CARMEL RIVER LAGOON ECOSYSTEM PROTECTIVE BARRIER (EPB) AND SCENIC ROAD PROTECTION STRUCTURE (SRPS) PROJECTS

FEASIBILITY REPORT

May 29, 2013

Prepared for:

Monterey County Water Resources Agency 893 Blanco Circle Salinas, CA 93901-4455

Monterey County Department of Public Works 168 W. Alisal St., 2nd Floor Salinas, CA 93901

Prepared by:

Whitson Engineers WE # 2487.01 & 2487.02 9699 Blue Larkspur Lane, Suite 105 Monterey, CA 93940

Carmel River Lagoon EPB and SRPS Projects Feasibility Study May 29, 2013 Page 2 of 43

Consultant Team:

Whitson Engineers 9699 Blue Larkspur Lane, Suite 105 Monterey, CA 93940

Balance Hydrologics, Inc. 800 Bancroft Way, Suite 101 Berkeley, CA 94710

Pacific Geotechnical Engineering 16055-D Caputo Drive Morgan Hill, CA 95037

Moffat & Nichol 2185 N. California Blvd., Suite 500 Walnut Creek, CA 94596-3500

H. T. Harvey & Associates Ecological Consultants 983 University Ave, Bldg D Los Gatos, CA 95032

EPB feasibility study funding was provided by:

California Wildlife Conservation Board California Department of Fish and Wildlife California Department of Water Resources

SRPS feasibility study funding was provided by:

Monterey County Community Service Area No. 1 (CSA 1)

Special Thanks To:

California Department of Parks and Recreation Monterey Peninsula Water Management District Carmel River Watershed Conservancy

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Contents I. Funding ...... 6 II. Background ...... 6 III. Project Datum ...... 7 IV. Project Area, and Upstream Developed Areas ...... 8 A. Project Area ...... 8 B. Other Developed Areas ...... 8 V. Project Objectives ...... 10 VI. Objectives of this Planning and Feasibility Study ...... 10 VII. EPB Project Alternatives ...... 10 A. Alignment ...... 11 B. Elevation ...... 12 C. Interior Drainage System ...... 12 D. Grading ...... 14 E. Barrier Materials and Construction ...... 15 F. Operation and Maintenance...... 16 G. Aesthetics ...... 17 H. Alternatives Included in this Study ...... 17 VIII. SRPS Project Alternatives ...... 20 A. SRPS Alternative #1 – Revetment (Rock Rip Rap) Located at the Toe of Slope...... 20 B. SRPS Alternative #2 – Seawall Located at the Toe of Slope ...... 21 C. SRPS Alternative #3 – Reinforced Earth Wall Located at Mid-Slope ...... 21 D. SRPS Alternative #4 – Pile Wall Located at Top of Slope ...... 22 IX. Other Potential Projects ...... 22 X. Right of Way ...... 22 XI. Environmental Permitting ...... 23 A. Biological Baseline...... 24 B. Potential Biological Effects and Potential Mitigation Measures ...... 24 C. Biological Resources Permitting Summary ...... 25 D. NEPA and CEQA...... 26 XII. Public Outreach ...... 26 XIII. Cost ...... 30 XIV. Flooding Impacts ...... 31 A. FEMA 100-Year Flood Model ...... 31 B. Qualitative Evaluation of Cessation of or Reduction in Lagoon Management ...... 32

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Exhibits A. Conceptual Carmel Lagoon Ecosystem Protective Barrier Map, Monterey County Water Resources Agency B. EPB Project Aerial Topographic Maps C. SRPS Project Aerial Topographic Maps D. Lagoon Stage-Storage-Area Map E. EPB Project Alternatives Maps and Cross-Sections F. SRPS Project Alternatives Map and Cross-Sections G. Community Service Area (CSA) Maps for CSA 1 and CSA 50 H. Excerpt from FEMA Flood Insurance Rate Map (FIRM) #06053C0320G

Appendices 1. Preliminary Project Cost Estimates 2. Public Comment Letters 3. County’s PowerPoint Presentation from General Public and CSA 1 and CSA 50 Meetings, and Meeting Sign-In Sheets 4. Project Site Photographs 5. Photographs of April 10, 2013 EPB mock-up, and mock-up location map 6. Brochure and Photographs, Carpinteria Salt Marsh Enhancement Project, Martinez Marina, and Redwood Shores Levee Project. Materials Courtesy Crane Materials International and B&B Hughes Construction.

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Technical Reports Developed Under This Contract Balance Hydrologics, Inc. Memorandum: Carmel River Lagoon EPB – Interior Drainage Design Options Analysis, March 5, 2013. Balance Hydrologics, Inc. Memorandum: Carmel River Lagoon EPB – Carmel River Lagoon EPB - Riverine Flooding Impacts Assessment, May 28, 2013. H.T. Harvey & Associates Ecological Consultants. Memorandum: Carmel River Lagoon Ecosystem Protective Barrier and Scenic Road Protection Project, Environmental Assessment Focusing on Biological Evaluations and Permitting Issues, HTH Project # 3420- 01, May 23, 2013. Moffat & Nichol. Memorandum: Carmel River Lagoon Restoration, Scenic Road Protection Options, M&N Job No. 7871. February 25, 2013. Pacific Geotechnical Engineering. Report: Feasibility Geotechnical Investigation, Proposed Ecosystem Protection Barrier and Scenic Road Protection Structure, Monterey County, California, Projects 2012.0133 and 2013.0134, May 28, 2013. Whitson Engineers. Memorandum: Carmel River lagoon EPB – Opportunities and Constraints. WE Nob No. 2487.01, November 16, 2012. Whitson Engineers. Memorandum: Carmel River Lagoon Ecosystem Protective Barrier, Lagoon Stage-Volume-Area Analysis, WE Job No. 2487.01, January 29, 2013.

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I. Funding Monterey County Water Resources Agency (MCWRA) received funding to complete the Environmental Protective Barrier (EPB) portion of this Feasibility Study from the Wildlife Conservation Board under Grant Agreement WC-1092 WR. MCWRA is the grant administrator for the EPB portion of this Study and is administering the EPB portion of the contract.

Monterey County Resource Management Agency (RMA) received funding to complete the Environmental Protective Barrier (EPB) portion of this Feasibility Study from the Monterey Peninsula Water Management District (MPWMD) via funds obtained from the Department of Water Resources (DWR), Integrated Regional Watershed Management Planning (IRWMP) grant program. Monterey County Community Service Area 1 (CSA 1) provided the funding for the Scenic Road Protection Structure (SRPS) portion of this Feasibility Study. Monterey County Resource Management Agency, Public Works (RMA-PW) is administering the SRPS portion of the contract.

II. Background The Carmel River Lagoon, located at the mouth of the Carmel River, is a very productive estuary which serves as rearing habitat for juvenile South-Central California Coast steelhead. The Carmel River was designated as critical habitat for steelhead in September 2005 (County of Monterey et. al, 2012). The ecosystem in and around the Carmel River Lagoon also supports other threatened species such as the California red-legged frog, Western snowy plover, and Smith’s blue butterfly.

The lagoon is not connected to the ocean during times of low or no river flow, when ocean waves build a barrier beach across the mouth of the lagoon and close the river’s outflow channel. When river inflow is relatively low, an equilibrium is reached between river and groundwater inflow, outflow through the barrier beach, and evapotranspiration. With even relatively moderate river flow increases in the fall and early winter, however, lagoon water levels can rise to flood stage within a number of hours, and can threaten private properties along the northern edge of the lagoon.

Since at least the early 20th century, and until 2011, when the Lagoon has risen to levels that threatened private property, landowners or agencies would breach the barrier in order to lower the lagoon’s water level to below flood stage. Beginning in 1973 emergency actions were carried out by Monterey County Public Works, Monterey County Water Resources Agency, and/or California Department of Parks and Recreation (State Parks). On average at least one management action has occurred yearly, with as many as three or four actions occurring in some years.

The motivation to pursue a Project occurred in 2005 when, in January, Monterey County graded an outlet channel along a “non-traditional” north-northwesterly alignment based on consultation with NOAA NMFS. The intent was that this new channel alignment would result in a decrease in both the rate of lagoon draw-down, and a reduction in the total drop in lagoon level. The breach was considered by some to be a success, as the new, longer breach channel was able to moderate flow rates and total volume of draw-down.

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This was the impetus for the Carmel River Watershed Conservancy (CRWC) and National Marine Fisheries Service (NMFS) to begin coordinating in the summer of 2005 with the various agencies, organizations, and individuals that had an interest in lagoon management with the intent of developing a long-term solution to the “breaching issue”. This process ultimately yielded the formation of a Technical Advisory Committee and, in 2007, the publication of the Final Study Plan for Long Term Adaptive Management of the Carmel River State Beach and Lagoon, which identified the baseline studies needed to find a long- term solution to managing Carmel River.

In response to a threat of litigation from the Carmel River Steelhead Association, a northerly channel was attempted again in 2010. However, due to significant river flows, the channel scoured the base of the bluff supporting Scenic Road, to the point that road stability was threatened, and washed away a portion of the Carmel River State Beach parking lot and very significantly undermined the park’s restroom building. The potential loss of Scenic Road was especially worrisome to the County, as, in addition to providing public access to the State Beach, it is the sole access to six private homes, and contains public utilities, including water and sanitary sewer. Damage to the restroom or sewer line could pose a significant environmental risk.

In 2011, the RMA began managing lagoon levels in consultation with the regulatory agencies (US Army Corp of Engineers, National Marine Fisheries Services, US Fish and Wildlife Service, California Coastal Commission, California Fish and Wildlife, Regional Water Quality Control Board).

Sandbar management costs the County approximately $200,000 per year on average, with recent annual expenditures ranging from approximately $150,000 to 350,000. (personal communication, Carl Holm to Nathaniel Milam)

In September 2012, the County and the Army Corps of Engineers, in consultation with NMFS, drafted the Memorandum of Understanding (MOU) Regarding Flood Prevention and Habitat Protection at the Carmel Lagoon. The MOU lays out a 5-year Interim Sand Bar Management Plan, with the understanding that the agencies’ long-term goal is to develop plans for 1) “a flood protection system, including but not limited to an Ecological Protection Barrier (EPB)” and 2) “armoring bluffs along Scenic Road, that would protect properties while allowing the Lagoon to breach naturally”, which is the focus of the SRPS Project.

The EPB and SRPS projects were therefore specified as the scope of this Feasibility Study. There are not herein compared to other potential project alternatives, but such other projects are anticipated to be considered as part of subsequent environmental permitting work.

III. Project Datum This Study and the project technical reports reference the North American Vertical Datum of 1988 (NAVD88), except where specifically noted otherwise.

Readers should note that the National Geodetic Vertical Datum of 1929 (NGVD29) was the most commonly used and referenced datum until recently, and water level data in source documents generally reference NGVD29. Where an elevation is listed in a source document in NGVD29, values have been converted to NAVD88 for use in this Study.

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The conversion from NGVD29 to NAVD88 at the project site is a difference of +2.74’, with NAVD88 “reading higher”. (An elevation of 10.00’ NGVD29, for example, equates to an elevation of 12.74’ NAVD88.) Where sources report values to only to the nearest tenth of a foot or the nearest whole foot, a conversion of +2.7’ or +3’ was used, respectively, to maintain the original precision.

IV. Project Area, and Upstream Developed Areas This section discusses the areas which are within the project description of the EPB and SRPS projects, as well as facilities which are outside the project description, but which may potentially be affected by implementation of the EPB and/or SRPS projects, or by cessation of or reduction in management of the river’s outflow channel through barrier beach.

