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HomeMy WebLinkAbout3307; CARLSBAD BLVD SHORE PROTECTION; FEASIBILITY STUDY; 1988-08-08Project No. 885 1268E-SIO1 FEASIBILITY STUDY CARLSBAD BOULEVARD. SHORE PROTECTION CARLSBAD BEACH STATE PARK - AREA 3 CARLSBAD, CALIFORNIA for the . . . City of Carlsbad by WOODWARD-CLYDE CONSULTANTS August 8, 1988 Woodward-Clyde Consultants TABLE OF CONTENTS Page No. INTRODUCTION 1 GENERAL SITE CONDITIONS 2 Surface Conditions 2 Subsurface Conditions 3 Tides, Wind and Wave Climate 4 STATEMENT OF PROBLEM . 5 CONSIDERATION OF POSSIBLE SOLUTIONS 5 COASTAL ENGINEERING CONSIDERATIONS 8 PROPOSED PRELIMINARY DESIGN 9 ECONOMIC CONSIDERATIONS 10 Construction Cost Estimate 10 Maintenance Cost Estimate 11 Benefit Estimate 11 Average Annual Value of Benefits Lost Per Year 12 Benefit-Cost Ratio 12 References Figures Figure No. 1 - Location Map Figure No. 2 - Site Plan Figure No. 3 and 4- Pictures Appendices Geotechnical Investigation Coastal Considerations User Benefit Calculations Shore Protection Structures a/1j12 Woodward-Clyde Consultants FEASIBILITY STUDY CARLSBAD BOULEVARD SHORE PROTECTION CARLSBAD STATE BEACH - AREA 3 CARLSBAD, CALIFORNIA INTRODUCTION Carlsbad State Beach - Area 3 generally covers the area from the south end of the jetties at the entrance to Agua Hedionda Lagoon to the north end of the residential development along Tierra del Oro street in the city of Carlsbad (Figure 1). The subject portion of Carlsbad Boulevard within Area 3 where the shore protection is proposed is approximately 2,600 feet long and is situated along the beach between the entrance jetties to Agua Hedionda Lagoon and the outlet jetties for the San Diego Gas and Electric powerhouse. Carlsbad Boulevard drops down to its lowest level through this area where the elevations along the centerline of the boulevard generally range from approximately +13 to +16 feet (City of Carlsbad - Mean Sea Level Datum). The existing roadway along this area is approximately 40 feet wide and there is parking for cars along the west side of Carlsbad Boulevard. The parking area is separated from the roadway by an asphalt berm and abuts directly against the beach. For several miles, Carlsbad Boulevard runs parallel with and adjacent to Carlsbad State Beach and is the primary access to the beach in this area. It is also the only roadway west of Interstate Highway 5 to cross Agua Hedionda Lagoon. As such it carries a large amount of north-south traffic through the area. A Site plan is presented on Figure No. 2. The beach in this area is historically thin and narrow. Almost every year the winter storms strip away the thin layer of sand, leaving a discontinuous layer of gravel and cobbles over the underlying sands and gravels. The spring and summer swells generally rebuild the beach with another thin layer of sand. In addition, approximately every 2 to 3 years the beach in this area is replenished by sand placed on the beach from dredging of the lagoon by San Diego Gas and Electric Company. During the more severe winter storms, the large waves' impact on and overtop Carlsbad Boulevard in this area. This usually results in erosion of the parking area and damage to the roadway. The parking area along the west side of Carlsbad Boulevard is gradually being destroyed and public access to the beach is being limited. The paved parking area has been reduced from approximately 300 to about a/1j12 -1- Woodward-Clyde Consultants 60 spaces. Neither the City of Carlsbad nor the California Department of Parks and Recreation has the funds to properly maintain this area on an annual basis. Repairs that have been made in the past have been damaged again or destroyed. Current pictures of the beach area are shown on Figure Nos. 3 and 4. The City of Carlsbad is planning to widen and improve Carlsbad Boulevard in the subject area. These improvements will include a divided roadway with a median, parallel parking on the west side, and pedestrian walkways on both sides. New landscaping and lighting are also planned. In order to protect these improvements the City desires to study the feasibility of constructing some type of shore protection along the west side of Carlsbad Boulevard in the low area between the two jetties. A summary of the preliminary Geotechnical Investigation for the study is presented in Appendix A; an evaluation of the Coastal Conditions is summarized in Appendix B; the Benefit Calculations are shown in Appendix C and typical shoreline protections solutions are discussed in Appendix D. GENERAL SITE CONDITIONS Surface Conditions The Carlsbad State Beach - Area 3 is an extremely popular sandy beach area through which Carlsbad Boulevard passes. It is bounded on the east by Agua Hedionda Lagoon and on the west by the Pacific Ocean. The lagoon side of Carlsbad Boulevard contains a small (40+ car) parking lot developed by San Diego Gas and Electric Company for fishing access. Carlsbad Boulevard is currently a two-lane road in this area with an approximately 235-car parking lot extending along the ocean side of the road (much of this parking area has been damaged or destroyed by storms during the past few years). A new bridge for Carlsbad Boulevard has been constructed at City expense over the entrance to Agua Hedionda Lagoon at an elevation of approximately +23 feet near the north end of the project. In addition, the roadway (which drops down in elevation from the bridge) has been widened and improved for a distance of approximately 400 feet south of a/1j12 -2- Woodward-Clyde Consultants the bridge. The proposed new road improvements will continue south (including the study area) within the 100-foot wide right of way and will generally consist of a divided roadway with a center median with pedestrian walkways along both sides. The new roadway along the west side (beach) will be wider to allow for parallel parking. The roadway will also be provided with new landscaping and lighting. The elevations of the roadway along the approximately 2,600-foot long study area will generally range from approximately +13 to +16 feet (MSLD). The roadway south of the outlet rises again above the beach to elevations above +20 feet (MSLD). Carlsbad Boulevard is also or will be underlain by existing utilities, including a 12-inch water main, a 4-inch H.P. gas main, telephone lines, electrical lines and storm drains. The beach along the west side of the subject length of Carlsbad Boulevard is typically about 150 to 200 feet wide; it narrows at the north end near the Jetty at the entrance to Agua Hedionda Lagoon and widens at the south end near the Jetty for the powerhouse outlet. There is typically a relative level sandy berm about 50 feet wide adjacent to the roadway and the face of the berm (with exposed cobbles) slopes down at inclinations on the order of 6:1 to 10:1 (horizontal to vertical) to the Mean Sea Level waterline. The beach generally flattens to inclinations of about 30:1 to 50:1 beyond this point. There are no significant existing improvements along this portion of the beach other than a few fire rings. Several portable