HomeMy WebLinkAbout3618; PARKING CARLSBAD BLVD AT PONTO BEACH; RECONNAISSANCE REPORT; 1994-01-01k~,oaU
I US Army Corps
of Engineers
Los Angeles District
I .. - -- - -
I
*
f
RECONNAISSANCE REPORT
I -
I PACIFIC COAST SHORELINE, CARLSBAD
I - SAN DIEGO COUNTY, CALIFORNIA
I 4
I 4
MAIN REPORT
I *
I - U.S. Army Corps of Engineers
- '. Los Angeles District
300 North Los Angeles Street-
I • - -
Los Angeles, California 90053 -
January 1994
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£ H'i L I21 1 7 iE4
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TABLE OF CONTENTS
1.0 INTRODUCTION 1-1
1.1 Study Authority ....................................1-1
1.2 Purpose and Scope .................................1-1
1.3 Study Conduct .....................................1-1
1.4 Public Involvement ............. . ....................
1-2
1.5 Prior Studies ..... ................................1-2
1.5.1 Corps of Engineers Studies ......................1-2
1.5.2 Studies by Others ............................1-4
2.0 THE STUDY AREA ......................................2-1
2.1 Location ........................................2-1
2.2 Description ......................................21
2.2.1 Reach 1 .... ................................ .2-1
2.2.2 Reach 2 ....................................2-1
2.2.3 Reach 3 ...................................2-4
2.2.4 Reach 4. . .
.-. .. . . . . .-L .. .. .. . . .. . . . .. -............ 24
2.3 Physical Characteristics ..............................2-5
2.3.1 Bathymetry ................................2-5
2.3.2 Local Geology/Sediment Characteristics .............. 2-5
2.3.4 Tides and Sea Level ..........................2-7
2.3.5 Water Levels ...............................2-8
2.3.6 Currents ..................................2-8
2.3.6.1 Offshore Currents ......................2-8
2.3.6.2 Longshore Currents .....................2-8
2.3.6.3 Cross-shore Currents ....................2-9
2.3.7 Waves and Storms ...........................2-9
2.3.8 Littoral Processes ...........................2-12
2.3.8.1 Sediment Sources and Sinks ..... ......... 2-13
2.3.8.2 Existing Structures, Beachfills, and Dredging
History..............................2-14
2.3.8.3 Erosion and Accretion Rates ..............2-16
2.3.8.4 Historic Shorleine Changes ...............2-17
2.3.8.5 Historic Profiles .......................2-17
2.3.8.6 Longshore Transport ...................2-18
2.3.8.7 Sediment Budget ......................2-18
2.4 Social and Economic Factors .........................2-22
2.4.1 Location and Description ......................2-22
2.4.2 Demographics .............................2-22
2.4.2.1 Population ............... ...........2-23
2.4.2.2 Tourism and Recreation as Major Industries . . . 2-23
2.4.2.3 Employment . 2-24
2.3.2.4 Income ............................2-24
2.5 Existing Environment ...............................2-24
2.5.1 Biological Resources .........................2-25
2.5.1.1 Marine Resources .....................2-25
2.5.1.2 Terrestrial Resources ...................2-25
2.5.1.3 Lagoon Resources .....................2-26
2.5.1.4 Coastal Barriers .......................2-27
2.5.2 Threatened and Endangered Species ...............2-27
2.5.3 Water Quality ..............................2-27
2.5.4 Ambient Noise and Air Quality ..................2-28
2.5.4.1 Ambient Noise .......................2-28
2.5.4.2 Air Quality ..........................2-28
2.5.5 Cultural Resources ..........................2-28
2.5.6 Aesthetics ................................2-28
3PROLEMIDENTCA1]ONJ 3-31
3.1 Statement of the Problem ...........................3-31
3.1.1 Reach 1 ..................................3-31
3.1.2 Reach 2 ..................................3-31
3.1.3 Reach 3 ..................................3-31
3.1.4 Reach 4 ..............................
Ci 5 Reach 5 332?
3.2 Summary of the Analysis .............................3-33
3.3 Damages.......................3-16
3.3.1 Inundation Damages .........................3-16
3.3.2 Damages to Protection ........................3-17
3.3.3 Structural Damages ......... .................. 3-19
3.3.4 Roadway Damages ..........................3-21
3.4 Economic Loss ...................................3-23
\3.5 Recreation / ....................................3-27
3.6.1 Reach 1 ...................................3-28
3.6.2 Reach 2 ............. . ..................... 3-28
3.6.3 Reach 3 ..................................3-29
3.6.4 Reach 4 ........ . . . 3:29
3.6,5 --Reach
4.0 PLAN FORMULATION ..................................4-32
4.1 Rationale of Formulation ............................4-32
4.1.5 Costs ....................................4-34
4.2 Plan Alternatives ..... .............................4-34
4.2.1 Plan 1 - Beachfill in Reaches 1 and 2 ...............4-35
4.2.1.1 Description ..........................4-35
4.2.1.2 Engineering Evaluation . 4-8
4.2.1.3 Environmental Evaluation .................4-9
4.2.2 Plan 2 - A Groin System with Beachfill in Reaches 1
and2 ....................................4-13
4.2.2.1 Description ..........................4-13
4.2.2.2 Engineering Evaluation ..................4-13
4.22.3 Environmental Evaluation ................4-13
4.2.3 Plan 3 - An Offshore Breakwater System in Reaches 1
and2 ....................................4-18
4.2.3.1 Description ..........................4-18
4.2.3.2 Engineering Evaluation ..................4-18
4.2.3.3 Environmental Evaluation ................4-18
4.2.4 Plan 4 - New and Repaired Revetments in Reach 1 . . . . 4-23
4.2.4.1 Description ...........................4-23
4.2.4.2 Engineering Evaluation ..................4-23
4.2.4.3 Environmental Evaluation ................4-23
4.2.5 Plan 5 - Beachfill and North Intake Jetty Extension
in Reach 1 ................................4-28
4.2.5.1 Description ..........................4-28
4.2.5.2 Engineering Evaluation ..................4-28
4.2.5.3 Environmental Evaluation ................4-30
4.2.6 Plan 6 - Beachfill in Reach 3 ....................4-33
4.2.6.1 Description ..........................4-33
4.2.6.2 Engineering Evaluation ..................4-33
4.2.6.3 Environmental Evaluation ................4-36
4.2.7 Plan 7 - A Groin System with Beachfill in Reach-3 . . . 4-39
4.2.7.1 Description ..........................4-39
4.2.7.2 Engineering Evaluation ..................4-39
4.2.7.3 Environmental Evaluation ................4-39
4.2.8 Plan 8 - An Offshore Breakwater System in Reach 3 . . . 4-43
4.2.8.1 Description ..........................4-43
4.2.8.2 Engineering Evaluation ..................4-43
4.2.8.3 Environmental Evaluation ................4-43
4.2.9 Plan 9 - A Seawall in Reach 3 .....................4-48
4.2.9.1 Description ...........................4-48
4.2.9.2 Engineering Evaluation ...................4-48
4.2.9.3 Environmental Evaluation ................4-48
4.2.10 Plan 10 - A Rubble-Mound Revetment in Reach 3 . . . . 4-53
4.2.10.1 Description .........................4-53
4.2.10.2 Engineering Evaluation .................4-53
4.2.10.3 Environmental Evaluation ...............4-53
4.2.11 Plan 11 - Beachfill and Structures in Reaches 1, 2, and
3 .......................................4-56
4.2.11.1 Description ........................... 4-56
4.2.11.2 Engineering Evaluation .. 4-59
4.2.11.3 Environmental Evaluation -.................4-59
14
r4 iee ri ivatidn T. 74- 627
? t2
f23 EviroñneñtaIEvãlTãti&n' - --
4.2.13 Plan 13 - A Groin System-with Beachfill in Reach 1 . . 4-65
4.2.13.1 Description ..............; ..............4-65
4.2.13.2 Engineering Evaluation .......4-65 I 4.2.13.3 Environmental Evaluation . .:.-............4-67.
4.2.14 Plan 14 - A T-Groin with Beachfill in Reach 3 .......4-70
4.2.14.1 Description....... .................... 4-70
4.2.14.2 Engineering Evaluation ....... .... ........ 4-70
4.2.14.3 Environmental Evaluation . . .,. . .., .........4-70.
4.3 Identification of ,Justified Projects . •. . . ............4-77 I
5.0 FEDERAL INTEREST DETERMINATION ................... ... ....... 5-1
5.1 General .......... ..................5-1 I
5.2 Purposes of Federal Participation .. .......................... 5-1
5.2.1 Hurricane and Storm Damage Reduction ..... ......... 5-1
5.2.2 Recreation .....................................5.4
5.2.3 Mitigation of Shore Damage Due to Federal. Navigation
Projects ......................., .............54
5.3 Shore Ownership ..............................................54
5.3.1 Non-Federal Public Shores-Park and Conservation Areas . . 5-5
5.4 Beach Creation . . . ....................................5-5
5.5 Periodic Nourishment ................................... 5-5
5.6 Maintenance ....................... ...........5-6
5-6 I 5.7 Local Cooperation Requirernets. . .... . ........
15 8; DeterrninaonfF'eraI'Interest IrLShore Protection Plansat
Carlsbad!CaIIfornia .......................... ... S...........5-7
.8.1 Requirement for Plans to be Justified Primarily on Storm
Damage Reduction Benefits ., .....................5-7
5.8.2 Requirement for Public Use, Access, and Parking .......5-8
5.8.3 Mitigation of Impacts from
Sh6rtenReach45 tc
58.5 Conclusion of Federal Interest Determination ..........5-9
59 Federal and Non-Federal Requirements For lmplementationof
Shore Protection in Reach 3 ........................... . . . . 5-9
5.9.1 Cost sharing of First Cost . .,. ......- . ..............5-9
5.9.2 Cost sharing of Periodic Nourishment and Maintenance . . 5-10
5.9.3 Other non-Federal requirements; ....................5-10
6.0 IPMP/FEASIBILITY PHASE REQUIREMENTS .........................6-1 I
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- 7.0 CONCLUSIONS ......................................... 7-1
8.0 DISTRICT ENGINEER'S RECOMMENDATION ....................8-1
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LIST OF FIGURES
Figure 2.1 Vicinity of Carlsbad, California................... . . . 2-2
Figure 2.2 Five Reaches of Carlsbad Coastal Area....................2-3
Figure 2.3 Oceanside Littoral Cell...............................2-6
Figure 2.4 Statistical Distribution of Higher Water at San Diego..........2-10
Figure 2.5 Wave Exposure for San Diego Region....................2-10
Figure 2.6 Future Without Project Sediment Budget..................2-21
Figure 3.1 Beach in Front of Carlsbad Boulevard ................... .3-4
Figure 3.2 Reach 4 - View towards Encinitas Creek...................3-4
Figure 3.3 Reach 4 - Bluffs of South Carlsbad State Beach..............3-4
Figure 3.4 Schematic Profile of Carlsbad-Reach 1 Cross Section 1 ..........3-6
Figure 3.5 Schematic Profile of Carlsbad-Reach 1 Cross Section 2.. ...... 3-6
Figure 3.6 Schematic Profile of Carlsbad-Reach 1 Cross Section 3 ... ..... 3-7
Figure 3.7 Schematic Profile of Carlsbad-Reach 1 Cross Section 4 ... ..... 3-7
Figure 3.8 Schematic Profile of Carlsbad-Reach 2....................3-8
Figure 3.9 Schematic Profile of Carlsbad-Reach 3....................3-9
Figure 3.10 Schematic Profile of Carlsbad-Reach 4 .......... ........ 3-10
Figure 3.11 Schematic Profile of Carlsbad-Reach 4 Cross Section 2.......3-10
Figure 3.12 Schematic Profile of Carlsbad-Reach 5 .......... ........ 3-11
Figure 3.13 Typical Structure of Carlsbad-Reach 4, Cross Section 1 ... ... 3-12
Figure 3.14 Typical Structure of Carlsbad-Reach 1, Cross Section 2 ... ... 3-12
Figure 3.15 Typical Structure of Carlsbad-Reach 1, Cross Section 3 ... ... 3-12
Figure 3.16 Typical Structure of Carlsbad-Reach 1, Cross Section 4 ... ... 3-13
Figure 3.17 Typical Structure of Carlsbad-Reach 4, Cross Section 1 ... ... 3-13
Figure 3.18 Typical Structure of Carlsbad-Reach 4, Cross Section 2 ......3-13
Figure 3.19 Schematic of Structure on Bluff.......................3-20
Figure 3.20 Bluff Erosion versus Excess Wave Runup .......... ...... 3-21
Figure 4.1a Beachfill-Reaches 1 and 2 ................ ............ 4-5
Figure 4.1b Typical Cross Section of Beachfill-Reaches 1 and 2 .... ...... 4-6
Figure 4.1c Identified Potential Borrow Areas ......... .............. 4-7
Figure 4.2a Plan 2-Beachfill with Groins, Reaches 1 and 2 ....... ...... 4-13
Figure 4.2b Typical Cross-Section of Groin .............. ......... 4-14
Fiaure 4.3a Plan 3-Offshore Breakwaters, Reaches 1 and 2 ........ .... 4-19
Figure 4.3b Typical Cross-Section of Offshore Breakwater,
Reaches 1 and 2 .................... ............ 4-20
Figure 4.4a Plan 4-Revetment, Reach 1 ................ .......... 4-24
Figure 4.4b Typical Cross-Section of Revetment, Reach 1 ..............4-25
Figure 4.5 Plan 5-Beachfill and Jetty Extension, Reaches 1, 2 and 3. . . . 4-29
Figure 4.6a Plan 6-Beachfill, Reaches 1 and 2 ............ ......... 4-34
Figure 4.6b Typical Cross Section of Beachfill-Reach 3 ........ ....... 4-35
Figure 4.7 Plan 7-Beachfill with Groins, Reach 3 ........... ........ 4-40
Figure 4.8a Plan 8-Offshore Breakwaters, Reach 3 ........... ....... 4-44
Figure 4.8b Typical Cross-Section of Offshore Breakwater ......... .... 4-45
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Figure 4.9a Plan 9-Seawall, Reach 3 . 4-49
Figure 4.9b Typical Cross-Section of Seawall, Reach 3................4-50
Figure 4.10a Plan 10-Rubble Mound Revetment, Reach 3..............4-54
Figure 4.10b Typical Cross Section of Revetment, Reach 3.............4-55
Figure 4.11 a Plan 11-Beachfill with Structures, Reaches 1, 2 and 3 .... ..4-57
Figure 4.11b Plan 7-Beachfill with Groins, Reach 3 ............ ...... 4-58
Figure 4.12 Plan 12-Rubble Mound Revetment, Reach 5...............4-63
Figure 4.13 Groin System with Beachfill .................... . ...... 4-66
Figure 4.14 T-Groin with Beachfill...............................4-71
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LIST OF TABLES
Table 2.1 San Diego Tidal Characteristics ..........................27
Table 2.2 Oceanside Harbor ...... .............................2-1 1
Table 2.4 Major Coastal Structures Affecting Longshore Transport .......2-14
Table 2.5 Beach Fills and Relevant Dredging at Agua Hedionda .........2-15
Table 2.6 Dredging and Beachfills in Oceanside ....................2-16
Table 3.1 Typical Cross-Sections by Reach .................. .. ... ...3-7
Table 3.2 Storm Recession versus Return Period .....................3-15
Table 3.3 Wave Runup Level (Feet Mllw) Present Condition ............3-16
Table 3.4 Damage to Revetment ..............................3-18
Table 3.5 Data used for Calculation of Bluff Retreat ...... ........... 3-20
Table 3.6 Carlsbad Reach 3 Present Withour Project Physical
Table 3.7
Damages......................................3-22
Carlsbad Reach 3 Futer Without Project Physical
Table 3.8
Damages .....................................3-22
Carlsbad Reach 5 Present Without Project Physical
Table 3.9
Damages.....................................3-23
Carlsbad Damages Under Existing Conditions ............. 3-24
Table 3.10 Carlsbad Expected & Equivalent Annual Damages
Table 3.11
Without Project .................................3-25
Carlsbad Expected & Equivalent Annual Damages
Without Project by reach ......... ...................3-26
Table 3.13 Average Daily Number of Persons Accommodated at 75
ft2/person ..........................................3-28
Table 4.1a Carlsbad - Wave Runup Statistics at Reaches 1 & 2 - With
Project............................................
...
Table 4.1b Carlsbad Revetment Damages - With Project Conditions .......4-9
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Table 4.1c Plan 1 - Beachfill in Reaches 1 and 2- Cost Estimate ........4-11
Table 4.1d Annual Benefits -- Alternative 1 ........................4-12
Table 4.2a Plan 2 - A Groin System with Beachfill in Reaches 1 and 2 -
Cost Estimate .......................................4-16
Table 4.2b Annual Benefits -- Alternative 2 .......................4-17
Table 4.3a Plan 3 - An Offshore Breakwater System in Reaches 1 and 2 -
Cost.............................................4-21
Table 4.3b Annual Benefits -- Alternative 3 ........................4-22
Table 4.4a Plan 4 - New and Repaired Revetments in Reach 1 - Cost
Estimate ...........................................4-26
Table 4.4b Annual Benefits -- Alternative 4 .......................4-27
Table 4.5a Plan 5 - Beachfill and North Intake Jetty Extension in Reaches 1,
2, and 3 ............................................4-31
Table 4.5b 4-32
Table 4.6a
Annual Benefits --Alternative 5 ...............
.... .... Carlsbad Reach 3 - Road Damage with Project Beachfill ......4-36
Table 4.6b Carlsbad Revetment Damages - With Project Conditions ......4-36
Table 4.6d Annual Benefits -- Alternative 6 .......................4-38
Table 4.7a Plan 7 - A Groin System with Beachfill in Reach 3 - Cost
Estimate.............................................4-41
Table 4.7b Annual Benefits -- Alternative 7 .......................4-42
Table 4.8a Plan 8 - An Offshore Breakwater System in Reach 3 - Cost
Estimate............................................4-46
Table 4.8b Annual Benefits -- Alternative 8 .......................4-47
Table 4.9a Plan 9 - A Seawall in Reach 3 - Cost Estimate .............4-51
Table 4.9b Annual Benefits -- Alternatives 9, 10 ...................4-52
Table 4.10a Plan 10 - A Rubble-Mound Revetment in Reach 3 - Cost
Estimate...........................................4-56
Table 4.11 a Plan 11 - Beachfill and Structures in Reaches 1, 2, and 3 - Cost 4-60
Table 4.11b Annual Benefits -- Alternative 11 ....................4-61
Table 4.12a Plan 12 - A Rubble-Mound Revetment in Reach 5 - Cost
Estimate ........................................ .... 4-64
Table 4.12b Annual Benefits -- Alternative 12 .....................4-64
Table 4.13a Plan 13 - A Groin System with Beachfill in Reach 1 - Cost
Estimate............ ...............................4-68
Table 4.13b Annual Benefits -- Alternative 13 .....................4-69
Table 4.14a Plan 1,4 - A T-Groin with Beachfill in Reach 3 - Cost Estimate . . 4-72
Table 4.14b Annual Benefits -- Alternative 14 ......................4-73
Table 4.15 Summary of Descriptions of Alternatives and Cost Estimates . . 4-74
Table 4.15 '(continued) Carlsbad - Summary Cost Estimate of Alternatives 4-75
Table 4.16 Benefit Cost Ratio and Net Benifits
By Alternative ..................................4-76
Table 5.2 Estimated Cost-Sharing of Federal Shore
Protection Project for Reach 3 ..........................5-9
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1.0 INTRODUCTION
1.1 Study Authority
The study was authorized by House Public Works and Transportation
Committee Resolution adopted 15 March, 1988 which reads as follows:
"Resolved by the Committee on Public Works and
Transportation of the United States House of Representatives, That
the Secretary of the Army, in Accordance with Section 110 of the
River and Harbors Act of 1962, is hereby requested to conduct a
study of the shoreline in and adjacent to the City of Carlsbad, Sand
Diego County, California, with a view to determining the effects of
beach erosion upon the infrastructure, and the cause of damage to
public and private property and determining solutions which are
engineeringly, economically, and environmentally feasible."