A. Project Area The areas considered for protection by the EPB and SRPS projects were initially outlined on the Monterey County Water Resources Agency Draft Carmel Lagoon Ecosystem Protective Barrier Map (Exhibit “A”). The areas considered for protection include (listed downstream to upstream):

Scenic Road Protection Project: 1. Scenic Road, from the southerly terminus of Ocean View Avenue, to Carmelo Street. Scenic Road is supported by a sand embankment that rises as much as 30’ above the beach. The roadway varies from approximately 17’ elevation at Carmelo Street to approximately 43’ elevation at Isabella Avenue. 2. The Carmel River State Beach parking lot and restroom, located at the southern end of Carmelo Street. The parking lot varies from 13’ to 16’ elevation, and the restroom finish floor is above 18’ elevation. Note that even though the parking lot is within the FEMA-designated 100-year flood plain, pursuant to coordination with State Parks, the parking lot is not included in the EPB portion of this Study.

Environmental Protective Barrier Project: 1. Carmelo Street between Scenic Road and the Fourth Addition neighborhood (between 16th and 17th Avenues). Roadway elevation varies from below 14’ elevation to above 19’. 2. Approximately 28 residences in the Fourth Addition neighborhood (lowest grade adjacent to residences = 14’ ±, lowest residence finished floor = 14.5’ ±) 3. The Carmel River Elementary School track and outbuildings (lowest grade on track = 13.7’ ±, lowest grade adjacent to outbuildings = 13’ ±) 4. Portions of Mission Ranch which lie within the FEMA 100-year flood plain (if EPB Extension #3A or #3B is pursued): o a pasture, commonly referred to as the “sheep pasture” (elevation varies from approximately 10’ to 14’), and ancillary facilities o the tennis clubhouse and “quadplex” buildings (lowest grade adjacent to buildings = 15.9’, lowest finished floor = 18.2), o the parking lot serving the lower Mission Ranch complex (elevation varies from approximately 14.5’ to approximately 18.3’), and o six tennis courts (elevation varies from 16.2’ to 17.1’).

B. Other Developed Areas The developed areas which are not part of the project description, but which could potentially be affected by upstream effects include:

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1. Portions of Mission Ranch which lie within the FEMA 100-year flood plain (if EPB Extension #3A or #3B is not pursued). 2. The Carmel Area Wastewater District (CAWD) Waste Water Treatment Plant (WWTP). The treatment plant site is leveed to approximately 18’ elevation, though grades inside the plant are as low as approximately 15’, and the plant’s entry drive has a section which is approximately 17’ elevation. Some facilities within the plant (e.g., mechanical equipment) may extend significantly below grade. 3. Community Service Area 50 (CSA 50). CSA 50 was established in 1967 for extended County services and is assessed for drainage maintenance. The area includes the Mission Fields neighborhood west of State Route 1 and the commercial and residential areas around Rio Road east of State Route 1. 4. Community Service Area 1 (CSA 1). CSA 1 was established in 1959 for extended County services. The area consists of homes within the Scenic Point area, including homes along Scenic Road. A portion of CSA 1 is within the EPB and SRPS projects’ tributary watersheds, so would contribute urban runoff to the projects. Five properties within CSA 1 (along the east side of Carmelo Street) would abut the EPB, and approximately nine properties within CSA 1 would abut the SRPS.

The CAWD WWTP and CSA 50 are located just upstream of a 16’ BFE contour identified on the FEMA Flood Insurance Rate Map (FIRM). The BFE at the CAWD WWTP varies from above 16’ at the western levee, to approximately 19’ at the eastern levee. At the southern end of Larson Field (the most downstream point in Mission Fields) the BFE is approximately 20’.

Fourth Addition Mission Ranch CAWD WWTP neighborhood

Mission Fields

Scenic Road

Carmel River State Beach Parking Lot

Figure IV-1. Excerpt from FIRM #06053C0320G (NAVD88)

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V. Project Objectives The objectives of the EPB project are: 1. To improve the functions and values of the ecosystem in and around the Lagoon by allowing lagoon levels to rise and the lagoon to breach naturally (versus mechanically breaching the lagoon). For the purposes of this study, the ability to breach naturally is primarily evaluated based on the increase in the allowable lagoon water surface elevation prior to initiating mechanical breaching activities. 2. To improve the existing level of flood protection in the low-lying developed areas located immediately north of the Lagoon.

The objectives of the SRPS project are: 1. To protect public infrastructure (Scenic Road embankment, State Parks restroom, and parking facilities) from scour resulting from a northerly-aligned lagoon outflow channel. 2. To protect the Scenic Road embankment from erosion resulting from ocean storm surge.

VI. Objectives of this Planning and Feasibility Study

The objectives of the EPB portion of this Study are to:

1. Assess whether the proposed Ecosystem Protective Barrier (EPB) could reduce or eliminate the necessity of mechanical breaching of the barrier beach, and thereby restore a natural breaching regime to the beach; 2. Evaluate the upstream and downstream effects of installing the EPB; 3. Determine whether the EPB could reduce or prevent flooding of residences, a local school yard, nearby commercial buildings, and streets, without causing damaging dry- side effects; 4. Assess the degree of support or acceptance of the neighborhood residents who live along or near the north side of the Lagoon; and 5. Describe the likely permit requirements that must be met in order to install the EPB.

The objectives of the SRPS portion of this Study is to:

1. Develop conceptual alternatives and provide recommendations for the protection of Scenic Road from scour caused by flow through a northerly-aligned outflow channel, and for protection from ocean waves. 2. Describe the likely permit requirements that must be met in order to install the SRPS.

VII. EPB Project Alternatives Early in this Study it was determined that the opportunities and constraints presented for the EPB project are such that it would be most appropriate to independently evaluate “bounding cases” for individual project variables (e.g., EPB elevation and location), rather than evaluate specific “project alternatives” in the typical sense. In this way, individual variables may be discussed and evaluated independently.

It is anticipated that additional project alternatives will be developed as part of future environmental work for comparison to the Preferred Project, including project alternatives

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The basic design variables, and the “bounding alternatives” selected, are presented below. A synopsis of why each alternative was chosen is also provided.

A. Alignment 1. Alignment #1: EPB at the minimum setback off property line. A setback of 15 feet from property line minimizes encroachment into State Parks property while still providing the area required for installation of storm drainage and subsurface drainage facilities and providing a maintenance access corridor along the length of EPB. This alignment provides approximately 2.5 ac-ft of stormwater detention volume on the interior side of the EPB if no fill is placed behind the EPB (EPB Alternative 1A), and approximately 1 ac-ft if fill is placed behind the EPB to create an accessway (EPB Alternative 1B).

An alignment closer to the property line was not considered technically feasible, due to 1) the need for access along the barrier for operation and maintenance activities, 2) the size of pumping equipment that would be required (due to the reduction in stormwater detention volume provided), and 3) the resulting lack of right of way for implementation of stormwater treatment facilities. A closer alignment is also considered logistically infeasible because easements would need to be obtained from approximately 14 residential property owners, in addition to State Parks and Mission Ranch.

2. Alignment #2: EPB located a minimum of 40’ off property line. This alignment alternative was chosen so as to minimize the required storm drainage infrastructure (piping, subsurface drainage, and pumping), while balancing potential impacts to regulated habitat. The alignment provides approximately 8 ac-ft of stormwater detention volume on the interior side of the EPB. The alignment also maintains a setback of approximately 20 feet from an existing depressed area. The approximate northerly and westerly limits of the depressed area are shown on the attached EPB Alternative 1B map. In aerial imagery the depressed area is noted by its contrasting vegetation, and in some cases, standing water.

The expanded stormwater detention volume provided by this alignment allows for a significant reduction in both the physical extent and the overall capacity of storm drainage infrastructure required. This will translate to a reduction in the need for access and maintenance, and therefore a reduction in the facility’s long-term operation and maintenance cost.

3. Alignment Extensions #3A and #3B: EPB Extended to Protect Lower Mission Ranch Complex Alignment Extensions #3A and #3B are potential independent extensions of EPB Alternative #1A, #1B, or #2A, for the purpose of protecting low-lying areas of the Mission Ranch property which could have their operations impacted if portions of the site are flooded for extended periods. Extension #3A would begin at the most easterly extent of EPB Alternative #1A/1B/2A, and would extend southerly along the Carmel Unified School District / Mission Ranch property line approximately 300 feet. This southerly limit was selected so as to avoid significantly impacting FEMA flood levels in upstream developed areas. The EPB alignment would then turn and extend westward across the “sheep pasture”, and then along the

WE # 2487.01 & 2487.02 Carmel River Lagoon EPB and SRPS Projects Feasibility Study May 29, 2013 Page 12 of 43 southerly edge of Mission Ranch’s sheep enclosures, parking lot, and tennis courts. EPB Extension #3B differs from #3A only in that it takes a more direct route through the sheep pasture. EPB Alignment Extension #3A is approximately 1,700 feet long, and #3B is approximately 1,200 feet long.

The originally envisioned EPB Extension around Mission Ranch (illustrated in Exhibit “A”) tied into the existing levee located to the south of Mission Ranch. In doing so, however, the alignment also crossed an overflow channel which conveys significant flood flows from the Mission Fields neighborhood during flood events. An EPB alignment which would cross this overflow channel would therefore be anticipated to negatively affect flood elevations in Mission Fields. The EPB Extensions analyzed herein were therefore revised from the original alignment to represent the most southerly extent which would not result in negative upstream impacts.

B. Elevation 1. Top of EPB at 16’ elevation (NAVD88) An elevation of 16’ NAVD88 was chosen as the “lower bound” of elevations anticipated to produce a positive cost-to-benefit result. Elevation 16’ is equal to the current FEMA 100-year flood elevation for the lagoon, and is 0.6’ higher than the highest lagoon level on record (15.4’ on January 2008). It is also approximately equal to the elevation of the County’s sandbag barrier which was constructed along the periphery of the Fourth Addition neighborhood in the fall of 2012.

Note that the top of EPB Extensions #3A and #3B for the 16’-elevation alternative would be slightly sloped, and not a constant 16’ elevation, to account for the rise in the FEMA base flood elevation from 16’ to approximately 17.3’ along the length of the Extension. For simplicity, references made to the 16’ elevation alternative should be interpreted to include a sloping section along the length of Mission Ranch as required to preclude floodwaters from overtopping the EPB at the upstream end.

2. Top of EPB at 19’ elevation (NAVD88) An elevation of 19’ NAVD88 was chosen to represent an “upper bound” EPB elevation, assuming the project intends to provide a combination of the following: 1) preclude the necessity of managing the barrier beach during the design life of the project (herein assumed to be 50 years); 2) provide a design freeboard typical of this type of facility; and 3) address sea level rise without modification (i.e., raising) during the design life of the EPB. (Sea level is predicted to rise between 0.5 and 2 feet during the design life of the structure.)

3. Top of EPB at 17.5’ elevation (NAVD88) An elevation of 17.5’ NAVD88 was chosen as the preferred EPB elevation for this Study. This elevation was selected as representative of the highest barrier elevation which is anticipated to be feasible, due to the stated position of several of the residents of the Fourth Addition, and our anticipation that the level of community opposition will increase in parallel with barrier visibility.

C. Interior Drainage System The EPB project, in addition to acting as a barrier to lagoon waters from crossing into developed areas, also will act as a barrier to stormwater flowing from developed areas out into the lagoon. Under existing conditions, approximately 100 acres drain from as far north as 11th Avenue in Carmel, ultimately entering the lagoon as surface flow off the ends of WE # 2487.01 & 2487.02 Carmel River Lagoon EPB and SRPS Projects Feasibility Study May 29, 2013 Page 13 of 43

Camino Real, River Park Place, Monte Verde Street. During the design storm event, a total of approximately 15 acre-feet of runoff, at a peak rate of approximately 107 cfs, crosses EPB Alignments #1 and #2.