lifeguard towers are currently located along the parking area. Subsurface Conditions The subject area is located at the "buried mouth" of the Agua Hedionda Lagoon. Bedrock is exposed at the base of the bluffs and offshore to the north and south of the inlet and outlet jetties, respectively; however, it extends below a depth of 40 feet along the subject. area. The subsurface profile in this area generally consists of 1 to 3 feet of loose beach sand underlain by a 8- to 10-foot thick layer of 1- to 6-inch diameter cobbles which grades into medium dense to dense layers of fine to. medium sand with scattered gravel and cobbles. The groundwater along this stretch of Carlsbad Boulevard generally follows the tides and is typically encountered about 10 to 12 feet below the ground surface. a/1j12 -3- Woodward-Clyde Consultants Tides, 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 diurnal 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 form 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 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 interferences, 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 as acted as an a/1j12 -4- Woodward- Clyde Consultants 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. STATEMENT OF PROBLEM Carlsbad Boulevard in the area of Carlsbad State Beach - Area 3 between the inlet and outlet jetties for Agua Hedionda Lagoon is at a relatively low elevation (+13 to +16 MSLD) and as such is subject to erosion and damage due to winter storm waves and high tides. This is a heavily used beach area and Carlsbad Boulevard is a main north-south traffic roadway. The City of Carlsbad has plans to widen and improve Carlsbad Boulevard in this area to provide better access to the business and recreational facilities in Carlsbad. If these new improvements, as well as existing utilities within the roadway, are not protected, considerable repair and maintenance costs may be realized, as well as possible loss of utility services. North-south through traffic would be disrupted and vehicular access to and parking for a considerable length of beach may be lost for extended periods of time. This would in turn cause distress to many businesses located along Carlsbad Boulevard to the north and south of this area. This roadway is also marked for and is the only north-south access across Agua Hedionda for bicycles. CONSIDERATION OF POSSIBLE SOLUTIONS The alternative to constructing shore protection along the subject portion of Carlsbad Boulevard is to do nothing, in which case continued erosion and damage to the roadway would occur during high tides and winter storms. This would result in continued high maintenance costs for this area, damage and repair costs to the new improvements and possible future costs for replacement of portions of Carlsbad Boulevard and existing utilities. This alternative does not appear to be consistent with the current use of the area and the cost of planned improvements for this area. Beach nourishment or offshore protection are also possible alternative 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 a/Ijl2 -5- Woodward-Clyde Consultants 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 under construction for Oceanside harbor entrance to provided a Continuous sand replenishment system. It is possible that the sand replenishment program may also provided an additional source of sand along Carlsbad's beaches. It will be several years before the results of this program can be evaluated. Based on historic records of beach levels along Carlsbad and the monitoring of the effect of the current sand replenishment program in this area, it does not appear that beach replenishment would be feasible as a long term solution to erosion for Carlsbad Beach State Park. It also appears that any offshore structures in this area would not be economically feasible or desirable. At the present time, the most appropriate solution for protection of the subject roadway appears to be some type of seawall or rock revetment. For such construction it is important to address encroachment on the beach; the visual aesthetics, the current use of the area; the potential for future erosion; the potential for damage and loss of benefits; the cost of maintenance; the engineering design criteria; and the cost for design and construction. We have identified and reviewed general advantages and disadvantages of several structural alternatives. The structures evaluated included the following: Rock revetment Various types of vertical seawalls without toe protection Various types of vertical seawalls with toe protection 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 provide lifeguard tower areas and overlook areas above the beach; the use of different types of structures along the alignment; the use of a curved alignment; and provisions for beach access. Currently, Carlsbad Boulevard in this area is at beach level and beach access is provided along the entire length of the roadway. It is apparent that beach accessways will have to be provided through any shore protection structure built along this portion of Carlsbad Boulevard. a/1j12 -6- Woodward-Clyde Consultants Some typical cross-sections of alternative methods are presented in Appendix D. A general summary of the selection considerations and the relative ratings for various types of construction are presented on Table 1. • Table Shore Protection Selection Considerations Anticipated Relative Type of Beach Ease of Level of Visual Cost per Protection Encroachment Construction Maintenance Appearance Lineal EL. Stone revetment High Easy Low Satisfactory Lowest Reinforced concrete - vertical seawall on piles Low Haiti Low Good Highest Reinforced earth Low to wall with toe stone Medium Average medium Good Medium Stresswall with toe stone Medium Average Medium Satisfactory Medium Fabriform (concrete filled bags) with toe stone Medium Average Low Poor Low H-pile with wood or concrete lagging and toe stone Medium Average High Satisfactory Medium Anchored steel-pile sheeting with concrete cap Low Average Low Good High Anchored concrete- pile sheeting Low Average Low Good High Steel-pile sheeting with concrete cap Low to and toe stone Medium Average Medium Good Medium Concrete-pile sheeting with Low to toe stone Medium Average Medium Good Medium a/1j12 -7- Woodward-Clyde Consultants It is anticipated that all structures would be provided with beach accessways approximately every 300 feet and that the structures would be designed for a 40 to 50 year life. The project would also include a walkway behind the structure for lateral access and one or two ramps for handicapped beach access and lifeguard vehicle access. Based on our preliminary review of the various alternative methods of shore protection, it appears that a suitable structure would be a vertical, anchored steel sheet pile wall with a concrete cap which ties into rock revetments near the jetties at each end. It is anticipated that the wall would be approximately 2,200 feet long and that the repaired rock revetments would be approximately 250 and 175 feet