1.2 Purpose and Scope
The purpose of this Reconnaissance Study is to (1) determine whether there
is justification for proceeding to the Feasibility Phase based upon preliminary
appraisal of cost, benefits, and environmental impacts of potential solutions, (2) an
assessment of the Federal level of interest based on Federal laws, policies, and
other guidance, (3) support of the non-Federal interests in the identified potential
solutions, (4) development of and Initial Project Management Plan (IPMP) including
scope, cost. and assigned responsibilities for feasibility studies, and (5) approval of
the cost-sharing agreement for the feasibility phase. The primary area of concern
to be addressed in this study in response to the study resolution and coordination
with the City of Carlsbad is storm damages resulting from erosion along the study
area coast.
1.3 Study Conduct
The Reconnaissance Study was performed by the Los Angeles District in
coordination with the City of Carlsbad, consistent with the principles and
guidelines contained in ER 1105-2-100. The study includes preliminary
engineering, economic, and environmental studies using available information,
interviews with agency and public interests to define problems, needs, solutions,
and potential impacts of alternative solutions.
1-1
1.4 Public Involvement
The non-Federal sponsor of this project is the City of Carlsbad. Throughout
the course of this study, consultation With the City was made through the
Community Development Office and the Carlsbad Beach Erosion Committee. A
public workshop was conducted on April 15, 1993. Federal and State agencies
were contacted for their interests in the project and specific comments relative to
their jurisdictional or professional concerns.
1.5 Prior Studies
1.5.1 Corps of Engineers Studies
U.S. Army Corps of Engineers, Oceanside, Ocean Beach, Imperial Beach, and
Coronado, San Diego County, California, Beach Erosion Control Study, House
Document No. 399. 1957. Recommended a project consisting of placing a
900,000 yd protective beachfill at Oceanside, generally 200 feet wide and 10,000
feet long from the vicinity of 9th street to Witherby Street, at one-third federal
cost. The views of the Beach Erosion Board concurred with the District Engineer's
opinion that jetties constructed at Camp Pendleton Harbor as a wartime measure in
1942 were primarily responsible for the erosion problem at Oceanside.
U.S. Army Engineer District, Los Angeles, General Design of Shore Protection
Works near Oceanside, California. 1960. This memorandum presented the design
basis for a 1.3 million cy protective beachfill which was placed between the San
Luis Rey River and Loma Alta Creek, and for the combined groin and jetty
constructed at Oceanside's Municipal Harbor. The report described maintenance to
include replenishment of a protective beach at suitable intervals and maintenance
of the groin. At the time of the project document study, protective beach
maintenance was estimated to be 25,000 cy/year, anticipated to be supplied
through normal periodic maintenance of the Camp Pendleton Harbor (Del Mar Boat
Basin).
U.S. Army Corps of Engineers, Interim Survey of Oceanside Harbor, Oceanside
(Camp Pendleton), California, House Document No. 76. 1965. Report
recommended the Federal adoption of the Oceanside Harbor by providing federal
maintenance dredging of channels and turning basins, and the maintenance of a
1,000-foot south jetty, a 710-foot north groin, and about 1,200 feet-of stone
revetment. Maintenance dredging was predicted to be required on a biennial basis
with removal of an averageof 200,000 cy/yr. Placement-of dredge material on the
beach below the Oceanside pier to replenish downcoast beaches was
1-2
I recommended and found to be in conformance with the needs of the beach
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erosion control project.
U.S. Army Engineer Waterways Experiment Station, Miscellaneous Paper H-78-8,
Coastal Processes Study of the Oceanside, California, Littoral Cell. 1978. This
I study concluded that the gross longshore transport rate at Las Flores, Oceanside,
and Encinitas is approximately 800,000 cy/yr, 1.2 million cy/yr, and 1.8 million
cy/yr, respectively. Also, an estimated 100,000 cy/yr net of littoral drift was
I estimated to be moving southerly past Oceanside, California, with a net volume
increase in southerly direction south of the vicinity of Oceanside. The report also
suggested a continuous sand bypassing system as a partial solution to the erosion
I problem.
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U.S. Army Engineer District, Los Angeles. 1980. "Survey Report for Beach
Erosion, San Diego County, Vicinity of Oceanside, California," September, 1980
(Draft Report). Though the authorized study area was the 7.2-mile shoreline
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between the Santa Margarita River and Agua Hedionda Lagoon, the erosion
occurring between Buena Vista Lagoon and Agua Hedionda Lagoon was considered
insufficient as to justify consideration for improvement.
U.S. Army Engineer District, Los Angeles. 1984. "Appraisal Report, Small
Navigation Project, Agua Hedionda Lagoon, Carlsbad, California," December 1984.
The purpose was to develop the information required to decide whether there was
a Federal interest in dredging the shoaled area in the Agua Hedionda Inner Lagoon
in order to maintain recreational activities. The result of an initial economic
analysis indicated a benefit/cost ratio of 0.8 to 1.0.
U.S. Army Engineer District, Los Angeles. 1989. "Section 103 Small Project,
Reconnaissance Assessment Report, Carlsbad, San Diego County, California,"
February 1989. The study area was the causeway section of Carlsbad Blvd.
fronting Agua Hedionda Lagoon between the intake and outlet jetties. The report
developed and evaluated several preliminary alternative solutions and identified the
groin system alternative as the most feasible one with a benefit/cost ratio of 1.1 to
1.0. The report recommended that funds should be provided for continuation of
studies to the Reconnaissance Study phase.
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U.S. Army Engineer District, Los Angeles. 1990. "Section 103 Small Project,
Carlsbad Beach Erosion Control Reconnaissance Study, Carlsbad, San Diego
County, California," May 1990. This report (a) provided the current status of the
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Carlsbad Beach Erosion Reconnaissance Study; (b) addressed the problem of storm
damages to the causeway section of Carlsbad Blvd. between the intake and outlet
jetties; (c) gave an estimate of potential damage savings, recreation benefits, and
I equivalent project first costs. However, no project cost data were developed for
comparison with the potential benefits, because the study was discontinued at the
1-3
request of the local sponsor when it appeared that the California Department of 1 Boating and Waterways would fund the design and construction of a project.
U.S. Army Engineer District,Los Angeles. 1990. "Sediment Budget Report, I
Oceanside Littoral Cell," CCSTWS 90-2, Coast of California, Storm and Tidal
Waves Study, November, 1990. The MSL shoreline retreated-at an average rate of
1 ft/year from Central Oceanside to Batiquitos, Lagoon. The result was obtained
from compilation of all the data: the NOS maps (1888 to 1982), aerial photos
(1938 through 1988), and 10 Corps profiles taken at 26 range lines between 1954
and 1988.
U.S. Army Engineer District, Los Angeles. 1991. "State of the Coast Report, San I Diego Region," Volume 1 - Main Report, Coast of California, Storm and Tidal.
Waves Study;: Final - September 1991. This report summarized the results of the
(CCSTWS) for the San Diego Region. The following has been obtained for,the I information of changes in the mean higher high water (MHHW) shoreline:,_ (a)
during the first two phases (1940-1960 and 1960-1980), there were minor
changes with occasional small accretions, (b) during the third phase (1980-1990),
the shoreline is experiencing erosion rates which range from about 1.6 ft/year near
the southern reach of the Carlsbad shoreline, 6.5 ft/year at Agua Hedionda Lagoon,
and 10 ft.year near Buena Vista Lagoon.
1.5.2 Studies by Others .
City of Carlsbad. 1989. "City of Carlsbad Proposal for the Carlsbad Beach
Erosion Study and Coastal Shore Protection Project," April 1989. This report
recommended as a feasible solution a 2,200-foot long concrete-capped sheetpile
seawall with revetments at both.the north and south ends of the causeway section
of Carlsbad Blvd. between the intake andoutlet jetties.
Tekmarine, Inc. conducted a series of semi-annual beach profile surveys for
the City of Carlsbad during the 1987 to 1991 period. The most recent report is:
Tekmarine, Inc. 1992. "Semi-Annual Beach Profile Surveys and Analysis -for
October 1991," submitted to City of Carlsbad; California, March 1992. This report
concluded that two major factors have been influencing the beaches near Carlsbad
study area: wave climate and sand supply. .
2.0 THE STUDY AREA
2.1 Location
The City of Carlsbad is located about 90 miles south of Los Angeles in San
Diego County. The area of study is defined by Buena Vista Lagoon to the north
and Batiquitos Lagoon to the south and is approximately seven miles in length
(Figure 2.1).
2.2 Description
Due to the length of the area involved, the diversity of the protective
structures and the varying potential for storm damage, the study area was divided
into five reaches (Figure 2.2). This section describes the relevant physical
characteristics of the reaches.
2.2.1 Reach 1
I At the northern end of the city, Reach 1 is defined by Buena Vista Lagoon to
the north and the city-installed seawall to the south. Approximately 3900 feet in
length, the reach consists of a very narrow cobble beach which ranges in width
I . from 50 feet in summer to virtually non-existent in winter. The beach is backed by
bluffs which range in elevation from 35 to 50 feet and average approximately 43
feet MLLW. At the toe of the bluffs, the back of the beach ranges in elevation
I from 10.5 to 18.5 feet MLLW (summer conditions), with the average elevation
being approximately 13 feet. Forty-eight of the fifty-seven structures have some
form of privately installed protection, either revetment or a seawall. The structures
I tend to be situated on the face of the bluff such that first floor elevations range
from 18.5 to 42.8 feet MLLW.
2.2.2 Reach 2
U Reach 2 is backed by the city-constructed public seawall. The wall,
approximately 4000 feet in length, extends from Oak Avenue in the north to the
I
Tamarack Street parking lot entrance in the south. At elevation +23.25 feet
MLLW at its crest, the seawall protects the toe of the bluffs which front Carlsbad
Boulevard (SR 21) some 30 feet above. This reach benefits from the annual
I dredging of Agua Hedionda Lagoon by San Diego Gas and Electric (SDG&E). In
spite of this, the beach is still primarily cobbled in the winter.
1 2-1
1
Santa ,-':
Margarita ( River I
Oceanside Oceanside
Harbor
Carlsbad
Route 78
Buena
Vista
Lagoon
Pacific Ocean
Agua
J( Hedionda
Lagoon
\ \
Batiquitos
Lagoon \ \
Leucadia
U
Encinitas
12491005M
Figure 2.1 Vicinity of Carlsbad. CA
Oceanside
Route 78 FreewaY
Buena Buena
Vista
Lagoon
Ocean St *
Reach 1
Carlsbad
State
Beach
Reach
Tamarack
\ Parking Agua Lot Hedionda
\ Reach 3 5 Lagoon
Reach 4 Omer NrPor'
Cre .nas
7 miles
Pacific Ocean
Batiquitos
Lagoon -
12491004M
Figure 2.2 Five Reaches of Carlsbad Coastal Area
2.2.3 Reach 3
Reach 3 is the 4300 foot stretch between Tamarack Boulevard and the Terra
Mar housing development in front of Agua Hedionda Lagoon and Carlsbad
Boulevard. Carlsbad Boulevard reaches its lowest elevation in this reach (+ 16.95
feet MSL). The three-
quarter mile length of this reach between the inlet and outlet jetties was the study
area for the May 1990, Section 103 Small Project Carlsbad Beach Erosion Control
Reconnaissance Study.
In the northern end. of this reach, the Tamarack parking lot is protected by
approximately 400 feet of one to two-ton stone. Immediately south of the Agua
Hedionda intake jetty, Carlsbad Boulevard is protected by 350 feet of half-ton
stone. Due to annual dredging of Agua Hedionda Lagoon, the 2700 foot reach
between the intake and outlet is significantly wider during the summer than under
normal winter conditions. The geology is different in this reach, in that non-
erodible material is at -6.25 feet MLLW.
2.2.4 Reach 4
The fourth reach is made up of the Terra Mar housing development, which
stretches 2200 feet along the coast from south of Agua Hedionda to the northern
edge of South Carlsbad State Beach. This segment features twenty-nine
structures which are on top of the bluffs; the average first floor elevation is +38
feet MLLW. Sixteen of the structures are protected by riprap and thirteen by
gunite walls. The non-erodible material in this reach, a cemented sandstone, is
completely exposed during the winter and only a thin layer of sand exists at the
foot of the bluffs under normal summer conditions.
2.2.5 Reach 5
Reach 5, composed primarily of South Carlsbad State Beach, is
approximately 18,400 feet in length. It consists of a narrow beach backed by
unprotected, bluffs. Behind the beach, the cliffs rise between forty and sixty-five
feet, though at one point they are as low as fifteen feet. With the exception of
Carlsbad Boulevard, the camping area on top of the bluffs, and a few state park
stairways and lifeguard towers, there are no structures in this reach.
Currently, most of the beach is cobbled year-round. However, most
probable future conditions include the Batiquitos Lagoon Enhancement Project
2-4
which is being done in mitigation for the Port of Los Angeles expansion.
Approximately 1 .5 million cubic yards of sand dredged from the lagoon will be
placed in this reach,.. specifically, at Encinas Creek, and jetties will be constructed
at the mouth of the lagoon. Port officials anticipate that the project will be
completed in March, 1997.
2.3 Physical Characteristics
2.3.1 Bathymetry
The deep water bathymetry offshore of Carlsbad is shown in Figure 2.3.
Carlsbad is located in the central portion of the Oceanside littoral cell bounded by
Dana Point in the north and Point La Jolla in the south. Figure 2.3 shows that the
bottom contours throughout much of this cell are gently curving and uniform. The
nearshore contours at Carlsbad are relatively straight and parallel, except where
Carlsbad submarine canyon approaches the shoreline. The head of this canyon is
located at approximately the 100-foot isobath. Nearshore slopes are steeper south
of the canyon.
2.3.2 Local Geology/Sediment Characteristics
Based on data gathered in connection with the Coast of California Study
from 1983 to 1986, the mean grain size in the littoral zone varied from 0.15 mm
to more than 0.4 mm depending on the season.
The City of Carlsbad made available to the Corps a number of geotechnical
reports that were done by private firms for both the city and private individuals in
preparation for the construction of seawalls. In Reaches 1, 2, and 4, the non-
erodible material at the foot of the bluffs was a cemented sandstone, at
approximately mean sea level (+2.75 feet MLLW). Standard Penetration Test
(SPT) blow counts were in the range of 60 to 70 blows per foot. The bedrock was
generally under 5 to 8 feet of cobbles and sand. In Reach 3, bedrock was found to
at -6.25 feet MLLW, lying under silty sand. No reports were available for Reach 5
although it is reasonable to assume that the composition and location of the
bedrock is the same as in Reach 4.
2.3.3 Climate
The climate of coastal southern California is generally considered to be of a
I
semi-arid Mediterranean type, with mild winters characterized by about 10 to 20
inches per year of rainfall. According to USAED, Los Angeles (1986), the local
I 2-5
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SCALE IN MILES I I I ! l LA JOLLA 32 Ow
SOUNDINGS IN FATHOMS FALSE POINT / \\
II8°40 fl8°30 / 1 / I18°70' \ -:.- 1I8°I0'
Figure 2.3 Oceanside Littoral Cell
I_.
I .
I -•:
I--H-
i:
IH .,
I
I - average wind speed is approximately 7 7 miles per hour, only slightly higher than
those measured in inland areas. Ocean-landmass temperature variations result in
I daytime wind patterns dominated byonshore winds, and nightly patterns
dominated byoffshore flows. Exceptions occurduring occasional winter storms.
where wind directions vary, and during Santa Ana conditions when winds are
I usually out of the northeast.
2.3.4, Tides and Sea Level
I
Tides along the southern California coastline are of the mixed semi-diurnal
type, c - onsisting of two high and two10w tides each of different magnitude. The
lower-low normally follows the higher--high by about 7 to 8 hours, whereas the
next higher-high (throughlower-highancLhigher-low 'Waters) -follows in about 17 ..
I hours.--
- -
I The NOAA collected 7 months of tide measurements at Agua Hedionda, Gijlf
of Santa Catalina and 18 years of measurements at Là Jolla, Pacific Ocean in -.
establishing tidal datums of the 1960 to 1978 tidal epoch. While the former are
I - directly applicable to the project at the Carlsbad coastal area, extreme highs nay
- not be represented due tôthe lack of measurement in the 1982-83 storm season;
Tidal characteristics of both of these tidal stations are shown in Table 2.1.
2.3.5 Water Levels
A review of yearly mean sea level data recorded at.San Diego indicates that
a rise of 0.7 feet per century has occurred (Flick and Canan,i984). If past trends
are projected into the'future at San Diego, a sea level rise of at least 0.2, feet
would be expected over the next 25 years. Positive departures from the annual
mean occur during strong El Nino episodes.. These meteorological anomalies are
characterized by low atmospheric pressures and persistent onshore winds. Tidal
data indicate that five episodes (1914, 1930 through 1931, 1941, 1957 through
1959, and 1982 through 1983) have occurred since 1905. Further analysis
suggests that these events have an average return period of 14 years with 0.2-
foot tidal departures lasting for two to three years; The added probability of
experiencing more severe winter storms during El Nino periods- increases the -
likelihood of coincident storm waves and higher storm surge. According to Flick
and Cayan (1984), the record water level of 8.35 feet MLLW observed at San
Diego in January 1983 includes an estimated 0.8 feet of surge and seasonal level
rise. Figure 2.4 shows the statistical distribution of Higher High Water in the
Carlsbad area. V ...
-Storm is relatively small along the Southern California coast when
compared with tidal fluctuations. According to the U.S. Army- (1991), storm
surges driven primarily by atmospheric pressure can raise the sea level on the order
of 0.5 feet for two to six days on the average. Extreme stillwater level departures
from astronomical water levels may be as much as one foot or greater for the
severest extratropical events.