An additional area of approximately 35-acres is tributary to EPB Extensions #3A and #3B. The interior drainage system which would serve EPB Extension 3A or 3B would operate independently from the system serving EPB Alternatives 1A, 1B and 2A, and so is described separately.

1. Drainage Alternative A The intent of Drainage Alternative A is to minimize the overall cost and complexity of the required interior drainage improvements. In this alternative the entire 100-acre drainage area would continue to surface drain (down street gutters) into the Fourth Addition neighborhood, eventually flowing off the ends of Monte Verde Street, River Park Place, and Camino Real, as it does currently. With the EPB in place, this runoff would collect in the low- lying area between the EPB and the Fourth Addition neighborhood.

This collected storm water would be treated using stormwater Best Management Practices (BMPs) located behind the EPB. BMPs could include treatment wetlands, bioretention areas, and/or biofiltration areas, in addition to mechanical filters at the pump station, such as pump inlet screens. This treated water would then gravity flow to the lagoon through one or more flood gates during times that the lagoon is sufficiently low. When lagoon levels are sufficiently high, rising water levels in the detention area would activate a pump station which would pump the collected storm water into the lagoon.

This alternative would require either a larger ponding volume or a larger pumping system, as compared to Alternative B, because the Alternative A system would need to accommodate flows from the entire drainage area (100 acres), instead of only from the Fourth Addition neighborhood (28 acres). In EPB Alternative 1A, a larger (20,000 gpm) pump station is provided; for EPB Alternative 2A, a larger detention volume (8 ac-ft) is provided.

The benefits of Drainage Alternative A are: 1) it minimizes the complexity and cost (both construction and long-term O&M) of the interior drainage system, 2) it provides opportunity for implementation of larger detention and retention-based storm water Best Management Practices (BMPs), such as treatment wetlands, as compared to Drainage Alternative B, and 3) it reduces the frequency of pump cycling, due to the detention volume provided.

2. Drainage Alternative B The intent of Drainage Alternative B is to minimize the volume and rate of stormwater which would need to be detained and pumped during the design storm event. In this alternative, storm drain inlets would be constructed at strategic locations within the drainage area and up-slope of the Fourth Addition neighborhood so as to collect and gravity drain as much of the tributary drainage area as possible. This storm drain would bypass the low-lying Fourth Addition neighborhood because the Fourth Addition is too low to be able to gravity drain into the lagoon at higher lagoon stages. The “bypass storm drain” would enable approximately 75% of the project drainage area to gravity drain to the lagoon. Some of the bypass storm drain system would be located within CSA 1.

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Runoff from the remaining area (the Fourth Addition neighborhood) would collect in the low-lying area between the EPB and the Fourth Addition neighborhood. This collected storm water would be collected and pumped into the lagoon when lagoon levels are relatively high. When lagoon levels are relatively low, all runoff from the drainage area would gravity flow to the lagoon through one or more flood gates.

This alternative minimizes the required stormwater detention volume behind the EPB, which in turn allows the EPB to be placed relatively close to the property line, and/or allows the area behind the EPB to be filled in for use as an access corridor.

The attached memorandum, Draft Carmel River Lagoon EPB - Interior Drainage Design Options Analysis, presents the results hydrologic and hydraulic modeling for two alternative interior drainage systems.

3. Drainage for EPB Extensions 3A and 3B An area of approximately 35 acres is tributary to EPB Extensions 3A and 3B. This area currently drains into the lagoon to the east of the Fourth Addition neighborhood. If EPB Extension 3A or 3B is constructed, the separation between these two watersheds would be maintained by “returning” a segment of the wall to higher ground between the two watersheds (along the western property line of Mission Ranch). In this way any failure in the EPB Extension 3A or 3B drainage system would not negatively affect lower-lying residences in the Fourth Addition.

The majority of the 35-acre tributary drainage area currently enters the lagoon through a storm drain which runs through the Mission Ranch property (labeled “existing Mission Ranch bypass storm drain” on the EPB Extensions 3A and 3B map). This system would need to be modified as part of the project to enable the hydraulic grade line in the system as it passes through the tennis courts, to rise in parallel with lagoon levels. Modification is anticipated to generally entail replacement of the existing concrete channel (which is concealed beneath a wooden boardwalk) with a low-pressure rated storm drain pipe, and a flood gate at the barrier penetration.

Specific analyses were not performed for the interior drainage systems for EPB Extension 3A and 3B. We anticipate that the system serving this additional area will be located in the “sheep pasture” on Mission Ranch property, at or near the natural low point in the drainage area. Pump sizing was estimated based on the results of the analyses performed for Drainage Alternatives A and B, for the sole purpose of preliminary cost estimating.

D. Grading 1. Minimized Fill (No Access Road) Alternative In this alternative, the barrier, pump station, and outfall structure(s) would be constructed, but otherwise the project would avoid placing fill in the depressed area between the EPB and Fourth Addition neighborhood. This alternative has the advantage of minimizing the amount of fill placed in any wetland and riparian areas which may be identified, thereby maintaining, to the extent practicable, the existing wetland nature of those areas. It is also anticipated to be lower cost than importing and placing engineered fill.

Not constructing an access road along the EPB, however, would present significant access limitations for future operation and maintenance (O&M) activities. Nonetheless, it is the preferred project alternative, as it best achieves the project objectives. For this Minimized

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Fill alternative, therefore, materials and systems should be selected so as to minimize the need for and they type of access which would be required for long-term O&M of the structure.

This grading alternative also may present unique permitting issues for long-term operation and maintenance of the facility, as outlined in Section XI of this report.

2. Access Road Alternative In this alternative, in addition to the barrier, pump station, and outfall structure(s), approximately 3,000 cubic yards of fill would be imported and placed behind the barrier to create a minimum 12’-wide all-weather access road. This access road would be utilized for operation and maintenance of the facility. In order to address storm drainage and subsurface seepage flows along the length of the EPB and access road, and to provide for wet-weather use of the roadway, storm drainage and subsurface drainage systems would need to be provided along the length of the EPB under the roadway. Vegetation along the road would also need to be managed (mowed).

1. Berm Across Sheep Pasture (for EPB Extensions #3A and #3B only) Based on communication with Mission Ranch, EPB Extensions #3A and #3B include the placement of approximately 2,700 cubic yards of earth fill for Extension #3A, or 1,600 cubic yards for Extension #3B, to create a berm that would conceal the sheet piling as it crosses through the sheep pasture.

E. Barrier Materials and Construction The following materials and configurations were considered for construction of the barrier:

1. Vinyl Sheet Piling and Fiber Reinforced Polymer (FRP) Sheet Piling Vinyl sheet piling was identified as the material of choice for the project as early as 2010, and appears in the project’s Proposition 84 Grant Application prepared by MPWMD in 2011. Vinyl and FRP sheet pilings are functionally very similar, with the primary difference being that FRP is both stiffer and stronger than vinyl. The primary concern raised regarding the use of vinyl and FRP sheet piles is that vinyl and FRP may be damaged in a fire, whereas the more traditional steel sheet piling would generally not be. This particular concern was not deemed to be a significant concern on this project, and is outweighed by the benefits which vinyl and FRP have over steel sheet piling, namely that they do not corrode and they do not require periodic application of protective coatings. There is therefore no required maintenance, other than annual inspections to ensure that the wall has not been damaged (e.g., by vehicular impact or fire). FRP is preferred over vinyl due to the anticipated barrier heights on project.

2. Steel Sheet Piling Steel has traditionally been used for sheet piling flood wall projects in the U.S. due to its strength and durability. Since steel rusts, its thickness is selected in order to provide the desired life span. Steel sheet piling is, however, not preferred for the EPB project because it would require regular painting, and so would require that access be provided along the length and on both sides of the EPB. It is also anticipated to be a more expensive alternative than FRP.

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3. Earthen Berm An earthen berm was also considered, as it could be a more aesthetically pleasing, more “natural-looking” alternative. The earthen berm would require a sheet pile “core” for seepage control. Benefits of an earthen berm are that it can be raised relatively easily to address sea level rise by adding earth fill, and temporarily raised if needed by sandbagging. Also, access would be very good. However, it was rejected from further consideration in this Study because of both its significant permanent impacts (primarily, the amount of fill in wetlands, both in terms of volume and area) and its significant temporary construction impacts (due to the amount of imported fill required, total construction footprint, and duration of construction). This alternative also would provide significantly less stormwater detention volume on the interior side of the EPB than a sheet pile wall along the same alignment, and thus the required pump station size and cost would also be significantly increased. The import of the required earth fill would be in addition to a sheet pile core, and this would also represent an additional cost over a stand-alone sheet pile wall.

F. Operation and Maintenance Operation and maintenance (O&M) is one of the primary considerations in project selection and design. Some of the primary variables which will affect O&M of the facility are:

1. Types of maintenance activities which would be required: painting of exposed metal components; replacement of broken electrical and mechanical components; cleaning of storm drain pipes, inlets, and outfalls; etc. 2. The ease and adequacy of access for maintenance activities, including access by work vehicles and specialized equipment 3. Number and type of outfalls into the lagoon; permits required to operate and/or maintain the outfalls 4. General complexity of the system; ease of managing the system 5. Long-term (life cycle) O&M costs, including equipment design life and replacement costs, ongoing permitting costs, and yearly operator time 6. Anticipated environmental permitting requirements for O&M activities: permits required for pump-down of interior detention volume; permits required for certain anticipated maintenance activities, such as inspections, graffiti and painting; permits required for significant system modifications / replacements. 7. Can or need the EPB be modified to address sea level rise

The above considerations, with the exception of items 2 and 6, all tend to suggest EPB Alignment Alternative #2 in conjunction with the Minimized Fill alternative, due to the resultant simplicity of the interior drainage system. The lack of ready access along the barrier (see item #2 above) in this scenario is offset (as much as practical) by minimizing the required maintenance of the barrier through the use of FRP sheet piling instead of the more traditional steel sheet piling. Access to the lagoon side of the completed barrier (e.g., for painting) would be very limited in any case.

The proposed pump stations and gravity outfalls would therefore be the primary focus of O&M activities. Regular access for normal operation of the facilities would be required, and occasional access for replacement of pumps, motors, generator equipment, and other mechanical and electrical system components should be anticipated. The proposed pump stations were therefore located where they would be easily accessible by County forces.

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Selection of stormwater Best Management Practices (BMPs) are also important from an O&M perspective. BMPs for the project may include treatment wetlands, “biofiltration”, and/or “bioretention” areas if sufficient area is made available (such as in Alternatives #1A and #2A), or the project may include subsurface “structural” BMPs, such as underground chambers or sand filters, if dictated by project constraints (such as in Alternative #1B). From an O&M perspective, surface BMPs are preferable, as they are more readily and inexpensively accessed, cleaned, and rehabilitated. Treatment wetlands and biofiltration and bioretention areas are also generally preferred by project regulators over subsurface facilities.

G. Aesthetics The primary aesthetic consideration for the EPB project is how it would impact existing views of the lagoon from public areas (Carmelo Street, Camino Real, River Park Place, Monte Verde Street, and Carmel River State Beach). A secondary concern, expressed by residents, is the project’s effect on views from private homes.

Mock panels were erected at the end of River Park Place to help assess potential visual impacts of the various project alternatives. The panels represented EPB Alignment Alternatives #1 and #2, at both 16’ and 19’ elevations. The barrier’s elevation and location are the two primary drivers of aesthetic impacts.