long at the north and south ends, respectively. It is also anticipated that there would be 2 ramps and 5 stairways through the wall. COASTAL ENGINEERING CONSIDERATIONS The coastal engineering design criteria used for this feasibility study is in general accordance with the criteria contained in the U.S. Army Corps of Engineers' Shore Protection Manual, Volumes I and II, 1984, and is based on information provided in the List of References attached to this report, by the City of Carlsbad, and from Woodward- Clyde Consultants' files.. The Design Calculations are presented in Appendix B. The following coastal engineering criteria were selected for use in the preliminary design of the vertical seawall and the stone riprap at the ends of the seawall. Elevations are referenced to City of Carlsbad - Mean Sea Level Datum. Highest Estimated Still Water Level Wave Height at Toe of Seawall Maximum Depth of Scour Average Near Shore Slope (range) Kd for two layers of Quarry Stone = +5.7 feet = 6.0 feet =0(MSLD) = 1 ft. in 30 feet to 1 ft. in 50 feet = 2.0 a/1j12 -8- Woodward-Clyde Consultants Specific Weight of Quarry Stone = 165 lb/ft3 Maximum Run-up - 1-1/2:1 rock slopes = +15 feet Maximum Run-up Vertical concrete wall = +18 feet Vertical seawalls and handrailings will also be subject to pressures due to breaking and broken waves. These forces include both dynamic wave forces and hydrostatic forces. PROPOSED PRELIMINARY DESIGN The subject 2,600-foot long portion of Carlsbad Boulevard is characterized by a relatively low sand and cobble berm extending along the beach between two existing rock jetties. The ground surface is relatively flat with ground surface elevations ranging from approximately +13 to +16 feet (MSLD). The beach generally consists of 1- to 6-inch diameter cobbles with a thin (1- to 3-foot thick) sand cover during the summer months. The beach is typically about 150 to 200 feet wide and has a foreshore slope of about 6:1 to 10:1 (horizontal to vertical). The inshore bottom has a slope of about 30:1 to 50:1 and the offshore bottom slopes at.about 60:1 to 70:1. For preliminary-design, an anchored, vertical driven treated steel sheet pile wall with a reinforced concrete cap is proposed. A typical design would place the top of the wall (concrete cap) at elevation +17.5 and the toe of the sheeting at approximate elevation -20 feet. The concrete cap would extend to approximate elevation +3 feet (7 to 9 feet below natural beach level). For this design, it is anticipated that the steel sheeting would not be exposed except during the worst high tide and storm conditions. Some overtopping of the wall should be expected during major storms and some general maintenance will be required. Beach accessways are placed at approximately seven locations (approximately every 300 feet). They would include about 5 stairways and two ramps. Portions of the wall would be extended westward onto the beach for accessways, lifeguard towers and equipment, and a/1j12 -9- Woodward-Clyde Consultants for overlook areas above the beach. This may require some easements from the State Department of Parks and Recreation. The existing rock revetments at the north and south ends of the wall would be improved and tied into the new wall ECONOMIC CONSIDERATIONS Construction Cost Estimate The proposed seawall extends approximately 2,200 feet along the shoreline. In addition, it is estimated that the existing rock revetments for approximately 250 feet at the north end and 175 feet at the south end would have to be replenished and/or repaired (see Figure Nos. D- 1 and D-5 in Appendix D for typical sections). For purposes of estimating costs, it is also assumed that there will be 5 beach access stairs and two beach access ramps which will occupy approximately 240 feet along the seawall. 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. 5,000 5,000 Earthwork (excavation & backfill) 15,0.00 cu. yds. 10 150,000 Anchored Steel Sheetpile Wall 1960 In. ft. 800 1,568,000 Reinforced Concrete Cap 1960 In. ft. 200 392,000 Beach Access Stairs - concrete 5 each 25,000 125,000 Beach Access Ramp - concrete 2 each 100,000 200,000 Rock Revetment 425 In. ft. 600 255.000 Subtotal . $2,720,000 Contingency (15%) $408.000 Total, Estimated Construction Contract Cost $3,128,000 Engineering and Design $100,000 Supervision and Administration $100000 TOTAL PROJECT COST $3,328,000 a/1j12 -10- Woodward-Clyde Consultants Maintenance Cost Estimate It is estimated that some minor damage to the shore protection and associated facilities would take place primarily during major storms. The maintenance should generally consist of some periodic treatment of the concrete cap and the stairs (and the ramps); possible repainting portions of the steel sheeting; painting and replacement of handrails; and occasional replenishment of the revetment stone. There may also be a continuing maintenance in regard to graffiti on the wall. In general, it is assumed that the accrued maintenance costs will be small. Fort this cost estimate, we have assumed the annual maintenance costs to be on the order of 1/10 percent of the estimated contact cost. Annual Maintenance = 0.0010 x $3,600,000 = $3,600 per year Benefit Estimate Benefits are calculated comparing the existing facilities, proposed improvements to Carlsbad Boulevard, and area use to the probable conditions, repairs and maintenance required assuming no protection is provided for the proposed new improvements and that erosion and damage occurs on a periodic basis. For this latter condition, it is anticipated that the loss of benefits will occur about every 2 to 3 years and will last until they are restored by repair and maintenance. The loss of benefits include temporary loss of parking area and access to beach; temporary closure of road resulting in detour of north-south vehicle traffic; temporary loss of bicycle travel lane; temporary loss of utilities; and reduced tourist use of the area. The value of these benefits is estimated from the value of lost time and the cost for repairs and maintenance. For our estimating process, the following assumptions were made: A 50 year useful life for the project; Major damage due to storms once in five years; Minor damage due to storms twice in five years; An average beach use of 3,000 persons per day; An average future daily traffic for Carlsbad Boulevard of 27,000 per day; a/1j12 -11- Woodward-Clyde Consultants An average daily bicycle traffic of 200 per day; and Gas, water, electric and storm drain facilities destroyed once in fifty years. Computations are presented in Appendix C. Average Annual Value of Benefits Lost Per Year: Improvement Replacement/Maintenance Costs $47,000 Beach user benefits lost 81,000 Bicycle lane use lost 14,400 Vehicle operating cost on detour 162,000 Lost time value on detour 115,715 Utility Replacement Costs 36,126 Other Losses 50,000 Total annual Benefits Lost $506,241 Benefit-Cost Ratio Construction costs are spread over the estimated 50-year useful life of the project at an interest rate of 12 percent and added to the annual estimated maintenance cost. The annualized construction cost is determined by multiplying the total cost by 0. 