2.3.6 Currents . V
2.3.61 Offshore Currents V
The offshore currents consist-of two components: (1) major, large scale
coastal currents which constitute the "mean" seasonal circulation and range from
5 cm/s to 40 cm/s, and (2) fluctuation's in durations of 3 to 10 days resulting from,
tides and other phenomena which are expected'to be superimposed on the "mean"
seasonal circulations These tidal currents have peak longshore velocities of,
roughly 20 cm/s. Both components are detailed in Section 4.2 of the Coastal
Engineering Appendix. V :
2.3.6.2 Longshore Currents
Longshore currents in the coastal zone are driven primarily by waves
impinging on the shoreline at oblique angles. This wave generated current and
turbulence is the major factor in littoral transport. The surf zone currents along the
Oceanside Littoral Cell is nearly balanced between northerly and southerly flows,
as predicted by previous littoral transport studies (Hales, 1980). Typical summer
swell conditions produce northerly drifting currents while the large winter storms
from the west and northwest produce southerly currents. Overall, the persistence
of the northerly drift dominates, however, the strength of the southerly drift during
major storm events results in a net southerly longshore transport.
2.3.6.3 Cross-shore Currents
Cross-shore currents exist throughout the study area, particularly at times of
high surf. These currents tend to concentrate at creek mouths and structures, but
can occur anywhere along the shoreline in the form of rip currents and the return
flows of complex circulation cells. To date, no information is available on the
quantification of these currents, nor their effect on sediment transport. However,
the occurrence of summer-type and winter-type profiles along the southern
California coastline has been well documented. A detailed analysis by Aubrey
(1979) of 5-year profile records at Torrey Pines (in the Oceanside Littoral Cell),
provided quantitative estimates of on-offshore sediment transport associated with
this seasonal profile transition. In his study, on-offshore transport rates in the
profile were inferred from the comparison between a summer-type berm profile and
a winter-type bar profile. Material involved in this process moved onshore from the
depth range of 7 to 20 feet to form a berm in the summer profile, returning to the
same depth range to from a bar in the winter profile. The pivot point for this on-
offshore exchange of material was located at a 10 foot depth, across which an
average of about 34 yd3/yr of material was estimated to move on the seasonal
basis. Another pivot point was recognized at a depth of 20 feet, across which the
rate of sediment movement was much smaller, about 6 yd'/ft. The sediment
exchange at the second pivot point was also seasonal, consisting of winter
offshore movement and summer onshore movement.
During storms, strong winds generate high, steep waves. When the waves
I break, the remaining width of the surf zone is not sufficient to dissipate the
increased energy. The remaining energy is spent in erosion of the beach, berm,
I and bluffs. The eroded material is carried offshore in large quantities where it is
deposited on the nearshore bottom to form an offshore bar. Methods to quantify
the growth of this bar do not exist at this time.
I 2.3.7 Waves and Storms
I The coastal areas of Carlsbad are sheltered somewhat from deep ocean
2-9
I
San Diego Tide - Higher High eater
1 S
Probability
of
Exceedance
0.25
0
1 2 3 4
Voter Elevation (ft 9 SL)
Figure 2.4 Statistical Distribution of Higher High Water at San Diego
O
SANTA BARBARA
CHANNEL ISLANDS LOS
ES
2770 SANTA CATALINA I.
2730 :.:. SEA
2700 . BREEZE OCEANSIDE
SAN NICOLAS I. WAVES TO 5
SEC PERIOD :.
26cf SAN CLEMENTE I DIEGO (SUMMER)
NORTHERN HEMISPHERE POINT - - -
SWELL TO 20 SEC. PERIOD OMA - -
SOUTH AND
SOUTHWESTERLY SEAS
-
. TO 10 SEC PERIOD
(WINTER I
00
SOUTHERN
HEMISPHERE SWELL
TO 22 SEC. PERIOD
SUMMER)
-I 0 0
Figure 2.5 Wave Exposure for the San Diego Region
waves by the offshore Channel Islands. Waves can approach the Carlsbad coastal
area through three wave window. The southerly window is located between the
coastline of Southern California and San Clemente Island, at approximately 160
degrees to 245 degrees. A westerly window exists between San Clemente Island
and Santa Catalina Island, at approximately 245 degrees to 285 degrees. A north-
westerly window exists between Santa Catalina Island and the coastline of
southern California, at approximately 285 degrees to 305 degrees. Figure 2.5
shows the wave exposure.
The data on storms waves are obtained from the wave studies described in
the Design Memorandum of Oceanside Harbor of the USAED, Los Angeles (1992).
These studies were based on hindcast of 67 severe storm events that occurred
during the period 1900 to 1983 and measured storm events through 1988. Deep
water waves were transformed to account for island sheltering, refraction,
shoaling, and depth limitations. An extreme value statistical analysis results in a
set of wave conditions representative of various recurrence intervals. Table 2.2
shows the wave statistics at Oceanside Harbor (at depth of approximately 30
feet). These values were transformed to determine the waves at Carlsbad. Table
2.3 shows historical deep water storm waves.
TABLE 2.2 OCEANSIDE HARBOR EXTREME:
WAVE HEIGHTS
Return Period Significant
(years) Wave Height
(feet)
1 • 10.0
10 13.5
25 15.9
50 17.9
100 20.0
2-11
TabLe 2.3 HistoricaL Deep Water Storm
Waves (Unsheltered)
Hs Dir I
I Date (ft) (deg) (sec)
12/22/77 8 250 12
01/10/78 13 255 13
01/13/78 11 263 14
01/16/78 15 282 16
02/10/78 13 280 16
03/01/78 14 247 12
03/05/78 15 271 14
01/16/79 12 268 17
03/28/79 7 259 11
12/31/79 14 277 18
01/13/80 12 263 13
02/20/80 16 250 14
01/20/81 12 258 15
01/22/81 15 265 17
01/28/81 22 265 17
11/12/81 15 285 17
11/14/81 17 - 277 17
03/08/82 10 245 13
11/30/82 18 287 11
12/17/82 22 287 19
12/22/82 8 248 11
01/24/83 17 278 17
01/27/83 21 282 20
01/29/83 16 273 16
02/10/83 20 281 20
02/13/83 19 275 16
03/02/83 31 258 18
03/17/83 .15 269 14
12/25/83 10 248 11
03/09/8.4 15 280 19
11/13/86 9 256 12
01/17/85 11 263 18
11/25/85 9 251 11
12/03/85 21 271 18
01/14/86 14 272 16
02/01/86 24 276 19
02/03/86 15 277 17
02/15/86 24 253 17
02/28/86 13 270 15
03/11/86 21 280 17
03/06/87 11 243 13
12/16/87: 11 269 14
01/17/88 30 267 16
12/03/89 15 275 17
02/03/91 12 274 17
03/02/91 16 280 17
12/29/91 16 270 17
01/06/92 11 271 15
01/14/93 11 258 12.
01/18/93 12 265 13
Source: Pacific Weather AnaLysis. 1993
2.3.8 Littoral Processes
The Carlsbad is in the central sub-cell of the Oceanside Littoral Cell (see
Figure 2.3). This central element runs from San Mateo Point in the *north, to the
Carlsbad Submarine Canyon (between Batiquitos and Agua Hedionda Lagoons) in
the south. The following sections discuss the various components and the effect
that these have had on the shoreline. Section 2.3.8.7 concludes with the
2-12
presentation of the anticipated future without project sediment budget.
2.3.8.1 Sediment Sources and Sinks
There are a variety of sources that supply sediment into the littoral zone.
These sources include erosion from the adjacent watershed with sediments
transported to the beaches via natural streams, creeks and storm drains; coastal
bluff erosion; beach erosion; and artificial beachfills. These sources are discussed
as follows with the exception of artificial beachfills which are discussed in Section
2.3.8.2.
Two rivers contribute to the littoral cell. The Santa Margarita River is
located about six miles north of the study area and the San Luis Rey River with its
mouth emptying to the sea about four miles to the north. The total sediment load
arriving at the coast from the river systems of this littoral cell varies from 53,000
y3/year to 426,000 y3/year. The contribution of the San Luis Rey is the lesser of
the two and is within the reach considered in the sediment budget. It has been
assumed to contribute 10,000 y3/year to the sediment budget.
Active bluff retreat is still occurring along the undeveloped shoreline of the
Camp Pendleton marine base. In highly developed communities south of
Oceanside harbor, the majority of the bluffs are stabilized by revetments and gunite
and would only contribute sediments to the littoral zone during extreme storm
events.
The Oceanside Littoral Cell has three submarine canyons, namely, the
Carlsbad Submarine Canyon in the cell's central portion and the Scripps and La
Jolla Submarine Canyons at the cell's south end. The head of the Carlsbad
Submarine Canyon is in water depths of about 100 ft. According to CCSTWS 88-
2, this depth is deep enough to prevent transport of littoral sediments into the
head of the canyon.
I
Breakwaters, groins, jetties and headlands effect sediment transport. Depending upon length and location, jetties and groins can reduce or even block
sediment flow. The north breakwater of Oceanside Harbor is responsible for
I
retention of approximately 50,000 yd3/yr of material upcoast in an existing fillet,
whereas, the beach immediately south of the harbor is confined by the groin/south
jetty of Oceanside Harbor and the north jetty of the San Luis Rey river. In the
I
study area, approximately 130,000 y3 /year are trapped in Agua Hedionda Lagoon,
but this is bypassed annually by SDG&E as shown is Table 2.5.
Sedimentation at the Oceanside Harbor entrance is estimated to trap about
200,000 yd3/yr on average. Dredged material from the harbor entrance is normally
2-13
deposited along the Oceanside beaches. Due to the relatively fine sizes of this
material and the lack of adequate containment, it is assumed that 75 percent of
the disposed material is immediately integrated into the nearshore sediment
budget.
2.3.8.2 Existing Structures, Beachfills, and Dredging History
Existing Structures
A series of man-made coastal structures are located within and adjacent to
the Carlsbad study area. These structures are presented in Table 2.4.
Table 2.4 Major Coastal Structures Affecting Longshore Transport
Structure Location Type Year Built
north breakwater Oceanside Harbor rock rubbLe mound 1942. 1958
south jetty Oceanside Harbor rock rubbLe mound 1961
south groin adjacent to and north rock rubbLe mound 1968
of San Luis Rey River
2 groins Wisconsin Ave. rock rubbLe mound 1952
intake and outLet Agua Hedionda Lagoon rock rubbLe mound 1954
Jetties
groin south of outLet jetty rock rubbLe mound 1954
Beachfills and Dredging History
Following the 1954 project at Agua Hedionda, a Federal beach nourishment
project which was completed in 1963 placed 3.375 million cy of material on the
beach downcoast from the harbor from a borrow source which was developed into
the Oceanside Municipal Harbor. Federal beach nourishment projects in 1981 and
1982 accounted for 863,000 and 922,000 cubic yards of sand, respectively.
There have been numerous other beachfills as a result of maintenance of Agua
Hedionda Lagoon and the Oceanside Harbor (see Tables 2.5 and 2.6). The total
nourishment from the Harbor alone amounts to 11.9 million cy since 1954 or
about 200,000 cy/yr.
Chapter 3 of CCSTWS (Sept. 1991) relates the affect that these
nourishment projects have had on the beaches. The beaches of Oceanside showed
2-14
definite accretion during the period 1960 to 1980 when 8.9 million yd of sand
was placed on the beach (443,000 yd3/yr). Carlsbad also showed accretion during
this period, but it was less dramatic.
Table 2.5 Beach Fills and Relevant Dredging at Agua Hedionda
YEAR QUANTITY PLACEMENT with respect to
the LAGOON
1954 4,000,000 NEW SAND: NORTH AND
SOUTH
1955 111,000 SOUTH
1957 232,000 SOUTH
1960 370,000 SOUTH
1961 225,000 SOUTH
1963 307,000 SOUTH
1965 222,000 SOUTH
1967 159,000 SOUTH
1969 97,000 SOUTH
1972 259,000 NORTH & SOUTH
1974 341,000 NORTH & SOUTH
1976 331,000 NORTH & SOUTH
1973 398,000 NORTH &SOUTH
1981 392,000 NORTH & SOUTH
1983. 200,000 NORTH & SOUTH
1985 447,000 NORTH & SOUTH
1988 334,000 NORTH
1991 465,000 NORTH & SOUTH
Average = 129,972 yd/year from 1955 to 1991
Data obtained from CCSTWS of USAED, Los Angeles (1991)
2-15
Table 2.6 Dredging and Beachfills in Oceanside
YEAR QUANTITY (YD 3)
1,955 800,000
1960 . V 410,000
1961 481,000
1963 3,800,000
1965 111,000
1966 684,000
1967 178,000
-. 1968 434,000
1969 . 353,000
1971 552,000
1973 434,000
1974 560,000
1976 . 550,000
1977 318,000
1981 . 863,000
1982 922,000
1984 475,000
1986 . .. 450,000
1988 V
V 220,000
V
1990
Vf
V 249,000
1992 . . 168,000
TOTAL •• ..- 11,892,000
Data obtained from CCSTWS of USACE - LAD, 1991 V
2.3.8.3 Erosion and Accretion Rates
Shoreline changes within the Oceanside littoral cell have been studied
extensively through analysis of historic surveys of the U.S. Army and Geological
Surveys, comparison of aerial photography and comparisons of relatively recent
profile surveys taken for CCSTWS (USAED, 1991). In general, the shoreline
between Oceanside Harbor and the southern boundary of the City of Carlsbad at
Batiquitos Lagoon has fluctuated fri absolute location over the years due to major
storms and coastal construction.
2.3.8.4 Historic Shoreline Changes
The earliest shoreline position available in the comparisons are based on a
1887-1889 USGS survey -- the plan location of the "shoreline" by these surveys
were approximately equal to mean high water. Relative to more recent surveys in
1972 or the shoreline mapped from January 1988 aerial photography, the present
shoreline is located seaward of the shoreline of 100 years ago throughout most of
the City of Carlsbad. This is largely the result of coastal construction of the power
plant at Agua Hedionda. In 1953-54, the San Diego Gas and Electric Company
constructed two pairs of stone jetties; one to stabilize the inlet of Aqua Hedionda
Lagoon and the second pair to serve as a channel for the discharge of the thermal
effluent from the power plant across the beach. Between March and November
1954, over 4 million cubic yards were dredged from Aqua Hedionda Lagoon and
deposited on the beach extending from about 3,500 feet north of the lagoon inlet
to 2,000 feet south of the discharge trench. This beachfill widened the Reach 3
beach about 400 feet and widened the beach an average of 100 feet for a
distance of two miles downcoast of the disposal area (Reaches 4 and 5).
The furthest seaward shoreline location occurred in the mid 60's or.the early
80's as testimony to the effects of the major beachfill from the Agua Hedionda
power plant in 1954 and the beachfills in Oceanside in 1964 and 1983. Since that
time beach widths have fluctuated with some profiles showing erosion and some
showing accretion. One of the more recent shoreline position was mapped from
aerial photography flown subsequent to a major wave event in January 1988. This
shoreline shows an eroded condition demonstrating the effects of major storms.
The time history of shoreline positions at selected profiles analyzed in
CCSTWS(1991) are included at the Attachment to Coastal Engineering Appendix.
2.3.8.5 Historic Profiles
Five comparative profiles in the Carlsbad were analyzed in CCSTWS and are
shown at the end of this appendix. These profiles document changes across the
nearshore zone between 1934 and 1988, although the data are not always
complete. Like with the shoreline positions, seasonal or storm induced erosion
masks any discernible long-term trend in profile degradation. Significant depth
changes are observed generally to the 20- to 30-foot water depth, and seasonal
changes in the plan location of MLLW have been at least as large as 200 feet.
Also evident in the comparison between profile locations for the same survey in
April 1986 is the pronounced steepening in the nearshore bathymetry in the
2-17
southerly direction from Oceanside Harbor to the Carlsbad submarine canyon. A
rocky, erosion resistant shelf in water depths of 5 to 10 feet apparently extends to
about 1000 feet offshore of reaches 4 and 5 (Profiles CB760 and CBBOO). Like
the shoreline positions described above, the most recent profile was taken close
after the January 1988 storm event and shows an eroded profile.
2.3.8.6 Longshore Transport
A number of longshore sediment transport studies have been performed and
reviewed in the Coast of California Study. The general conclusion of these
findings is that the net littoral transport in the Oceanside coastal vicinity is directed
towards the south, with a net transport potential at a rate of 100,000 to 250,000
cubic yards annually.
2.3.8.7 Sediment Budget
Historic Sediment Budget
A sediment budget provides a conceptual model of littoral processes by
accounting for volume changes and sediment fluxes within cells and across cell
boundaries. The sediment budget presented in Chapter 9 of CCSTWS (USAED Los
Angeles, 1991) covers possible scenarios over the past 90 years by examining the
previously described historic changes in the coastline, sources and sinks, and
coastal process elements. Carlsbad is located within the central sub-cell of the
Oceanside littoral cell. Three historic time periods were analyzed: 1900-38, 1960-
78, and 1983-90.
The first period can be viewed as the "natural" shoreline condition prior to
Oceanside Harbor and the power plant at Agua Hedionda. However; by 1900 the
watershed and coastal lagoons had been significantly altered by construction of
roads, railroads and water supply and flood control works. During this period, the
beach cell gained material with large contributions from bluff erosion and from
major flood events on the Santa Margarita and San Luis Rey Rivers. Large losses
were assumed to the offshore while the net longshore transport downcoast is
assumed equal to the transport potential of available wave energy.
Prior to 1942, longshore sediment transport in the Oceanside littoral cell was
not significantly influenced by man-made structures. In 1942-43, the U.S. Navy
constructed Camp Pendleton Harbor (now known as the Del Mar Boat Basin) with
two arrow head jetties about 1,300 feet long. The northern jetty was extended by
about 2,300 feet by the Navy in 1957-58 to form the North Breakwater, and
further jetty construction and dredging in the 60's and 70's by the City of
2-18
Oceanside and the Corps of Engineers eventually evolved into what is now the
Oceanside Municipal Harbor. Since the initial construction of the original jetties,
I
the shoreline immediately up and downcoast of the harbor has advanced seaward,
while the shore fronting the City of Oceanside experienced severe erosion. This
erosion has been somewhat mitigated by beachfill projects and the placement of
I dredge material from Oceanside Harbor on the Oceanside beach area.
The second period, between 1960-78, includes the effect of the Oceanside
I Harbor and the power plant over what some have considered a relatively benign
period of storm and wave activity. In this scenario the central sub-cell gained
I
40,000 cy/yr. Significant contributions are shown from beachfills and bluff
erosion. Oceanside Harbor is shown deflecting 80,000 cy/yr to the offshore and
the net downcoast transport is equal to the previous period.
The last period between 1983-90 is a period thought to be of unusually
larger than normal northerly directed longshore transport. The beach cell gained
material at a rate of 60,000 cy/yr with most of the beach material derived from
eroded bluffs. The net downcoast transport is estimated at 70,000 cy/yr for this
time period due to the aforementioned unusual wave climate.