EPB Alignment Alternative 1 (located near the property line) would be visible given any EPB elevation, though visual impact could possibly be mitigated by adding vegetation in the 15’-wide area between the park boundary and the barrier. If an access road were constructed along the EPB, opportunity for mitigating the barrier’s visual impact would be limited, as the roadway would need to be maintained relatively free of tall vegetation.

For EPB Alignment Alternative 2, the mock-up illustrates that at 16’ elevation the EPB would likely generally below the tops of the rushes (Cattails), and therefore would be relatively shielded from view. At 19’ elevation the EPB would likely generally be above the tops of the rushes, and so would be more exposed to view. The preferred project elevation of 17.5’ is anticipated to correspond roughly to the top of vegetation elevation.

Additional vegetation density and height may be provided as a mitigation measure after construction by planting around the barrier. Other mitigations may include providing an aesthetic treatment to the barrier.

H. Alternatives Included in this Study Of all the possible combinations of the above elements, nine EPB Alternatives were selected for consideration herein, of which one is the Preferred Project.

EPB Project Alternatives analyzed in this Study are outlined in Table VII-1, below.

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Table VII-1. Summary of EPB Alternatives Included in This Study

EPB Alternatives 1A-16’ and 1A-19’: EPB Alignment: #1 EPB Elevation: 16’ and 19’ Barrier Description 2,020 LF of FRP sheet pile wall, plus reconstruction at 16’ Elevation: of 400 LF of Carmelo Street to 16’ elevation Barrier Description 2,460 LF of FRP sheet pile wall (Carmelo Street at 19’ Elevation: would not be raised) Interior Drainage: Drainage Alternative “A” (20,000 gpm pump station) Grading: Minimized Fill (No Access Road) Alternative

EPB Alternatives 1B-16’ and 1B-19’: EPB Alignment: #1 EPB Elevation: 16’ and 19’ Barrier Description 2,020 LF of FRP sheet pile wall, plus reconstruction at 16’ Elevation: of 400 LF of Carmelo Street to 16’ elevation Barrier Description 2,460 LF of FRP sheet pile barrier (Carmelo Street at 19’ Elevation: would not be raised Interior Drainage: Drainage Alternative “B” (42” bypass storm drain & 5,000 gpm pump station) Grading: Access Road Alternative

EPB Alternatives 2A-16’ and 2A-19’: EPB Alignment: #2 EPB Elevation: 16’ and 19’ Barrier Description 1,920 LF of FRP sheet pile wall, plus reconstruction at 16’ Elevation: of 400 LF of Carmelo Street to 16’ elevation Barrier Description 2,360 LF of FRP sheet pile wall (Carmelo Street at 19’ Elevation: would not be raised) Interior Drainage: Drainage Alternative “A” (5,000 gpm pump station) Grading: Minimized Fill (No Access Road) Alternative

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Table VII-1, continued.

EPB Extension 3A-19’: EPB Alignment: #3A (as an extension of #1A, #1B, or #2A) EPB Elevation: 19’ Barrier Description: 1,400 LF of FRP or vinyl sheet pile wall Interior Drainage: Separate drainage system for EPB Extension 3A (24” bypass storm drain & 2,000 gpm pump station) Grading: Construct berm to hide sheet piling where it crosses through sheep pasture

EPB Extension 3B-19’: EPB Alignment: #3B (as an extension of #1A, #1B, or #2A) EPB Elevation: 19’ Barrier Description: 1,400 LF of FRP or vinyl sheet pile wall Interior Drainage: Separate drainage system for EPB Extension 3B (24” bypass storm drain & 2,000 gpm pump station) Grading: Construct berm to hide sheet piling where it crosses through sheep pasture

Preferred EPB Project: EPB Alignment: #2 EPB Elevation: 17.5’ Barrier Description: 1,920 LF of FRP sheet pile wall, plus reconstruction Of 400 LF of Carmelo Street to 17.5’ elevation Interior Drainage: Drainage Alternative “A” (5,000 gpm pump station) Grading: Minimized Fill (No Access Road) Alternative

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VIII. SRPS Project Alternatives NOAA NMFS has stated that they believe the river would breach and remain flowing in a northerly direction if the beach were not managed. It is also known that under certain conditions, such as during high river flow events, the beach bluff adjacent to Scenic Road is subject to erosion. The SRPS concept was developed to protect public infrastructure along Scenic Road from damage in the event of northerly river flows or from large ocean swells. Damage to Scenic Road could result in the loss of access to eight private residences, in negative environmental impacts (such as discharge of raw sewage into the ocean), and impairment to public access to important coastal resources.

Four conceptual project alternatives were developed for this Study based on a review of photographs and reports from historic northerly-directed breaches, both naturally occurring and mechanical; discussions with Monterey County Public Works personnel; and review of the results from the geotechnical investigation and testing performed as part of this Study, as well as a review of available geotechnical data. The sections below describe the SRPS Project Alternatives and discuss the primary project variables. Additional technical information may be found in Moffat and Nichol’s Memorandum titled “Scenic Road Protection Options” (2013).

A. SRPS Alternative #1 – Revetment (Rock Rip Rap) Located at the Toe of Slope SRPS Alternative #1 consists of rock slope protection, also known as rock rip-rap or revetment, placed at the toe of the road embankment. The rock would extend up as needed to protect Scenic Road from river scour and wave erosion, and would extend down below the anticipated outlet channel scour elevation. The outer rock layer would be sized to withstand extreme ocean wave and river current forces, with a thinner layer of smaller rock and/or a geotextile fabric underneath to prevent the soil from being eroded through the revetment.

The purpose of SRPS Alternative #1 would be to prevent erosion of the bluff below Scenic Road by preventing erosion at the bluff’s toe. Above the top of the revetment, the slope would be permanently planted and maintained to control erosion.

Revetment is the lowest-cost material alternative. Burying the revetment at the toe of the slope, and extending the revetment up the slope only far enough to protect against river scour and wave erosion, minimizes the project’s visual impact and cost. It is anticipated that the top of revetment would generally be low enough to be re-buried naturally if and when the river scours out the sand in front of it. For these reasons, SRPS Alternative #1 is the preferred alternative.

SRPS Alternative #1 would, however, be located significantly outside the County’s right-of- way (on State Parks owned land), and within a public beach. Acquisition of the needed right of way could represent a significant difficulty for the project, though at this stage this is still an unknown.

Because revetment would be placed within the beach area, Alternative #1 would tend to reduce the beach width available for a northerly-breaching lagoon, as compared to the other project alternatives studied. A target beach width was not provided, nor established as part of this Study, so it is not known if this will have any significant effect on the outlet channel’s behavior, hydraulics, etc. This will need to be investigated further if project

WE # 2487.01 & 2487.02 Carmel River Lagoon EPB and SRPS Projects Feasibility Study May 29, 2013 Page 21 of 43 proponents desire to increase the probability that a relatively long northerly breach alignment would occur, in addition to the stated project goal of simply providing protection for Scenic Road.

B. SRPS Alternative #2 – Seawall Located at the Toe of Slope SRPS Alternative #2 consists of two sections of wall: the northern half of the wall would be a retaining wall constructed vertically (or near vertically) at the toe of slope, along an alignment similar to that of Alternative #1; and the southern half would be revetment identical to Alternative #1. Revetment is continued to be proposed for the southern half of the project because beach topography in this area lends itself well to installation of revetment. Also, continued vehicular beach access from the beach parking lot, both for breach management and emergency response, lends itself to a revetment alternative. For the purposes of developing the preliminary cost estimates presented herein, a tangent or secant pile wall is used as the retaining wall structural system.

SRPS Alternative #2 is very similar to Alternative #1 in terms of the alignment and profile of the earth slope above the wall, and in terms of the type of protection provided to Scenic Road. The right of way required for Alternative #2 is slightly less than for Alternative #1, however, due to reduced encroachment onto the beach. The beach width available during a northerly-aligned breach is also slightly greater for Alternative #2 than for Alternative #1. The major differences between Alternatives #1 and #2 are the estimated project costs, and the ability to provide an aesthetic treatment to the face of the wall for Alternative #2.

C. SRPS Alternative #3 – Reinforced Earth Wall Located at Mid-Slope SRPS Alternative #3 consists of a retaining wall constructed at some location mid-slope, below Scenic Road, but above beach level. A reinforced earth structural system (a soil nail wall with shotcrete facing) was used for the northern portion of the project for the purpose of estimating costs. (Future geotechnical investigations will need to verify if this structural system is the most optimal, based on proposed wall elevations, embankment slopes, soil properties, and construction costs.) The southern half of the project is revetment placed in the same locations and at the same elevations as Alternatives #1 and #2.

SRPS Alternative #3 is not favored for a variety of reasons, but is presented herein specifically to indicate what the SRPS project could entail should additional beach width be desired, such as for the purpose of increasing the probability of a northerly breach. (Note that an evaluation of the likelihood for the river to take a northerly route is beyond the scope of this Study.) Wall heights (and project cost) increase for each foot moved away from the toe of slope, and therefore project aesthetics, scope, and cost are very sensitive to the barrier’s location relative to the toe of slope. For the purpose of developing preliminary cost estimates, a mid-slope alignment was assumed. As noted above, additional study is required if project proponents desire to increase the probability of a naturally occurring, relatively long northerly breach alignment.

Because of the higher top of wall elevation (compared to Alternative #2), if the river were to scour the beach from in front of the wall, an approximately 25’-tall portion of the wall could become exposed. Summer and fall wave action would tend to re-build the beach in front of the wall, but the top half of the wall would remain exposed, as it would be above normal beach elevations. As such, the entire face of the wall would most likely receive an aesthetic treatment to address long-term visual considerations.

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A pedestrian guard rail would be required along the top of the wall, or alternatively along Scenic Road. A vehicular guard rail may also be required.

D. SRPS Alternative #4 – Pile Wall Located at Top of Slope SRPS Alternative #4 consists of a retaining wall constructed along the edge of Scenic Road, within the County’s right of way. An additional section of revetment extends around and protects the beach parking lot. A pile wall with tiebacks is the structural system utilized for the purpose of preliminary cost estimating.

This Alternative is included so as to illustrate what the SRPS project would entail if the structure were required to be constructed within County right of way (with the exception of the revetment, which would solely protect the beach parking lot and restroom). SRPS Alternative #4 is the least favored alternative of those identified herein, as it would result in the highest potentially exposed wall height – approximately 30 feet – and the highest project cost. It would also have the most significant visual impact from Scenic Road, since pedestrian guard railings and vehicular guard railing would be required along the top of wall (which would be at the level of Scenic Road).

IX. Other Potential Projects

It should be noted that the EPB and SRPS projects are only two of several potential projects which have been suggested as a means to achieving the Project Objectives. Other such projects include the following (adapted from the 2007 Study Plan):

1. Remove buildings that flood 2. Raise or otherwise flood-proof buildings that flood 3. Provide temporary / seasonal flood protection measures (e.g., sand bagging) 4. Provide variable-height EPB (e.g., rubber bladder floodwall) 5. Provide mechanical control of lagoon level (e.g., additional outfalls) 6. Manage sandbar maximum elevation to keep the lagoon below flooding level by mechanically grading to lower the berm’s crest in preferred locations; also, time breaching to occur when wave, climate, tide, and inflow rates and optimum 7. Manage base elevation of outflow channel by maintaining a channel over a bedrock sill, or by installing a temporary or permanent weir structure, or by maintaining a relatively long outflow channel (e.g., along Scenic Drive) 8. “No Project”

Evaluation of these other alternative projects, or comparison of these other projects to the EPB project, is beyond the scope of this Study.

