Option B site. As with Option A, wetland enhancement would include the replacement of exotic riparian woodland with native wetland species within and along the banks of Chollas Creek (Photo Point 4). In addition, the disturbed native southern willow scrub and coastal and valley freshwater marsh could be enhanced via removal of invasive species, which would allow for greater native recruitment. Similar hydrologic conditions found upstream within Site A are found at Site B and are expected to accommodate the expansion of wetland vegetation types such as southern willow scrub and coastal and valley freshwater marsh. A linear band of non-native vegetation exists on the south side of the Creek and totals approximately 0.67 acres (Photo Point 5). Although this north-facing slope is relatively steep, there is a minor terrace that supports a mix of hydrophytic and non-hydrophytic vegetation. However, since the terrace is outside of the ordinary high water mark (of the Creek) and devoid of drainage patterns, the habitat has been identified as non-native vegetation rather than exotic riparian woodland. Nonetheless, it is possible for the non-native vegetation on the lower portion of this slope to be converted to wetland habitat (CDFG only). This would require minor contouring of the slope as well as a formal wetland delineation to accurately identify jurisdictional boundaries. Merkel & Associates, Inc. #

7 Chollas Parkway Mitigation Project Assessment Letter February 23, 2009 Wetland Creation Approximately 0.4 acre of wetland creation potential occurs within Option B site. All areas are limited to non-native grassland habitat located to the north of the creek (Photo Point 6). In order to create floodable conditions, approximately 5 feet (on average) and 15 feet (on average) of cut would be required at the western and eastern portions of the property, respectively. This is based on a 2:1 slope leading from the edge of the northern boundary down to the edge of the proposed wetlands. Approximately 2,400 yards of cut (west end of the site) and 13,300 yards of cut (east end of the site) would be removed and disposed of off-site at an approved location. If wetland creation were not feasible, these areas could be converted into native upland habitat (refer to the below discussion). Coastal Sage Scrub Creation Approximately 0.95 acres of creation area for Diegan coastal sage scrub occurs within Option B site. Creation would involve conversion of non-native grassland on the north side of the creek and nonnative vegetation on the upper slopes of the south side of the creek (Photo Point 7). If wetland creation occurs on the north side of the Creek (rather then creation of native upland habitat), then coastal sage scrub creation would be limited to approximately 0.15 acres. CONCLUSION Overall, the Chollas Parkway Mitigation Project primarily supports wetland enhancement opportunities via removal of exotic riparian woodland and replacement with native species. Minimal wetland creation opportunity also exists; however, this would require a relatively high cut and soil removal component to achieve floodable conditions. Specifically, the Streets Division right-of-way of Option A supports wetland creation opportunity at a relatively high cut and soil removal requirement. If wetland creation were not feasible, the area could serve as a creation site for Diegan coastal sage scrub with inclusion of native grassland habitat. Wetland creation is extremely limited within the Parks Department right-of-way within Option A due to steep slopes and existing native vegetation. Option B site also supports wetland creation opportunity; however, as with Option A, a large amount of cut and removal of soil would be required to achieve floodable conditions. If wetland creation were not feasible, the area could serve as a creation site for Diegan coastal sage scrub with inclusion of native grassland habitat. Table 2 provides a summary of potential mitigation opportunities within Option A and B site and addresses the maximum wetland creation potential. As described above, if wetland creation were not feasible, the non-native upland area could be converted to native upland habitat. Merkel & Associates, Inc. #

8 Chollas Parkway Mitigation Project Assessment Letter February 23, 2009 Table 2. Summary of Potential Mitigation Opportunity within the Study Area Existing Habitat (acreage) Vegetation Community 1 2 MSCP Tier Habitat Type Potential Mitigation Opportunity (acreage) Option A 1 Option B Option A Site Option B Site Parks Streets Parks Parks Streets Parks Total Total Total Enhancement Creation Enhancement Creation Enhancement Creation 2 Total Wetland Habitat: Total Upland Habitat: ; 0.40 Total Study Area: Option Site A is owned by the City of San Diego s Parks and Recreation Department (Parks) and a portion is owned by the City of San Diego s Street Division (Streets), while all of the Option B site is owned by Parks. Approximately 0.67 acres of non-native vegetation are located on a terrace associated with the south slope of the Creek. It is possible for the lower portion of the terrace (aprox acres) to be converted into wetland habitat (CDFG only) while the upper portion of the terrace could be converted into native sage scrub habitat (aprox acres). All remaining non-native upland habitat (0.40) would be converted into native upland. Merkel & Associates, Inc. #

