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Home My WebLink About3307; CARLSBAD BLVD SHORE PROTECTION; FEASIBILITY STUDY; 1984-11-01FEASIBILITY STUDY CARLSBAD BOULEVARD SHORE PROTECTION CARLSBAD BEACH STATE PARK FOR THE City of Carlsbad by Woodward-Clyde Consultants November 1984 Project No. 54268E-0002 Woodward-Clyde Consultants TABLE OF CONTENTS Page INTRODUCTION GENERAL SITE CONDITIONS 3 Surface Conditions 3 Bluff and Beach Conditions 4 Geologic and Groundwater Conditions 5 Bluff Erosion 6 Tide, Wind and Wave Climate 8 STATEMENT OF PROBLEM 10 PRELIMINARY ENGINEERING DESIGN CRITERIA 15 PROPOSED PRELIMINARY DESIGN 16 ECONOMIC CONSIDERATION 18 Construction Cost Estimate 18 Maintenance Cost Estimate 19 Benefit Estimate 20 Benefit Cost Ratio 21 REFERENCES 22 FIGURES Location Map Site Plan and Location Pictures at Hemlock and Tamarack Avenues Pictures at Ocean Street and Juniper Avenue Bluff Profiles - Tamarack and Hemlock Avenues Bluff Profiles - Acacia and Chestnut Avenues Profiles - Walnut Avenue and Ocean Street Conceptual Design Section - Riprap Revetment Conceptual Design Section - Reinforced Earth Concrete Seawall Conceptual Design Section - Cribwall APPENDIXES: A. GEOLOGIC INVESTIGATION Field and Office Investigation A-i Geologic Setting A-i Geologic Units and Erosion Characteristics A-2 Geologic Structure A-3 Woodward-Clyde Consultants TABLE OF CONTENTS (CONT.) Page APPENDIXES (CONT.)': GEOLOGIC INVESTIGATION (CONT.) Ground Water Conditions A-3 Seismicity and Faulting A-4 Bluff Erosion and Slope Stability A-4 COASTAL DATA AND ENGINEERING DESIGN CALCULATIONS Evaluate Deepwater Wave B-i Check Largest Wave That Will Break on Seawall B-3 Design of Stone B-4 Wave Run-up B-4 BENEFIT CALCULATIONS Loss of Property C-i Loss of Beach User Benefits C-i Loss of Bicycle Lane Use C-i Traffic Reduction Costs C-2 Facility Replacement Costs C-2 U Woodward. Clyde Consultants FEASIBILITY STUDY CARLSBAD BOULEVARD SHORE PROTECTION CARLSBAD BEACH STATE PARK CARLSBAD, CALIFORNIA INTRODUCTION The subject portion of Carlsbad Beach State Park is approximately 4500 feet long and generally located along the coast between Oak Street and the entrance to Agua Hedionda Lagoon in the City of Carlsbad, California (See Figure No. 1). It is bounded by Carlsbad Boulevard and Ocean Street on the east and the Pacific Ocean on the west. A 20 to 40 foot high bluff is situated between Carlsbad Boulevard and the beach .Carlsbad Boulevard is a main thoroughfare along the Pacific Coast in the City of Carlsbad (See Figure No. 2). For a couple of miles, Carlsbad Boulevard runs parallel with and adjacent to Carlsbad State Beach and is the primary access to the beach in this area. Carlsbad Boulevard is also the only roadway west of Interstate Highway 5 to cross Agua Hedionda Lagoon. Therefore, it not only carries a large amount of north-south traffic, but also has all the area's major utilities buried beneath the roadway. In the subject area, approximately 3,500 feet of roadway with the included utilities is constructed on a 30 to 40 foot high bluff of relatively easily eroded sandy terrace deposit which backs the beach from Pine Avenue to Sequoia Avenue (See Pictures - Figures Nos. 3 and 4). At the south end, the Boulevard drops down in a length of about 500 feet to an elevation of approximately +20 feet at the bridge across the inlet to Agua Hedionda Lagoon. At the north end of the project Ocean Street extends along the bluff top for about 500 feet between Pine and Oak Avenues. The beach here is historically thin and narrow. Almost every year the winter storms strip away the thin layer of sand, leaving a discontinuous layer of cobbles over the wave cut bedrock platform. Then the spring and summer swells rebuild the beach with another thin layer of new sand. During the more severe winter storms, the large waves rush across the cobble beach and attack and undercut the upper portion of the bluff. Project No. 54268E-0002 Woodward-Clyde Consultants During the storms of 1983, a few areas of the bluff eroded back to the edge of the roadway requiring the City of Carlsbad to make emergency repairs in the most critical areas. Due to the exposure to storm waves along this stretch of shoreline, •and the easily erodible characteristic of the bluff, continuing erosion is inevitable without construction of some type of shoreline protection. Ma Project No. 54268E-0002 Woodward-Clyde Consultants GENERAL SITE CONDITIONS Surface Conditions North of Agua Hedionda Lagoon, Carlsbad Boulevard extends generally parallel to and along the top of the bluff above Carlsbad Beach State Park. The boulevard is generally set back from the bluff edge distances varying between as little as 2 feet to as much as 50 feet. Public parking is available along the west side of Carlsbad Avenue between Tamarack and Cherry Avenue. At the intersection of Pine Avenue, Carlsbad Boulevard turns inland away from the coastal bluffs. At this point, Ocean Street continues northerly adjacent to the bluff top. Parking is also available along Ocean Street. Private homes have been built- along the top of the bluff north of Oak Avenue. At the south end of the study area, two parallel rock jetties extend seaward about 200 feet from the mouth of Agua Hedionda Lagoon. A paved public parking area is located north of the jetties and generally south of Tamarack Avenue. The parking area includes approximately 2 acres and is located generally west of and below Carlsbad Boulevard along the toe of the bluff. Grading for the parking area apparently consisted of placing fill from the back beach area, adjacent to the toe of the bluff, out to near the end of the jetties. This resulted in a relatively level pad several feet above the elevation of the beach. Some rock riprap has been placed along the seaward limits of the northern portion of the parking area as a means of temporary slope protection. The riprap generally consists of a single layer of 2 to 4 ton stone placed upon a cobble berm. A local park area, which extends along a portion of the top of the bluffs, consists of a landscaped picnic area with a concrete walkway leading generally through the picnic area and along the top of the bluff. This park extends from south of Tamarack Avenue north to approximately Cherry Avenue. The landscaping includes trees, grassy areas, picnic tables and a low wooden railing along the top of the bluff. A public restroom is located near the top -3- Project No. 54268E-0002 Woodward-Clyde Consultants of the bluff near Tamarack Avenue. Public beach access stairways, which lead down from the top of the bluff, are located at the restroom facility (Tamarack Avenue) and across from Cherry Avenue. A vehicular beach access ramp is also located near the north end of the park at Ocean Street. Beach access is also available at the parking lot at the south end of the park. The public access at Cherry Avenue consists of a concrete stairway elevated several feet above the bluff by columns and pier foundations. The stairway was originally located adjacent to a second public restroom located at beach level. During the winter storms of 1983, this restroom, and the lower stairway landing were heavily damaged by storm waves and were subsequently demolished and removed. Portions of the concrete-slab foundations below the old restroom area remain in place on the beach. The stairway landing has been repaired and replaced with a wooden structure. A portion of the natural slope below the upper landing has been rebuilt with stacked sand-filled sacks. Drain pipes are located upon the bluff at many locations. Several of the pipes lead down from storm drains and man-holes located along Carlsbad Boulevard to concrete box culverts built at the toe of the bluff. Other pipes collect surface water run off from along Carlsbad Boulevard and adjacent areas. It is our understanding that these pipes are to be relocated and surface water runoff diverted away from the bluffs , as part of a future improvement project. Bluff and Beach Conditions The coastal bluffs along Carlsbad Beach