Sediment Budget for Future Without Project
Historic sediment budget analyses and the assumption that there will be no
new beachfills in the future forms the basis for estimating a future sediment
budget. The most probable future wave climate is expected to be similar to the
1900-78 time period. Site investigations also revealed that bluff erosion will be
negligible south of Oceanside Harbor to at least Batiquitos Lagoon due to
protective seawalls and gunite slopes. The continued maintenance dredging of
Oceanside Harbor with placement of about 200,000 yd3/yr on beaches to the
south is assumed, and a net downcoast transport which is less than or equal to the
transport potential of available wave energy is predicted due to the paucity of
sand.
Development of the sediment budget, for future without project conditions,
assumes the following:
Net southerly potential long shore transport of 270,000 yd'/year. This rate is
assumed to be uniform along the littoral subcell extending from Oceanside Harbor
to the northern reach of Carlsbad area (Agua Hedionda Lagoon).
Historic shoreline erosion rates vary from about 4 ft/year at Oceanside northern
I
reaches to approximately 1 ft/year at Agua Hedionda Lagoon. This assumption is
made based on the findings of the Coast of California Storm and Tidal Wave Study
2-19
(1991) on the long term shoreline movements (1940-1989). The Coast of
California Storm and Tidal Wave Study also indicated linearly decreasing erosion
rates starting from. Oceanside beaches to Agua Hedionda. Though there may be a
number of reasons for this, the seasonal and year around absence of erodible
material is probably that which dominates.
Based on the volume of sand losses/shoreline retreat analysis, shown in the
Coast of California Storm and Tidal Wave Study, beach material erosion rates of
approximately 60,000 yd3/yr occur along the four mile Oceanside shoreline, and
roughly 30,000 yd3/yr along the northern 2 miles in Carlsbad (Reaches 1, 2, and
3).
An annual deposition rate of 200,000 yd3/yr was also assumed to take place at
Oceanside Harbor entrance.
It is also assumed that dredging materials from Oceanside Harbor entrance will
be placed along Oceanside beaches at a rate of 200,000 yd3/year.
The quantity of sediment deflected off the Oceanside Harbor is the most
difficult component of the sediment budget to estimate. Based on the estimate of
Inman (CCSTWS, September, 1991) the offshore sediment losses are estimated at
70,000 yd3/year. Another 30,000 yd3/yr is assumed lost in the vicinity of
Carlsbad.
An annual supply of 10,000 y3 is assumed from the San Luis Rey River.
Figure 2.7 shows the sediment budget for both Oceanside and Carlsbad
subcells. The shown budget presents a reasonable way of assessing the problem
and presents an overall estimate of the sediment activities along the study area.
The sediment budget analysis indicates that future without project conditions
would cause erosion to continue along the Carlsbad and Oceanside shorelines. The
northern reaches of Carlsbad, Reaches 1 and 2, are dependant upon material from
Oceanside and have the potential for the most erosion (1 to 3 feet/year), though in
actuality these rates are less due to the amount of available erodible material. The
erosion rate in Reach 3 is approximately 1 foot/year. Due to the confined nature of
much of this reach (between the intake and outlet to Agua Hedionda Lagoon) this
material will be lost offshore. The southern reaches (Reaches 4 and 5) will
experience lower rates due to the absence of erodible material.
2-20
Santa
Margarita
River
San Luis
Rey
River
Oceanside
I
270
,/\lo
I 10_9•• Buena c 100 -60 Vista
\ \ 200 Lagoon
\oo
70 N Agua
N -30 Hedionda N Lagoon N Pacific Ocean
30 S Carlsbad
Batiquitos
Lagoon
LEGEND \
Change in \ - F--6-01 Littoral Sediment
Volume (000s y3/yr)
Sediment Flux Rate 270 (000s y3/yr) 270
Harbor Dredging
200
Without Project Sediment Budget
(000's y3/yr)
Sources Sinks
Northern Boundary: 100 -100 Northern Transport into Harbor
Harbor Dredging: 200 -270 Net Southern Transport
S.L.R. River 10 -30 Offshore Losses
Total: 310 -400 Total
NET VOLUME CHANGE = -90
Figure 2.6 Future Without Project Sediment Budget
2.4 Social and Economic Factors
2.4.1 Location and Description
The City of Carlsbad is a coastal community located in Northern San Diego
County. The city is bordered by the City of Oceanside to the north, the Pacific
Ocean to the west, the cities of Vista and San Marcos to the east, and Encinitas to
the south. Directly west of the city lies approximately 6.5 miles-of coastline.
As discussed in Section 2.2, the project area was broken down into five
adjacent shoreline reaches separated by unique physical characteristics, which
were determined by the study team. This sub-section will deal with the relevant
social and economic factors of these reaches.
Reach 1 is composed of high density residential development. The
structures consist of single family residences, multi-family residences, a hotel and a
school. This area is well known as a resort center; many of the apartments are
rented on a short-term basis so as to accommodate vacationers. Five public
access stairways allow sufficient public entry to the reach.
Reaches 2 and 3 constitute the North Carlsbad State Beach. and are very
popular areas with beachgoers due to ample parking, a good surfing climate, and a
beach which benefits from the annual dredging of Agua Hedionda Lagoon. The
city seawall, which contains a built in sidewalk, is in Reach 2. Agua Hedionda
Lagoon is located in Reach 3 east of Carlsbad Blvd. The lagoon serves a multitude
of uses, including, a body of cooling water for the San Diego Gas & Electric Power
Plant, a research facility, a fishing area, and a feeding spot for wildlife.
Reach 4 consists of low-medium density residences stationed atop high
beach bluffs. Moderate beach visitation, primarily the result of surfers, was noted
in this area. Public access is only available at the northern and southern limits of
this reach.
Reach 5 extends southward of the Terra Mar housing development,
representing the South Carlsbad State Beach. The state park offers year-aroUnd
campground.sites, including hook-ups for recreational vehicles, public restrooms,
and a convenience store. The state park also houses the state of California
lifeguards' facilities and equipment. As a result of the extensive cobble coverage,
recreational use of the beach is somewhat limited. The area does support water
activities, mainly surfing, in particular spots containing good surf.
2.4.2 Demographics
2-22
I
2.4.2.1 Population
I San Diego County ranks second largest in population out of the 58 counties
in California. The county population density in 1990 was 594 persons per square
mile. In contrast, the City of Carlsbad population density was 1,674 persons per
I square mile in 1990.
I The population of Carlsbad was 65,661 as of January 1, 1992. From 1980
to 1990, Carlsbad's population grew 77.8% and is projected to grow another 79%
between 1990 and 2015. This equates to an average annual growth rate of
I 2.35% for the city in comparison to a 1.5% growth rate for the county.
Although these forecasts portray continual growth in population and
I development through year 2015, experts contend that this rate will decline, if
current growth management policies prevail. Under current conditions, Carlsbad
will have developed all available single-family and multiple-family urban land by the
I year 2015 as the population approaches 115,000 persons. This could prove to be
an important factor in projected beach visitation. If the city chooses to preserve
the growth management plan, development of residential and commercial beach
I property will be limited after the year 2015, affecting the future number of beach
visitors stemming from the local region and the availability of hotel
accommodations.
2.4.2.2 Tourism and Recreation as Major Industries
Tourism is a primary component of the City of Carlsbad's taxable sales and
revenue, especially for the area included within the study site. The city is largely a
beach resort town which has traditionally attracted beachgoers and tourists
interested in the major attractions within San Diego county. Between the period of
1981 to 1990, an estimated 31 ,000,000 persons visited San Diego County
annually. Carlsbad beaches alone accounted for 9.4% of annual average
visitorship for the county during this time period. The hotel occupancy rates
ranked above the national average of 64% in 1990. Although local concerns of
over expansion have induced growth management planning, the tourist population
has remained relatively constant subsequent to 1987.
Reaches 2 and 3 support the main bulk of visitors to Carlsbad's beach,
though Reaches 1 and 4 are attended. Though there is essentially no beach above
the MHHW line, the city has provided five public accessways in Reach 1 to support
public use. In addition, public use of the beach in Reach 4 was evident during the
beachwalk. During the site visit, it was apparent that both areas are experiencing
moderate use from surfers, beach strollers, and sunbathers. Thus, these beaches
are assumed to provide reasonable access to the general public. Beach use in
2-23
Reach 5 has dwindled in recent years due to the eroded and cobbled condition of
the beach. During the site visit, recreational use of the beach was scarcely
noticeable. Thus, the beach visitation counts provided by the State Department of
Parks and Recreation for Reach 5 are assumed to be associated primarily with the
state campgrounds, rather than with the actual beach. Thus, beach counts,
enumerated by the State Department of Parks and Recreation, for Reaches 1
through 4 were assumed represent the area of coastline supporting the majority of
the beach visitors to Carlsbad's coastline.
2.4.2.3 Employment
Employment data for San Diego County depicts a less prosperous picture for
fUture conditions in relation to the previous decade. Although the total number of
jobs in the civilian labor sector is expected to rise an average of 27% between
1990 and 2015, this equates to an average 23,000 fewer jobs per year than
during the 1980's: Between the years 1990 and 1993 alone, the region is
predicted to suffer a total loss of 45,000 jobs (SANDAG, Series 8 Regional Growth
Forecast: Revised Regionwide Forecast 1990-2015).
Employment data for the Cityof Carlsbad, shows that the rate of
unemployment for the civilian population was 4.9% in 1990. The State of
California's unemployment rate for the civilian population in 1990 was 5.6%. The
city's figure compares favorably with both the state's average and the San Diego
regional average of 6.5%. The primary source of employment in Carlsbad stems
from the retail sales sector.
2.3.2.4 Income -
The per capita incomein 1990 for Carlsbad ranked well above the county
level, along with the median family and household incomes. Real per capita
income for the whole of San Diego County is expected to decline an average of
8.2% between the years 1990 and 2015. The current recession trends caused
real per capita income to decline 10% between 1990 and 1993. A general growth
in income of 1.8% by year 2015 is assumed to result from the predominant lower
paying job expansion within the region.
2.5 Existing Environment
2-24
2.5.1 Biological Resources
1 2.5.1.1 Marine Resources
Marine vegetation that occurs in the study area includes surfgrass and kelp.
I Eelgrass occurs in lagoons in the study area. Several species of marine algae are
also present in the ocean and lagoons. The California Department of Fish and
Game has constructed an artificial reef off of Batiquitos Lagoon. This reef, and I other natural reefs in the area, provide additional habitat for marine flora and fauna.
I Prominent fauna associated with the kelp bed includes gorgonian coral and colonial ascidian. A narrow shelf in the study area provides limited nearshore
benthic habitat. Sandy marine habitat supports over 200 taxa of benthic
I invertebrates representing 14 phyla. Polychaetes, crustaceans, and molluscs are
important prey items for fishes and shorebirds. This habitat provides the main
source of food for surf fish and flatfish, both of which are important components
I . of the food chain and significant recreational resources of the study area. In
addition, walleye surfperch, barred surfperch, queenfish, and topsmelt are
abundant in nearshore waters. Northern and deepbody anchovies are important ' non-game fishes, due to their particularly high seasonal abundances in the winter
months. These species serve as prey for shore and seabirds, marine mammals,
I
and larger fishes.-
Emergent sand beaches provide a breeding area for the California grunion.
Spawning activity commences in the spring and summer when the grunion deposit
I their eggs in the sand on the high intertidal portions of the beach, during high
tides. The eggs subsequently incubate in the sand, and hatch during the ascending
series of high tide conditions before the following full or new moon.
I 2.5.1.2 Terrestrial Resources
Vegetation on the shoreline is sparse, consisting primarily of landscaping
I plants such as palm trees and iceplant. Beachgrass, an invasive species, occurs in
some locations. Coastal strand vegetation occurs near the Agua Hedionda Lagoon,
and possibly in other areas, as well. This vegetation includes grandiflora, sea
I . rocket, salt grass, and tree tobacco.
The open sand beach provides an important feeding and resting habitat for
I shore and diving birds. These open areas are favored because the lack of nearby
cover prevents predators from approaching undetected. Killdeer, plovers,
sanderlings, western sandpiper marbled godwits, and willets probe in the sand for
I crustaceans while others, such as the brown pelican , terns, western grebe,
surfscoter, common loon, and cormorants, dive for fish offshore. Gulls, including
2-25
ringbill, frequent the beaches.
Other wildlife observed in the study area includes a variety of sparrows,
blackbirds, doves, pigeons, squirrels, and lizards.
2.5.1.3 Lagoon Resources
The salt and freshwater marshes in the area's three lagoons are ecologically
important and productive habitats. Algae provide the basis for the food chain in
the marsh. Herbivores, such as small crustaceans and snails, consume the algae;
birds eat algae, invertebrates, and fish.
Buena Vista Lagoon
This 350 acre lagoon is at the northernmost edge of the study area. It is fed
by runoff from a watershed extending 12 miles east. Buena Vista Lagoon
represents a unique low salinity coastal habitat, because it is artificially maintained
at 5.8 feet above mean sea level by a weir across the lagoon mouth. Salt and
brackish marsh vegetation typical of nontidal lagoons of southern California covers
130 acres of the lagoon, and the other 220 acres are submerged. Mullet,
mosquitofish, green sunfish, catfish, bass, and crappie are known in the low
salinity waters of Buena Vista Lagoon. Over 50 species of marsh vegetation is
present. Bordering the lagoon is riparian and marsh vegetation with an upland
community of California sage scrub. Buena Vista Lagoon provides a unique low
salinity coastal habitat of important value to migratory waterfowl. Over 20 species
of birds regularly utilize the lagoon, and nearly 200 species of birds have been
known to occur in the area. Mammals known to inhabit the area include coyotes
and voles.
Agua Hedionda Lagoon
The Agua Hedionda Lagoon serves a multitude of uses; including a body of
cooling water for the adjacent San Diego Gas and Electric (SDG&E) Power Plant,
research area, fishing, and feeding spot for wildlife. This lagoon's intake and
outlet jetties are armored with rip-rap. In 1990, the Center for Marine Studies at
San Diego State University was growing eelgrass and kelp in the lagoon, and both
Occidental College and the National Marine Fisheries Service were involved in
halibut studies. In addition, Sea Farms West, a private firm, was involved in the
mariculture of mussels and clams. Previous storms, although damaging to the
surrounding community, did not appear to damage the lagoon or the projects
within it. Agua Hedionda Lagoon supports populations of nearly 150 species of
estuarine and marine invertebrates, as well as 65 species of marine fishes, 65
species of birds, and 46 species of other animals.
2-26
Batiquitos Lagoon
Plans for restoration of Batiquitos Lagoon include the dredging and beach
disposal of one million cubic yards of sediment. One purpose of this dredging is to
keep the mouth of the lagoon open to tidal influences.
2.5.1.4 Coastal Barriers
A coastal barrier is a depositional feature which is subject to wave, tidal,
and wind energies and protects landward aquatic habitats including adjacent
wetlands, marshes, estuaries, inlets, and nearshore waters. Coastal barriers can
be threatened by extensive shoreline manipulation or stabilization, canal
construction and maintenance, major dredging and disposal projects, and intensive
development projects.
Section 6 of the Coastal Barrier Improvement Act of 1990 requires the
Secretary of the Interior to provide to Congress maps identifying the boundaries of
those undeveloped coastal barriers of the United States bordering the Pacific
Ocean south of 49 degrees north latitude which the Secretary and the appropriate
Governor consider to be appropriate for inclusion in the Coastal Barrier Resources
System. Recommendations made by the Secretary will be advisory only; any
changes to the System will require an act of Congress. The U.S. Fish and Wildlife
has proposed the areas around Agua Hedionda and Batiquitos lagoons for inclusion
in the Coastal Barrier Resources System.
2.5.2 Threatened and Endangered Species
Upon request, the U.S. Fish and Wildlife Service sent an extensive list of
Federally-listed endangered, threatened, proposed, and candidate species that
potentially occur in the study area. This list is included in Appendix A of the
Environmental Appendix.
2.5.3 Water Quality
Water resources in the study area include the Pacific Ocean and the lagoons.
Possible contaminants in the study area could come from Oceanside Harbor,
polluting activities upstream of the lagoons, spills of oil and other products carried
by ships offshore of the study area, wastewater treatment plants, loôal industries,
and urban runoff. The Encina Sewer Plant, located between the Agua Hedionda
and Batiquitos lagoons, treats sewage to the secondary level before discharging
into the ocean. Water quality is probably diminished in the lagoons, particularly
2-27
where tidal circulation is limited. Thissituation does not necessarily result in
degraded habitat values,, however.
2.5.4 Ambient Noise and Air Quality
2.5.4.1 Ambient Noise
Sources of noise in the area include vehicular traffic on Carlsbad Boulevard,
the San Diego Freeway, and other major highways, and trains on the Santa Fe Rail
Line. Residential neighborhoods are among the sensitive noise receptors in the
area. '
2.5.4.2 Air Quality
Air quality is 'usually good, but it varies with seasonal and meteorological
conditions; Federal and State standards for air pollutant levels are sometimes
exceeded in the study area. Generally,.air quality decreases during the summer,
which is a period of high recreational use. Pollution sources include automotive
exhaust and emissions from the SDG&E power plant.
2.5.5 Cultural Resources
Archeological studies to identify cultural resources within the proposed
project area have not been conducted. There is a potential for historic and
prehistoric sites that are eligible for listing on the National Register of Historic
Places in both the land and underwater portions of the project. More specifically,
there are approximately six shipwrecks, and one World War II Japanese airplane,
within or near the proposed project area.
2.5.6 Aesthetics
The view along Carlsbad Boulevard is of narrow sand and cobble beaches;
beach-front homes, condominiums and restaurants; and an expanse of the Pacific
Ocean relatively unobstructed by the presence of -man-made structures such as
groins, breakwaters, and harbors. The lagoons, as well as being vital ecological
resources; provide open space between developments.
2-28
3.0 PROBLEM IDENTIFICATION
3.1 Statement of the Problem
The fundamental problem along the study area is that a loss of protective
beaches has left the unsheltered coastline vulnerable to extreme waves and runup
in a severe storm. In addition, long-term erosion is anticipated to increase the
potential for storm damage and reduce beach recreation. As a result of these
conditions, it is estimated that, under current conditions, the 50 year event will
cause flooding, damage to protective structures, structural damages, and roadway
damages, potentially totaling in excess of $2.7 million.
At the public workshop, and throughout the course of the study, the local
description of the problem has been that the beaches have narrowed substantially
and are frequently cobbled in certain reaches. The resulting effects of this
condition are that the beaches are less aesthetically pleasing, that tourist dollars
are lost, and that the shorefront structures are more susceptible to damages in a
significant storm.