9 Chollas Parkway Mitigation Project Assessment Letter February 23, 2009 If you have any questions regarding this assessment letter please do not hesitate to call me at (858) Sincerely, Amanda K. Gonzales Senior Biologist/Project Manager Adam H. Behle Senior Biologist/Program Manager Attachments: Figure 1. Project Vicinity Map Figure 2. Existing Biological Resources Map Photo Page #s 1-4 Merkel & Associates, Inc. #

10 M&A # Project Site µ1:24000 Project Vicinity Map Chollas Parkway Mitigation Project Figure 1 Source: USGS 7.5' National City, CA Quadrangle Merkel & Associates, Inc.

11 M&A # Vegetation Communities exotic riparian woodland southern willow scrub disturbed southern willow scrub mule fat scrub coastal and valley freshwater marsh Option A - City of SD Streets Division Diegan coastal sage scrub disturbed Diegan coastal sage scrub non-native grassland disturbed habitat eucalyptus woodland non-native vegetation Jurisdictions - Informal Assessment ACOE, CDFG CH CDFG Only Sensitive Resources (label = count) Palmer's sagewort (Artemisia palmeri) S Option A - City of SD Parks and Rec Y 54TH ST Other LA OL W PK assessment areas Option B - City of SD Parks and Rec µ 0 Biological Resources - Existing Conditions Chollas Parkway Mitigation Project Feet Figure 2 Merkel & Associates, Inc.

12 Chollas Parkway Mitigation Project Assessment Letter Photo Point 1. General overview of Option A. Wetland enhancement opportunity occurs within Chollas Creek via removal of exotic riparian woodland and replacement with native riparian flora. Line within the photo represents general location of the Creek bed. Photo directed northwest and taken on 02/10/09. Photo Point 2. Internal view of Chollas Creek along Option A. Photo direct downstream (west) and taken on 02/10/09. Merkel & Associates, Inc. # Photo Page 1

13 Chollas Parkway Mitigation Project Assessment Letter Creek Wetland Creation Opportunity Photo Point 3. View of wetland creation opportunity within Option A. Cut and removal of soil would be required to achieve floodable conditions. If wetland creation not feasible, upland creation of sage scrub with native grassland components would be another option. Photo directed west and taken on 02/10/09. Wetland Enhancement Photo Point 4. View of wetland enhancement opportunity within Option B. Enhancement would require the removal of existing exotic riparian woodland from Chollas Creek and replacement with native riparian flora. Photo directed west and taken on 02/10/09. Merkel & Associates, Inc. # Photo Page 2

14 Chollas Parkway Mitigation Project Assessment Letter Upland Creation Opportunity Creek bed Terrace adjacent to Creek Photo Point 5. View of terrace located along Chollas Creek within Option B. This terrace is located on the southern side of the Creek and generally supports non-native vegetation. The non-native vegetation could be converted to wetland habitat and/or serve as an upland buffer to the Creek. Photo directed west and taken on 02/10/09. Wetland Creation Opportunity Creek Photo Point 6. View of wetland creation opportunity within the southern portion of Option B. Cut and removal of soil would be required to achieve floodable conditions. If wetland creation not feasible, upland creation of sage scrub with native grassland components would be another option. Photo directed northeast and taken on 02/10/09. Merkel & Associates, Inc. # Photo Page 3

15 Chollas Parkway Mitigation Project Assessment Letter Creek Creek Upland Creation Opportunity Photo Point 7. View of upland creation opportunity on the north side of the Creek within Option B (upstream portion of the creek). Photo direct westward and taken on 02/10/09. Merkel & Associates, Inc. # Photo Page 4