generally rise between 30 to 40 feet above the beach. Elevations along the top of the bluff range from about 40 to 50 feet above sea level (Mean Sea Level Datum). Gullies and deep ravines are developed nearly continuously along the face of the bluff. Many of the wider, more extensively gullied areas extend -from the beach level up to the top of the bluff. The upper portions of many of the deeper gullies and ravines have been partially filled with material dumped from the top of the bluff. The materials used for the dumped fill include concrete and asphalt p rubble. -4- Project No. 54268E-0002 Woodward-Clyde Consultants As part of this study, topographic profiles of the coastal bluffs were surveyed at the six locations, shown on Figure 2. The results of the topographic profiles are shown as Figures 5, 6 and 7. Typical bluff inclinations range from about 1:1 to 2:1 (horizontal to vertical) with localized steeper and flatter areas. In general, the steepest portion of the bluffs lies along the toe of the bluff at the back edge of the beach. Along much of the area, a relatively flat sandstone ledge which is typically 15 to 20 feet wide is exposed along the base of the bluff. Much of the bluff face is barren; vegetation along the bluff consists of scattered patches of iceplant and native grasses with locally dense stands of bamboo. The beach along the base of the bluffs is typically about 100 to 150 feet wide. Abundant cobbles form a low berm several tens of feet wide along the back edge of the beach. Seasonal variations in longshore drift, wave height and wave frequency result in varying beach levels and volumes of sand. The slope of the beach generally ranges from approximately 12:1 to 10:1 where sand is predominant and 6:1 to 5:1 where cobbles are predominant. Recent profile measurements by Scripps Institution of Oceanography indicate that the bottom slope starting at approximately 100 to 150 feet offshore is about 40:1 or flatter. Geologic and Groundwater Conditions The upper portion of the coastal bluffs along Carlsbad Beach State Park are composed of Late Pleistocene marine deposits. These sediments generally consist of soft, friable fine-to coarse-grained sand. The Pleistocene sediments were deposited upon a wave-cut platform (marine terrace) that was cut during a high stand of sea level estimated at about 85,000 to 120,000 years ago. The Pleistocene deposits are underlain by Eocene marine sandstone of the Santiago Formation. The sediments comprising this formation are indurated and generally well-cemented. The sandstone is exposed as a resistant ledge along the toe of the coastal bluffs. The contact between the Eocene sandstone and the overlying Pleistocene sand generally lies at elevations ranging from about +6 to +11 along the toe of the bluffs and dips -5- Project No. 54268E-0002 Woodward-Clyde Consultants down to as low as -3 feet at the south end of the study area (near Tamarack Avenue). Bedding within both geologic units is essentially horizontal. The slope of the sandstone under the beach is estimated to be on the order of 10:1 to 7:1. A perched ground water table typically occurs at the •contact between the Pleistocene deposits and the Santiago Formation. This conditions is common along the north San Diego County coastline. Abundant ground water seepage was noted at many locations along the toe of the bluff within the study area. The source of the ground water is thought to be primarily surface water introduced locally as rainfall and irrigation that percolates into the permeable terrace sands. When the ground water reaches the relatively impermeable Santiago Formation, it flows laterally along the seaward-sloping contact until it reaches the bluff face. A line of vegetation commonly grows at this point on the bluff. A more detailed Geologic report is presented in Appendix A. Bluff Erosion The coastal bluffs along Carlsbad Beach State Park appear to be actively eroding at variable rates as a result of several erosional processes. Active erosion is indicated by such features as steep near vertical slopes at the toe of the bluffs, lack of vegetation in areas along the bluff face, lack of talus and material eroded from the bluff face, and the presence of erosion gullies along the bluff face. It appears that the most significant erosion of the bluffs occurs chiefly by wave action during high tides and storms. The Pleistocene sand exposed in the upper portions of the coastal bluffs is friable and weakly cemented and is subsequently easily eroded by high wave action. Undercutting along the toe of the bluffs results in near vertical exposures of the sand. These steep faces are only marginally stable and quickly slough back to a less steep slope inclination. Comparison of old topographic maps with current profiles indicates that up to 10 to 15 feet of erosion has taken place along portions of the bluff during the past ten years. -6- Project No. 54268E-0002 Woodward-Clyde Consultants Perhaps the most dramatic recent bluff erosion occurred during the winter storms of 1983 (see cover photograph). During this period, very rapid coastal erosion coincided with spring tide conditions and a ten- to twelve-foot swell coupled with extremely strong winds. At Carlsbad State Beach, two bathhouses were undermined and submerged, the lower foundation of a main stairway was lost and the •parking lot south of Tamarack Avenue was undermined. Portions of Carlsbad Boulevard, both adjacent to Carlsbad Beach State Park and the Encino Power Plant were severely damaged and collapsed in places during this storm. Carlsbad Boulevard was closed due to flooding. To the south, at South Carlsbad State Beach, the coastal bluffs were reported to have retreated by as much as 15 to 20 feet in a single storm (Kuhn and Shepard, 1984). Locally, two areas of the upper bluff adjacent to Carlsbad . Avenue have required fairly extensive temporary slope repair. This slope rebuilding was required in 1983 along two approximately 50 foot wide stretches of the bluffs west of Walnut Avenue and Acacia Avenue. This temporary slope repair generally consisted of rebuilding the slope by placing a fill slope down to the level of the beach, and using riprap to protect the toe of the fill slope. Jute netting was laid upon the slope to retard surface water erosion. It is estimated that the cost of this and other associated temporary remedial work along this stretch of beach was in excess of $100,000. Surface water runoff also contributes to erosion of the upper bluffs. Much of the upper bluff is extensively gullied and rilled. Several drain, pipes from storm drain inlets located along. Carlsbad Boulevard empty surface water onto the bluffs. Some of the storm drains supports also appear to be partially undermined. At South Carlsbad Beach State Park, severe erosion of the bluff face, on the order of several tens of feet back from the bluff edge, resulted following the collapse of a similar drain pipe. Pedestrian traffic also appears be contributing to the erosion of the upper bluff areas as many foot paths are present across the bluffs. Localized areas of the upper bluff are also affected by animal burrowing. -7- Project No. 54268E-0002 Woodward-Clyde Consultants Tide, Wind and Wave Climate Tides in the study area vary over a maximum 9 to 10 foot range; the highest astronomical tide for the vicinity being approximately 4.9 feet (MSL Datum). There are two high and two low tides each day with approximately 6 hours between each high and low tide. The mean tide range is 3.8 feet and the diurinal range is 5.3 feet. Winds are predominantly from the northwest throughout the year, with wind velocities averaging from 5 to 10 miles per hour. Storms moving in from the Pacific Ocean occasionally bring somewhat stronger winds but the duration is relatively short. Tropical cyclones from the south reach the area on rare occasions. Extreme sustained wind speeds approaching 50 knots are expected off the southern California coast below 35 degrees latitude statistically once in a 100 years (NOAA, 