3.1.1 Reach 1
Reach 1 is the highly developed reach in the north of the city, containing
approximately fifty-seven residences. Residents of Reach 1 report that the total
cost incurred as a result of the severe storms of the 1980's was approximately
$200,000 in structural and content damage. Additional damage was incurred to
the protective structures, but is not included in this value. *
3.1.2 Reach 2
This reach is defined by the city-installed seawall. There are no reported
damages to this reach since the installation of the wall.
1 3.1.3 Reach 3 . ' The City of Carlsbad reports that Carlsbad Boulevard is closed approximately
every two years due to overtopping. According to the Section 103 report,
Carlsbad Beach Erosion Control Reconnaissance Study, May 1990, the worst. I extent of damage occurred in the spring of 1981 when the highway was closed for
five days and 200 paved perpendicular parking spaces were lost to erosion. It was
1 3-1
estimated that 200,000 square feet of the road pavement (2000 by 100 feet)
were severely damaged and the repaircosts were estimated at $500,000. The
double perpendicular parking was replaced with a single row of angled parking.
During the storms of 1983, this angled parking was destroyed as approximately
100,000 square feet were lost.
Prior to the January 1988 storm, the city installed riprap along the shoulder
of the boulevard. Runup from that event did not cause' serious erosional damage
to the roadway but did result in clean-up and repair costsof $158,256. Figure 3.1
shows the scour at the base of the sidewalk.
The Tamarack parking lot, north of the Agua Hedionda inlet, contains
approximately 200 parking spaces. Though fronted by revetment, the lot is
situated at + 12.75 feet MLLW and is very close to the water line, and is thus
exposed to flooding and erosion. In 1983, this parking lot experienced
considerable damages which resulted in a reduction in width of approximately 30
ft. and loss of its curbing gutter. Emergency repairs were installed; but also lost in
the 1988 storms. Following this storm season, the state performed temporary
repairs on the parking lot.
3.1.4 Reach 4
While undercutting of the bluff from specific storm events is not a major
concern to homeowners within Reach 4, damages to proteôtive structures have
been sustained over time from severe wave force. Following the 1978 and the
1983 events, a portion of the structures protected by riprap required stone
replacement resulting from wave damage. In addition, gunite structures protecting
the remainder of the seafront homes in this reach required substantial repairs.
After the 1983 event an estimated $65,000 was spent to repair gunite protective
structures on thirteen homes, while an estimated $150,000 was spent to rebuild
riprap revetments on sixteen homes.
3.1.5 Reach 5
Although Reach 5, the South Carlsbad State Beach, contains few
developments prone to damage, it has been damaged in recent years: the 1983
storm caused $96,602 in damage resulting from debris clean-up of destroyed
restrooms, stairways, and parking lot repairs. The most critical area in the reach is
at Encinas Creek where Carlsbad Boulevard is + 18.25 feet MLLW and a box
culvert crosses over the creek at a particularly narrow part of the beach. The
exposed length is approximately 1000 feet long. The city reports that during the
storms of 1988 this structure was undermined and closed for several days. Repair
3-2
costs were between $5,000 and $10,000. Furthermore, the structure is old (circa
1923), in poor condition and appéärs exposed to erosion at the abutments. Figure
3.2 is a view from Carlsbad Boulevard towards Encinas Creek.
The bluffs fronting South Carlsbad State Beach campgrounds are an area of
particular concern for the local sponsor. The popular campgrounds bring in an
estimated $430,000 per year in revenues but are suffering from erosion. The
erosion is primarily due to runoff and other subaerial factors but waves and runup
have had some effect, albeit difficult to quantify. It is known that the beach
fronting the bluffs is denuded of sand virtually all year and therefore narrower and
thus has reduced protective capabilities. Figure 3.3 shows these bluffs.
3.2 Summary of the Analysis
The primary problem identified along the study area is the lack of protective
beach which leaves existing development exposed to storm waves and excessive
runup. Long-term erosion and storm recession further exacerbate the problem.
This section will summarize the analysis presented in the Coastal Engineering
Appendix for the potential for these problems to cause damage.
3-3
Figure 3.1 Beach in front of Carlsbad Boulevard.
- - - p
_m "
-411
Figure 3.2 Reach 4— View towards Encinas Creek.
- - - - - - - - - - - - - - - - - - -
Fiaure 3.3 Reach 4— Bluffs of South Carlsbad State Beach.
3.2.1 Cross-Sections
The typical cross-sections and pictures of sites the which were developed
for the study area are shown in Figures 3.4 through 3.12. Reaches 1 and 2 have
multiple cross-sections. Figures 3.13 to 3.18 indicate the type of structures these
cross-sections represent. Table 3.1 summarizes the characteristics of the sections.
The beach condition that was used to analyze the runup was the near-fully scoured
profile that was surveyed in January 1988 following that month's severe storm.
This profile presents the maximum winter scour as outlined in the Coastal
Engineering Appendix.
Reach/Section I Number of
Structures
Applied to
Reach 1
Cross-Section 1 44
Cross-Section 2
3
Cross-Section 3
1
Cross-Section 4 9
Reach
Reach 3
Reach 4
Cross-Section 1 16
Cross-Section 2 13
Reach 5
Comments
Typical section for this reach
Structures are close to water
line with low first floor elevation
Large condo complex with low
first floor elevation and unique
protective structure
Unprotected structures at south
end of reach
City seawall
Carlsbad Blvd at low elevation
Protected by riprap
Protected by gunite
Cobble beach/steep cliffs
3-5
Carlsbad
Reach I - Section 1
1-la
50
rd Pan ~3.3' MLLW Profiles:
I Earth Slope 1:7 Maximum
Revetment 1:2 Minimum
Mean
Re
Horizontal Distance (ft)
Figure 3.4 Schematic Profile of Carlsbad - Reach 1, Cross-Section 1
. Carlsbad
Reach 1 - Section 2 Profiles:
Maximum
,- Hard- Pan 43•3' MLLW - -- - Mean
- / r Glass Door --- Minimum
/ First Floor +16.8' MLLW
/• Sea Wall
Sand Beach 1:5
-0 50 • 100
Horizontal Distance (ft)
C 0
C
>0 0
w
Figure 3.5 Schematic Profile of Carlsbad - Reach 1, Cross-Section 2
C
0
4)
to
> a)
w
Carlsbad
Reach 1 - Section 3 Profiles:
Maximum
r 1-lard Pan -3.3' lvi LLW ---- Mean
I ---- Minimum
/ First Floor -17.8' MLLW
/
Rlprop 1:3 (1-ton Stones)
-50 0 50 /00
Horizontal Distance (ft)
Figure 3.6 Schematic Profile of Carlsbad - Reach 1, Cross-Section 3
Carlsbad
Reach 1 - Section 4
+)5Q
First Floor -43' MLLW
Hard Pan ~3.3' MLLW
Earth Slope 1:1.5
/ r— Sand Beach 1:5
Profiles:
Maximum
Mean
Minimum
-50 0 50 /00
Horizontal Distance (ft)
Figure 3.7 Schematic Profile of Carlsbad - Reach 1, Cross-Section 4
Carlsbad.
Reach 2 Profiles:
Hard Pan '/2.8' MLLW Maximum
- Earth Slope 1:2 Mean
Minimum
Sea Wall
Sand Beach 1:5
-50 50 /00
Horizontal Distance (ft)
Figure 3.8 Schematic Profile of Carlsbad - Reach 2
CQ C -' CD
(0
Cl, 0
CD
3 .
-. C,
-' 0 -4,
CD
0 -4'
C) 0,.
-,
Cr 0,
CL
CD 03 C)
Ar
Carlsbad - Profiles:
R each 3 Maximum
Mean
_j Minimum _J
50-- - Carlsbad Blvd. -16.8' MLLW
0
/- Hard Pan -6 Sand Beach i5
Ui -50 6 So 160 60 200 250 300
Horizontal Distance (ft)
Carlsbad
Reach 4 - Section 1 Profiles:
First Floor 38' MLLW Maximum
50 FHord Pon
#2ffMLLW
Minimum
ftrop 1:2 (2-ton Stones)
/ Sand Beach 1:4
0 - - a)
-50 0 50 /00
Horizontal Distance (ft)
Figure 3.10 Schematic Profile of Carlsbad - Reach 4, Cross-Section 1
Carlsbad
Reach 4 - Section 2 Profiles:
First Floor 4/' /VILLW Maximum
Earth Slope
MLLW Minimum
50
Gun/fe Slope I:!
C Sand Beach 1:4
••
Horizontal Distance (ft)
Figure 3.11 Schematic Profile of Carlsbad - Reach 4, Cross-Section 2
Carlsbad
Reach 5
_J State Park Campground '63 / MLLW
--
50 - -
Earth Slope I:!
- Hard Pon #0.8' MLLW
C Cobble Beach 1:4
fo
0
Lij
-50 0 50 /00
Horizontal Distance (ft)
Profiles:
Maximum
Mean
Minimum
Figure 3.12 Schematic Profile of Carlsbad - Reach 5
- - - - - - - - - - -. - - - - - - - -
Figure 3.13 Typical Structure of Carlsbad - Reach 1, Cross-Section 1. Figure 3.14 Typical Structure of Carlsbad - Reach 1, Cross-Section 2.
Figure 3.15 Typical Structure of Carlsbad - Reach 1, Cross-Section 3.
;!Lit !1111
-
V.
V
3.2.1 Long-Term Erosion
The long-term evolution of the future without project shoreline considers
temporal changes in the sediment budget. From the sediment budget analysis in
Section 2.3.8.7, the shoreline at mean sea level is predicted to retreat at an
average rate of 1 foot per year for the next 50 years. Thus, a 50-foot shoreward
recession in the present shoreline has been obtained for the future without project
condition. However, the retreat rate of 1 foot per year only applies to the summer
beaches, due to the fact that the winter beaches have already moved to about the
limit of shoreward retreat. The winter recession of the shoreline for all the
reaches, with the exception of Reaches 3 and 5, is limited by the non-erosive
hardpan, revetment, and seawall. At Reach 3, in the 2700 foot element between
the inlet and outlet to Agua Hedionda Lagoon, the limit of erodible material is at -
6.25 feet MLLW. Consequently, it is anticipated that the beach will erode to the
roadway and then continue to scour vertically. As a result, the depth at the toe
will continue to deepen, and the road will be exposed to greater wave energy.
Based upon experience with unprotected,. unconfined beachfills, it is expected that
the beachfill on Reach 5 will be lost within seven years due primarily to longshore
transport to the south.
3.2.2 Storm Recession
The January 1988 survey is representative of the eroded profile condition
during a severe winter storm condition. During damaging storm events, a winter or
storm profile would typically exist. This storm profile is deepened in the nearshore
depending on the severity of the individual storm and the cumulative effects of the
storm season. Storm effects on the profile were super-imposed on the present and
future shoreline. It is rationalized that storm profile response would be directly
related to storm severity and wave height, and therefore return period. Based on
the analysis of the shoreline data presented in CCSTWS of USAED, Los Angeles
(1991), shoreline retreat can be correlated with return period. The recession that
would be expected as a result of the 10, 25, 50, and 100 year events is presented
in Table 3.2. Since the runup analysis was based upon the scoured 1988 winter
profile, this recession was only applied to Reach 3.
3-14
Table 3.2. Storm Recession versus Return Period
Event
Shoreline Retreats (ft)
MHHW MSL MLLW
10 43 89 225
25 47 96 237
50 50 -100 245
11 100 52 104 252
3.2.2 Runup
Runup has been calculated using the reaches and cross-sections presented in
Section 3.2.1. The beach conditions used are the profiles taken after the storm of
January 1988. Due to the bedrock conditions, only the profile in Reach 3 will
deepen over the 50 year period considered. As a result, only in Reach 3 will runup
increase. Due to the anticipated temporal nature of the beachfill in Reach 5, the
runups presented for this reach are done over the fully-scoured'profile. Table 3.3
presents these runups.
3-15
4
4
I
1••
I
II .•;',
IH
.:
I
••r, •- •- • - U - - - 1. •.•. '--. - -4 - - 4.. - - •• -.
S. 4
I 3.3 Damages
-.
•' 4
The lack of adequate protective beaches leaves backshore structures.•
exposed to excessive runup and increased wave attacks. Factors-suh as.
inundation, damage to protective structures, damage to structures, and erosion of
Carlsbad Boulevard, will be examined.
I -
3.3.1 Inundation Damages-
- •. -. - - . . -
Excessive runup will cause significant content and structural damage to four
large structures in Reach 1. •The remaining structures in Reaches 1 and 4 are all
I above the elevation of the maximum runup. Inundation damage will occur when
I 3-16'
jp
4 4
.. -:- - ..:. •-_-• .-.-.
the runup elevation exceeds the first floor elevation. The depth of inundation in
the structure was estimated by deriviriga factor which relates the historical data
and the FEMA curves to-account for the difference between traditional-flooding
and flooding as a resulfof runup. The product of this factor and the elevation
difference was then applied to the FEMA curves.
Three of these structures are of Cross-Section 2 (Reach 1) and have first
floor elevations (feet MLLW) of 20.75, 19.75, and 18.75. Runupfor both the
1983 and 1988 events wascalculated to be ±23.65 feet MLLW for this section.
One owner reported that $17,000 of damages occurred in 1983 and $8,000 in
1988.
The other structure, a large condominium complex, is of Cross-Section 3
(Reach 1). Runup for the 1983 event was to +20.35 feet MLLW and +20.65
feet MLLW for the 1988 event. Two of the eight units exposed to inundation
reported (total) damages of $10,000 and $2,000 for the 1983 and 1988 events,
respectively.
-
Potential inundation damages have been calculated and are included in Table
3.11.
3.3.2 . Damages to Protection
There are approximately 3200 linear feet of one half to two ton riprap
protecting the Carlsbad coastline. During the July site walk, the size, slope
characteristics, and condition of the revetments were recorded. It was noted that
ten of the structures in Reach 1 were especially vulnerable in that since the
revetment was under-designed (the site had not been excavated to solid material
and no measures were taken to provide filtering), its ability to protect had seriously
deteriorated. In addition, the stone is small and can be easily displaced by wave
action.
Damage to revetments was estimated by calculating the forces acting on the
revetment due to breaking waves. Variables include stone size; slope, and wave
height. The Hudson formula was used to calculate the damages.
Table 3.4 displays the estimated damages under wave action of various I return periods. - -
-
I
3-17 1
- V, -
.3,
.............. ...............
TABLE 3
.................... .. ...
DAMAGE TO REVETMENT PRESENT CONDITION
Reach Linear Ft DAMAG 2 5 10 25 50 100 200
E._'
,DAMAG 8,' 14 17 19 ' 21 24k '27
70 E (%) -
I
DAMAG . 2300 3900 4800 5400 5900 6800 W, 7600
• ,t.. ' . DAMAG ,16 ' 26 31 37 41 45 .. 50
750 E
DAMAG .40000 64000 77000 91000, 101000 111000 12300
E 10 ($}
DAMAG 8 14:.17 VV.19, 21 24 - 27
400 E(%)
DAMAG
-
15000 .25000 31000 35000 38000 44000 49000 I E(S)
DAMAG 0 ... 5 . .. 13 25 43 .60 '. 61
450 E
I . 3" V.
- .
. DAMAG 0 4000 11000 20000 35000 49000' -49000
I •V DAMAG 12 ' 38 70 - 100 . 100 100 V ±100
-350 . -
5 V '•,':'
V3 ... V I V V DAMAG 6000 18000 33000 47000 47000 47000' 47000
DAMAG - 5-
V
12 . VV 16 18 ' 19,
1200 E
4 -
V . DAMAG 27000 49000 65000 81000 86000 .97000. 10300
I V ' E($)
V
•-
50-YEAR FUTURE CONDITION V
V
- ' 'V ' '• -
V
DAMAG 100 100k , 100 100 - 100 100' ' 100' -
V 450 • E
*
' 3 , .
DAMAG 81000 81000 81000 81000 81000 81000 81000. I E($)
DAMAG 100 . 100 100
V
100 100 100 , 160.
• '
-3,
350 E(%)
• - 5 V V
- DAMAG. 47000 47000 47000- 47000 47000 47000 47000
'E($)
REVETMENT AT REACH 3
l I 3-18
I .
. .
' :
V
V
' ••
'- . V , - -'.
. V
.
, '
3.3.3 Structural Damages due to Bluff Retreat
Approximately 20 structures are subject to structural damage due to erosion
of the bluff and undermining of foundations. To facilitate analysis, ten
representative structures located along a 620 foot length of Reach 1 were
analyzed. The bluff in front of all ten structures was unprotected; therefore, they
are of Cross-Section 4. The structures are typically built with concrete grade
beams and slab foundations cut into the bluffs backing the beach. The foundation
elevations range from about +24.5 to +38 feet MLLW, while the toe of the bluffs
is located at + 12.75 feet MLLW. Table 3.5 shows the foundation elevations of
ten structures. Also shown in-the table are horizontal distance of: foundation to
+ 12.75 feet MLLW, projected by the 1.5:1 slope, and structure to bluff edge.
Figure 3.19 shows a schematic drawing of a structure on the bluff.
Extreme storm events have resulted in erosion at the toe of these coastal
bluffs and the-slumping of the bluffs fronting these structures. Although little
historic information on magnitude and extent of bluff retreat are available for this
specific location, anecdotal reports and review of aerial surveys suggest that bluff
retreats along Reach 1 were as high as 13 and 20 feet in localized areas during the
1983 and 1988 storms, respectively, while over a longer 170 foot length of
shoreline at the north end of the Carlsbad shoreline, bluff retreat appears to have
averaged about 8 feet as the result of the 1988 storm event. Figure 3.20 displays
a simple linear correlation of bluff retreat with runup level above the toe of the
bluff through the available data. Approximating the distance of lateral retreat as
proportional to excess runup allows assigning a return-period estimate to bluff
retreat distance. Excess runup is the result of runup elevation subtracting the bluff
toe elevation of + 12.75 feet MLLW.
The damage assumptions applied to the loss of structures are as follows:
Structure foundation are grade beam or slab.
Limiting stable bluff slope is 1.5H:1V.
Initiation of damage ocáurs when top of the average eroded bluff with a
slope at 1.5H:1V reaches the closest foundation and complete damage occurs
when the bluff erosion reaches the furthest recessed structure.
Utilizing these assumptions, initiation of damages due to bluff retreat
undermining structure foundations initiate at the 50-year event, while complete
structural damage occurs along this vulnerable reach at the100-year event.