12082. Annualized Construction Cost = 3,128,000 x 0. 12042 = $376,675 Annual Maintenance Cost = 3.600 Total Annual Cost $380,275 The total annual cost compared to the total annual benefits lost gives a benefit-cost ratio of approximately: Benefit-Cost Ratio = 506,244 -- 380,275 =1.33 a/1j12 -12- 1• WY FWY r7 .\ At PLAZA CIN'S AWNOAL Ooqp Vko 31 32 . I :cc thiuI F)' Lk\\ ' ' '(—' . .•s1& 0 City I I5 I tc 1 \ cc - - Ply Palk ct VII 0• I R ORY Sil 'G AW PL 1VIGup_ IJ •Ap '1sJ 91 / >(\kCi !V MS 111 A cliday ulty 0 ' pk 0 - City — -- - 4 -- Park - 4'L Cc lily,1 WV 7 4 ",. lDR : J * 4 ., 'I . .\RL>E3.\D 26 wl Ity Palk __ SCALE: 1" = 2000' LOCATION MAP CARLSBAD BOULEVARD SHORE PROTECTION DRAWN BY: eb I CHECKED BVJ/21 PROJECT NO: 8851268E-SIQ1J DATE: 7-28-88 FIGURE NO: 1 WOODWARD-CLYDE CONSULTANTS -1 \ \ Rrap: Aqua Hedlonda Lagoon Stirs -'•.._cI :.•. Handicap Ramp SEAWALL 414. RlW- Approx. Centerline -. - - of Road -••. - -Aw P-2 - - SEAWALL B1 -, Stairs Outlet 134,.fr Stairs LEGEND: Indicates approximate location of test boring. Indicates approximate location of survey profile V line. Nei A '" Ocean_Note: Rrap Plan is a portion of "County of San Diego - Topographic Map?? dated 9-17-75 - USC&GS 1929 sea level datum 1 Entrance SITE PLAN CARLSBAD BOULEVARD SHORE PROTECTION SCALE: 1" = 200' DRAWN BY: cb JfI4ECKEO BY:%'/ö( j FIGURE NO: 2 DATE: 7-28-88 1 PROJECINO: 8851268E-Slfli - W000WARO-CLYDE CONSULTANTS PICTURE NO. 1 - BACKSHORE SANDY BEACH PARKING AND ROCK JETTY - SOUTH END (LOOKING SOUTH) PICTURE NO. 2 - COBBLE BERM EXPOSED ALONG BEACH FORSHORE MIDDLE (LOOKING NORTH) PICTURES CARLSBAD BOULEVARD SHORE PROTECTION ORAWNBV: cb I CHECKEOBV:f/'j J PROJECT NO:885].268E-SIOlJ DATE: 7-28-88 I FIGURE NO: 3 J W000WARUILYDL LUIIULIANI L - ; ----•-'. - -: - --- • 71 AN Pi COBBLE BEACH, PARKING AND RIPRAP - NORTH END (LOOKING . SOUTH) PICTURE NO. 4 DUMPED RIPRAP AND DEBRIS AND ROCK JETTY - NORTH. END (LOOKING NORTH) I PICTURES I CARLSB:AD BOULEVARD SHORE PROTECTION DRAWN BY: eb I CHECKED BYJ(/ I PROJECT NO: 8851268E_SIO11 DATE: 72888 FIGURE NO: 4 91 W000WARD-CLYDE CONSULTANTS 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. Flick, Reinhard E., and Cayon, Daniel R., 1984, "Extreme Sea Levels on the Coast of California," reprint from the 19th Coastal Conference Proceedings, AS CE. Howe, Steve, 18978, "Wave Damage along the California Coast, Winter, 1977-78" prepared for California Coastal Commission. Inman, Douglas L., 1976 "Man's Impact along 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. 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 6," Department of Navigation and Ocean Development. National Oceanic and Atmospheric Agency, 1980, "A 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. Tekmarine, Inc., 1988, "Semi-Annual Beach Profile Surveys and Analysis for September 1987," City of Carlsbad. Tekmarine, Inc., 1988, "Semi-Annual Beach Profile Surveys and Analysis for April 1988," City of Carlsbad. a/1j12 -1- Woodward-Clyde Consultants U.S. Army Corps of Engineers, 1984, "Shore Protection Manual," volumes I and II, U.S. Army Coastal Engineering Research Center. 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." S 1 Reference No. 83-6. a/1j12 -2- Woodward- Clyde Consultants APPENDIX A GEOTECHMCAL INVESTIGATION FOR CARLSBAD BOULEVARD SHORE PROTECTION CARLSBAD BEACH STATE PARK - AREA 3 Field Investigation The surface conditions at Carlsbad State Beach - Area 3 were documented during several visual reconnaissances of the area between July 11 and July 22, 1988. On July 11, 1988, four test borings were drilled at the approximate locations shown on Figure No. 2. The borings were advanced to depths ranging from approximately 3 feet to 42 feet. The drilling was performed by an 8-inch diameter hollow stem auger mounted on a B-61 drill rig and under the direction of an engineering geologist from Woodward-Clyde Consultants. The geologist logged the borings as they were advanced. Samples of the subsurface materials were obtained from the auger cuttings and using a modified California drive sampler (2- inch inside diameter and 2-1/2-inch outside diameter) with thin brass liners. The sampler was generally driven 18 inches into the material at the bottom of the hole by a 140-pound hammer falling 30 inches. The sampler was driven less than 18 inches where gravel or cobbles prevented penetration or caused excessive damage to the sampler. The disturbed cuttings from the auger were placed in plastic bags and the thin metal liner tubes containing the relatively undisturbed samples were removed from the sampler, sealed to preserve the natural moisture content of the sample,and returned to the laboratory for examination and testing. A Key to Logs is presented as Figure A-i. Final Logs of the Test Borings are presented on Figures A-2 through A-6. The descriptions on the logs are based on the field logs, sample inspection, and laboratory test results. The ground surface elevation at the boring location was estimated from the topography on the Plans for the Improvement of Carlsbad Boulevard," City of Carlsbad, Project No. 3205. Laboratory Tests The materials observed from the auger cuttings and in the samples obtained from the test borings were visually classified and evaluated with respect to strength, dry density, and moisture content. The classifications were substantiated in the laboratory by performing grain size analyses of representative samples of the soils. Moisture content and dry density determinations were made on relatively undisturbed samples. The results of the moisture content and dry density tests are presented on the Logs of Test Borings •at the corresponding sample location. The results of the grain size analyses are shown on Figures A-7 and A-8. General Geologic Setting and Subsurface Soil Conditions The study area is located along the low-lying coastal margin of Agua Hedionda Lagoon. Agua Hedionda Lagoon represents the backfilled channel or "drowned river mouth" of Agua Hedionda Creek. Like other river courses in coastal San Diego County, Agua Hedionda creek incised (or eroded down into) its channel during the last major late a/1j12 A-i Woodward-Clyde Consultants Pleistocene glacial low stand of sea level (approximately 15,000 to 20,000 years ago). During the past 10,000 years (Holocene epoch), post-glacial sea level rise to its present level resulted in a reduced capacity of the creek to transport sediment. Consequently, predominantly fine-grained sediment was deposited within the channels. Similar to other coastal lagoons, longshore drift has produced a barrier beach along the mouth of the lagoon. The migration of the lagoon's outlet channel at the mouth of the lagoon has, in the recent geologic past, eroded away older Pleistocene and Eocene sediments and deposited the sand and gravel materials encountered in our subsurface explorations. Elevations along the existing Carlsbad Boulevard, which extends along the top of the beach, vary from roughly 13 to 16 feet above Mean Sea Level. Our