X. Right of Way One of the primary constraints to the implementation of the EPB and SRPS projects may be acquiring the necessary right of way, as the majority of both projects are proposed to be implemented on properties outside the control of the County. Of particular concern is the use of land owned by the California Department of Parks and Recreation (State Parks). As of the time this report was prepared, there has been no commitment by State Parks for the use of this land. Use of this land will require some agreement between the agencies and may require legislative action.

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EPB Alternatives 1A, 1B, and 2A would be constructed on a California Department of Parks and Recreation (State Parks) owned parcel (APN 009-491-001) and on a Carmel Unified School District (CUSD) owned parcel (APN 009-511-007, Carmel River Elementary School). EPB Alternatives 1A, 1B, and 2A also run along the property line between Carmel River Elementary School and Mission Ranch (APN 009-511-006), and as a result, both temporary and/or permanent easements are anticipated to be required from Mission Ranch as well. Temporary construction easements are also anticipated to be required for up to 14 residential parcels (i.e., the Fourth Addition parcels which abut the lagoon) for the EPB project.

EPB Extensions 3A and 3B would be constructed entirely on Mission Ranch property, and therefore easements would be required for construction and maintenance of these Extensions, unless the facility were constructed, owned and maintained by Mission Ranch.

SRPS Alternatives 1, 2 and 3 would also necessarily be constructed on State Parks owned land (APNs 009-472-001 and 009-481-004). Only SRPS Alternative 4 has the potential to be constructed generally within County right-of-way (excepting the rock rip rap which would extend along the southerly edge of the beach parking lot, solely for the protection of the parking lot), though the construction cost and visual impact of SRPS Alternative 4 make it the least desirable of the four SRPS alternatives evaluated.

Table X-1. EPB Right of Way Summary Alt 1A Alt 1B Alt 2A Ext 3A Ext 3B State Parks Area Between Park Boundary and 0.9 ac 0.9 ac 2.4 ac 0 ac 0 ac EPB Carmel Unified School District 30’ Easement Along EPB 0.4 ac 0.4 ac 0.4 ac 0 ac 0 ac Mission Ranch 30’ Easement Along EPB 0.1 ac 0.1 ac 0.1 ac +1.0 ac +0.8 ac

Table X-2. SRPS Right of Way Summary Alt 1 Alt 2 Alt 3 Alt 4 State Parks Area Between Park Boundary, 2.0 ac 1.5 ac 1.3 ac 0.5 ac* Southerly Edge of Parking Lot, and Toe of SRPS * Area reflects revetment placed to protect the beach parking lot and restroom.

XI. Environmental Permitting This section outlines the anticipated environmental technical reports (e.g., biological surveys and delineations), the anticipated environmental document (under CEQA and NEPA), and the anticipated permits for the EPB and SRPS projects.

Preliminary biological work was also performed in order to establish the current biological baseline conditions for listed species, and evaluate the effects of the various project alternatives on those species.

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A. Biological Baseline Habitat types within the EPB and/or SRPS project footprints include:

 emergent marsh (semi-permanent),  emergent marsh (seasonal),  ruderal grassland/scrub,  ruderal coastal dune,  coastal strand (SRPS project only),  coastal dune swale (SRPS project only), and  coastal dune scrub.

No rare or special status plants have been previously documented in the project footprint, and no suitable special status plant habitat has been identified, with the exception that the field/pasture located on Carmel Unified School District and Mission Ranch properties might provide suitable habitat for the Pacific Grove Clover.

In addition to special status plant species, natural communities are considered sensitive if they support vegetation alliances listed as sensitive on CDFW’s List of Vegetation Alliances and Association. Within the project footprint, the semi-permanent emergent marsh supports the Schoenoplectus californicus (California bulrush) Alliance, which is listed as a sensitive natural community by CDFW, with a global/state conservation status rank of G5 S4. California bulrush marsh at the Carmel River Lagoon represents an important occurrence of this habitat type in the region. The coastal dune scrub habitat supports the Artemisia californica (California sagebrush scrub) Alliance, which is listed as a sensitive natural community by CDFW, with a global/state conservation status rank of G5 S5. The occurrence of this habitat type in the project area is small with a fairly high level of disturbance.

Eight special status animal species have been documented within 5 miles of the project site, and of these, suitable habitat occurs at the project site for five species:

 California red-legged frog (CRLF)  South-Central California Coast steelhead Distinct Population Segment (SCCCS-DPS),  western pond turtle,  western snowy plover, and  Smith’s blue butterfly

B. Potential Biological Effects and Potential Mitigation Measures The potential effects of the EPB Project which have primary bearing on the project description are as follows:

1. Potential Effects to Wetlands and Other Waters of the US: a. Potential enhancement and increase in area of wetland habitats within the lagoon due to a reduction in the frequency of mechanical breaching, and potentially higher lagoon elevations and larger aerial extent of inundation. b. Temporary disturbance of wetland habitats (during construction). c. On-going disturbance of wetland habitats (due to maintenance activities). d. Permanent loss of wetland areas (due to placement of permanent fill). e. Alteration of existing hydrologic patterns on the lagoon side of the EPB resulting from collecting urban runoff behind the EPB, and discharging it at locations, rates, and volumes which differ from existing conditions. WE # 2487.01 & 2487.02 Carmel River Lagoon EPB and SRPS Projects Feasibility Study May 29, 2013 Page 25 of 43

f. Alteration of existing hydrologic patterns behind the EPB because urban runoff which currently flows into the lagoon would be detained behind the EPB, and because the lagoon, which currently is able to extend to the edge of the Fourth Addition neighborhood when the lagoon reaches its highest stages, would be limited by the alignment of the EPB. g. Loss of existing jurisdictional wetlands behind the EPB because the areas would be re-designated as “treatment BMPs” to enable long-term operation and maintenance of this component of the interior drainage system. 2. Potential Effects to the California Red-Legged Frog: a. Potential enhancement and increase in area of habitat due to increased statistical lagoon levels. b. Loss of habitat if vegetation is removed c. Long-term maintenance activities, such as clearing of vegetation, could cause injury, mortality, and disturbance of individuals, or destruction of habitat. d. If water is allowed to collect behind the EPB, this could attract frogs to breed; subsequently draining standing water out of the area could dry out egg masses, causing reproductive failure. 3. Potential Effects to the South-Central California Coast Steelhead DPS a. Potential benefit due to a reduction in the frequency of mechanical breaching, potentially higher lagoon elevations (water depths), and larger lagoon volumes.

Several potential mitigation measures were identified which could have significant effects on the project. These include:

1. Minimization of the amount of fill placed in wetland areas. 2. Conducting construction activities during the dry season. 3. Limiting the footprint of construction activities in sensitive areas. 4. Designing the interior drainage system to minimize the potential impact to red- legged frogs during draw-down of the stormwater detention area behind the EPB. 5. Conducting frog surveys prior to draw-down, to ensure that red-legged frogs or their egg masses are absent from these areas.

C. Biological Resources Permitting Summary Table XI-1, below, lists the biological permits anticipated to be required for the EPB and SRPS projects. Permits for impacts to other resources, such as air quality, cultural and historical resources, and hazardous materials, were not investigated.

Table XI-1. Anticipated Biological Permits and Compliance Agency Permit or Agreement US Army Corps of Engineers Section 404 or Section 10 permit, NEPA US Fish and Wildlife Service Section 7 consultation, possibly Incidental Take Statement National Marine Fisheries Service Section 7 consultation, possibly Incidental Take Statement California Department of Fish & Long Term Streambed Alteration Agreement, Wildlife, Region 4 possibly “Section 2081” Incidental Take Permit

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Agency Permit or Agreement Central Coast Regional Water 401 Certification, Construction General Permit Quality Control Board (stormwater) California Coastal Commission Coastal Development Permit County of Monterey CEQA/NEPA, consistency with Local Coastal Plan and draft General Plan Update

Further information can be found in H. T. Harvey & Associates’ memorandum, attached hereto.

D. NEPA and CEQA USACE is likely to be the Lead Agency under the National Environmental Policy Act (NEPA).

Monterey County is anticipated to be the Lead Agency under the California Environmental Quality Act (CEQA). Monterey County Planning Department anticipates a MND will be the CEQA document based on the potential effects on species, and other potential environmental impacts such as aesthetics and noise, and implementation of appropriate mitigation measures. (Personal communication, Carl Holm to Nathaniel Milam)

XII. Public Outreach A focused meeting was held on January 24, 2013 with Monterey County Department of Public Works personnel to discuss operation and maintenance (O&M) considerations related to the EPB. County personnel recommended that access for O&M activities such as routing painting, component repair/replacement, and graffiti removal be considered.

An informational meeting was held with representatives from NOAA National Marine Fisheries Service, US Fish and Wildlife Service, California Fish and Wildlife, the Central Coast Regional Water Pollution Control Board, California Coastal Commission, California State Parks, and the Army Corps of Engineers on January 31, 2013. This meeting focused on describing the technical work performed to date and outlining the project alternatives under consideration, for the purpose of beginning to discuss the priorities of the regulatory agencies and of State Parks, as the primary land owner. The primary priorities of the project regulators were minimization of fill placed in wetland areas; minimization of impacts to regulated habitats; and maximization of the lagoon’s ability to operation naturally. Additional State Parks priorities included compliance with applicable statutes regarding public land and resources, minimization of project impact on State Parks property, and avoidance of project elements which could enable adjacent landowners from expanding private yard areas onto State lands. State Parks also noted that if the project were to occur on State Parks property, legislative action may be required, including cost-neutrality to the State.

The project’s first general public meeting was held on March 25, 2013 at the Carmel River Elementary School. Monterey County presented the work completed on the EPB and SRPS projects to date, and received public comment. The public’s primary comments are summarized in the Public Comments Summary below.

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On March 26, 2013, special Community Service Area citizen advisory board meetings were held for CSA 1 and CSA 50. The public was also invited to attend. Similar to the March 25 meeting, the County presented the work completed on the EPB and SRPS projects to date, responded to questions from the CSA Boards, and took public comment. Comments were of a similar nature to comments received the previous day, though they were more focused on the upstream impacts to CSA 50. Commenters during the CSA 50 meeting noted that the project should have no significant flood impact on CSA 50, including the portion of CSA 50 which lies east of Highway 1.

The County’s PowerPoint presentation used in both the March 25 and March 26 meetings is attached as Appendix 3. The event sign-in sheets are also provided.

One follow-up meeting was held with Mission Ranch representatives Michael Waxer and Sue Carota on April 4, 2013. The main concern stated by Mission Ranch was the possibility that cessation of lagoon management could inundate portions of the sheep pasture, the lower parking lot, a lawn area, and walking paths near the “Quadplex” for extended periods of time, such as days or weeks, and potentially on a relatively frequent (e.g., annual) basis. Flooding of site features during an extreme (e.g., 10-year or 100-year) event did not seem to be as concerning, as such an event would not be a regular occurrence, and also because such peak lagoon levels have tended to last for only a few hours, and generally occur during inclement weather.

An additional concern was raised by M. Waxer was that historic/statistical lagoon levels may not be representative of the post-project condition, due to the historical lagoon management, and that therefore the effects of the project, and of cessation of lagoon management in particular, are unknown.

Monterey County also coordinated with the Carmel Area Wastewater District (CAWD) during the preparation of this Feasibility Study. Concerns raised by CAWD include: the project’s encroachment into the flood plain, and the potential effect on FEMA flood levels; potential increases in flood levels due to cessation of lagoon management; and potential increased groundwater levels. CAWD requested that the project be extended to include protection of the wastewater treatment plant.

Public comments were also received in writing. Copies of written comments received are included as Appendix 2. Significant comments are summarized and included in the Public Comment Summary below.