3-19
/J \
/
h I '-1 /.J I
A
-\40
b
E
fi
fa
Figure 3.19 Schematic of Structure on Bluff
Carlsbad
MIJ
'-' 30
6 7 8'
Excess Runup (ft)
a t
5
'1
-' CD
N C
cc
-4' -4'
M
0 cn
0
CD
Cn C Cl,
I.!,
C) CD Cl, U,
0,
CD
C
C
40 1983 Storm Data
1988 Storm Data
A
30 Localized Retreat
Average Retreat
20
Farthest House
Closest House
10
HorizontaL Distance (ft) of
EL -vat ion of Foundation Projected Structure to
House Foundation (ft) to +1O'MSL by 1 5 1 SLope BLuff Edge
1 25 46 38 8
2 25 46 38 8
3 32 75 48 27
4 32 65 48 17
5 27 50 41 9
6 30 55 45 10
7 32 70 48 22
8 25 70 38 32
9 22 60 33 27
10 35 65 53 12
Table 3.5 Data used for Calculation of Bluff Retreat
Due to the uncertainty involved in projecting these failures resulting from the
scatter of the data, and due to the concerns of the city regarding the effect of this
uncertainty on the outcome of the study, the Economics Section preformed a
sensitivity analysis which entailed shifting the failure curve of the structures such
that the structural damages would begin at the 25 year event and complete failure
would occur at the 100 year event. In the originally assumed failure scenario
(present conditions), the 25-, 50-, 100-, and 200-year events resulted in structural
damages of $6,580, $227,550, $3,320,560, and $3,611,700, while the
sensitivity analysis indicated that damages would total $198,350, $1,706,960,
$3,293,400, and $3,511,700 for the same return periods. This resulted in an
increase in the equivalent annual damages (EAD) by $37,620, or 27%. From the
alternatives presented in Chapter 4 (see Table 4.16 on page 4-76), it can be seen
that the use of this alternate scenario does not increase the ratio of storm damage
reduction to cost above 0.5 for any alternative, indicating that the use of this
scenario will not alter the position on Federal interest presented in Chapter 5.
The original damaging return periods were used in evaluation of federal
interest because the storms of January 1983 and January 1988 were calculated to
be the 25 and 50 year events, respectively, yet no significant bluff erosion
occurred in the areas of concern.
3-22
3.3.4 Roadway Damages
Significant damages to Carlsbad Boulevard have occurred in Reach 3 and
less significant damages have occurred further to the south in Reach 5. A unique
feature of Reach 3 is that the bedrock is located at elevation -6.25 feet MLLW,
thus making the reach more susceptible to both storm-induced scour and long-term
erosion.
As previously discussed, it is assumed that over a fifty year period, Reach 3
will experience recession of 1 ft/yr and it-is anticipated that the beach will erode to
the roadway and then continue to scour vertically. As a result, the depth at the
toe will continue to deepen, and the road could be exposed to greater wave
energy.
Damages to Carlsbad Boulevard in Reach 3 were based on the 1983 storm
event which produced an excess run-up of 4.1 feet over the top of the road. The
excess run-up was based on the portion of the boulevard exhibiting the lowest
elevation. The area of road eroded during each storm frequency was determined
and a replacement cost based for the required construction materials and labor was
applied. Tables 3.6 and 3.7 present the quantity of erosion which occurs to Reach
3 as the result of particular events. The economic loss as a result of this erosion is
included in Table 3.11.
The same excess runup-erosion relationship was used to analyzed the box
culvert in Reach 5. Table 3.8 presents the quantity of erosion which occurs as the
result of particular events. This area will initially have a substantially wider beach
as a result of the Batiquitos Enhancement Project. However, this beachfill is
anticipated to dissipate in approximately seven years. After that period, it is not
expected to provide measurable protection. Also after this period, no long-term
erosion will occur in this reach (due to the cobbles and a higher bedrock),
therefore, damages will not increase. The runup/damage analysis was performed
on this reach using the latter condition, but the economics analysis was done
assuming the damages would not begin until seven years after the beachfill had
been placed.
3-23
I
r ',
1 .,•
-' t
RETURN
PERIOD
WAVE
RUNUP
(FT)
EXCESSIVE
RUNUP (Fr)
EROSION
(Fr)
AREA
LOST (SQ.
Fr)
2 19.85 1.6 0 0 11
5 21.45 3.2 9 9,000
10 22.45 4.2 55 55,000
25 23.45 5.2 100 100,000
50 23.85 5.6 100 100,000
100 24.45 6.2 100 100,000
200 24.85. 6.6 100 100,000
3.4 Economic Loss
Damages expected to result in each storm interval (2, 5, 10, 25f'50, 100
year exceedence frequency) were weighted by the probability of the storm
frequency by combining the depth-damage, stage-frequency, and stage-damage
curves. Equivalent annual damages were computed for an 8 percent discount rate,
the study year (1993), and the project base year (1997). Damages under existing
conditions for each storm interval are shown in Table 3.9. Total expected and
equivalent annual damages are shown in Table 3.10 and are separated by reach in
Table 3.11.
Damages to revetments are presented as calculated previously (see Section
3.3.2). Due to the difficulty in establishing maintenance costs for gunite walls, it
was assumed that these valueswere equal to those of revetments.. Landscaping
losses were estimated on the July 1993 site walk.
3-25
I 4!
I
' Table 3 9
Carlsbad
Damages Under Existing Conditions
October 1993 Prtce LaveJs
I ... m l:
0.
No=
I CONTENTS
EVENT 25-YEAR 50-YEAR 100-YEAR 200-YEAR
$179.90 - ' $240.30 $304.90 $317.40
STRUCTURES $6.58 $227.55 $3320.56 $3611.70
1 LANDSCAPING! . $23.84
STAIRS
$68.06 $134.97 $143.48
I REVETMENTS
ROADWAYS .
$348.80
$1368.00'
,
-
$390 10
$1632.00 4 . •!
$437.90
$1908.00
..
$466.15
$2184.00
-
I EMERG & CLEAN-
UP.
$0.00 - •. $152.70 $157.70 $161.80
I TOTAL
DETOUR . $27.73
$1954.85:.
- $28.48. ...
s2;739.19
. •. $29;23
' $6,293.26
$29.98.••
'$61914.51
:- . - - --
I -' -
-
1 - • .
- 4! . .4. - 4. 1__- • I -- -
. -.. . - . _t -. .• . !•
....• - -. )
I
I
I r
1
4
4_Il
I -
I
-
,
1 3-26
I *
REACH
NUMBE
R
CROSS-
SECTION
.
Contents
*
Detour
- ,.
Emerg/
Clean-up
Inundation
*
Other!
Landscapin
g
Revetments
.
Roadways Structure
. -
Equivalent
Annual
Damages
2
* 1
- :- 4
TOTALS REACH I
N/A N/A N/A N/A $1.51 $49.63 N/A -$21.73 -
-
- $8.11 N/A N/A, $16.47 $57 N/A $7.92
$2.29 N/A N/A $5.68 $42 N/A $1.98
N/A
$1040
N/A 1
N/A
N/A
N/A
N/A
$2215
$91
$341
N/A .
$4963
N/A
N/A
$21.65
$5328 $13887
2_L -[ 1 0
N/A $5.20 $1.49 N/A N/A $31.73 $244.82 1 . N/A $283.24
.4. - I
.
-.
2
•j-
TOTALS REACH 4
N/A N/A J N/A J N/A J $71 $26.25 N/A .N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
.
N/A
$31 4-
01.02
$21.96 4-
$48.21
N/A
N/A
4-. N/A
N/A $49.23
- 0 0 0 0 . 0 0 $60.96 0 . $60.96
TOTAL: $10.40 1 $5.20 $1.49 1 $22.15 4.43 $129.57 $318.38 $53.28 $532.30
Inundation damages and content damages resulting from structural failure are aggregated in the previous two tables but are listed separately in order to illustrate that double-counting wa
avoided.
Revetment dmagee for cross-sections 1,2. and 3 were computed for a single wave height for the entire reach. Thus. $48890 represents total revetment damages for all of Reach 1.
r - $ I *
-
4 3
3-28
3.5 Recreation
As a result of the assumed 1 ft/yr erosion rate, for without project
conditions, beach area will decrease by approximately 466,400 square feet over
fifty years. The entire length of the Carlsbad coastline measures 33,000 feet with
an average width of36 feet above the MHHW line. Total area, of the beach under
current conditions, weighted by the actual beach width,, is 1,200,770 square feet.
The percent loss of beach under these conditions is 39%. As a result, a decrease
in carrying capacity will result, and diminished beach area will be forced to supply
a growing number of beachgoers. The end result will be diminished recreational
experience to the beach user and, thus, a reduction in the willingness to pay for
this experience. Table-3.12 presents the presentand future areas above the
MHHW line per reach.
Table 3.12 Present and 50 - Year Future Areas Above the MHHW Line per
Reach
Period Reach 1 Reach 2 Reach 3 Reach 4 Reach 5
Present (ft2) 19,500 364,000 452,950 0 364,320
Present (acres) 0.45 8.36 10.40 0 8.36
Future Future (tt2) 0, 164,000 237,950 0 0
Future (acres) 0 3.76 5.47 0 ' ' 0
Beach attendance numbers were based upon the California Department of
Parks and Recreation's counts. Using a methodology developed in Section 6 of the
Economic Appendix, these numbers were broken down to determine the average
daily visitors per acre at any one time per m'nth. The methodology then employed
a point system to calculate the recreational value of the experience. The value of
the experience does not begin to decrease until there are more than 100 persons
per acre.
Under without project conditions, parking conditions are assumed to be
sufficient to accommodate existing and anticipated parking requirements
The increased beach width as a result of the Batiquitos Enhancement Project
was not considered into these without project conditions because the recreation
value of the Carlsbad beaches will not decrease until after the first seven years.
Afterthat seven year period, the beachfill is assumed to have been dissipated, and
the will be approximately in their without enhancement project condition
3-29 -
Table 3.13 presents the existing and future capacity levels of the state
beaôhes in the years 1990, 2010, and 2040. The table represents the loss in
beach visitation and beach acreage, based upon the erosion rate of 1 ft/yr for
Reaches 1 through 4.
Table 3.13 Average Daily Number of Persons Accommodated at 75 ft2/person
Beach Area in 2,124,100 1,797,937 326,162 1.299,100 498,837
sq.ft.
Daily # of visitors
at 75 sq.ft per 28,321 23,972 4,349 17,321 6,651
person
By a methodology detailed in the Economic Appendix, the total average
annual recreation value under without project conditions is $10,729,635.
3.6 Definition of the Problem
Based upon the historical and anticipated damages, a number of problems
have been identified.
3.6.1 Reach 1
The analysis indicates that this reach will suffer storms damages to
landscaping, protective structures, contents, and to the structures themselves.
Structural damages occur as a result of both inundation and erosion of the bluff. It
is anticipated that if the, 50 - year event were to occur under present conditions,
approximately $600,000 in damages would occur to this reach. In addition, the
recreational value of the beach has been decreased as the beach has narrowed as
a result of past storms, and the summer width is anticipated to continue to narrow
due to a deficit of sand supply in the sediment budget.
3.6.2 Reach 2
3-30
This reach is defined by the city-installed seawall. At the typical cross-
section, the crest of the wall is at elevation + 23.25 feet MLLW, incorporates a ten
foot wide sidewalk at elevation +20.25 feet MLLW, then rises again to elevation
+23.25 feet at the back of the wall. Therefore, while runup calculations indicate.
that some overtopping will occur in events with return periods larger than 25
years, the quantity will be insufficient to erode or, de-stabilize the slope backing the
wall. In addition, since the bedrock under the wall is approximately at elevation
+ 12.75 feet MLLW and the seawall is keyed into the bedrock, it is unlikely that
the seawall can be undermined. There are no reported damages to this reach since
the installation of the wall. Therefore, the conditions within this reach do not
reflect imminent danger to structures or infrastructure.
The recreation value ofthis reach is anticipated to decrease as the summer
width continues to narrow at one foot per year.
3.6.3 Reach 3
Three factors combine to make this reach very susceptible to storm
damages. First, the beach is extremely narrow. Second, Carlsbad Boulevard
reaches its lowest point (elevation + 16.95 feet MLLW) in this reach. Third, the
depth to bedrock.is deeper here than in any other reach (elevation -6.25 feet
MLLW), thus increasing the susceptibility of the reach to both storm-induced scour
and long-term erosion.
Based upon the historical record and the analysis, it is concluded that
substantial maintenance costs are being incurred to protect Carlsbad Boulevard and
the Tamarack parking lot from storm effects. In addition, this portion of the road is
the primary thoroughfare connecting key elements of the city. The shortest detour
is approximately 1.1 miles. It is estimated that if the 50 year event were to occur
under existing conditions, damages to this reach would total $865,180 and $1.8
million if the same storm were to occur in the fifty year future condition.
The recreation value of this reach is anticipated to decrease as the width
continues to narrow at one foot per year. . .
3.6.4 Reach 4
Most of the erosion appears to have subsided due to the loss of available
erodible material and the construction of protective structures. The remaining
beach material is a cemented sandstone similar to the bedrock described in other
3-31
locations in Carlsbad. The privately placed protective structures are composed of
large riprap (two ton) and gunite. It is anticipated that $160,000 in damage to
protective structures will occur in the 50 year event. Homes are high enough and
set back far enough to warrant no need for further protection from inundation.
The revetment and gunite protecting the bluff appear to be preventing further bluff
erosion and therefore, the condition will not worsen with time.
Since there is essentially no beach above the MHHW line even during the
summer, the recreation value of this reach will not decrease with time.
3.6.5 Reach 5
As mentioned in Section 2.3.5, without project conditions include the
Batiquitos Lagoon Enhancement Project, which will initially provide a sufficient
level of protection to the box culvert. However, since the beachfill is to be
unconfined, it is expected that this protection will reduce to none within seven
years. Analysis indicates that the box culvert will then be exposed to storm
damages. After the removal of this protection, damages from the fifty year event
are anticipated to exceed $600,000.
The bluffs fronting South Carlsbad State Beach campgrounds are ' experiencing erosion. While coastal processes have had some effect, the erosion is
primarily due to runoff and other subaerial factors. A review of aerial photos and
an inspection of the site, along with the absence of verifiable data to the contrary,
I indicate that this threat is not substantial enough for this problem to merit further
investigation.
I Historically, the beach in Reach 5 is virtually completely cobbled in both
winter and summer. The beachfill will initially provide significant recreation
benefits, but these will decrease as the fill is dissipated. After this has occurred,
I the reach will return to its cobbled state and the recreational value of this reach
will decrease no further with time.
I
' 3.7 Conclusions
Four conclusions can be reached concerning the problems in the Carlsbad
Coastal Area:
1. Reach 3 suffers the most damage, primarily as a result of the exposure
I of Carlsbad Boulevard between the inlet and outlets to Agua Hedionda
Lagoon to undermining during severe storms. The equivalent annual damage
I 3-32
1
associated with this 2700 foot reach is $275,000. The Tamarack parking
lot, north of the intake, is also exposed to damage, however to a lesser
extent and primarily to revetment.
The equivalent annual damages for Reach 1 total $138,000. The most
substantial components of this number are damages to buildings and
damages to protective structures ($52,000 and $50,000, respectively).
While damages to protective structures are fairly evenly distributed
throughout the reach, damages due to structural failures are concentrated to
the southern and mid-sections of this 5,000 foot area.
The Carlsbad Boulevard in Reach 5 will be vulnerable to damages over
the box culvert at Encinas Creek once the beachfill from the Batiquitos
Lagoon Enhancement Project dissipates. Equivalent annual damages are
calculated as being $61,000.
The total recreational area of the Carlsbad beaches will decline by
approximately 39% over the life of the project.
3-33
4.0 PLAN FORMULATION
4.1 Rationale of Formulation
The Pacific Coast Carlsbad Reconnaissance Study was conducted usinga
multi-objective planning process, consistent with the planning requirements of
Section 904 and 905 of the Water Resources Development Act of 1986 and the
U.S. Army Corps of Engineers Engineering Regulation 1101-2-100. The objective
of this planning process is to guide planning for the conservation, development,
and management of water and related land resources. This planning process
results in information necessary to make effective choices regarding resource
management under existing and projected land use, and economic and
environmental conditions in the study area.
4.1 .1 National Objective
Federal and Federally-assisted water and related land planning activities
attempt to achieve National Economic Development (NED). Contributions to NED
are increases in the net value of the national output of goods and services,
expressed in monetary units. Plans are formulated to alleviate
problems and take advantage of opportunities in ways that contribute to the NED
objective.
4.1.2 Public Concerns
Public concerns are perceptions about existing problems or needs and their
I desires for improvements to facilities which they use or which affect them. By
eliciting information from the public, subsequent planning efforts can be directed to
respond to these perceptions and desires. Public concerns may be expressed
I directly, such as at a public meeting, or indirectly through government
representatives and agencies. Concerns are expressed through public meetings
and workshops with public, private and commercial interest groups. Additional
I comment was obtained through input and coordination with representatives of
government agencies and the general public.
I The major concerns expressed regarding the Carlsbad Coastline by all public
and private interests are the following:
the erosion of public beaches,
the loss of tourist revenues as a result of the loss of recreation beaches,
and,
the potential for storm damages throughout the Carlsbad Coastal Area.
1 4-1
4.1.3 Planning Objectives
The planning objectives for Pacific Coast Carlsbad Reconnaissance Study I
reflect the concerns expressed by officials of the City of Carlsbad, the Carlsbad
Beach Erosion Committee, beach users, and other local interest The planning
objectives are as follows:
to reduce coastal storm related damage potential to public and
S private property in Reaches 1, 3, and 5;
to restore and improve the area's beaches with respect to their I recreational value in all reaches;
to preserve and enhance the environment by restoring nesting, I feeding and resting areas for species dependent upon sandy beaches.
4.1.4 Evaluation Criteria S
This section describes the information required by ER 1105-2-100 to be 1
included in reports to ensure endorsement.
I
4.1.4.1 Economic Criteria
The general economic criteria that apply in formulating and comparing
alternatives are summarized as follows;
Tangible project benefits must equal or exceed economic costs.
The benefit-to-cost (B/C) ratio is a measure of this criterion. The B/C
ratio must exceed 1:1 to achieve economic justification. I
The scale of development should consider maximization of net
benefits (benefits minus costs). S S I
The objectives cannot be attained by a more economical solution.
Principles and Guidelines for Federal water resources planning require that,
during plan formulation, a plan be identified that produces the greatest contribution
to the National Economic Development (NED). This plan, called the NED plan, is
defined as the plan providing the greatest net benefits as determined by
subtracting annual costs from annual benefits. The Corps of Engineers policy
requires recommendation of the NED plan unless there is adequate justification to
4-2
5 1
do otherwise.
4.1.4.2 Environmental Criteria
The process in evaluating environmental considerations to formulate and
compare alternatives is as follows:
Alternatives will be evaluated for their potential environmental
impact, either beneficial or adverse. The relationship between short-
term uses and long-term productivity of impacted resources will be
determined. Irreversible and irretrievable commitments of resources
will be explicitly identified.
Efforts will be made to avoid detrimental environmental effects;
when adverse effects are unavoidable, feasible mitigating features will
be included wherever justified.
4.1.5 Costs
Costs are based on October 1993 price levels and include costs as required
for PED, contract administration and contigencies at 25%. Annual costs are based
I on an 8% interest rate and an economic period of fifty years. -
As indicated in the Real Estate Appendix, the beaches are generally publicly
owned.
a. Paragraph 3, Policy Guidance letter No. 11, dated 13 October 1986,
indicates "Land needed for placement of project features that prevent the
loss of the land itself has no value for crediting purposes".