subsurface investigation encountered beach and channel sands and gravels to depths of up to 41-1/2 feet from the ground surface. The upper 9 to 11 feet of each boring was composed of 1 to 3 feet of recently dredged sand underlain by rounded gravel and cobbles approximately 1 to 6 inches in diameter. These recent gravel and cobble deposits represent back-beach berm deposition by high energy winter storm events. The gravel and cobbles are also exposed on the beach foreshore. Underlying the cobble berm are interbedded sand and gravel deposits of probable beach and channel origins. The sampler penetration values in these materials generally ranged from approximately 20 to over 70 blows per foot. Most of the higher values were influenced by gravels. The moisture contents and dry densities in these materials generally ranged from approximately 15 to 25 percent and 90 to 100 pounds per cubic foot, respectively. The current groundwater level along the proposed shore protection alignment generally follows the tide level. It should be anticipated, however, that there may be some lag of the water level behind any shoreline protection structure. a/1j12 A-2 Project: Carlsbad Boulevard Shore Protection KEY TO LOGS Date Drilled: Water Depth: Measured: Type of Boring: Type of Drill Rig: Hammer: .c .?CA . Material Description 1 - co Co Surface Elevation: 0 .- - - DISTURBED SAMPLE LOCATION Obtained by collecting the auger cuttings in a plastic bag. - — — MODIFIED CALIFORNIA SAMPLER - • Sample With recorded blows per foot was obtained with a - Modified California drive sampler (2" inside diameter, 2.5" 5 - outside diameter) lined with sample tubes. The sampler - was driven into the soil at the bottom of the hole with a 140 pound hammer falling 30 inches. - Fill 10 — - Sand • Sand/Gravel 15 - • Gravel *GS - Grain Size Distribution - 20- - 25- - 30 Project No: 8851268E-Slo1 I Woodward-Clyde Consultants Figure: A-i Project: Carlsbad Boulevard Shore Protection Log of Boring No: 1 Date Drilled: 7-11-88 Water Depth: 14.5' Measured: At time of drilling Type of Boring: 8" HSA Type of Drill Rig: B-61 Hammer: 140# at 3D" drop seeKey to Logs, Fig. A-i — .2 Material Description W.. a W Surface Elevation: Approximately 14' MSL 0 2.5" Asphalt concrete; 7.5" gravel base over moist, light • gray brown, silty sand - FILL • 11 GS Loose to medium dense, moist, gray, sandy gravel and gravelly sand with 2" to 4" cobbles (GP-SP) - 5- Medium dense wet, gray with light reddish brown (mottled locally) 1 0 - poorly graded fine sand (SP) - 12 17 - 18 96 GS 15 - 1-3 - Dense wet gray, gravelly sand (SP) with sandy gravel (GP) layers - 14 12/ - 6'* "On gravel 20- - 15 31/ - 6'* "On gravel Very dense wet gray, poorly graded fine to medium sand - (SP SM) with silt and pebbes and shells locally 25- - - 1-6 76" "On gravel 18 iii GS 30. Project No: 8851268E-SIO1 I Woodward-Clyde Consultants Figure: A-2 Project: Carlsbad Boulevard Shore Protection Log of Boring No: 1 (Cont'd) . 1 Material Description a 0 ! - 30 1-7 74 (Continued) very dense, wet, gray, poorly graded fine to medium sand (SP SM) with silt and pebbles and shells - locally - 35 - - 18 60 • 17 112 GS 40 - - 19 95 Bottom of Boring at 41.5 feet : 45 - - 50 - .. - 55 - - 60-. - 65. Project N8851268E-SI01 I Woodward-Clyde Consultants Figure: A-3 Project: Carlsbad Boulevard Shore Protection Log of Boring No: 2 Date Drilled: 7-11-88 Water Depth: 13' Measured: At time of drilling Type of Boring: 8" HSA Type of Drill Rig: B61 Hammer: 140# at 30" drop * see Key to Logs, Fig. A-I Cl) CA- Material Description . Cl) FM Surface Elevation: Approximately 13' MSL 0 21 3" Asphalt concrete; 6" gravel base over moist, gray, silty sand 2-2 FILL Loose to medium dense, moist, gray, sandy gravel (GP) with rounded cobbles (2"-4") 5 ----Grades to— ------------------ 10 - Dense, wet, gray, gravelly sand to sandy gravel (SP-GP) - 2-3 51 Medium dense wet gray, poorly graded fine sand (SP) with layers of shells and pebbles locally 15- - 24 10/ gravel 6..On 24 90 GS 0111 ] Sandy gravel layer (GP) with shells - 20 -1 25 45/ 6* *On gravel - - Bottom of Boring at 21.5 feet - 25— - 30 ________________________ Project No: 8851268E-S1 I Woodward-Clyde Consultants Figure: A-4 Project: Carlsbad Boulevard Shore Protection Log of Boring No: 3 Date Drilled: 7-11-88 Water Depth: None encountered Measured: At time of drilling Type of Boring: 8" HSA Type of Drill Rig: B61 Hammer: 140# at 30" drop * see Key to_Logs, Fig. A-i o U) E Iz-- - o Material Description. - 1010 • 00 CD - 0 __ ( CO (_) Surface Elevation: Approximately 13' MSL 0 - Dry to moist, brown, silty sand with gravel • FILL ___ Loose to medium dense, moist, gray, sandy gravel (GP) with - - . - --- ,rounded cobbles (3"-4") - Refusal at 2.5' on cobbles - 5- - 10- - 15- 20- 25 - 30 -- _________________-•_ ____ Project No: 8851268E-Slo-1 I_ Woodward-Clyde Consultants Figure:A-5 Project: Carlsbad Boulevard Shore Protection Log of Boring No: 4 Date Drilled: 7-11-88 Water Depth: 14' Measured: At time of drilling Type of Boring: 8" HSA Type of Drill Rig: B61 Hammer: 140# at 30" drop see Key to Logs, Fig. A-i .2 — Material Description .— a cc Surface Elevation: Approximately 15.5' MSL 0 6" Asphalt concrete over moist, olive brown, sandy gravel FILL - 4-1 Moist, olive brown, gravelly sand - FILL 4-2 : Loose to medium dense, moist, gray, sandy gravel (GP) :• 5- :•: d# :.:.. Medium dense moist light gray, poorly graded fine sand (SP) 10 - with interbeds of silty sand shells and fine gravel layer4-3 - 6 16 94 GS 15- - - 44 10/ 6"* On gravel 24 98 GS 20 - - Dense wet gray, gravelly fine sand (SP GP) - 45 61* *On gravel Dense, wet, dark gray, poorly graded fine sand with gravel (SM)_ - - — Bottom of Boring at 22.5 feet 25- - 3O, Project No: 8851268E-SIo1 Woodward-Clyde Consultants Figure: A-6 100 LF 60 40 KE 0 I ) )O UNIFIED SOIL CLASSIFICATION COBBLES I GRAVEL I SAND I COARSE FiNE Icoi4 MEDIUM J FiNE U.S. WEVS me IN INCU I u. ST*NDâIW ==No. I SILT OR CLAY GRAIN SIZE IN MIILIMFER SYMBOL BORING D If 0 H &s &\ DESCRIPTION o 1-1 POORLY GRADED SAND WIIH GRAVEL (SP) O 1-2-4 POORLY GRADED FINE SAND (SP) 1-6-4 POORLY GRADED FINE TO MEDIUM SAND WITH SILT O 1-8-4 POORLY GRADED FINE TO MEDIUM SAND (Sp-sM) (Sp) Remark : 885 1268E 5101 CARLSBAD BLVD. SHORE PROJECT Woodward Clyde. Consultant. GRAIN SIZE DISTRIBUTION Figure No. A-7 San Diego, CA UNU'IED SOIL CLASSIFICATION GRAVEL I SAND I cs SILT OR CLAY u.s. sixvs ME is mcn I 11 . STAND= SIEVE NO. I MDROURM H ENI!