1980). Waves reach the study area from both the southern and northern hemispheres. Waves from the south are low, typically less than 3 feet, and occur quite frequently during the summer months. The primary source of waves is from the northern swell, with periods of 6 to 12 seconds and onshore directions of northwest to west. Large waves can be expected to arrive at any time during the year and to continue for three to four days at a time. These high wave episodes are often not associated with local storms. Waves 12 to 15 feet in height have been observed on occasion and breakers with estimated heights of 15 to 20 feet have been observed off the coastline. Maximum wave heights observed along the San Diego County coast during the storms in January and February of 1983 were on the order of 6 to 12 feet with wave periods of 5 to 9 seconds. Carlsbad Beach is exposed to wave action from the south through northwest. The outer islands, as well as the Cortez and Tanner Banks tend to shelter the coastline from long period waves. Deepwater waves unaffected by island -8- Project No. 54268E-0002 Woodward-Clyde Consultants interference, only arrive from the southwest between Cortez Banks and the Los Coronados Islands. A study of tsunamis in San Diego County, conducted for the Office of Civil Defense in 1968, indicated that the relatively wide continental shelf and borderland has acted as an effective diffuser and reflector of energy that arrives from remotely generated tsunamis. Only two or three locally generated tsumanis, none of which reached the San Diego County Area, are known to have occurred off southern California since 1800. -9- Project No. 54268E-0002 Woodward-Clyde Consultants STATEMENT OF PROBLEM The western edge of Carlsbad Boulevard, between Cherry Avenue and Pine Avenue, is generally located within several feet of the top of the coastal bluffs. Several stretches of this portion of the bluff have recently required fairly extensive slope repair in order to prevent the roadway from becoming undermined. In the event of severe storm conditions and accompanying high waves, it is apparent that the existing roadway and utilities along this stretch of the park are in danger of being undermined. The toe of the bluff slope along this stretch of Carlsbad Boulevard is completely exposed to winter storm waves when the narrow beach is eroded. Progressive undercutting of the bluff by waves and slope sloughing will continue and increase in magnitude until the coastal bluff, which forms a buffer zone between the beach and Carlsbad Boulevard, has been eroded away and the roadway has started to collapse. If this bluff retreat is allowed to continue, heavy losses to public property may result along with loss of utility services to a large area and loss of vehicular access to a considerable length of beach. North-south through traffic would also be completely disrupted causing distress to many businesses located along Carlsbad Boulevard. The portion of Carlsbad Boulevard south of Cherry Avenue and north of Tamarack Avenue appears to be in a relatively more favorable location with respect to potential distress resulting from bluff erosion or collapse, as the roadway in this area is generally set back several tens of feet from the top of the bluff. It is anticipated that the public parking area, and possibly the paved access road below Tamarack Avenue, will require a more substantial means of shore protection than is currently in place. The western edge of Ocean Street at the north end of the project between Pine Avenue and Oak Avenue is also relatively close to the top of the bluff and may be subject to undermining due to erosion. -10- Project No. 54268E-0002 Woodward-Clyde Consultants CONSIDERATIONS OF POSSIBLE SOLUTIONS Several alternatives to constructing shore protection structures are possible. One alternative would be to do nothing, in which case, continued bluff erosion would be expected to occur. The rate and degree of such erosion would be dependent upon the severity of future storms. At the present, it is estimated that the average rate of erosion is on the order of 1 to 1.5 feet per year with local variations. It is estimated that possibly within several years, portions of Carlsbad Boulevard may be unuseable and the utilities would have to be relocated. Another alternative would be to relocate Carlsbad Boulevard and all utilities further east or to make Garfield Street the main street and to relocate utilities along Garfield Street. This solution would require the City of Carlsbad to obtain ownership of portions of land east of Carlsbad Boulevard. Neither of these options are consistent with the general plan for this area and complete relocation of street and utilities is not considered economically feasible. Beach nourishment or offshore protection are also possible alternate considerations. The Army Corps of Engineers suggested several alternatives for stabilizing and maintaining sand as a protective buffering beach at Oceanside. These measures included rock revetments, groin systems, sand fills, breakwaters, and a permanent sand by-pass system. Only the sand fill program has been attempted to date and was only temporarily successful. However, a sand by-pass is currently being designed for Oceanside harbor entrance to provide a continuous sand replenishment system. It is possible that the sand replenishment program may also provide an additional source of sand along Carlsbad's beaches. This in turn may provide some protection for the bluffs. It will be several years before the results of this program can be evaluated. Based on historic records of beach levels along Carlsbad, it does not appear that beach replenishment would be feasible for Carlsbad Beach State Park. It also appears that any offshore structure in this area would not be economically feasible. At the present time ,the most appropriate solution for protection of the subject bluffs appears to be some type of seawall or rock revetment. For such -11- Project No. 54268E-0002 Woodward-Clyde Consultants construction it is important to address encroachment on the beach; the visual aesthetics; the current use of the area, the hazards associated with potentially unstable, oversteepened slopes; the potential for future erosion; the potential for damage and loss of benefits; the engineering design criteria; and the cost. We have identified and reviewed advantages and disadvantages of several structural alternatives. The structures evaluated included the following: ° Rock Revetment ° Vertical Seawall 0 A Combination Vertical Seawall - Rock Revetment In order to enhance the visual appearance of the project, and to provide additional benefits, other features should also be considered. These may include the effective use of walls to reclaim eroded land to provide new park areas or overlook areas above the beach; the use of different types of structures along the alignment; the use of a curved alignment; and the improvement of drainage. As a part of the proposed shore protection construction, beach access should also be taken into consideration. Currently, beach access is provided along public access stairways located at Tamarack Avenue and Cherry Avenue and an access ramp at Ocean Street. Also, many unimproved foot trails lead down to the beaches from the top of the bluff. Emergency vehicle access is possible at the south end of the public parking area at beach level and along an unimproved dirt road leading down to the beach at Ocean Street near Pine Avenue. It is apparent that the existing accessways within the subject study area need to be improved and that additional beach access is needed along a this stretch of shoreline. Improvement of lateral access along the top of the bluff should also be considered. -12- Project No. 54268E-0002 Woodward-Clyde Consultants A general summary of the selection considerations and the relative ratings for various types of construction are presented on Table 1 below. Table 1 Shore Protection Selection Considerations Anticipated Relative Type of Beach