Paragraph 9d (1), of ER 1165-2-130, indicates that a project
"sponsor may in fact incur costs in acquiring requisite interests.
Accordingly, a sponsor will be credited for his actual costs or for the net
reduction in total market valuation of the parcels." Since the lands
concerned are owned by the state, it is expected cost of any will be limited
to procuring right of entry.
4.2 Plan Alternatives
In order to mitigate the problems identified in Section 3.5.6, various
measures were considered, including: revetments, seawalls, protective beaches
(both with and without containment structures), and detached breakwaters. From
these measures fourteen alternatives were formulated. The following sections
discuss the alternatives that were developed, their evaluations, and the
corresponding indications of Federal Interest. All the plans are summarized in
Table 4.15. Three of these alternatives (Alternatives 7, 13, and 14), satisfy the
evaluation criteria presented in Section 4.1.4.
4.2.1 Plan 1 - Beachfill in Reaches 1 and 2
4.2.1.1 Description
As shown in Figure 4.1 a, a 200-foot wide, 5000 foot long berm is
constructed at the coastal area of Reaches 1 and 2. Although Reach 2 is not an
area in which damage is anticipated, the beachfill is to extend approximately 1 500
feet into this reach in order to insure that the vulnerable structures at the southern
end of Reach 1, as well as those in middle of the reach have adequate protection
(see Figure 4.1a for the location of the structures). This same level of protection
would not be assured should an unconfined fill be terminated at the end of Reach
1. In addition to storm protection, this plan provides incidental recreational beach
area.
The elevation of the beachfill is + 10 feet MLLW and the beach face slopes
downward approximately 1 vertical on 20 horizontal from the berm crest to the
natural nearshore bottom. Figure 4.1b shows a typical cross-section of. the
beachfill. An initial fill of 1,516,700 yd will be required. Assuming 170,000
yd3/yr are lost (see below), 850,000 yd of renourishment would be placed at five
year intervals (the optimization is included in the Coastal Engineering Appendix).
Adequate borrow sites for sand have been identified off the coast of both
Carlsbad and Oceanside. In Beach Nourishment Sources Along the
Carlsbad/Oceanside Coast (USAED,Los Angeles, 1993), the results of a program
which included 45 vibratory cores from potential sources identified in the Coast of
California Study were presented. Mechanical analysis and specific gravity analysis
were preformed on promising samples. Cost estimates were developed based
upon recent experience.
Sites I and Ill in Figure 4.1c were identified as being most promising,
possessing substantial quantities of material in the 0.2 to 0.3 mm range. It is
estimated that 5.5 million yd of quality sand are seaward of the 40 foot isobath in
Site I, while there is in excess of 1 million yd of similar material in Site Ill. Site Ill
contains approximately 400,000 yd of material, but very little of it is of good
enough quality. In addition, this site would not be recommended for use in that it
4-4
Ocean St
Inadequate
Figure 4.1 a Beachfill - Reaches I and 2
Line CB-850, Pine Avenue
10
5
0
-5
19
—15
1000
50
45
40
35
30
25
-J -J
20
0 15
>
10
5
0
—5
—10
Carlsbad - Reach 1 and
- Typical Cross-Section of Beachfifl
200'
- October 1991
* October 1990
20 —fl
MLLW
-IJ -
0 100 200 300 400 500 600 700 800 900
Range (ft Seaward of Range Line Monument)
Figure 4. lb Typical Cross Section of Beachfihl - Reaches I and 2 1 1888 123M - - - - - - - - - - - - - - - - - - -
Santa
Margarita
River
San
Luis Rey
Oceanside
Buena
Vista
Lagoon
Carlsbad
Agua
Hedionda
Lagoon
Pacific Ocean
\
\','
\ Batiquitos
\., Lagoon
Scale
0 1 2 miles
Encinitas
11888124M
Figure 4. ic Identified Potential Borrow Areas
is entirely within the 40 foot isobath and dredging in this area could disrupt the
littoral process.
4.2.1.2 Engineering Evaluation
To maintain a minimum width of 200 feet for the protective beach, an extra
volume of sand will be required during the initial construction of the beachfill. The
extra volume will account for the sand loss which takes place between the time
interval of replenishment, because there isa net longshore transport of 270,000
cubic yards per year. Since there is continuous dredging at Oceanside Harbor and
beach disposal of the dredged materials south of the harbor, it is assumed that
Reaches 1 and 2 will receive 100,000 cubic yards per year from this sand bypass
operation. Thus, the replenishment rate of the beachfill becomes 170,000 cubic
yards per year. Optimizing, the beachfill will be replenished on a 5-year cycle for
the case without any stabilizing structures.
An analysis of the shoreline retreat similar to that summarized in Section
3.2.2 has been performed to estimate the probable berm width for use in the
calculation of wave runup. The shoreline data are obtained from the CCSTWS of
USAED, Los Angeles (1991). The MHHW shoreline retreat associated with return
periods of 5, 10, 25, 50, and 100 years are 160, 188, 218, 237, and 255 feet;
respectively. The with project beachfill will have a berm width varying between
200 feet and 400 feet wide, depending on when in the replenishment cycle the
storm occurs. For storms with less than 200-foot shoreline retreat, the200 feet
wide initial berm width is assumed to calculate wave runup because the residual
damage for these events will be negligible. For storms with shoreline retreat
greater than 200 feet, the runup can be the same as without project if the
protective beach is narrower than the storm recession. To approximate residual
damages with project beachfill, it is estimated that the return period would double
for events with recession greater than 200 feet or that the 50-year without project
runup would be equivalent to the 100-year with project runup. Table 4.1a
presents the with project runup in Reaches 1 and 2.
Table 4.1a Carlsbad - Wave Runup Statistics at Reaches 1 & 2 - With Project
CarLsbad Wave Runup LeveL (ft MSL)
Line 2-yr 5-yr 10-yr
------------------------------------------------------------
25-yr 50-yr 100-yr 200-yr
Ri Si 13.7 15.3 16.1' 20.8 21.1 21.4 21.9
Ri S2 13.9 15.6 16.5 23.2 23.5 23.8 24.4
Ri S3 13.7 15.2 16.0 20.2 20.5 20.8 21.3
Ri S4 13.7 15.3 16.2 21.1 21.4 21.7 22.2
REACH 2 14.2 15.6 16.5 23.4 23.8 24.2 24.5
Using the results of wave runup, the reduction in damage to ancillary
improvements and flooded structUres can be obtained. As shown in Figure 3.20,
bluff erosion will start to occur at an excess wave runup of about 8.6 feet.
Utilizing the assumptions stated in Section 3.3.3, damages due to bluff retreat
undermining structure foundations will initiate at the 100-year event while
complete structural damages along this unprotected reach occurs at the 200-year
event. Since the berm provides protection from wave attack, structural damage to
revetment is reduced as shown in Table 4.1 b.
Table 4.1b Carlsbad Revetment Damages - With Project Conditions
Item 2-year 5-year 10-year 25-year 50-year 100-year 200-year
ResuLts of PLans 1, 2, 5, 11 at 2445 Ocean, 70 IF at $402.86/ft = $28,200
Damage(%) 0 0 0 6 14 21 24
Damage 0 0 0 $1,700 $3,900 $5,900 $6,800
ResuLts of PLans 1, 2, 5, 11 at 2505-2643 Ocean, 750 IF at $329.20/ft = $246,900
Damage(%) 0 0 0 12 27 41 45
Damage 0 0 0 $30,000 $67,000 $101,000 $111,000
Results of Plans 1, 2, 5, 11 at 2723-2751,2955 Ocean, 400 IF at $455.00/ft = $182,000
Damage(%) 0 0 0 6 14 21 24
Damage 0 0 0 $11,000 $25,000 $38,000 $44,000
4.2.1.3 Environmental Evaluation
Replenishment would be required every several years, resulting in repeated large-
scale disruption of marine habitats. The area covered by sandfill would be permanently lost
as habitat for benthic infauna and fish feeding. Because this would be in an area that
formerly comprised supralittoral beach, however, mitigation would not be required. Also,
colonization of new beach areas by terrestrial invertebrates would be expected to occur
soon after project completion.
Routine beach replenishment may require dredging areas not currently maintained.
By affecting their food source, this could result in a localized population reduction of marine
fish species. This, in turn, could affect the foraging success of larger fish, marine
mammals, and birds. Invertebrates in the dredge area would also be killed. Water quality
would also be temporarily impacted in the dredge and disposal areas.
Beach disposal of sediments could potentially affect the nesting areas of least terns,
snowy plovers and other shore birds. However, this impact could be beneficial, since due
to the extreme narrowness of the without project beach, the project could prevent erosion
of existing nesting sites, or create additional areas. The creation of a gently-sloping beach
would also benefit the grunion.
4-9
Due to the location of the plan site with reference to Buena Vista and Agua Hedionda
Lagoons, it is anticipated that there Will be no significant impacts to either.
4.2.1.4 Economic Analysis
Tables 4.1c, and 4.1d present the cost estimate and the benefits, respectively. Both
tables demonstrate these costs in annualized form. Table 4.1e shows the Benefit - Cost
Ratio.
Table 4.1c Plan 1 - Beachfill in Reaches 1 and 2 - Cost Estimate
Contingency
Unit Cost without ----------------- Cost with
Item Quantity Unit Price Contingency Amount % Contingency
Mobilization and Demob 1 Job L.S. $500,000 $125,000 25
-------
$625,000
New BeachfiLl. 666,700 cu yd $3.00 $2,000,100 $500,000 25 *25500,100
Advanced Nourishment 850.000 cu yd $3.00 *2.550.000 *637.500 25 *3.187.500
SUBTOTAL $5,050,100 $1,262,500 $6,312,600
PLANNING/ENGINEERING/CONSTRUCTION
8 % Planning, Engineering, and Design $404,000 $101,000 25 $505,000
3 % Engineering during Construction $151,500 $37,900 25 $189,600
7 % Construction Management *353.500 *88.400 25 *441.900
SUBTOTAL $909,000 $227,300 25 $1,136,300
INTEREST DURING CONSTRUCTION $219,200 $54,800 25 $274,000
TOTAL FIRST COST OF CONSTRUCTION *6.178.300 *1.544.600 *7.722.900
ANNUAL COSTS
Annual Cost of First Costs $505,000 $126,300 $631,300
Annual Cost of BeachfiLt Replenishment' *613.500 *153.300 *766.800
Total Annual Cost $1,118,500 $279,600 $1,398,100
Replenishment = 5-year Cycle at 170,000 yd3/year (See Table 7.1 for sensitivity analysis of replenishment cycle)
'-4
SM
Table 4.1d Annual Benefits -- Alternative 1
($1000)
STORM DAMAGE REDUCTION BENEFITS
REACH 1 DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BENEFITS
Landscaping 3.41 1.98 1.43
Revetment 49.63 5.03 44.60
Structure 53.28 26.13 27.15
Content 22.15 8.18 13.97
Content 10.40 0.00 10.40
Subtotal, Reach 1 138.87 41.32 97.55
F- REACH 0 0 0
TOTAL STORM DAMAGE REDUCTION BENEFITS 97.55
RECREATION BENEFITS (incidental)
Reaches 1 and 2 447.45
TOTAL BENEFITS, ALTERNATIVE 1 545.0
Lontent uamage resulting irom structural iaiiure
Methodology for determining recreation benefits detailed in Economic Appendix
Table 4.1e Plan 1: Economic Summary
Annual Benefits ($1000) 545
Annual Costs ($1000) 1,398
Benefit - Cost Ratio 0.39
4-11
4.2.2 Plan 2 - A Groin System with Beachfill in Reaches 1 and 2
4.2.2.1 Description
As shown in Figure 4.2a, a system of three groins are used to stabilize the beachfill
in Reaches 1 and 2. The rationale for extending the project into Reach 2 is the same as in
Alternative 1: to insure that the vulnerable structures at the southern end of Reach 1, as
well as those in middle of the reach have adequate protection (see Figure 4.2a for the
location of the structures). In addition to storm protection, this plan provides needed
recreational beach area.
The groins are 600 feet long and 2,000 feet apart. Figure 4.2b shows a typical
cross-section of the groin. Sites for quarry stone include Catalina Island, Twin Oaks in
Oceanside, and Otay (just north of the Mexican border, 15 miles east of Imperial Beach)
There is a quarry in Carlsbad, but the size of the material limits its use to bedding.
An initial fill of 1,516,700 yd will be required and 315,000 yd of renourishment vould
be placed at nine year intervals (the optimization is included in the Coastal Engineering
Appendix). The elevation of the beachfill is + 10 feet MLLW and the width of the berm is
200 feet. The beach face slopes downward approximately 1 vertical on 20 horizontal from
the berm crest to the natural nearshore bottom. Figure 4.2b shows a typical crOss-section
of the beachfill. As cited in Section 4.2.1.1, offshore sand sources have been identified off
of Carlsbad and Oceanside.
4.2.2.2 Engineering Evaluation
Groin construction will result in the shoreline reorienting itself more nearly parallel
with the prevailing incident wave crests. Net longshore transport rates along the reoriented
shoreline will be lower because the angle between the average incoming wave crests and
the new shoreline will be smaller. By assuming that the angle is reduced by a factor of
two, the resulting net longshore transport rate will be reduced by about the same factor for
small angles. Thus, a net longshore transport rate of 135,000 cubic yards per year has
been assumed. It is also assumed that Reaches 1 and 2 will receive 100,000 cubic yards
per year from the sand bypass operation at Oceanside Harbor. Thus, a beachfilI
replenishment rate of 35,000 cubic yards per year has been used in the optimization of the
replenishment frequency. Optimizing, the beachfill will be replenished on a 9-year cycle
with a groin system acting as stabilizing structures.
Except for a longer project life for the beachfill, the results of wave runup and
damages to coastal structures are the same as those of Plan 1.
4.2.2.3 Environmental Evaluation
4-12
0 400 800 1200
0• S
11888102M
Figure 4.2a Plan 2 - Beachfihl with Groins, Reaches I and 2
Sym About
Elev Varies
-
16
;H1eth 12 >1
Bottom Existing
11888122M
Figure 4.2b Typical Cross-Section of Groin
I
I
Structural solutions such as groins would replace a certain amount of benthic habitat
I with rocky habitat. This could cause a change in the present community structure. The
U.S. Fish and Wildlife Service (USFWS) often views this as an adverse impact, requiring
mitigation. The Corps, in the past, has viewed this kind of project as self-mitigating. This
I groin system would cover about five acres of sandy-bottom habitat.
Placement of fill material (sediment or rocks) on the beach, or in intertidal or subtidal
areas, would result in the loss of invertebrates in those areas. Sediment-dwelling organisms
would likely be replaced by a more diverse community. Rocky structures act as an artificial
reef, providing substrate for algal and invertebrate attachment. These invertebrates, in
turn, are used as a forage base for a variety of fish and birds. Interstitial spaces provide
protective habitat for a variety of marine life. Some species, however, are only associated
U with soft bottom habitats. Also, groins and breakwaters have a large central area that is
not exposed, and therefore, provides no habitat value to aquatic organisms. Groins do
provide relatively undisturbed roosting areas for sea birds, such as the brown pelican.
In the presence of groins, beach replenishment would be required less frequently,
thus resulting in less disruption to marine habitat. An initial beachfill will decrease the
likelihood of downcoast erosion.
4.2.2.4 Economic Analysis
Tables 4.2a, and 4.2b present the cost estimate and the benefits, respectively. Both
tables demonstrate these costs in annualized form. Table 4.2c shows the Benefit - Cost
Ratio.
I
n
I
H
I
I
I 4-15
Table 4.2a Plan 2 - A Groin System with Beachfill in Reaches 1 and 2 - Cost Estimate
Contingency
Unit Cost without ----------------Cost with Item Quantity Unit Price Contingency Amount % Contingency
GROINS
600 ft groin:
A-12 Stone 4,800 tons $50.00 $240,000 $60,000 25 $300,000 A-7 Stone 4,800 tons $45.00 $216,000 $54,000 25 $270,000 B-i Stone 9,600 tons $35.00 $336,000 $84,000 25 S420,000 C-Stone 9,600 tons $30.00 $288,000 $72,000 25 $360,000 Excavation 25,000 Cu yd $6.50 $162,500 $40,600 25 $203,100 BackfilL 15,000 Cu yd $6.50 $97,500 $24,400 25 $121,900 Grouting 1 Job L.S.$100,000 $25,000 25 $125,000
Cost of each groin $1,440,000 $360,000 $1,800,000 SUBTOTAL (Cost of 3 groins) $4,320,000 $1,080,000 $5,400,000
BEACHFILL
Mobilization and Demob 1 Job $500,000 $500,000 $125,000 25 $625,000 New BeachfiLL 666,700 cu yd $3.00 $2,000,100 $500,025 25 $2,500,125 Advanced Nourishment 350.000 cu yd $3.00 $1,050,000 $262,500 25 $1,312,500 SUBTOTAL (BeachfiLt) - $3,550,100 $887,525 . $4,437,625
SUBTOTAL (BEACHFILL + 3 GROINS) $7,870,100 $1,967,525 . $9,837625
PLANNING/ENGINEERING/CONSTRUCTION
8 % Planning, Engineering, and Design $629,600 $157,400 25 $787,000 3 X Engineering during Construction $236,100 $59,025 25 $295,125 7 % Construction Management $550,900 $137.750 25 $688,650 SUBTOTAL $1,416,600 $354,175 $1,770,775
INTEREST DURING CONSTRUCTION $321,600 $80,400 $402,000
TOTAL-FIRST COST OF CONSTRUCTION S9.608.300 $2.402.100 *12.010.400
ANNUAL LUSTS
Annual Cost of First Costs $785,600 $196,400 $981,800 Annual Cost of beachfitt replenishment' $126,300 $31,500 $157,800
Annual O&M Cost of Groins $25,500 $6,400 $31,900
TOTAL ANNUAL COST $937,200 $234,300 $1,171,500
l Replenishment at 10-year Cycle at 35,000 yd3/yr
(See Table 7.4 for sensitivity analysis of replenishment cycle)
4-16
Table 4.2b Annual Benefits -- Alternative 2
(1OOO)
STORM DAMAGE REDUCTION BENEFITS
REACH 1 DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BENEFITS
Lènciscaping 3.41 1.98 1.43
Revetment 49.63 5.03 44.60
Structure 53.28 26.13 27.15
Content 22.15 8.18 13.97
Content 10.40 0.00 10.40
Subtotal, Reach 1 138.87 41.32 97.55
REACH J 0 0 0
TOTAL STORM DAMAGE REDUCTION BENEFITS
RECREATION BENEFITS (incidental)
Reaches 1 and 2 447.45
TOTAL BENEFITS; ALTERNATIVE 2 545.00
I LI IL UØI I iøy Ir—JUMIly II UI II btfuUtuldl iuiure
Methodology for determining recreation benefits detailed in Economic Appendix
Table 4.2c Plan 2: Economic Summary
Annual Benefits ($1000) 545
Annual Costs ($1000) 1,172
Benefit - Cost Ratio 0.47
4-17
42.3 Plan 3 - An Offshore Breakwater System in Reaches 1 and 2
4.2.3.1 Description
As shown in Figure 4.3a, three offshore breakwaters are used to provide protection
from wave action to the shoreline of Reaches 1 and 2. Damages will be reduced by the
protection provided by both the breakwaters and the salients. Each breakwater is 800 feet
long and the gap between the' breakwaters is 800 feet. Sources for rock are discussed in
Section 4.2.2.1. Figure 4.3b shows a typical cross-section of the offshore breakwater.