_I 0 mmmlmmm '~ ! I__I 11MEN I__ II___11111 E111011111MEN. — II nil ii' E110011 - a lIn.i...tfl ap - 11a S — IIIIIIIIIIIIIja GRAIN SIZE IN MILLIbTEER SYMBOL BORING DH 1'i t% DESCRIPTION 2-4-4 POORLY GRADED FINE, SAND (SP) 4-3-4 POORLY GRADED FINE SAND (SP) 4-4-4 POORLY GRADED FINE SAND (SP) Remark: 885 1288E 8101 CARLSBAD BLVD. SHORE PROJECT Woodward Clyde Consultants GRAIN SIZE DISTRIBUTION Figure No. A-8 San Diego, CA Woodward-Clyde Consultants ~;QMK11811 COASTAL CONSIDERATIONS FOR CARLSBAD BOULEVARD SHORE PROTECTION CARLSBAD BEACH STATE PARK - AREA 3 General The subject area is located along a barrier beach at the mouth of the Agua Hedionda lagoon between the inlet and outlet jetties for the outer portion of the lagoon. The elevations along Carlsbad Boulevard in this area, which extends along the berm at the back of the beach, generally range from approximately +13 to +16 feet (MSLD). Carlsbad Boulevard is partially protected by the beach which is typically 150 to 200 feet wide and is partially composed of gravel and cobbles. The sand levels vary seasonally and are mostly removed during high tides and storms during the winter. The subject area is generally situated near the middle of the Oceanside littoral cell. A recent report by Tekmarine, Inc. indicated that the Oceanside littoral cell is basically "sand-starved." However, despite the deficiency of sand, the coastline of Carlsbad manages to maintain a finite beach width; this appears to be due to the abundance of gravel and cobbles in the area. The subject area also receives sand nourishment every 2 to 3 years from dredging of the lagoon. Erosion of the beach and damage to the roadway due to high tides and storm waves occurs on a periodic basis. Maximum Tide and Still Water Level Based on records from 1925-1953 and 1956-1970, the Army Corps of Engineers' Shore Protection Manual (S PM) gives a maximum observed water level at San Diego of +7.6 feet above MLLW. Tidal predictions for this area are based on daily predictions for San Diego. The corrections to the high water predictions are 0.90 for La Jolla, south of Carlsbad, and 0.91 for San Clemente, north of Carlsbad, implying that conditions along this portion of the coast, including those at Carlsbad, are fairly uniform. Flick and Cayan (1984) have examined extreme high water levels at San Diego, including the 198243 winter, which included high astronomical tides, meteorological effects associated with the many storms, and the extreme effects of El Nub. The highest recorded level at San Diego is +8.5 feet in late January, 1983. This was nearly a foot above the predicted level. Applying the correction for La Jolla - San Clemente gives a value of 0.91 x 8.5 = +7.74 feet for the Carlsbad site. Adding an allowance for 0.35 feet sea level rise in 50 years, and 0.5 feet for local wave set-ups, gives the following Design Still Water Level: Maximum Observed Tide 7.74 feet MLLW (Mean Low Low Water) Sea Level Rise .35 Local Wave Set-Up .50 Design Still Water Level. 8.59 or approximately 8.6 feet MLLW (or 5.7 MSLD) a/1j12 B-i Woodward-Clyde Consultants NOTE: In the calculations, Mean Lower Low Water (MLLW), the datum for both nautical charts and tide tables, is taken as the vertical datum. The Mean Sea Level Datum of 1929, which is generally used for onshore topographic maps, is approximately 2.9 feet above MLLW. Beach Profiles Beach profiles have been made in the area by Walton, Flick, and Murray in 1982 and 1983; by the Army Corps of Engineers in 1983 and 1984; and Tekmaiine, Inc. in 1987 and 1988. As a part of our study, Woodward-Clyde Consultants also made four beach profiles on July 19, 1988 at the approximate locations shown on Figure No. 2. These latter profiles are attached as Figure B-i. An evaluation of the various beach profiles indicates that the sand on the backshore beach area generally varies about 4 to 5 feet in thickness and is typically completely removed after major storms. The beach width (to MLLW line) near the middle of the site varied from a maximum of approximately 300 feet after nourishment to a minimum of approximately 150 feet after major storms during the period between 1982 and 1988. A small sand berm generally develops in the profile during the winter at about 250 to 350 feet offshore. This berm also appears to be removed during a major storm. The inclination of the foreshore (where cobbles are generally exposed) generally ranges from about 6:1 to 10:1 (horizontal to vertical). The bottom flattens below the MLLW line to inclinations on the order of about 30:1 to 50:1. Beyond a distance of about 500 feet offshore the bottom inclination is generally about 60:1 to 70:1 extending to at least 2,000 to 3,000 feet offshore. For purposes of design it is assumed that the beach slope in front of the shore protection structure will be approximately 30:1 to 50:1. Design Scour Depth The current beach profiles and test borings indicate that the top of the cobble berm at the site generally ranges between approximate elevations of +8 to +12 feet (MSLD), is about 8 to 10 feet thick and extends about 50 to 100 feet out (west) from the proposed shore protection alignment. The available beach profiles indicate that since 1982, the top of this berm near the middle of the site has not eroded below approximate elevation +8 feet (MSLD) and that the face of the berm near the middle of the site has not been eroded any closer than about 30 feet from the proposed alignment. The erosion at the north end of the site appears to be somewhat more severe and the erosion at the south end somewhat less severe than at the middle of the site. For purposes of preliminary design, it is assumed that the maximum depth of scour in front of the shore protection structure along the west side of Carlsbad Boulevard will be elevation zero (MSLD). a/1j12 B-2 Woodward-Clyde Consultants Design Wave Height The breaking wave height in front of the shore protection will depend upon the beach inclination in front of the structure, the design scour depth in front of the structure and the maximum still water level. Based on the above information, it is estimated that maximum design water depth at the toe of the structure will be approximately 5.7 feet and the maximum breaking wave height will be about 6 feet. It is further estimated that the maximum runup on a 1-1/2:1 inclined rock revetment and a vertical seawall would be approximate elevations +15 feet and +18 feet, respectively. Typical calculations for design are attached. a/1j12 B-3 CL R/W +18 I 9 +16- pRiprap +14-, J . -. +12- PçRiPaP\\ ID b' 0-0-00 P-3 (South End) I 'o \ 'A c +6- I P2 +4 0 4-2.. (North End) 0, D..o• 00_0_0__0 0.-o Profilés on 7-19-88 -2 • See Figure 2 for profile locations Centerline elevation from Plan for 4. Improvements of Carlsbad Boulevard City of Carlsbad Project No. 3205 -6- Ct, - Centerline of Carlsbad Boulevard R/W - Westerly edge of Carlsbad Boulevard -8.. Improvements right of way. I I I 0 100 200 300 DISTANCE FROM CENTERLINE OF CARLSBAD BOULEVARD (Feet) W000WARD-CLYDE CONSULTANTS to o.00ni (2. 0,Oo(7-3 9) (C o.oO Ti'r- cna /rt (c. 10 ) 0,00r'71 0,00 t.3 (,2. Oo 1.6 0,00 06 2.7L1 I 5.53 .5-i- flo Z.( .1os tL' 3 j'y . -i°r-H o 2 ALfa ,-16-L - /'1?1(2 / ,T, -' Sb 0. 02. cX L rA,v i?i, F&. 7-'( / ((' go.) )P•1 sr-; Otiar)-t) 0. o 32. /f - 6P ,wKvtz 'iv f((6-HT T Nb Woodward-Clyde Consultants 0 1550 Hotel Circle North San Diego, California 92108 PROJECT NAME ZC$2 f? 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CHECKED BY UI- (A IQ 5 flr3 p. 7-1 YT 3z.zC) w0.-i_ ., -S.PtL F-r-. !-( - 7,0 P/,- ^-r Ski L ( cz.c- € c Woodward-Clyde Consultants ArA qW JOB NO. 1550 Hotel Circle North t? San Diego, California 92108 DATE 7 — DRAWN BY PROJECT NAME ••.•(:tr1.IsYi _.