Ease of Level of Visual Cost Per Protection Encroachment Construction Maintenance Appearance Lineal Ft Stone revetment Highest Easiest Low Satisfactory Lowest Reinforced concrete vertical seawall Lowest Hardest Lowest Good Highest Reinforced earth wall with toe stone Medium Medium Low Good Medium Cribwall with toe stone Medium Medium Medium Satisfactory Medium Fabriform (concrete filled bags) Medium Medium Low Poor Low H-pile with wood Medium or concrete lagging to and toe stone Medium Medium Highest Satisfactory High Currently there is a rock ledge exposed along much of the bluff. For preliminary design, it is anticipated that the proposed structures would be located on or landward of this ledge and that the encroachment onto the usable beach area would be limited. The structures would be curved to match the existing topography and vertical walls would be used to reclaim land and provide a more pleasing - visual appearance. Both Reinforced Earth Walls (which can be colored and textured) and crib walls (which can be planted) have been used in this regard. It is anticipated that the structures would be designed for a 30 to 50 year life with relatively low maintenance. The current accessways should be improved and one or two accessways added. -13- Project No. 54268E-0002 Woodward-Clyde Consultants Based on our preliminary review of the various alternative methods of shore protection, it appears that the most suitable structural method of bluff protection consists of a stone revetment incorporated with vertical seawalls in some areas and no protection in others. Some typical cross sections of alternative methods are presented on Figures 8, 9 and 10. It appears that two additional accessways would be adequate; typical details are shown on Sheet Nos. 1 thru 4. -14- Project No. 54268E-0002 Woodward-Clyde Consultants PRELIMINARY ENGINEERING DESIGN CRITERIA The design of a seawall or a stone revetment, which are considered in this report, is in general accordance with the information and procedures contained in the U .S. Army Corps of Engineers' Shore Protection Manual, Volumes I, II and III, 1975 and information contained in the List of References attached to this report. The following coastal engineering criteria were selected for use in the preliminary design: 1. Tidal Range MLLW datum Highest estimated water level +7.79 feet Mean higher high water +5.61 " Mean high water +4.89 Mean Sea Level (NGVD datum) +2.88 " Mean Lower Low Water +0.00 " Lowest estimated water level -2.18 " *NGVD datum +4.91 feet +2.73 " +2.01 " +0.00 " -2.88 ". -5.06 " Estimated storm surge and wave set-up,, 2.1 feet Highest estimated still water level (SWL): +9.9 feet (MLLW datum) Deep water wave period: 16 seconds Elevation at toe of revetment: +3 feet (MLLW datum) Assumed worst condition: sand scoured down to toe of revetment so water depth (ds) = 6.9 feet Average inshore slope: 1 to 25 (m=0.04) Maximum wave height of wave breaking on revetment: Hb=8. 6 feet Stability coefficient for two layers of armor stone: X = 2.0 Specific gravity of armor stone: S r = 2.64 *NGVD - National Geodetic Vertical Datum (formerly called Sea Level Datum of 1929) -15- Project No. 54268E-0002 Woodward-Clyde Consultants PROPOSED PRELIMINARY DESIGN The subject 4500 foot long portion of the coastal bluffs is characterized by dramatic changes in topography; variations in bedrock exposures, vegetation and extent of erosion; and variations in current use. It therefore appears that a variation in the type of remedial treatment or shore protection used might also be appropriate. For preliminary design, a stone revetment type of seawall with a curved alignment is proposed to be the basic type of shore protection along the base of the bluff within the Carlsbad Beach State Park study area. A typical design would place the top of the revetment at a maximum elevation of +22 feet (NGVD), the toe at elevation +3 feet, the slope inclination at 2 to 1 (horizontal to vertical) and the armor stone would consist of 4 ton stone. The revetment -would generally follow the toe of the bluff at approximate elevation +6 feet and would be located approximately 100 to 150 feet west of the west edge of Carlsbad Boulevard. In areas where the bedrock is higher than +6 feet the top of the revetment could be lowered. Engineering design calculations are presented in Appendix B. In those areas where significant erosion has occurred into the bluff, a vertical reinforced earth wall or a sloped crib wall (both with toe stone) would be utilized. to provide a better visual appearance, to reclaim land and to provide overlook areas. It is anticipated that areas which might be considered for such treatment include, the bluff in the vicinity of Walnut Avenue, Maple Avenue, Acacia Avenue and Cherry Avenue. It is estimated that approximately 500 lineal feet of seawall would be constructed. In some areas where existing heavy vegetation is present or where Carlsbad Boulevard is set further back from the top of the bluff, such as between Tamarack and Juniper Avenues, providing a wider buffer zone, no treatment may be a consideration. It is estimated that up to 400 to 500 feet of the project could be left in its current state. -16- Project No. 54268E-0002 Woodward-Clyde Consultants At the south end of the project at the parking lot, the existing stone revetment would be improved to provide better protection for this area. The existing accessways would be repaired and improved and two new accessways would be constructed. It is proposed that one of the new accessways be designed to accommodate handicapped persons or that the existing accessways at the north and south ends of the project be improved to provide better handicapped access. -17- Project No. 54268E-0002 Woodward-Clyde Consultants ECONOMIC CONSIDERATIONS Construction Cost Estimate The subject project extends along approximately 4500 feet of shoreline. For preliminary planning, it is estimated that approximately 3500 feet will be protected by a stone revetment that approximately 500 feet will be protected by a vertical seawall with toe stone protection, and that approximately 500 feet will be left in its existing state. For purposes of estimating costs, it is also assumed that the construction will include a new beach access stairway, a new handicapped beach access ramp and repair of the three existing beach accessways. The estimated cost of construction Is as follows: Quantity Unit Cost Amount Mobilization and Demobilization 1 L. S. $25,000 $25,000 Site Preparation 1 L. S. 10,000 10,000 Excavation• Terrace and Beach Deposits 10,000 cu.yds. 3.00 30,000 Bedrock 5,000 cu.yds. 25.00 125,000 Backfill, compacted 15,000 cu.yds. 2.00 30,000 Armor stone 85,000 tons 20.00 1,7001000 Underlayer stone 22,500 tons 20.00 450,000 Quarry run 14,000 tons 10.00 140,000 Filter cloth 37,500 sq.yd 2.00 75,000 Reinforced Earth/crib wall 8,500 sq.ft 25.00 21,250 Reinforced concrete foundation 500 L.F. 170.00 85,000 Reinforced concrete wave deflector 500 L.F. 55.00 27,500 Modifications repair/existing ramps and stairway 1 L.S. 85,000 85,000 -18- Project No. 54268E-0002. Woodward-Clyde Consultants Quantity Unit Cost Amount New concrete stairway 1 L. S. 25,000 25,000 New handicapped ramp 1 L. S. 85,000 85,000 Subtotal $2,913,750 Contingency (25%) 728,000 Total, Estimated Construction Contract Cost $3,641,750 Engineering and Design (0) 145,500 Supervision and Administration (4%) 145,500 Total Project Cost $3,932,750 Maintenance Cost Estimate The preliminary design criteria are considered relatively conservative and fairly large armor stone (4 ton) are proposed for the revetment and toe stone. It is therefore anticipated that the damages to the revement and seawall should be small during most of the design life. It is correspondingly assumed that the annual maintenance costs would also be relatively small. Annual maintenance costs are assumed to be I percent of the estimated contract cost. Annual Maintenance = 0.005 x 3,641,750 = $18,000 per year -19- Project No. 54268E-0002 Woodward-Clyde Consultants