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Summary of Primary Public Comments

EPB Project: 1. Upstream Flooding Impacts: Commenters requested that potential upstream flooding impacts to the CAWD wastewater treatment plant, Mission Ranch, and Mission Fields be addressed. Commenters are concerned that the project could negatively affect flood levels. Response: Implementation of the EPB project itself is not anticipated to have any negative impact on flood levels, though cessation of breach management is anticipated to affect flood levels. A detailed evaluation of such effects is beyond the scope of this Study. Such a study would be performed as the project moves into the environmental permitting and preliminary design phase. 2. Consideration of No Build Alternative: One commenter requested that the project consider a “Multi-Species Management Option” (“No Build Alternative”), wherein a physical barrier is not constructed, but rather, the lagoon would continue to be managed by breaching, though at optimal times and in a manner that would least harm threatened species. Response: Comparison to other potential projects was not a part of this Study, but is anticipated to be part of preparation of the Environmental Document. 3. Comparison to Other Projects: Commenters noted that other projects have been discussed in the past, in addition to the EPB project. Commenters asked why these other projects were not included in the present work, and requested that the EPB project be compared to other projects. Response: See #2 above. 4. Visualization: Commenters requested that the County provide the relationship between the lagoon stage marker and the proposed EPB elevation, noting that this marker is a familiar standard for residents who live near the lagoon, also noting that the recent conversion from the NGVD29 datum to NAVD88 is confusing to some. Response: Mock-ups were constructed to represent each of the two EPB alignments and the 16’ and 19’ EPB elevations. 5. Visual Impact: Several of the Fourth Addition residents stated concerns about obstruction of their views out into the lagoon. Response: We recognize that visual impacts are a primary concern of many of the Fourth Addition residents, and have taken this into account in developing the Proposed Project presented herein.

SPRS Project: 1. Northerly Breach: Some commenters requested that the benefits of a northerly breach be evaluated, relative to other potential alignments (e.g., a direct westerly alignment, or a southerly alignment). Commenter noted that if the outlet channel is managed in a southerly direction, the SRPS project may not be needed. Response: This Study assumes that the outlet channel will not be managed after implementation of the EPB. Historically the channel has naturally, on occasion, meandered to a northerly alignment, hence the necessity for the SRPS. If the SRPS were not implemented, the outlet channel would need to be managed if and when it would migrate in a northerly direction. 2. Beach Access: Commenters indicated that coastal access is a community priority, and requested that the SRPS design consider coastal access. Commenters were concerned that coastal access, which is primarily via two staircases off Scenic Road

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and via the beach parking lot, will be significantly limited when the river is flowing along the face of the SRPS, and that after the sand has been removed from in front of the structure by river flows, the resulting vertical drop could also hinder access. Response: Maintaining and improving existing coastal access is one of the primary project considerations, and will be developed more fully as the project moves into the preliminary design phase in consultation with the community, State Parks, and the Coastal Commission. Currently it is assumed that all the existing access points will be maintained or improved. 3. Structural Design: Commenters questioned the structural robustness of SRPS Alternative #1 during extreme river flows and ocean surge events. Some commenters were concerned that extreme river flows could carry large debris which could damage the structure. Some commenters were also concerned that the “toe” of the SRPS might not extend to a low enough elevation, and that river flows could undermine the structure. Some commenters were concerned that the top elevation of SRPS Alternatives #1 and #2 may not be high enough to preclude the outflow channel from “getting behind” the structure and scouring out the support for Scenic Road and further damaging the beach parking lot. Response: The conceptual designs outlined in this Study are based on protecting Scenic Road and the beach parking lot during various extreme ocean and riverine scenarios. Commenters should also note that the designs outlined in this Study are conceptual, for the sole purposes of preliminary project scoping and developing project budgets. 4. Wave Run-Up: One commenter inquired if Alternatives 1 and 2 would protect Scenic Drive from ocean swell / wave run-up (in addition to river scour), and if the rip rap is sized to handle ocean waves. Commenter noted that they have seen waves run all the way up the bluff to Scenic Road. Commenter recommended raising the top of wall elevation to provide better protection to the bluff from wave action. Response: Wave run-up for Alternatives 1 and 2 would be addressed by planting the bluff above the SRPS. Based on available information, the project team does not believe that wave run-up poses a significant threat to the upper portions of the slope, and therefore the primary focus of the armoring is to protect the base of the bluff. 5. Extent of SRPS: One commenter inquired why the EPB wall and SRPS structures are not “tied together,” and asked if this would increase the risk that river flow might “get behind” the SRPS, and scour out the beach parking lot. Commenter suggested extending the SRPS to the EPB (or vice-versa). Commenters also asked that the SRPS Alternatives be extended an additional 400 feet, more or less, to protect the northern end of the beach. Commenters were concerned that the river might migrate around the northern “hooked” end of the SRPS, and threaten the portion of Scenic Road north of the SRPS. Response: The northerly and southerly extents of the conceptual alternatives developed as part of this Study were established based on available information and professional judgment; see response to SRPS Comment 3. If, as part of project design, it is determined that the SRPS needs to be extended farther to the north or south in order to provide the required level of protection, the SRPS will be extended. 6. Aesthetics: One commenter asserted that it is likely that the SRPS would be exposed, and thus visible, for a long time if the river were to scour the beach from in front of the structure, even for SRPS Alternatives 1 and 2. Commenter stated that exposed rock rip rap and/or an exposed sea wall would not be aesthetically acceptable.

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Response: SRPS Alternative 1 is the Proposed Project because it is believed to be the least visually impactful SRPS alternative. Based on available information, it is believed that SRPS Alternative 1 would be naturally re- covered by sand over the course of several months after a northerly breach; a more detailed evaluation is not possible at this time. Subsequent design- level work will need to be done to verify this. Mitigation measures are also planned to be implemented, and could include specifying rock which is aesthetically similar to the locally occurring rock, and providing retaining wall aesthetic treatments for SRPS Alternatives 2, 3, and 4. 7. Tree Impacts: Commenters inquired how each SRPS alternative would impact the two existing cypress trees on Scenic Road. Response: Impacts to the existing cypress trees are anticipated to be minimal for SRPS Alternatives 1 and 2. SPRS Alternatives 3 and 4 could have greater impacts on the trees, though these impacts have not been evaluated at this time. Impacts to trees will be avoided/minimized to the extent practicable.

XIII. Cost Preliminary Estimates of Probable Construction Cost were prepared for each of the project alternatives, and are summarized in Tables XIII-1 and XIII-2, below. Detailed preliminary cost estimates are provided in Appendix 1.

Table XIII-1. EPB Construction Cost Summary Preliminary Estimate of EPB Total Project Cost Estimate Probable Construction Cost Alternative (2018 Dollars) (2018 Dollars) Preferred $8M $15M Project 1A-16 $8M $15M 1A-19 $11M $20M 1B-16 $10M $19M 1B-19 $13M $24M 2A-16 $6M $11M 2A-19 $9M $17M 3A-19 +$4M +$8M 3B-19 +$4M +$8M

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Table XIII-2. SRPS Construction Cost Summary Preliminary Estimate of SRPS Total Project Cost Estimate Probable Construction Cost Alternative (2018 Dollars) (2018 Dollars) 1 (Preferred $0.8M $1.3M Project) 2 $2.9M $3.8M 3 $3.2M $4.1M 4 $8.8M $11.8M

XIV. Flooding Impacts The EPB and/or SPRS projects, in conjunction with cessation of lagoon management, are anticipated to affect the lagoon’s response to both flood and non-flood events, and as such, may have impacts on upstream developed areas. Metrics to evaluate flooding impacts to developed areas include peak lagoon levels during extreme events (e.g., the 10- and 100-year events); peak lagoon levels during non-extreme events (e.g., “typical” lagoon peaks); and duration of the various flood events. A full evaluation and discussion of these impacts is beyond the scope of this study; however, for the purposes of evaluating project feasibility, identifying potential project impacts, and of selecting a Proposed Project, this report provides:

 A quantitative analysis of the effects of the EPB during the 100-year design flood, using the currently-effective FEMA HEC-RAS model.  A summary of published information, and a qualitative evaluation of the potential effects of cessation of or reduction in lagoon management, in terms of flooding impacts on upstream developed areas.

The scope of this Study does not specifically consider effects of the SRPS Project on upstream developed areas and as such the discussion that follows focuses on the EPB project and breach management only. It is not anticipated that the SRPS Project will have any effect on upstream developed areas additional to those discussed in reference to the EPB and lagoon management.

A. FEMA 100-Year Flood Model The currently-effective FEMA HEC-RAS model was used to assess whether installation of the proposed EPB will negatively affect the FEMA 100-year base flood elevations adjacent to, upstream, and downstream of the project area. Flood impacts, if any, would result from the project slightly reducing the area available to convey flood flows moving through the lagoon area. Such flood impacts are expressed as an increase in flooding depth at a given location.

Two analyses were run: EPB Alignment #2, and EPB Alignment #2 in conjunction with EPB Extension #3A. These were chosen for the analysis because they extend farthest out into the lagoon, and as such, would have the more significant impacts of the alignment alternatives considered herein. The EPB’s elevation, whether 16’ or 19’, does not have an effect on the analysis results since the base flood elevations in the study area are below the top of wall elevation.

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Table XIV-1, below, summarizes the results of the analysis. The results indicate that all EPB alignments considered herein would have a less than significant impact on upstream and downstream flooding elevations.

Table XIV-1. Results of FEMA 100-Year HEC-RAS Computational Flood Model Location Calculated Impacts Calculated Impacts EPB Alt. 2A EPB Alt 2A + Ext. 3A Monte Verde Street 0.00’ 0.00’ Mission Ranch (at Quadplex building) 0.00’ 0.02’ Mission Fields 0.00’ 0.00’ CAWD WWTP (at westerly WWTP levee) 0.01’ 0.04’ CSA 50 0.00’ 0.00’

Detailed discussion of the modeling approach and results of the HEC-RAS analysis are provided in the attached technical memorandum (Balance Hydrologics, April, 2013).

This analysis, however, takes into account only the construction of the EPB project. It does not take into account cessation of or reduction in sand bar management, which may affect statistical lagoon elevations. This is outlined qualitatively in the section that follows.

B. Qualitative Evaluation of Cessation of or Reduction in Lagoon Management The dynamics which drive lagoon breaching are variable and are driven by a combination of ocean, river, and lagoon conditions, in addition to human intervention (James, 2005). Specific variables include:

 Ocean conditions o Tide o Surf . Swell height . Swell period . Swell direction o Sea level rise  River Flow o Peak flows resulting from storm events o Sustained multi-day flows, commonly less than 100 cfs  Subsurface (groundwater) flow into the lagoon  Subsurface flow out of the lagoon to the ocean  Sand bar geometry  Outlet channel geometry  Human activity

1. Historic Lagoon Management Limited information was available for this Study regarding historic breach management activities prior to 2009. In general, the managed breach elevation and the graded outlet channel length have both tended to increase over time, primarily in response to consultation with permitting agencies. Also, very significantly, there has recently been a shift away from mechanically opening a channel, toward leaving a sand plug which the lagoon is then allowed to overtop, which is believed to result in a preferable response from juvenile steelhead.

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Mechanical management entails grading an outflow channel from the lagoon to the ocean side of the barrier beach. The specifics have varied considerably from year to year. Also, subsequent to the initial breach of the season, the outlet channel may meander, sometimes very significantly. In the winters of 2010/2011, for example, the outlet channel, which began as a graded northwesterly channel, meandered to achieve a relatively long northerly alignment in late winter, then meandered to create a relatively long southerly- directed alignment, and then meandered back to a northerly alignment in the spring.