-C'-' CHECKED BY L)L- I JOB NO. x-r 2 DATE fiP DRAWN BY CHECKED BY Woodward-Clyde Consultants qW 1550 Hotel Circle North San Diego, California 92108 PROJECT NAME 3.1 - J3, 76 &•6, 7-10 i!/'// /Zx-5 i.(of, -7 7 3,6 IKO Ile ~cAi Coa rrcy'J i1t.'( Tc& c)C•• Pc-, -t ( -z c (".(66 (.( Zr::.,.' ( ce' Fo(t.. flcJ -Op. 0. S ro fWL ( (? 05 C 1 bE&zt &-,u u. - tJC Fr—. - ( 9 '-C -• ccp - = . 03 S. 7 5 CIs kM3 (sc) 10 O.Oc)(11 6 6,04 (c)B ,- =- F H 1 FL to o C'a (17 1 0Oo3 '( ZJ7 C Woodward- Clyde Consultants AMU 1550 Hotel Circle North San Diego, California 92108 PROJECTNAME C(4(2Li &'-3 fl'2s, JOB NO. D5—f•7 (G DATE_ - ? —?7— 9-9 DRAWN BY - CHECKEDBY Li1- 2a"-€ 4-t) ;' —,i , -i Y-:t-s) , F&. ? d 5 / ): /, 6 hi I( •- /, S 9 ,?/,% / = O9 i_c. 7 -I1 /r1 •'62.io' O.° O// pC)Q -7-t 2:1 Q,7 r 77'.115 fr) e- c• 4'5 C,f/. t .. .- ,' I Woodward-Clyde Consultants ArA 1550 Hotel Circle North San Diego, California 92108 PROJECT NAME -'7") '7 --/V JOB NO. za-', DRAWN BY ________________ CHECKEDBY U C Woodward-Clyde Consultants APPENDIX C USER BENEFIT CALCULATIONS FOR CARLSBAD BOULEVARD SHORE PROTECTION CARLSBAD BEACH STATE PARK - AREA 3 General It is generally anticipated that loss of user benefits will be due to damage from high tides and storms. For this analysis, it is assumed that the Carlsbad Boulevard Improvements, are contructed and that damage will occur on a periodic basis. The value of the benefits lost is estimated from the value of lost time, lost use of the area, and cost of repairs and maintenance. The following assumptions are made for the evaluation: A 50 year useful life for the project; Major damage due to storms once in five years; Minor damage due to storm twice in five years; General maintenance required in years of no significant damage; A minimum average beach use of 3,000 persons per day; An average future daily traffic for Carlsbad Boulevard of 27,000 per day; An average daily bicycle traffic of 200 per day; and Gas, water, electric and storm drain utilities present in Carlsbad Boulevard. Loss of Beach Users Benefits It is generally considered that the beach season in Carlsbad is year around. Maximum use will be in the summer (May through September) weekends and holidays. Minimum use will be weekdays during the winter. The California Department of Parks and Recreation consider Area 3 as the most highly used beach in this area. Based on California Department of Parks and Recreation information, this approximately 2,600 feet of beach had an estimated total of 1,825,000 visitors in the 1980-81 fiscal year. Based on this information, it is estimated that park use will average about 5,000 persons per day and have a minimum use of about 3,000 persons per day. It is anticipated that most damage will occur in December, January and February and most loss of use due to restricted access and parking during repair and maintenance time will be in January, February, March and April. For this estimate, it is assumed that beach use will be reduced by 50 percent for four months (120 days) after a major storm and 25 percent for two months (60 days) after a minor storm. Thus, for a five year period it is estimated that Mjl2 C-i Woodward-Clyde Consultants 90 days of beach use would be lost or approximately 18 days per year. It is further assumed that this loss will be during minimum use time; thus, the average total user day• lost per year is 54,000. If the value of each recreation day benefit is assumed to be $1.50, the annual beach user benefit loss will be: Annual Beach user Benefit Loss = 1.5 x 54,000 = $81,000 Loss of Bicycle Lane Use Carlsbad Boulevard has a dedicated bicycle lane along its full length in the proposed project area. This is considered a main recreational bicycle travel lane in the 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. It is estimated that the bicycle lane would be closed during maintenance and repair for 120 days one year and 60 days for two years, for a total of 240 days during a 5 year period. This is an average of 48 days per year, or 9,600 trips per year. Thus, the annual bicycle user benefit loss will be: Annual Bicycle user Benefit Loss - 1.5 x 9,600 = $14,400 Loss of Time due to Traffic Reduction 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. It is estimated that traffic would be detoured for a period of 60 days after a major storm and 20 days after a minor storm, or a total of 100 days during a five year period. This is an average of 20 days per year which is equal to 540,000 vehicle trips. 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 $0.30 per mile would produce a total annual vehicle operating cost for using the detour of: Annual Vehicle Operating Cost = 0.30 x (0.6 + 0.4) x 540,000 = $162,000 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 lost time cost for use of the detour of: Annual Lost Time Cost = 5.00 x (0.6 + 0.4) x 1.5 x 540,000/35 = $115,715 a11j12 C-2 Woodward-Clyde Consultants Facility Replacement Costs It is assumed that each existing utility would have to be replaced over a length of 2,500 feet once during the design life of 50 years. The estimated cost for the replacement of each facility is as follows: High pressure gas main 140,000 Water main 120,000 Electrical lines 20,000 Telephone lines 20,000 Total Cost $300,000 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 = $300,000 x 0.12042 = $36,126 Improvement Replacement/Maintenance Cost It is anticipated that after each major storm (once every five years) the sidewalk, street lights, a portion of the pavement, the bike lane and storm drain inlets will have to be replaced. It is estimated that the cost for this work will be approximately $180,000 or an annual cost of $36,000. It is anticipated that some repair and maintenance will also be required after minor storms (twice every five years). It is estimated that this work will be approximately 25 percent of the major damage, or an annual cost of $9,000. During years where there is no storm damage, it is estimated that normal maintenance will be about $5,000 per year or a total of $10,000 for two years. This is an annual cost of $2,000. Total Annual Improvement Replacement/Maintenance Costs Other Losses It is also anticipated that temporary reduction to beach access in and travel through this area will reduce the tourist use of the area. This will in turn result in lost revenue to businesses in Carlsbad and corresponding losses of sale tax revenue. For purposes of this study, it is estimated that such losses might be on the order of $50,000 per year. a/1j12 C-3 Woodward-Clyde Consultants APPENDIX D SHORE PROTECTION STRUCTURES FOR CARLSBAD BOULEVARD FOR SHORE PROTECTION CARLSBAD BEACH STATE PARK - AREA 3 General The primary purpose of the shore protection structure in the subject area is to protect Carlsbad Boulevard and the associated improvements, including walkways, bicycle lane, parking and utilities. With this primary purpose in mind, various alternative structures may be considered taking into consideration several other objectives. The intent is to select a low cost alternative that has a low level