Benefit Estimate Benefits are calculated comparing the existing facilities and area use to probable conditions assuming no protection is provided and that erosion continues. The lost benefits include value of eroded property, lost user benefits, costs of vehicle travel due to detour and cost of facility replacement. For our estimation process, the following assumptions were made: a rate of erosion of 1.5 feet per year, a 50 year useful life for the project, a conservative $400,000/acre value for property, an interest rate of 12 percent, an average beach use of 2640 persons per day, an estimated future average daily traffic on Carlsbad Boulevard of 27,000/day, an average daily bicycle traffic on the bicycle lane of 200/day and the presence of gas, electric, telephone, water and sewer facilities and future storm drain and reclaimed water lines along Carlsbad Boulevard. Computations are presented in Appendix C. Average Annual Benefits Lost Per Year Value of eroded property - $62,000 Beach user benefits lost - $337,500 Bicycle lane use lost - $109,500 Vehicle operating cost on detour - $2,250,000 Lost time value on detour - $1,928,500 Facility replacement costs - $77,000 Total Annual Benefits Lost = $4,764,500 -20- Project No. 54268E-0002 Woodward-Clyde Consultants Benefit Cost Ratio Construction costs are spread over the estimated 50-year useful life of the project and added to the annual estimated maintenance cost to give a total annual cost of: Annualized construction cost - 3,900,000 x 0.12042 = $470,000 Annual maintenance cost - 0.01 x 469,638 = 18,000 Total Annual Cost - $488,000 When compared to the estimated total annual benefits lost of $4,764,500 this gives a ratio of benefits to cost equal to approximately 10. It is apparent that the loss of Carlsbad Boulevard as a north-south travel way is the most dominant factor in the Benefit Cost Ratio. Excluding the vehicle and lost time costs for the detour, the remaining benefits have an annual cost of $586,000 which gives a ratio of benefits to costs equal to approximately 1.20. -21- Project No. 54268E-0002 Woodward-Clyde Consultants REFERENCES Fischer, Michael L., 1983. "Preliminary Report on January, 1983 Coastal Storm Damage as prepared by Mary Lou Swisher, Geologist, Energy, Technical Services Division" preliminary report to California Coastal Commission. Howe, Steve, 1978, "Wave Damage along the California Coast, Winter, 1977-78 "prepared for California Coastal Commission. Inman, Douglas L., 1976, "Man's Impact on the California Coast Zone" prepared for State of California Department of Navigation and Ocean Development. Kuhn, G.G.., and Shepard F.P., 1984, "Sea Cliffs, Beaches and Coastal Valleys of San Diego County: Some Amazing Histories and Some Horrifying Implications" University of California Press. Kuhn, G.G. and Shepard, F.P. 1979, "Accelerated Beach - Cliff Erosion Related to Unusual Storms in Southern California," California Geology No. 32. Personal Communication, G .G. Kuhn, October, 1984. Marine Advisors, 1960, "Design Waves for Proposed Small Craft Harbor at Oceanside, California" prepared for U.S. Army Corps of Engineers, Los Angeles District. Meteorology International Incorporated, 1977, "Deep Water Wave Statistics for the California Coast, Station 611 , Department of Navigation and Ocean Development. National Oceanic and Atomospheric Agency, 1980 ,11A Climatology and Oceanographic Analysis of the California Pacific and Outer Continental Shelf Region." Scripps Institute of Oceanography, 1984, "Coast of California Storm and Tidal Wave Study," prepared for U .S. Army Corps of Engineers, Los Angeles District, Planning Division. State of California, 1977, "California Coastal Engineering Data Network, Second Annual Report, January 1977 through December 1977" Department of Navigation and Ocean Development. State of California, 1977, "Assessment and Atlas of Shoreline Erosion along the California Coast," Department of Navigation and Ocean Development. U. S. Army Corps of Engineers, 1980, "San Diego County, Vicinity of Oceanside, California - Survey Report for Beach Erosion Control" Main report including Draft Environmental Impact Statement. -22- Project No. 54268E-0002 Woodward-Clyde Consultants U. S. Army Corps of Engineers, 1975, Army Coastal Engineering Research Center. "Shore Protection Manual," U. S. Waldorf, B. Walton, Flick, Reinhard E. and Hicks, D. Murray, 1983. "Beach Sand Level Measurements - Oceanside and Carlsbad, California - December 1981 to February 1983 Data Report." S10-Reference No. 83-6. -23- I Scale : III LOCATION MAP CARLSBAD BOULEVARD SEAWALL PROJECTNO: 54268E-0002 ~, DATE: 10-11-84 W000WARD-CLYDE CONSULTANTS - OCEAN STRE / WALNUT PROFILE:.. /. PROFILE ' . - - Project Area 'Js-%r4L .IJIN I tUL I IUIN UI- , I AL L I-'AKK Lu IR IR 0 1 to T 09 LJ El Iq 09 Og 9 1 s 0/ AvA1HIH A CARLSBAD B6ULEV ARD - -- nvo co 7 77 413 ov _ I CHESTNUT -- - - / :. CIA ffILE:. 7 jA • - T TTTt . ; V 330 PROFILE I3vd •S - roject - S TOPOGRAPHIC BASE MAPS FOR CITY OF CARLSBAD, 0 200 40Q - - SITE PLAN AND LOCATION MAP SHEETS i-i AND K-i L OF - - MAP PREPARED PRIOR TO CARLSBAD BOULEVARD..BLUFF PROFILES M1 ti1kP A p. •,. ,•i --GRAPHIC SCALE (Feet r A DI CD A r ri ii mi A t r.. r- A ill Al v s lI I'd FACILIT1S. -- - - - / - - W000WARD-CLYDE CONSULTANTS BACK BEACH AND BLUFF AT LOCATION OF HEMLOCK PROFILE. ERODING BLUFF IS COMPOSED OF PLEISTOCENE TERRACE DEP- OSITS CONSISTING LARGELY OF FRIABLE SAND. THE UNDER- LYING SANTIAGO FORMATION IS EXPOSED AS A RESISTANT LEDGE AT THE BASE OF BLUFF. NOTE GRCUND WATER SEEP- AGE AT THE CONTACT OF THE TWO GEOLOGIC UNITS. II -. p. ' VIEW NORTH FROM AGUA HEDIONDA JETTY AT PARKING LOT AND TAMARACK AVENUE. RESTROOM FACILITY IN BACK- GROUND. NOTE LOCALLY SPARSE RIPRAP COVERAGE. CARLSBAD BOULEVARD SEAWALL DRAWN BY: ch CHECKED BY:7'i,LI PROJECT NO: 542 68E-00011 I DATE: 101184 FIGURE NO: 3 WOODWARD-CLYDE CONSULTANTS II - ..- / .--c - •- -- '- i _r, - ..-- - - - • ,-.. 'S -- — - _c -S. . . S • - i- ---•---..-------- _,±._.__i 'C - i .• - --------------5— .5,. I- ' '' ' •- -? .- - . — - - S - 4 , • - A ç .. • '' .__5 .As. •• . -. - ,, - - - '5 - - - -.- ": -. .:- •A ___. - - sT - •,• - — -. 5.... .--. - -,. _'___5__• k '' ".•. '-. - - •• .-.• :-- - -.:-.. - -- - ---c— .-- .. - - — -- FIGURE NO: 4 est West 60- .• ACACIA PROFILE .• Carlsbad Avenue 40- - FILL - PLEISTOCENE TERRACE DEPOSITS . - Bedrock Ledge eu- • - * - FILL 7 _____ •• - - ____ I Beach Sand SANTIAGO FORMATION 0- __ ..• ..... CHESTNUT PROFILE z. 0 I- 40 20- Carlsbad Avenue ro . I * 0 • PLEISTOCENE TERRACE DEPOSITS. . -. Exposed Bedrock ca t - - Ledge i Beach Sand SANTIAGO FORMATION 0 20 40 I _] GRAPHIC SCALE (Feet) W000WARD-CLYDE CONSULTANTS East 601 WALNUT PROFILE West Carlsbad Avenue a..J ,Guard Rail -. . FILL a. 4-a PLEISTOCENE TERRACE DEPOSITS I— Bedrock Ledge . ..... .Beach Sand T SANTIAGO FORMATION 2C 0 I-' E 4J -J u) —10 5 Ocean Street I Pirkinn OCEAN STREET PROFILE NZ FILL. co Bedrock Ledge PLEISTOCENE TERRACE DEPOSITS Cobble Berm 40 0 Beach Sand SANTIAGO FORMATION 0 20 40 BLUFF PROFILES -I CARLSBAD BOULEVARD GRAPHIC SCALE (Feet) DRAWN BY: ch I CHECKED BY: DATE: 10-11-84 PROJECT NO: W000WARO-CLYDE CONSULTANTS 20 [Ij ME 60-, WESTERLY EDGE 50 •.. / CARLSBAD BOULEVARD 40 PLEISTOCENE TERRACE DEPOSITS U- S z 0 I- 20- > -J w GENERALIZED NATURAL SLOPE S FILTER FABRIC LINING 1 /2-TON STONE -_EL. 22' 2 IIJ I 3 TO 4-TON ARMOR STONE CONSTRUCTION END OF FILTER FABRIC LAPPED BACK k\ BEACH LEVEL VARIES BEACH SAND EXCAVATION 10. _____ — EL. 61 0- _— SANTIAGO FORMATION QUARRY WASTE 0 10 20 GRAPHIC SCALE (Feet) ME W000WARD-CLYDE CONSULTANTS 60- WESTERLY EDGE CARLSBAD BOULEVARD 50- GENERALIZED NATURAL SLOPE * 40 D 30 PLEISTOCENE TERRACE DEPOSITS uj 10- SANTIAGO FORMATION COMPACTED EARTH BACKFILL WITH SELECT MATERIAL RECOMPACTED SLOPE REINFORCING STRIPS CONCRETE WAVE DEFLECTOR EL. 221 'I N ,- PRECAST CONCRETE WALL FACING ......... .... EL. 141 3-TON STONE TOE PROTECTION BEACH LEVEL VARIES I 7\c EL 61 / CUT OFF BEACH SAND WALL FOOTING CONSTRUCTION I A S A T I#I. I C.A'.iMVMuIjI GRAVEL DRAIN 0 10 