A direct, westerly-directed graded channel was generally favored until water year 2005 because it provided immediate flooding relief; though it also resulted in a rapid and near- total evacuation of the lagoon. (Water year is defined as October of the preceding calendar year, to September. Water year 2005 therefore extends from October of 2004 to September of 2005.) In January, 2005 a channel was graded along a previously untried north-northwesterly alignment at the urging of NOAA NMFS, with the intent of decreasing both the rate of lagoon draw-down and the total drop in lagoon level. The breach was considered to be a success, as the new, longer breach alignment was able to moderate the flow rate and total volume of draw-down. However, the channel scoured the base of the bluff supporting Scenic Road to the point that road stability was threatened. In 2010, the County again used the northerly alignment, with the result that river flows washed away a portion of the state beach parking lot and very significantly undermined the beach restroom building, leaving a scoured cut with a 10-foot drop from the edge of the parking lot pavement. Also, the bluff supporting Scenic Road was again threatened.

In early Fall 2011 Monterey County obtained an emergency permit to create a temporary sand ramp off Scenic road to replace access that was historically available from the State Parks parking lot

A southerly channel alignment has generally been used in recent years, and is preferred by Monterey County because:

 A northern channel alignment cannot be managed in high flows and as a result jeopardizes public infrastructure (based on historical actions).  It avoids access from the south that results in heavy equipment traversing through native buckwheat habitat and over sensitive cultural resources.  It allows for a relatively long outlet channel (relative to the direct, westerly outlet channel alignment), and the channel crosses a granite “sill”, which limits the channel’s down-cutting ability.  Mobilization and deployment of equipment can occur out of the State Beach parking lot.  Access remains to the majority of the beach from the parking lot, which is the primary access point for the public, for emergency personnel who need to gain access to the beach, and also for Monterey County Public Works equipment.

Until 2011, the graded channels were mechanically breached at the upstream (lagoon) end, at an elevation of approximately 10.7’, based on available information. Since 2011, however, a sand plug with a top elevation of approximately 12.7’ has been left in place at the upstream end of the channel, which the lagoon has been allowed to naturally overtop as lagoon levels increase. This revised approach, in addition to the relatively long southerly outflow channel alignment, is considered a significant improvement to historic breaching practices.

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Current management actions also include the annual installation and maintenance of a temporary sandbag barrier along the southern edge of the Fourth Addition neighborhood in order to provide a level of flood protection to the neighborhood, and minimize the mechanical management of the lagoon. The barrier is constructed to an elevation of approximately 15.7’, though there are significant limitations to the efficacy of this arrangement at lagoon levels above approximately 13.5’ elevation.

Under a draft Memorandum of Understanding between the County, USACE and NMFS (2012), which is anticipated to govern management activities until 2018, sand bar management is triggered at an actual lagoon elevation of 13.3’, or when river flows are expected to raise the lagoon water level to 12.7’ or more within 6 hours, or if tides or large ocean waves are predicted to cause significant wave wash-in.

2. Historic Lagoon Level Data Table XIV-2, below, summarizes the highest lagoon level for each water year from 1992 through present. The January 5, 2008 event is the highest on record (15.4’), with the January 24, 2001, January 11, 2000, and December 3, 2012 events being the second through fourth highest, respectively. A statistical summary is also provided. Important observations include:

1. The average annual maximum lagoon elevation of 12.8’ is approximately equivalent to the current managed breaching elevation. 2. Flooding of streets in the Fourth Addition neighborhood, which begins at approximately 13.5’ elevation, has occurred on average about once every 5 years. 3. For 13 of the 22 years of record, the maximum lagoon elevation for the year corresponded both to the first spike in lagoon level above 12’ elevation, and to a spike in river flow (caused by a storm event). These events also account for 10 of the 12 highest records. 4. In 8 of the 22 years, the annual maximum elevation occurs during the winter and springtime opening-and-closure cycle; this cycle generally occurs as long as flows are over approximately 100 cfs (James, 2005). 5. In one year the annual peak corresponded to the lagoon level reached after summer closure. 6. The river flows which caused extreme lagoon levels were relatively average. Results of Rich and Keller’s study (Rich and Keller, 2013) supports this observation: “At the 99% flow exceedence, it takes 12 hours to fill the [18’] high-berm estuary to breaching levels… Therefore, fairly common daily streamflow volumes are capable of breaching even the high-berm scenarios.” (pg 19-20)

3. Estimates of Natural Breaching Elevation Because the lagoon has been managed since at least the early 20th century, the lagoon’s natural breaching dynamics (e.g., elevation at breach, and outlet channel configuration) are, to an extent, unknown. Several previously developed estimates were reviewed in this Study. Future study is recommended.

A report by Curry (1984) is cited in the 1992 and 1999 PWA reports and the 2011 IRWM Work Plan. The original report was unavailable for this Study. The 1992 PWA report states that “Curry (1984) has estimated that absent human intervention, the lagoon would commonly

WE # 2487.01 & 2487.02 Carmel River Lagoon EPB and SRPS Projects Feasibility Study May 29, 2013 Page 35 of 43 rise to [14.2’ NAVD88] before breaking through the beach. This is based in part on the [14.5’ NAVD88] level reached in November, 1982, when the County Public Works Department failed to open the mouth.” It is unclear to what return frequency Curry was referring (whether to the average annual peak, or the 10-year, or the 100-year peak). We also note that subsequent to Curry’s study, the lagoon has peaked at 15.4’ elevation, one foot higher than the highest record available at the time of Curry’s study.

A lagoon breach model was developed by Rich and Keller (Rich and Keller, 2013) utilizing a beach berm elevation of 13.8’ based an evaluation of three years of historic lagoon data. “From three observations Carmel lagoon berm heights appear to vary from 4 – 5 m [13’ – 16’] NAVD88, though a dune formed in 2010 in the backbeach with elevations of 5.5 m [18’] NAVD88.” (pg 19)

The Draft Carmel Lagoon MOU reports that natural breaching is estimated to occur at an elevation of 15.8’ based on the lowest surveyed beach contour in March 1992 of 15.8’ NAVD88. The MOU also reports that “another estimate of natural breaching is 14.5’ NAVD88”, which was the peak lagoon level reached in November 1982, reported by Curry.

The project aerial topographic map (flown September, 2012) shows a beach crest elevation of approximately 14’, with the exception of the immediate vicinity of the previous year’s breach location. The low point at the previous year’s breach location is approximately 12’ elevation.

Sand bar surveys for the period 2001 – 2012 were also provided by the County for consideration in this Study. Ignoring the breached portion of beach (typically the southern end of the beach), the beach crest elevation generally is between 13’ and 15’. As was the case for the project topographic map, the actual low point on the beach is typically several feet lower than the general beach crest elevation, and corresponds to the location of the prior breach. The breach location also tended to occur on the narrow part of the beach. This reinforces statements made by County Public Works personnel that a primary driver of breaching location, and thus natural breaching dynamics, is the location of the previous breach.

Based on the prior estimates outlined above, and our review of historic beach berm topography, we estimate that the “natural” breach elevation could vary significantly by year, but generally may be expected to fall between 13’ and 16’ in elevation. This is a significant elevation range, and represents the very dynamic relationship between the lagoon, the river, and the ocean.

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Table XIV-2. Summary of Annual Peak Lagoon Water Surface Elevation, 1992 - 2013 Peak Lagoon Daily River Peak River WY Date Notes Elev (NAVD88)3 Flow (cfs)2 Flow (cfs)4 1992 Feb 11, 1992 11.8 452 S-F 1993 Feb 3, 1993 12.8 243 H-F 1994 Mar 27, 1994 12.2 21 L-C 1995 Jan 9, 1995 11.7 315 S-F 1996 Apr 13, 1996 12.6 133 H-C 1997 Dec 9, 1996 12.5 22 S-F 1998 Dec 8, 1997 13.3 165 L/H-C 1999 Jan 16, 1999 12.8 21 L-C 2000 Jan 24, 2000 14.1 1,240 S-F 2001 Jan 11, 2001 14.8 110 S-F 2002 Dec 3, 2001 13.6 289 625 S-F 2003 Dec 16, 2002 13.6 1,170 3,470 S-F 2004 Dec 30, 2003 13.3 240 S-F 2005 Dec 30, 2004 13.1 1,650 S-F 2006 Feb 10, 2006 12.9 56 L-C 2007 Apr 26, 2007 12.3 16 L-P 2008 Jan 5, 2008 15.4 436 4,800 S-F 2009 Feb 16, 2009 13.1 764 1,600 S-F 2010 Oct 14, 2009 13.3 682 5,100 S-F 2011 Dec 20, 2010 12.8 350 1,000 S-C 2012 Feb 20, 2012 13.1 20 40 L-C 2013 Dec 3, 2012 14.0 780 4,500 S-F 100-year 15.31 9,000 23,3001 10-year 14.01 3,900 9,8001 5-Year 13.4 3,300 Average 12.8 2,000

Notes: 1 From the Carmel River FIS – Coastal Analysis. 2 Daily river flow data from MPWMD records for gage at Highway 1 bridge. Daily quantiles calculated based on maximum annual daily flows for WY 1993 – 2012. 3 Peak lagoon elevation from MPWMD records 4 Instantaneous peak flow from USGS 11143200 (Robles del Rio station, 11 miles southeast of Carmel), multiplied by a factor of 1.3 to account for the smaller 193-ac drainage area at the Robles del Rio station, as compared to the project site’s 255-acre drainage area. L = Consistent multi-day flows less than 100 cfs preceded breach. H = Consistent multi-day flows greater than100 cfs preceded breach. S = Lagoon level peaks sharply; corresponds to a peak in river flow (storm event) -F = First event of the season which causes lagoon to rise to above ~12’ elev -C = Occurs during the wintertime cyclical breaching regime -P = Occurs post-summer closure

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4. Ocean Conditions (Tide and Surf) Ocean conditions (tide and surf) are anticipated to be the primary drivers of extreme lagoon levels (e.g., the 100-year event), based on an analysis and discussion of 14 years of data (October 1, 1991 to September 30, 2005) provided in MPWMD’s Technical Memorandum 05-01 (James, 2005). The primary numeric tool the report used to evaluate ocean conditions is the Coastal Flood Index (CFI). The index “assesses flooding potential and magnitude on oceanic coasts due to high surf and tides.” CFI is calculated using wave height, wave period, and tide, with higher values of CFI resulting from a combination of high tide and high surf. CFI does not take into account coastal geometry or swell direction, and therefore these factors must be qualitatively taken into account. High-CFI value ocean conditions with swells from the west (as opposed to the more frequently observed north- west swell) are estimated to produce the highest elevation in the Carmel River Lagoon.

CFI values in the range of 14 to 15 “have occasionally resulted in major wave in-wash, moderate coastal flooding, beach erosion, and property damage.” (James, 2005) Only two events in the 14 year period of study resulted in CFI values above 15 (on January 11, 2001, CFI = 17, lagoon peaked at 14.8’, and on November 8, 2002, CFI = 16, lagoon peaked at 11.5’). James notes that “artificial breaches at high tide tend to be ineffective at draining the lagoon due to the lack of lagoon-ocean gradient.”

5. Sea Level Rise Sea level rise (SLR) is an additional factor which will need to be addressed in the project planning and design. Specific recommendations from the State of California Sea-Level Rise Interim Guidance Document (2010, pgs 3-4) include:

 Use the ranges of SLR presented in the December 2009 Proceedings of National Academy of Sciences publication by Vermeer and Rahmstorf as a starting place and select SLR values based on agency and context‐specific considerations of risk tolerance and adaptive capacity.  Consider timeframes, adaptive capacity, and risk tolerance when selecting estimates of SLR.