of maintenance and is aesthetically pleasing. Other objectives include minimizing encroachment onto the beach, reduce construction-related impacts and provide both lateral and vertical beach access. The proposed structure will generally be located along the westerly edge of the Carlsbad Boulevard Improvements right-of-way. A walkway will be constructed behind and for the entire length of the structure within the right-of-way. The walkway , would have an elevation ranging from approximately +13 to +15 feet with a 3.5-foot high railing along the ocean side. It is anticipated that most vertical structures would be extended up to form the railing at an approximate top elevation +16.5 to +18.5. It is anticipated that stairways, ramps and lifeguard facilities will encroach onto the beach from 5 to 10 feet beyond the right-of-way in certain areas. Additional encroachment onto the beach would be required depending on the selected design. A general discussion of various alternative structures is presented in the following paragraphs. Rock Revetment The existing roadway is currently protected by dumped rock and rubble at the north and south ends of the project. These existing revetments do not appear to be designed and generally require annual maintenance and repair, particularly at the north end. Both revetments tie into the existing rock jetties for the inlet and outlet to Agua Hedionda Lagoon. It is anticipated that these revetments would be replaced for a distance of approximately 250 feet and 175 feet at the north and south ends, respectively. The revetment could also continue along the road between these two areas. It is anticipated that the top of the revetment would be of approximate elevation +16 feet (MSLD) for most of the alignment and raise up to approximately +20 feet at the north end. It would slope down at an approximate inclination of 1-1/2:1 (horizontal to vertical) to a toe elevation of about -2 feet. A typical section is shown on Figure No. D-1. Advantages of this shore protection method are that it provides good wave energy absorption, has a reasonable cost, can be rapidly constructed, has low maintenance requirements and will easily tie-into the existing rock revetments and rock jetties at both ends. Disadvantages include a relative wide encroachment onto the beach (approximately 30 to 40 feet), difficult access across and through the revetment, and collection of debris. a/1j12 D-1 Woodward-Clyde Consultants Reinforced Concrete Vertical Wall This structure would be a conventional reinforced concrete L-shaped wall. The top of the wall would be at approximate elevation +17.5 feet and the bottom of elevation +3 feet with a cut-off wall extending to approximate elevation -1 feet. The stem of the wall would be about 18 inches thick and the L-portion could extend back into the right-of-way. This wall would have to be supported on piles. Advantages of this seawall are that it has a low encroachment onto the beach (less than 2 feet), the anticipated maintenance is low and the stairways and ramps could be easily incorporated into the wall. Disadvantages include a high cost and difficult construction. Reinforced Earth Wall This type of wall is a patented structure that is composed of precast reinforced concrete face panels tied-back into a zone of compacted select fill by steel reinforcing strips. The face of the wall could be located along the edge of the right-of-way and the approximately 12 feet long reinforcing strips could extend back into and under the proposed walkway and other improvement. The toe of this wall would be at approximate elevation -1 feet and would be protected by rock extending about 10 feet out onto the beach below an elevation of +6 feet. A typical section is shown on Figure No. D-2. Advantages of this wall are that it is easy to construct, has a low cost and could be built with a moderate encroachment onto the beach. Access stairs and ramps can also be easily incorporated into the design. Construction would require additional excavation and compaction of soil and a larger encroachment into the right-of-way or out onto the beach. Corrosion of the reinforcing strips needs to be considered in the design. Stresswall Stresswall is another patented structure that is generally composed of precast reinforced concrete tie-backs and precast reinforced concrete panels backfilled with compacted select soils. The dimensions and construction area would be similar to the Reinforced Earth Wall. It would also require toe stone and a shallow cut-off wall. A typical section is shown on Figure No. D-3. The advantages and disadvantages of this wall are similar to the Reinforced Earth Wall; however, corrosion of steel strips is not of concern. Vertical Sheet Pile Walls Vertical sheet pile walls could be constructed of either steel or concrete and could either be cantilevered with toe stone or anchored with deeper penetration. The anchored wall would have minimum encroachment on the beach, but would require additional excavation and an underground anchor within the right-of-way. The steel sheeting is easier to drive than the concrete sheeting (which would probably require excavation of the cobble layer and jetting). a/1j12 D-2 Woodward-Clyde Consultants Corrosion of the steel needs to be considered in the final design. Typical sections are shown on Figures Nos. D-4 and D-5. Other Shore Protection Structures Other types of shore protection that could be considered include cribwalls, Fabriform (a patented product consisting of nylon bags filled with concrete) and steel H-piles with wood or concrete lagging. a/1j12 D-3 Street and Walk OM S Handrail Crest Elevation Varies +16' to +201 (MSLD) Approximate A-Stone (two ton) Beach Level E,ap Filter Cloth 51 B-Stone rili 6" Quarry Waste Base at -2' (MSLD) ' Lap Filter Cloth 5' W000WARD-CLYDE CONSULTANTS —+17.5' Walkway Filter Cloth 1il Reinforced Concrete Cap —+14.0' _Reinforced Earth Wall Typical Reinforcing Strips —+6.0' Toe Stone _-3.0 Filter Cloth 121. 91 Reinforced Concrete Footing "REINFORCED EARTH WALL" WITH TOE STONE CARLSBAD BOULEVARD SHORE PROTECTION DRAWN BV:cb I CHECKED BY:144 I PROJECT NO:8851268E-5101 J DATE: 8-3-88 FIGURE NO: D-2 WUUUWAKU-CLYDEUNSULTAN1 Reinforced Concrete Cap +17.5' Walkway +14.0' Reinforced Concrete Stresswafl. Filter Cloth Typical Beach Level 6.0' +50' Toe Stone 12' Concrete Cut-Off 09, 'Filter Cloth -1' I REINFORCED CONCRETE "STRESSWALL" WITH TOE STONE CARLSBAD BOULEVARD SHORE PROTECTION [DRAWN BY: cb I CI.4ECKEDBY:f,/41 PROJECT NO: 8851268E-SI01J DATE:8-3-88 FIGURE NO: D-3 WOODWARD-CLYDE CONSULTANT 1P7 ? I STEEL SHEET PILE WALL WITH CONCRETE CAP AND TOE STONE I CARLSBAD BOULEVARD SHORE PROTECTION DRAWN BY: cb CHECKED BY:j/LI PROJECT N02851268E-8851268E J DATE:8-3-88 I FIGURE NO: D-4 WOODWARD-CLYDE CONSULTANTS 7 L Walkway I Reinforced Concrete Cap +14. 0 Typical Beach Level Anchor 471 - +3.0 Steel Sheet Pile I, -20 ANCHORED SHEET PILE WALL WITH CONCRETE CAP CARLSBAD BOULEVARD SHORE PROTECTION DRAWN BY: eb CHECKED BV:// I PROJECTNO:8851268E-SIO1J DATE: 8-3-88 I FIGURE NO: D-5 WOUDWAKU-CLYDE CUNSULTANTS