20 GRAPHIC SCALE (Feet) 8E-0002 I WUUUWMflU-LYU UIIUIMI W000WARD-CLYDE CONSULTANTS Project No. 54268E-0002 Woodward-Clyde Consultants APPENDIX A GEOLOGIC INVESTIGATION Project No. 54268E-0002 Woodward-Clyde Consultants APPENDIX A GEOLOGIC INVESTIGATION for CARLSBAD BOULEVARD SHORE PROTECTION Field and Office Investigation The geologic conditions at Carlsbad State Beach Park were mapped during October of 1984. The geologic mapping was completed on San Diego County orthophotos of the coastline flown at a scale of 1" -2001. Topographic profiles of the coastal bluffs were surveyed at the locations shown on Figure 2 of the Feasibility report; the profiles were made using a level and leveling rod. At each of the profile locations, shallow test pits were dug down through the beach to measure the bedrock elevation. During the geologic reconnaissance, field observations were made of the erosional conditions and characteristics of the coastal bluffs. In order to make a more thorough evaluation of the erosional processes and erosion rates along the study area, current observations of the bluff conditions were compared with historic photographs and maps that date back about 30 years. Photographs taken several years before, during and immediately after the winter storms of 1983 were particularly useful in evaluating the rate and nature of bluff retreat. Geologic Setting The shoreline along Carlsbad Beach State Park, like much of the coastline along San Diego County, is backed by low coastal bluffs. The bluffs are backed by a broad, low relief coastal plain that generally extends several tens of miles inland. Agua Hedionda Lagoon and Buena Vista Lagoon are two lagoons located immediately south and about I mile north, respectively, of the state park. The lagoons generally act as "sediment traps", as sand and sediment are largely discharged from the lagoons only during periods of A-i Project No. 54268E-0002 Woodward-Clyde Consultants sustained, high runoff. Longshore transport of sand in the littoral zone along this stretch of coastline is predominantly to the south. In order to maintain circulation and tidal action within Agua Hedionda Lagoon, the entrance to the lagoon is periodically dredged. The sediment dredged from the lagoon is distributed hydraulically along the beach area south of the lagoon inlet. Geologic Units and Erosion Characteristics The coastal bluffs backing the state beach area are underlain by Eocene sandstone of the Santiago Formation; the sandstone is typically exposed as a low ledge along portions of the toe of the coastal bluff. The Santiago Formation Is overlain by Pleistocene terrace deposits which are exposed along the face of the bluffs. The Pleistocene sediments were deposited upon a wave-cut platform (marine terrace) that was cut during a high stand of sea level estimated at about 85,000 to 120,000 years ago. The contact between the two geologic units generally varies in elevation along the toe of the bluff from +6 to +11 feet and dips down to as low as -3 feet at the south end of the study area. The Santiago Formation consists of greenish grey clayey sandstone; the sediment comprising this formation is indurated and is generally much more resistant to erosion than the Pleistocene sand. The upper bluffs are comprised of soft, friable, fine- to coarse-grained sand. These deposits are typically weakly cemented, and are not capable of standing for long periods as vertical exposures over several feet in height. Steep faces eroded into the Pleistocene deposits are only marginally stable, and quickly slough back to a less steep slope inclination. The Pleistocene deposits are also relatively easily eroded by surface water runoff. -Many relatively deep gullies and small ravines have been partially filled with material dumped from the bluff top. A-2 Project No. 54268E-0002 Woodward-Clyde Consultants Geologic Structure Local bedding attitudes within the Santiago Formation could not be determined from the current exposures. The regional dip of the Santiago Formation is generally to the northeast at inclinations typically less than 10 degrees. Bedding within the Pleistocene deposits is nearly horizontal; the lower sandy portion is highly cross-bedded. The contact between the two geologic units slopes seaward at several degrees. The presence of fractures, joints or faults may greatly accelerate the wave erosion process in the coastal environment. The Pleistocene terrace deposits are generally not a highly fractured or jointed unit; no faults were observed, nor have any faults been mapped that displace the marine terrace. The Santiago Formation, however, is typically jointed and fractured to varying degrees; many northeast-trending fractures and small faults commonly cut the Eocene bedrock. At other nearby locations along the coast, such features as surge channels and sea caves are commonly formed by wave action scouring the sedimentary rock adjacent to faults or fractures. Along the study area, bluff erosion does not appear to be greatly influenced by these features. Ground Water Conditions A perched ground water table typically occurs at the contact between the Santiago Formation and the Pleistocene deposits. This condition is common along the North County coastline and has been recognized as a contributing factor to bluff erosion. The source of the groundwater is thought. to be primarily surface water introduced locally as rainfall and irrigation that percolates into the permeable terrace sands. When the ground water reaches the relatively impermeable Santiago Formation, it flows laterally along the seaward-sloping contact until it reaches the bluff face. A line of vegetation commonly grows at this point on the bluff. Prominent ground water seepage was observed along the toe of the bluffs at many locations within the study area. A-3 Project No. 54268E-0002 Woodward-Clyde Consultants Seismicity and Faulting The faults within the study area do not displace the wave-cut terrace and are overlain by Pleistocene deposits, indicating that movement has not occurred during the past at least 85,000 and possibly 120,000 years. The nearest potential earthquake sources include the offshore continuation of the Rose Canyon Fault zone, mapped about 3 miles west of the study area. More distant earthquake sources include the Elsinore Fault zone, mapped about 25 miles to the northeast. Many historic moderate earthquakes have occurred on the Elsinore Fault, whereas no earthquakes of magnitude 4.0 or greater have been recorded on the Rose Canyon. In general, although the historic seismicity record of Southern California is relatively short, the San Diego area has historically been recognized as an area of relatively low seismic activity. Although no specific seismic evaluation was performed for this study it appears to be reasonable to estimate that the largest earthquake-induced ground acceleration at the site with an average recurrence of 100 years is about 0.15 to .20g. Bluff Erosion and Slope Stability The bluff areas along the state park are subject to wave run up and impact during periods of high waves accompanied by high tides. During these periods, much of the lower portions of the bluff slope are subject to undercutting by wave action. During the winter storms of 1983, significant erosion occurred along much of the state beach area. Localized areas of the bluffs apparently experienced much more severe erosion. In particular, several stretches of the bluffs generally west of Walnut Avenue and Acacia Avenue were undercut to the extent that subsequent, slope sloughing partially undermined portions of Carlsbad Avenue. These areas of slope failure were rebuilt with compacted fill slopes and a protective layer of riprap placed along the toe of the rebuilt slopes. A-4 Project No. 54268E-0002 Woodward-Clyde Consultants In general, the natural slopes comprising the coastal bluffs appear to be grossly stable in their present condition.. However, the sandy, friable terrace deposits, when undercut and oversteepened by wave action, are only marginally