The recommended sea level rise projections by Vermeer and Rahmstorf (using year 2000 as a baseline) are as follows:

Table XIV-3. Vermeer and Rahmstorf SLR Estimates Year Average of Models Range of Models 2030 7 in. 5 – 8 in. 2050 14 in. 10 – 17 in. Low 23 in. 17 – 27 in. 2070 Medium 24 in. 18 – 29 in. High 27 in. 20 – 32 in. Low 40 in. 31 – 50 in 2100 Medium 47 in. 37 – 60 in. High 55 in. 43 – 69 in.

The National Research Council in 2012 released an in-depth study of sea level rise and its implications focused specifically on the coasts of California, Oregon and Washington. The

WE # 2487.01 & 2487.02 Carmel River Lagoon EPB and SRPS Projects Feasibility Study May 29, 2013 Page 38 of 43 projected sea level rise for San Francisco for the year 2050 (using 2000 as a baseline) is 11 inches ±4 inches, with total range of estimates of 5 to 24 inches. (National Research Council, pg 96) A graphic showing the Council’s projected sea level rise to the year 2100 is provided in Figure XIV-1 below.

Figure XIV-1. Range of projections of global sea level rise (National Research Council, 2012).

The National Research Council’s study also notes that “changes in regional meteorological and climate patterns, including El Niños, coupled with rising sea level, are predicted to result in increasing extremes in sea levels. Models suggest that sea-level extremes will become more common by the end of the 21st century. Waves riding on these higher water levels will cause increased coastal damage and erosion—more than that expected by sea-level rise alone.” (ibid, pg 107)

The California Adaptive Planning Guide: Defining Local and Regional Impacts (2012) mirrors this statement: “The combination of SLR and potential increased storm frequency and severity is problematic: “Most severe impacts result from the coincidence of sea level rise with storm surge, tides, and other climatic fluctuations (like El Niño)” (CEC, 2009, p. 49).” (pg 28)

An EPB project design life of 50 years is utilized in this Study and an increase in ocean levels of 0.5 to 2 feet is therefore anticipated over the life of the project. For the purposes of this study, this increase is assumed to translate to an approximately parallel increase in statistical lagoon levels of 0.5 to 2 feet.

Due to project constraints (namely, impacting the existing views of residents of homes along the lagoon) it is anticipated that an EPB elevation which would accommodate the upper limits of sea level rise predictions would not be supported by the community, and could potentially face significant opposition. We recommend that the project proponent plan for as much SLR as can feasibly be accommodated within the EPB project.

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The SRPS project is less constrained than the EPB project, and can likely provide for a larger estimate of SLR, in combination with increased extreme event amplitude. Planning for SLR is also more important for the SPRS, as there is no option to mechanically reduce ocean extremes, as there is with the lagoon.

6. EPB Freeboard Considerations Freeboard is the designated “factor of safety” a flood-control facility employs against overtopping during various design events, to account for uncertainty inherent in computational models and meteorological forecasts. Typically 1’ to 2’ above the peak anticipated water level would be used for this type of facility if FEMA certification were not desired, and 3’ to 4’ if FEMA certification were desired.

Due to the stated concern of Fourth Addition residents for protecting their existing views of the lagoon, it may not be possible to provide a typical freeboard value in conjunction with sea level rise estimates.

Accommodating for both SLR and freeboard have a relatively small incremental cost as compared to the total project cost. It is therefore recommended that the County pursue the greatest EPB elevation which can feasibly be accomplished, as this would provide the most favorable cost-to-benefit calculation.

7. Lagoon Stage-Volume-Area Relationship, and Summer Lagoon Levels The attached Lagoon Stage-Volume-Area Analysis Memorandum analyzes and reports the relationship between the lagoon’s stage (water surface elevation), and its volume and surface area. These relationships may be used for flow routing analyses, which would be necessary if an evaluation of peak lagoon levels is needed during various barrier beach, riverine flow, and ocean conditions. The lagoon’s stage-volume-area relationship may also be used in the evaluation of project habitat impacts and benefits. Both of these additional analyses/evaluations are beyond the scope of this Study.

Since 2006, summer lagoon levels have been managed through early, mechanical closure of the lagoon outflow channel. These actions have been performed by Monterey County under the direction of NOAA NMFS. There are only seven years of data are available, but this early data indicates that the peak summer lagoon level has increased significantly as a result of management of the summer closure (by an average of 1.4’, from 9.4’ pre-2006, to 10.8’ post-2006).

Under the Draft Carmel Lagoon MOU, for the 5-year period under the MOU “the goal will be to maximize the lagoon water level up to a maximum elevation of 12.77’. A larger, deeper lagoon during the summer/fall period increases the quality and quantity of fish and wildlife habitat.” (Monterey County et al, 2013, pg 14) After installation of the EPB and SRPS projects, it is unknown if managed summer lagoon closures will continue, and if they do, who will carry them out.

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Table XIV-4. Summary of Historic Peak Summer Lagoon Level by Year Date Elevation Jun-96 9.8’ May-97 9.8’ Sep-98 8.9’ Jul-99 10.5’ Jun-00 8.7’ Jun-01 9.8’ Jun-02 10’ Jul-03 7.7’ May-04 9.9’ Jul-05 8.6’ Jul-06 10.2’ Apr-07 12.2’ May-08 11’ Jun-09 11.3’ Jul-10 10.2’ Aug-11 9.7’ Jun-12 10.7’ Maximum 12.2’ 3rd Quartile 10.6’ Average 9.9’ 1st Quartile 9.3’ Minimum 7.7’

8. Conclusion Different management results are anticipated for each EPB elevation alternative. It is anticipated that for the 16’ EPB elevation alternative, occasional grading of the sand bar will be required to protect against EPB overtopping, even ignoring the anticipated effects of sea level rise. The frequency of grading is unknown at this time, but it may not be infrequent enough to be performed under “emergency” conditions. Significant increases in “typical” lagoon levels, however, are anticipated to be realized. Sand bar management would likely need to occur between 14’ and 15’ elevation in order to limit lagoon levels to a design elevation of 15’. In this scenario sand bar surveys would need to be performed frequently during the winter and early spring months, with beach grading occurring when the beach berm elevation exceeds calculated limits based on forecast ocean, river, and lagoon conditions. Grading operations would generally occur prior to significant forecasted river flows and/or arrival of high ocean surf. Sea level rise is not addressed in this alternative.

The frequency of anticipated sandbar management drops off significantly with increased EPB elevation. The preferred 17.5’ EPB elevation may not completely remove the need for breach management (e.g., during extreme conditions when considering sea level rise over the life of the structure), though the frequency of beach grading will likely be significantly improved as compared both to existing conditions and to the 16’ EPB elevation alternative. WE # 2487.01 & 2487.02 Carmel River Lagoon EPB and SRPS Projects Feasibility Study May 29, 2013 Page 41 of 43

Estimation of the probable frequency of breach management for the 17.5’ EPB elevation alternative is beyond the scope of this Study.1

The 19’ EPB elevation alternative would likely eliminate the need for breach management. It would also provide freeboard during the design event, and anticipates an increase in lagoon levels due to future sea level rise. It is anticipated, however, that this alternative is likely infeasible due to its significant visual impact.

In conjunction with the design of the EPB, the County will need to develop updated lagoon management protocols to preclude both overtopping of the newly implemented barrier, as well as flooding of other facilities, most notably the CAWD WWTP, during various scenarios. For the 16’ EPB alternative, protection against EPB overtopping is anticipated to trigger lagoon management at between 14’ and 15’ elevation. For the 17.5’ EPB alternative, maximum allowable lagoon level would likely be similar for both the CAWD WWTP and the EPB.

1 A specific design-level analysis and quantification of the relationships outlined above is outside the scope of this Study. If the County pursues the EPB project, a subsequent study should evaluate these relationships during various riverine and coastal scenarios given various breach elevations and configurations, and considering potential sea level rise. This follow-up study would develop the basis for managed breaching to occur after implementation of the EPB project, considering the level of risk the managing agency is willing to accept for various ocean, river, and lagoon conditions and considering various outcome scenarios (e.g., EPB overtopping, or flooding the CAWD WWTP). WE # 2487.01 & 2487.02 Carmel River Lagoon EPB and SRPS Projects Feasibility Study May 29, 2013 Page 42 of 43

References A. A. Rich and Associates. (2005). Letter report to Mr. Dick Butler, NMFS. Carmel River Lagoon Mechanical Breaching – Steelhead Issues. California Emergency Management Agency, et al. (2012). California Adaptive Planning Guide: Defining Local and Regional Impacts. California Energy Commission and Scripps Institution of Oceanography. (2012) Climate Change and Sea Level Rise Scenarios for California Vulnerability and Adaptation Assessment. CEC‐500‐2012‐008. Carmel River Technical Advisory Committee. (2007). Final Study Plan for Long Term Adaptive Management of the Carmel River State Beach and Lagoon. Casagrande, Joel. (2006). Report: Wetland Habitat Types of the Carmel River Lagoon. The Watershed Institute, California State University Monterey Bay. County of Monterey, U.S. Army Corps of Engineers, & National Marine Fisheries Service. (2012). Memorandum of Understanding regarding Flood Prevention and Habitat Protection at the Carmel Lagoon. Curry, R.R. (1984). Hydrologic, historical and soils report, Mission Ranch site, Carmel, California. Unpublished report to the City of Carmel Planning Department. (Unavailable for this Report.) James, G. W. (2005). Monterey Peninsula Water Management District, Technical Memorandum 05-01: Surface Water Dynamics at the Carmel River Lagoon, Water Years 1991 through 2005. Kraus, N. C., Patsch, K., & Munger, S. (2008). Barrier beach breaching from the lagoon side, with reference to Northern California. Shore and Beach, 76(2), 33–43. National Research Council. (2012). Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future. Washington, DC: The National Academies Press. Northwest Hydraulic Consultants (NHC). (2006). Carmel River Flood Insurance Study, Coastal Flooding Analysis. Northwest Hydraulic Consultants (NHC). (2006). Carmel River Hydraulic Analyses, Monterey County, California, Unincorporated Areas and Carmel by the Sea, California. Prepared for FEMA. Philip Williams & Associates, Ltd. (1992) Carmel River Lagoon Enhancement Plan. PWA Ref. # 509 Philip Williams & Associates, Ltd. (1999) Carmel River Lagoon: Enhancement and Management Plan: Conceptual Design Report. PWA Ref. # 1250 Philip Williams & Associates, Ltd. (2002) Lower Carmel River Flood Control Project Final Report, prepared for Monterey County Water Resources Agency. August 9. PWA Ref. # 1526 Philip Williams & Associates, Ltd. (2007) Supplemental Carmel River Watershed Action Plan. Report prepared for the Planning and Conservation League Foundation. PWA Ref. # 1806.00. March 2007. Rich, A., & Keller, E. A. (2013). A Hydrologic and Geomorphic Model of Estuary Breaching and Closure. in review

WE # 2487.01 & 2487.02 Carmel River Lagoon EPB and SRPS Projects Feasibility Study May 29, 2013 Page 43 of 43

RMC Water and Environment. (2007). Hydrographic Survey and Stage-Volume Relationship. November 29. Sea‐Level Rise Task Force of the Coastal and Ocean Working Group of the California Climate Action Team (CO‐CAT). (2010). State of California Sea-Level Rise Interim Guidance Document. Thornton, E. B. (2005). Littoral Processes and River Breachings at Carmel River Beach. Naval Postgraduate School, Monterey, CA Thornton, E. B. (2006). Carmel River Beach Shoreline History. Naval Postgraduate School, Monterey, CA. April 9.

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