stable at relatively steep slope inclinations. Experience with this geologic unit in the subject area and at other locations along the coast has shown that once slopes are oversteepened, additional surface sloughing and/or relatively shallow slope failures are likely to continue to occur within and adjacent to the undercut area until more stable slope inclinations are reached. Factors that could influence slope failures within such potentially unstable areas include heavy rainfall, ground water seepage, earthquakes, and additional erosion by high wave action. Relatively minor slope failures or blockfalls could represent a potential hazard to beach users. A-5 Project No. 54268E-0002 Woodward-Clyde Consultants APPENDIX B COASTAL DATA AND ENGINEERING DESIGN CALCULATIONS Project No. 54268E-0002 Woodward-Clyde Consultants APPENDIX B ENGINEERING DESIGN CALCULATIONS for CARLSBAD BOULEVARD SHORE PROTECTION Evaluate Deepwater Wave - Based on the "San Diego County, Vicinity of Oceanside, California - Survey Report for Beach Erosion Control" prepared by the U .S. Army Corps of Engineers, Los Angeles Disrict and dated September 1980, there is an 80 percent chance that the highest significant wave height would range from 11.7 to 14.2 feet at a minus 32.5 foot depth. From these analyses, we selected a maximum non-breaking wave of 14.2 feet and a wave period of 12 seconds for preliminary evaluation. Observations of . the nearshore profiles show an average slope of the ocean floor on the order of 1-foot vertical to 25 feet horizontal. H0=14.2 feet T =12 seconds m =0.040 d =32.5 feet L0=5.12T 2=737 feet (Deepwater Wave Length) for d = 32.5 = 0.0441 ; d = 0.0877 Table C-i from Lo 737 L Vol. III - SPM h = 1.046 H 0 = H = 14.2 = 13.6' (equiv. deepwater wave height) 1.046 1.046 B-i Project No. 54268E-0002 Woodward-Clyde Consultants Determine type of wave hitting the structure for breaking wave conditions using Figures 7-2 and 7-3 from Vol. II - SPM H'0/Lo = 13.6/737 = 0.0185 H' /crT 2 = 13.6/32.2(12)2 = 0.0029 Hb/H'o = 1.35 ; so H = 1.35 x 13.6 = 18.4 feet Fig. 7.3 From Fig. 772, 0 = 1.025 , a = 1.520 HIgT 2 = 18.4/32.2 x 144 = 0.004 min d = 1.025 x 18.4 = 18.9 feet max d = 1.520 x 18.4 = 28.0 feet Assume a toe elevation at the seawall as 4-3 (MLLW), an extreme tide of 7.8 feet, a storm surge and wave set-up of 2.1 feet. Then design still water level = +9.9 feet and d5 = 6.9 feet. Comparing d5 to db: 6.9 <18.9 ft. (mm.) indicates that the maximum . design wave will start breaking before it reaches the seawall. Using a slope of m=0.04 and a breaking depth of 18.9 ft. (mm.) indicates that the maximum design wave will start breaking a distance of a = 18.9-6.9 = 300 feet from the seawall. .04 Breaker travel distance a = (4.0-9.25m)Hb Eq. 7-3 Vol. II SPM = (4.0-9.25 x 0.04) 18.4 = 66.8 feet ; this indicates that the wave will have finished breaking before it gets to the seawall, Project No. 54268E-0002 Woodward-Clyde Consultants Check largest wave that will break on seawall for d = 6.9 ft. - (use Fig. 7-4 and 7-2) S .T L0(ft) d8/gT2 Hb/ds Hb(ft) H/gT2 B = dblHb 6 184 0.0060 1.07 7.4 0.0064 1.16 12 .737 0.0015 1.21 8.3 0.0018 0.95 15 1152 0.0010 1.23 8.5 0.0012 0.93 17 1480 0.0007 1.24 8.6 0.0009 0.91 20 2048 0.0005 1.25 8.6 0.0007 0.90 T16 sec , Hb=8.6ft. (mm) db = 0.92 x 8.6 = 7 9 feet c*7.9-6.9=25ft. and a =(4.0-9.25x0..04) 8.631ft. 0.04 Design wave H = 8.6 ft. . B-3 Project No. 54268E-0002 Woodward-Clyde Consultants Design of Stone W = 165 lbs (unit of weight of armor stone) H = 8.6 ft. (design wave height = Hb) Sr = 2.64 (specific gravity) cot e = 2/1 (slope of seawall) = 2.0 (stability coef. of armor units) 165 (8.6) 104.949 W = 2 x (2.64 -1P x 2 = 17.64 = 5950 lbs = 3.0 tons Use four ton (4) average stone for armor for three layer section: Underlayer stone, W10 = 600; use I to I ton stone Bedding Material, W200 to W4000 = 30 to 1J lbs.; use quarry waste with 50 lbs. size maximum Wave Run-up d6.9ft. , T16sec., Hb=S.6ft. and m=0.040 H/gT2 = 0.0010 , from Fig. 7-5 Hb /HI o=2.32 H' = 8.6 = 3.71 and H' IgT 2 = 0.005 ° 2.32 d/H?0 = 6.9/3.71 = 1.86 and cote = 2 Fig. 7-10 and 7-11 Vol. II SPM R/H'0 = 5.3 for d5/H'0 = 0.8 R/H'0 = 4,1 for d5/H'0 = 2.0 Design R/H'0 = 4.24 R S = 4.24 x 3.71 = 15.7 ft. for smooth surface tane=0.5 , Hb=8.Gft. K = 1.19 from Fig. 7-13 Vol.IlSPM B-4 Project No. 54268E-0002 Woodward-Clyde Consultants R = 1.19 x 15.7 = 18.7 ft. (corrected run-up) = 18.7/3.71 = 4.23 (for smooth) = 3.0 (for riprap) Fig. 7-15 riprap = 3.0 = 0.71 smooth 4.23 Rriprap = 0.71 x 18.7 = 13.3 feet (run-up onriprap surface) Height of wall to prevent overtopping = 9.9 + 13.3 = + 23.2 ft. = + 23 ft. MLLW = + 20 ft. NGVD Use wall high of +22 ft.*NGVD * NGVD - National Geodetric Vertical Datum (formerly call Sea Level datum of 1929). B-5 I.' CALIFORNIA i'(A • ENGINEERING DATA NETWORK SECOND ANNUAL REPORT JANUARY 1977 THROUGH DECEMBER 1977 IN COOPERATION WITH SCRIPPS INSTITUTION OF OCEANOGRAPHY UNIVERSITY OF CALIFORNIA DATA ANALYSIS AND UTILIZATION (CONTINUED). In CD In CD In Cu C-U LU) tR]IH IAVM iNV]LdIN9IS FIGURE 7 -12- STATION JO. 4 OCEANSIDE 1977 TABLE CUMULATIVE HEIGHT P0BARILITIES HEIGHT PROBABILITY 295 0.0000 295 0.0000 275 0.0000 265 000000 255 0.0000 245 0.0000 235 0.0023 225 0.0034 215 0.0046 205 0.0046 195 0.0057 185 0.0057 175 0.0057 165 0.0057 155 0.0057 145 0.0069 135 0.0080 125 0.0103 115 o.oiso 105 0.0219 95 0.0311 85. 0.0519 75 0.0727 65 0.1200 55 0.1905 45 0.2806 35 0.4295 25 0.7170 15 0.9757 5 1.00.00 CUMULATIVE PEAK PFPIOD PROBABILITIES PERIOD PROBABILITY (SEC) 22+ 0.0000 20 0.0496 17 0.1558 15 0.3960 13 0.6004 11 O.6893 9 0.7875 7 0.9526 5 100000- -22- jo 300 290 9 280 270 EGO ao 240 230 220 210 200 G 190 ieo 170 io 140 130 120 Ho•LJJ > 10O 90 H LL 70 GO .c.fl Lr 50 40 30 20 10 :i 1jJ :1!I A _ 1 41 101 31 11 1 1 TOTAL OF BGG OBSERVATIONS ii 28+ 20 17 15 13 ii 9 7 5 PEAK PL1 IOO (SEC) .JOINT DISTRIBUTION TABLE IEANIDE 1977 FIGURE 17 -27- OCEANSIDE JAN. 1977 P E R S ISTENCE (CONSECUTIVE DAYS (3 OR MORE) SIGNIFICANT WAVE HEIGHT IS 'H' FEET OR LESS) FEET DAYS I 0, 2 5, 3 60 4 8 5, 5 81 5 b 81 5, 8 81 5 10 8, 5, 12 81 5 MAXIMUM DAILY SIGNIFICANT WAVE HEIGHT FOR JAN. 1977 DATE (JAN.) 1 2 3 4 5 6 ---------------------------------------------------------- SIG.HT (FT.) . 3 3 4 4 3. DATE (JAN.) 8 9 . 10 11 12 13 -------------------------------------------------- SIG.HT (FT.) DATE (JAN.) 15 16 17 18 19 20 SIG.HT (FT.) DATE (JAN.) 22 23 24 25 26 27 -. SIC.HT (FT.) 2 2 1 2 DATE (JAN.) 29 30 31 SIG.HT (FT.) 3- 4 3 -44- OCEANS IDE FEB. 197? P E R S I S T E N C E (CONSECUTIVE DAYS (3 OR MORE) SIGNIFICANT WAVE HEIGHT IS 'N' FEET OR LESS) FEET DAYS I 8. 2 4, 3 10, 5, 4. A 1 11 81 sli 5 20. 6, 6 28. 8 28, 10 28. 12 28. MAXIMUM DAILY SIGNIFICANT WAVE HEIGHT FOR FEB. 1977 DATE (FEB.) 1 2 3 4 5 6 7 SIC.HT (FT.) 4 2 ------------------------------------------------------------ 2 3 3 4 3 DATE (FEB.) 8 9 10 11 12 13 14 ------------------------------------------------------------ SIG.HT(FT.) 3 5 4 2 2 2 2 DATE (FEB.) 15 16 17 18 19 20 21 SIG.HT (FT.) 3 3 3 3 3 2 6 DATE (FEB.) 22 23 24 25 26 27 28 SIG.HT (FT.) 6 5 ------------------------------------------------------------ 3 3. 3 2 3 OCEANSIDE MAR. 19?? P E R S I S T E N C E (CONSECUTIVE DAYS (3 -OR MORE) SIGNIFICANT RAVE HEIGHT IS 'N' FEET OR LESS) FEET DAYS I 2 6 4, 3 7, 6 5, 3, 4 311, 5 38, 6 31, 8 31 18 31 12 :31, MAXIMUM DAILY SIGNIFICANT WAVE HEIGHT FOR MAR. 1977 DATE (MAR.) 1 2 3 4 5 6 7 SIC.HT (FT.) 6 4 4 . 3 2 22 DATE (MAR.) 8 9 10 11 12 13 14 SIG.HT (FT.) 2 4 ------------------------------------------------------------ 4 2 2 3 4 DATE (MAR.) 15 16 17 18 19 20 21 SIG.HT (FT.) 3 3 4 3 2. 2 2 DATE (MAR.) 2.2 23 24 25 26 27 28 SIG.HT (FT.) 2 2 2 4 3 2 3 DATE (MAR.) 29 311 31 ---------------. --------------------------------- SIGHT (FT.) 3 - 3 2 - OCEANSIDE P E R S I S T E N C E (CONSECUTIVE DAYS (3 OR MORE) SIGNIFICANT WAVE HEIGHT IS 'N' FEET OR LESS) 30 DAYS OF OBSERVATION APR. 1-309 1977 FEET DAYS 1 0, 2 49 39 39 39 3 159 89 49. 4 30. 5 30, 6 30, 8 30, 10 30, 12 30, MAXIMUM DAILY SIGNIFICANT WAVE HEIGHT FOR APR. 1977 DATE (APR.) 1 2 ------------------------------------------------------------ 3 4 5 6 7 STG.HT (FT.) 3 4 3 2 2 3 2 DATF (APR.) A 9 10 11 12 13 14 SIG.HT (FT.) 2 2 4 3 2 2 3 DATE (APR.) .15 16 ------------------------------------------------------------ 17 18 19 20 21 SIG.HT (FT.) 2 2 2 3 3 2 2 r)ATF (APR.) 22 23 24 ------------------------------------------------------------ 25 26 27 28 SIG.HT (FT.) 2 2 3 3 . 4 3 2 DATF (APR.) 79 30 ---------------------------------------------------------- SIC.HT (FT.) 2 2 • a. • . —. — - - — - . — ---- —-- -- — _____ - - a — — z I I I - — .1 - ..a ........ ..- ...... - a . . 5 a . _ . — . . : - . - • : . — - __....._ .....•t ........._a a a• - _.._.._I • .:. -:: 11IIIIUIIlII1lIItI!IIIIIlIlJ IJIIIllIIfIJllIIIII!flhllll!I.l ItIIIIIfII!IIIIII!tlll JflIsi FFR MAR ' i Wave Height Legend 11— > 8 METERS - '-1-6 TO 8 METERS 100, . fl-4 TO 6 METERS —3 TO 4 METERS loll 2 TO 3 METERS —1 TO 2 METERS .15 10 -05 <1 ale METER 'I \ 360 340 300 250 IVA - — -- L Kuh _L.----•.. ..... 260- -• -..--. . \ -c• /'i" -... I -S. 240 \ "1 /1'\ \ ,' '•120 / •5__ '-.-. \ 220 /---H---_\, 140 200 160 I80 All Years Figure III. I FREQUENCY DISTRIBUTION ROSE 1951 -1974 STATION 6 (31.5N 118.4W) COMBINED SEA/SWELL Iyu 360 340 .1.11 300 260 . September 360 340 320 300 250 60 -- October 360 340 320 300 10 260.j I-47) 260--'r / IT 240' • / / 140 220 200 ISO November 360 340 320 — — \,/• \ I 300 .' ••\ hi 5 ._•• I I,••.- ."5' • I .49 260 - - '5 / I 140 ,•"•- I 220 200 I 160 180 December 360 \34 . 0 300 \ i 280 — — I.t.t. .18 1 260.---k -.-- -- 240 220 - -.-------------- — - 280 -- — — 2 LESS 11.1 .05 260 ...... 6-111-2 360 340 320 \_----- rc 300 280 I — —t- 260 - .•-fT\ ' / 240 / 140 / 22$ i--- --H------ 200 160 180 January 360 340 320 .I?0 \ \ I 300 Ito 280 38 /\L LL a 'CUR 260 •-4\ .---2• '5-'120 '/—_i--- 240 140 >( / I / 22$ \t 200 1 16$ 180 February 360 340 be 300 Ito 280 LESS Tw-\ .22 26O---' ol 240 220' 200 March April 340 •. 360 - .- —- 'il -it 260-- 07 'S - 'S 5' 5- .5- - 360 340 — I >c\j111 360 \34 I 30$ K\, •iI -.:.s..\\ I1 '0 280 I OVER .22 260 May June July August 6-111-4 STATION 6 WAVE HEIGHT DURATION GRAPH 1946-1974 COMBINED SEA/SWELL HEIGHT' 1946-47 1947-48 1948-49 1949-50 1952-53 1953-54 1955-56 1956-57 1959-60 1960-6! 1961-62 1962-63 1963-64 1964-65 1965-66 1966-67 1967-68 1968-69 1969-70 1-72 1972-73 1973-74 1974-75 __________ • _.. ._ - _________ _ : :L....... LL• -- ____ !- - : . . _i - - .. - . - - - - - - --- - _-• - -, - .•. - -.....- !-. - _ETETEEL T.- c - -. -- - - - . - .•... - - -_- - - :-=-- - - - - .... - - •- ••-J - ___ - - - . .. - - - .. _______ - - -=.- _ :_=- • _ _... __. _,... ............................. -:•__-_- ___ -- - - -_- .. •. - -fl-- H- - - -•; -_•.....- - - . - - . - - I. ______ it -- _. =.. ___. • . ----•- - a-. - • - • -- - - r - -- =• - -=• •-.- - - I - - .. - -I -. - - I - - ............ JUL AUG SEP OCT NOV DEC JAN + DATA NOT AVAILABLE TIME INTERVAL = 24 HAS Figure III. 2 FEB MAR APR MAY JUN. - 4511 - 3-I II - 23 fl 3-I II - IAflLE 111.5 . • STATION 6 (31.5N 116.4W) EXTREME WAVE EVENT LISTING COMBINED SEA/SWELL •' 5 METERS • COMPILED FROM ONCE-DAILY WAVE COMPUTATIONS 1951-1974 CHRONOLOGICAL ORDERING WAVE HEIGHT ORDERING : PERIOD ORDERING DATA HEIGHT PERIOD DIRECTION : DATA HEIGHT PERIOD DIRECTION : DATA HEIGHT PERIOD DIRECTION 29 MAR 53 5.7 10 310 06 MAP 56 6.7 11 344 • 24 DEC 64 5.8 11 311 06 MAR 56 6.7 11 344 29 FEB 72 6.6 11 321 • 06 MAR 56 6.7 11 344 20 APR 62 5.4 10 327 24 DEC 64 5.8 11 -311 • 29 FEB 72 6.6 11 321 08 JUN 64 5.6 10 298 29 MAR 53 5.7 10 310 • 29 MAR 53 5.7 10 310 24 DEC 64 5.8 11 311 08 JUN 64 5.6 10 298 • 20 APR 62 5.4 10 327 26 MAY 67 5.3 10 299 20 APR 62 5.4 10 327 • 08 JUN 64 5.6 10 298 05 MAY 68 5.0 10 298 26 MAY 67 5.3 10 299 • 05 MAY 68 5.0 10 298 04 MAY 69 5.1 9 273 07 MAY 70 5.1 9 320 • 26 MAY 67 5.3 10 299 07 MAY 70 5.1 9 320 04 MAY 69 5.1 9 273 • 07 MAY 70 5.1 9 320 29 FEB 72 6.6 11 - 321 05 MAY 68 5.0 10 298 04 MAY 69 5.1 9 273 6.11182 TABLEIII.5 Project No. 54268E-0002 Woodward-Clyde Consultants APPENDIX C BENEFIT CALCULATIONS Project No. 54268E-0002 Woodward. Clyde Consultants APPENDIX C USER BENEFIT CALCULATIONS for CARLSBAD BOULEVARD SHORE PROTECTION Loss of Property It is estimated that the average rate of erosion is approximately 1.5 feet per year along the 4500 feet length of the subject study area. It is assumed that the value of the property is $400,000 per acre. 1.5 x 4500 Annual value of eroded property = 43,560 x $400,000 = $61,980 Loss of Beach User Benefits It is generally considered that the beach season in Carlsbad is year around. Maximum use will be in the summer, weekends and holidays. Minimum use will be weekdays during the winter. Based on City of Carlsbad data the average daily use for the 4500 feet of beach is 2640 persons which gives an annual use of approximately 963,600 persons. Using the Corps of Engineers' criteria of 100 square feet of beach required for each user and an average beach width of 100 feet gives a beach capacity of: 4500 x 100 100 = 4500 persons for peak periods This appears to be consistent with the estimated average daily use of 2640 persons. It is therefore estimated that the average user days per year with good access is 900,000. It is estimated restricted access and parking will reduce the average use by 25 percent. Thus, the total user days lost per year is 225,000. If the value of each recreation day benefit is assumed to be $1.50, and if good access and parking is not maintained, the annual beach user benefit loss will be: Annual Beach User Benefit Loss = 1.5 x $225,000 = $337,500 Loss of Bicycle Lane Use Carlsbad Boulevard has a dedicated bicycle lane along its full length 'in the study area. This is considered a main recreational bicycle travel lane in the C-' Project No. 54268E-0002 Woodward-Clyde Consultants area and Is conservatively estimated to have an average daily traffic of 200 and an annual traffic of 73,000. Each trip is considered equivalent to a recreation-day benefit at a value of $1.50 per trip. Thus, the annual bicycle user benefit loss will be: Annual Bicycle user Benefit Loss = 1.5 x $73,000 = $109,500 Traffic Reduction Costs Carlsbad Boulevard is a main north-south travel way which has an estimated future average daily traffic volume (ADT) of 27,000 vehicles. This traffic level is anticipated to be reached and exceeded within the next approximate 20 to 25 years. This gives an average yearly traffic of 9,855,000. For this analysis an annual vehicle traffic of 9,000,000 is used. Loss of Carlsbad Boulevard would require this traffic to go east on Tamarack Avenue approximately 0.6 miles to Interstate Highway 5, south on Interstate 5 to Cannon Road and then east on Cannon Road approximately 0.4 miles to the coast. Using a vehicle operating cost of $0.25 per mile would produce a total annual vehicle operating cost for using the detour of: Annual Vehicle Operating Cost = 0.25 x (0.6 + 0.4) x 9,000,000 = $2,250,000 This detour. would also result in lost time for the occupants of the vehicles. Assuming the average occupancy rate is 1.5 persons per vehicle, the average speed is 35 miles per hour, and the value of a person's time is $5.00 per hour, it will give an annual time cost for use of the detour of: Annual Lost Time Cost = 5.00 x (0.6 + 0.4) x 1.5 x 9,000,000/35 = $1,928,600 Facility Replacement Costs It is assumed that each existing utility would have to be replaced over a length of 4000 feet once during the design life of 50 years. The estimated cost for the replacement of each facility is as follows: 4" high pressure gas main - $240,000 12" water main - 200,000 12"-16" sewer main - 160,000 Electrical lines - 20,000 Telephone lines - 20,000 Total Cost $640,000 For a design life of 50 years and an interest rate of 12 percent, the annualized cost is determined by multiplying the total cost by 0.12042. Annualized facility replacement cost = $640,000 x 0.12042 = $77,000 Some additional costs may also be attributed to the proposed future storm drain and reclaimed water line. C-2