Figure 4.3a also shows the anticipated shoreline change associated with this offshore
breakwater system.
4.2.3.2 Engineering Evaluation
Assuming that there is enough longshore transport, salients will form as a response
to the breakwater system as shown in Figure 4.3a. As calculated in the Coastal
Engineering Appendix; these breakwaters would create a salient of about 490 feet and a
tombolo would notoccur.
Assuming that the breakwater system will effectively control erosion and retain sand
on the beach, the salients will provide better protection to the coastal structures than the
beachfill and groin systems. Thus, damages due to wave runup and wave action will'
reduce to a minimum.
4.2.3.3 Environmental Evaluation
Placement of fill material (sediment or rocks) on the beach, or in intertidal or subtidal
areas, would result in the loss of invertebrates in those areas. Compared togroins,
breakwaters would probably have less of an impact on overall community structure,
because they would affect only those species present at the -12 to -18 MSL depths. This
plan would modify approximately 11 .0 acres of soft-bottom habitat.
As with groins, breakwaters provide relatively undisturbed roosting areas for sea
birds, such as the brown pelican. A variety of marine life use these rocky areas for foraging
or refuge.
The formation of a tombolo would have an adverse impact on down coast beaches.
This plan indicates a tombolo will not be formed. In addition, this plan should have the
positive effects that a beachfill would have with fewer negative effects because the growth
of the salient would occur at a slow rate compared' to the time required to place an artificial
beachfill. Existing organisms would have time to adapt to changing conditions. Species
would still be impacted by construction of the breakwater. Temporary impacts to water
4-18
Ocean St
AInadequate N
Protection
I_N ••.
1 ... . ..
11888103M
Figure 4.3a Plan 3 - Offshore Breakwaters, Reaches I and 2
Shoreward Side
B-2
Stone
MLLW
Seeward Side
1 A-1 6 Stone
Fowl B-2
Stone
12' /
2-3'
11888121M
Figure 4.3b Typical Cross-Section of Offshore Breakwater - Reaches 1 and 2
quality would also occur.
4.2.3.4 Economic Analysis
The costs associated with this alternative are summarized in Table 4.3a and the
benefits are summarized in Table 4.3b. The Benefit - Cost Ratio is shown in Table 4.3c.
Table 4.3a Plan 3 - An Offshore Breakwater System in Reaches 1 and 2 - Cost Estimate
Contingency
Unit Cost without ----------------Cost with
Item Quantity Unit Price Contingency Amount % Contingency
OFFSHORE BREAK1LATER
800-ft Offshore Breakwater:
A-16 Stone 93.600 tons $56.00 $5,241,600 $1,310,400 25 $6,552,000
B-2 Stone 61,600 tons $42.00 $2,587,200 $646,800 25 $3,234,000
C-Stone 80,000 tons $26.00 $2,080,000 $520,000 25 $2,600,000
Cost of each breakwater $9.908.800 $2.477.200 $12.386.000
SUBTOTAL. (Cost of 3 breakwaters) $29,726,400 $7,431,600 $37,158,000
PLANNING/ENGINEERING/CONSTRUCTION
8 % PLanning, Engineering, and Design $2,378,100 $594,500 25 $2,972,600
3 % Engineering during Construction $891,800 $223,000 25 $1,114,800
7 % Construction Management $2.080.800 5520.200 25 $2.601.000
SUBTOTAL $5,350,700 $1,337,700 $6,688,400
INTEREST DURING CONSTRUCTION $3,542,000 $885,600 $4,428,000
TOTAL FIRST COST OF CONSTRUCTION 538.619.500 $9.654.900 S48.27440O
ANNUAL COSTS
Annual Cost of First Costs $3,156,900 $789,200 $3,946,100
AnnuaL O&M Cost of Breakwaters 5175.400 $43.800 $219,200
TOTAL ANNUAL COST $3,332,300 $833,000 $4,165,300
4-21
Table 4.3b Annual Benefits -- Alternative 3.
($1000)
STORM DAMAGE REDUCTION BENEFITS
REACH 1 DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BE
Landscaping 3.41 0.00 3.41
Revetment 49.63 0.00 49.63
Structure 53.28 0.00 53.28
Content 22.15 0.00 22.15
Content - 10.40 0.00 10.40
Subtotal, Reach 1 138.87. 0.00 138.87
REACH 2- 0 1 0
TOTAL STORM DAMAGE REDUCTION BENEFITS 138.87
RECREATION BENEFITS (incidental)••
Reaches I and 2 - 0
TOTAL BENEFITS, ALTERNATIVE 3 138.87
* 'Content damage resulting from structural failure
Methodology for determining recreation benefits detailed in Economic Appendix
Table 4.3c Plan 3: Economic Summary
Annual Benefits ($1000) 139
Annual Costs ($1000) 4,165
Benefit - Cost Ratio 0.03
4-22
I
I 4.2.4 Plan 4 - New and Repaired Revetments in Reach 1
1 4.2.4.1 Description
I As shown in Figure 4.4a, a 600-foot long revetment is built in Reach 1 to protect the
ten unprotected structures at the southern end of Reach 1 from erosion by waves and
currents. Also, the existing revetments in Reach 1 are to be repaired to bring them to the
I specifications of the new revetment. Figure 4.4b shows a typical cross-section of the
rubble-mound revetment. The toe would be excavated to the hardpan, at approximately
+ 2.75 feet MLLW. The crest would be at an elevation of + 17.75 feet MLLW. I Approximately 19,000 tons of rock would be required and is available at a number of
readily accessible quarries (see Section 4.2.2.1).
4.2.4.2 Engineering Evaluatibn
Construction of the new revetment and repair to the existing revetments at Reach 1
is anticipated to cause minimal effects to the existing sediment transport mechanism,
because the toes of the revetment are located at a landward setback distance. Thus, there
will be no adverse impact to the local coastal processes.
The results of wave runup within Reach 1 will be similar to those of the without
project conditions. Thus, there will be no reduction in damage due to flooding to the
coastal structures in Reach 1. Since the toe of the bluff is properly protected, structural
damage due to bluff retreat is reduced to a minimum.
Since the new revetment and the repaired revetments have been designed to
withstand a 25-year event, structural damage to the revetments will start for events
associated with return periods greater than 25 years. The revetment will experience 1.25
%, 2.50 %, and 4.38 % damage associated with the 50-, 100-, and 200-year events,
respectively. Thus, the damages to the revetments are negligible.
4.2.4.3 Environmental Evaluation
I The construction of seawalls or revetments would have no impact on benthic habitat.
Bluff structures would not create or stabilize beaches and, therefore, would not benefit
terrestrial resources. Seawalls or revetments would reduce or eliminate the bluffs' potential
I as a sand source, and as habitat for vegetation and wildlife. Due to its placement in an
already developed area, adverse impacts to biological resources and water quality would
probably not be significant.
I
I 4-23
HI
0 400 800 1200
Scale in feet
Unpi.. •••••••••\.
0•
00,
.01
Pacific Ocean
- 11888104M
Figure 4.4a Plan 4 - Revetment, Reach 1
Elevation +17.75' MLLW
Quarrystone Armor-..
Exisiting Beach 1
2 Gravel Blanket
1 FT Thick Over
Regraded Bank
Elev 2.75' MLLW
Bedrock
11888120M
Figure 4.4b Typical Cross-Section of Revetment - Reach 1
4.2.4.4 Economic Analysis
The costs associated with this alternative are summarized in Table 4.4a and the
benefits are summarized in Table 4.4b. The Benefit - Cost Ratio is shown in Table 4.4c.
Table 4.4a Plan 4 - New and Repaired Revetments in Reach 1 - Cost Estimate
Contingency
Unit Cost without ----------------Cost with
Item Quantity Unit Price Contingency Amount Contingency
REVETNENT
A-3 Stone 14,060 tons $43.00 $604,600 $302,300 50 $906,900
C-Stone 5.230 tons $30.00 $156.900 $78.500 50 $235.400
Subtotal Cost $761,500 $380,800 $1,142,300
PLAJINING/ENGINEERI MG/CONSTRUCT ION
8 % Planning, Engineering, and Design $60,900 $30,400 50 $91,300
3 % Engineering during Construction $22,800 $11,400 50 $34,200
7 X Construction Management $53,300 $26.700 50 $80.000
SUBTOTAL $137,000 $68,500 $205,500
INTEREST DURING CONSTRUCTION $8,700 $4,300 $13,000
TOTAL FIRST COST OF CONSTRUCTION $907.200 S453.600 $1 ,360,800
ANNUAL COSTS
Annual Cost of First Costs $74,200 $37,100 $111,300
Annual 0&M Cost 54.500 52.200 $6.700
TOTAL ANNUAL COST $78,700 $39,300 $118,000
Note: 50 % contingency includes resetting cost of existing stones.
4-26
Table 4.4b Annual Benefits - Alternative 4
($1000)
STORM DAMAGE REDUCTION BENEFITS
REACH 1 DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BENEFITS
Landscaping 3.41 2.18 1.23
Revetment 49.63 0.00 49.63
Structure 53.28 29.44 23.84
Content 22.15 19.41 2.74
Content' 10.40 8.11 2.29
ir--Subtotal, Reach 1 138.87 59.14 79.73
TOTAL BENEFITS, ALTERNATIVE 4 79.73
- onieni omage resuiting TrOM structural jaiiure
Methodology for determining recreation benefits detailed in Economic Appendix
Table 4.4c Plan 4: Economic Summary
Annual Benefits ($1000) 79.73
Annual Costs ($1000) 118.00
Benefit - Cost Ratio 0.73
11 4-27
4.2.5 Plan 5 - Beachfill and North Intake Jetty Extension in Reach 1
4.2.5.1 Description
As shown in Figure 4.5, a berm is constructed at the coastal area of Reaches 1 and U
2. The berm is 200 feet wide at the northern end near Buena Vista Lagoon and is 330 feet
wide at the southern end near the north intake jetty of Agua Hedionda Lagoon. This intake
jetty has been extended 400 feet, so that the total length of the jetty is 600 feet.
The rationale behind this alternative is that it provides adequate protection to the
structures of Reach 1 while enhancing the recreational value both Reaches 1 and 2.. Costs
are reduced by the jetty extension because shoreline will reorient itself sufficiently to
remove any costs associated with renourishment (see Section 4.2.5.2). Potential sand and
rock sources are the same as discussed in other alternatives.
The elevation of the beachfill is + 10 feet MLLW and the length of the beachfill is
about 7,400 feet. The beach face slopes downward approximately 1 vertical on 20
horizontal from the berm crest to the natural nearshore bottom. The typical cross-section
of the beachfill is similar to that shown in Figure 4.1 b. The typical cross-section of the
extended jetty is similar to that shown in Figure 4.2b.
4.2.5.2 Engineering Evaluation
Extension of the north intake jetty will result in the shoreline reorienting itself more I
nearly parallel with the prevailing incident wave crests. Net longshore transport rates along
the reoriented shoreline will be lower because the angle between the average incoming
wave crests and the new shoreline will be smaller. By assuming that the angle is reduced
by a factor of two, the resulting net longshore transport rate Will be reduced by about the
same factor for small angles. Thus, a net longshore transport rate of 135,000 cubic yards
per year has been assumed. It is also assumed that Reaches 1 and 2 will receive 100,000
cubic yards per year from the sand bypass operation at Oceanside Harbor. Since there are
continuous dredging of about 120,000 cubic yards per year at Agua Hedionda Lagoon and
beach disposal of the dredged materials north and south of the lagoon, it is further assumed
that Reach 2 will receive 60,000 cubic yards per year from this sand bypass operation.
Moreover, it is assumed that there is an offshore loss rate of 25,000 cubic yards per year.
Thus, beachfill replenishment is not required for this plan. Based on the typical cross-
sectional area of 4,560 ft2, the volume of beachfill (1,249,800 cubic yards) is estimated by
using the pertaining length of 7,400 feet.
The results of wave runup and damages to the coastal structures are the same as
those of Plan 1, except for the revetment situated north of the north intake jetty.
4-28 1
\' Hedionda Pacific Ocean \\Lagoon
11888105M
Figure 4.5 Plan 5 - Beachfihl and Jetty Extension, Reaches 1, 2, and 3
Structural damage to this revetment is reduced as shown in Table 4.2b.
4.2.5.3 Envirdnmental Evaluation
The jetty extension would have the same effects as groins and breakwaters on
bottom habitat, but to a reduced magnitude because less than one acre would be modified.
The beachfill would have the effects discussed in Section 4.2.1.3.
Increased public use of beaches could increase public use of the adjacent lagoon
environments. These impacts may be vegetation trampling, soil compacting, trash and
debris accumulation, encroachment of wildlife, loss of wildlife habitat, and a. lowering of
natural aesthetics. Sand replenishment, or changes in shoreline erosion patterns, could
increase shoaling at Agua Hedionda Lagoon. This increased shoaling could necessitate
increased dredging near the inlet. Disruption or change the lagoon environments could have
a detrimental impact on endangered species that use those habitats. Of particular concern
in the light-footed clapper rail, which has very specific habitat requirements.
Extension of the jetty could benefitthe environment by reducing the amount of
sediment trapped in the lagoon, thereby reducing the frequency of dredging. Also, this area
has already been disturbed to a certain extent by the structures and activities present at the
mouth of the lagoon.
4.2.5.4 Economic Analysis
The costs associated with this alternative are summarized in Table 4.5a and the
benefits are summarized in Table 4.5b. The Benefit - Cost Ratio is shown in Table 4.5c.
4-30
I
1 Table 4.5a Plan 5 - Beachfill and North Intake Jetty Extension in Reaches 1, 2, and 3 -
Cost Estimate
Contingency Unit Cost without ----------------Cost with
Item Quantity Unit Price Contingency Amount % Contingency
GROIN
400 ft north intake jetty extension
A-12 Stone 3,200 tons $50.00 $160,000 140,000 25 $200,000
A-7 Stone 3,200 tons $45.00 $144,000 $36,000 25 $180,000
B-i Stone
C-Stone
6,400
6,400
tons
tons
$35.00
$30.00
$224,000
$192,000
$56,000
- $48,000
25
25
$280,000
$240,000
Grouting 1 Job L.S. $100,000 $25,000 25 5125,000
SUBTOTAL (Cost of Jetty Extension) $820,000 $205,000 $1,025,000
BEACHFILL
New BeachfiLL
Mobilization &
1,249,800
Demob. 1
cu yd
Job
'53.00
L. S.
$3,749,400
$500.000
$937,400
$125,000
25
25
$4,686,800
$625,000
SUBTOTAL (Cost of BeachfiLL) $4,249,400 $1,062,400 $5,311,800
I SUBTOTAL (BEACHFILL + JETTY EXTENSION) $5,069,400 $1,267,400 $6,336,800
PLANNING/ENGINEERING/DESIGN - - I 8 X Planning, Engineering, and Design $405,600 $101,400 25 $507,000
3 % Engineering during Construction $152,100 $38,000 25 $190,100
7 % Construction Management $354,900 $88.700 25 $443,600
SUBTOTAL $912,600 $228,100 $1,140,700
I 25 - $122,000 INTEREST DURING CONSTRUCTION $97,600 $24,400 -
TOTAL FIRST COST OF CONSTRUCTION $6,079,600 $1,519,900 $7,599,500
I ANNUAL COSTS
Annual Cost of First Costs $496,800 $124,200 $621,000
Annual O&M Cost of Jetty $4,800 $1,200 $6,000
TOTAL ANNUAL COST $501,600 $125,400 $627,000
I Note: Replenishment = 0
n
I
I
I
I
4-31
Table 4.5b Annual Benefits -- Alternative 5
STORM DAMAGE REDUCTION BENEFITS
REACH 1 DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BENEFITS
Landscaping 3.41 1.98 1.43
Revetment 49.63 5.03 44.60
Structure 53.28 26.13 27.15
Content 22.15 8.18 13.97
Content 10.40 0.00 10.40
Subtotal, Reach 1 138.87 41.32 97.55 7771
I. REACH 0 . 0 0
REACH 3
Revetment at Parking lot 16.28 1.20 15.08
TOTAL STORM DAMAGE REDUCTION BENEFITS 112.63
RECREATION BENEFITS—
Reaches 1,2 and 3 450.37
TOTAL BENEFITS, ALTERNATIVE 5 563.00
ontent aamage resuiting irom structurai iaiiure
Methodology for determining recreation benefits detailed in Economic Appendix
Table 4.5c Plan 5: Economic Summary
Annual Benefits ($1000) 563
Annual Costs ($1000) 627
Benefit - Cost Ratio 0.90
4-32
I
I
4.2.6 Plan 6 - Beachfill in Reach 3
I 4.2.6.1 Description
I As shown in Figure 4.6a, a 200-foot berm is constructed between the inlet and
outlets to Agua Hedionda Lagoon in Reach 3. As detailed in Table 4.6d, this plan will
significantly reduce damages to Carlsbad Boulevard while enhancing its recreational
I benefits.
The elevation of the beachfill is + 10 feet MLLW and the length of the beachfill is
I about 2,700 feet. The beach face slopes downward approximately 1 verticaJ on 20
horizontal from the berm crest to the natural nearshore bottom. Figure 4.6b shows a
I
typical cross-section of the beachfill. An initial beachfill of 1,186,000 yd is to be
renourished at a rate of a of 840,000 yd every four years. Sand sources were discussed
in Section 4.2.1.1.
4.2.6.2 Engineering Evaluation
Since there are continuous dredging of about 120,000 cubic yards per year at Agua
Hedionda Lagoon and beach disposal of the dredged materials north and south of the
lagoon, it is assumed that Reach 3 will receive 60,000 cubic yards per year from this sand
bypass operation. Thus, the replenishment rate of the beachfill becomes 210,000 cubic
yards per year. Optimizing the interval of beachfill replenishment, without any stabilizing
structure, the beachfill in Reach 3 will be replenished on a 4-year cycle. The results of
wave runup and damages to Carlsbad Boulevard in Reach 3 for with project condition are
presented in Table 4.6a.
Using the results of wave runup, damages to the causeway section of Carlsbad Blvd.
between the intake and outlet jetties of Agua Hedionda Lagoon can be obtained. Based on
the road elevation of + 16.75 feet MLLW, the results of excess runup are shown in Table
4.6a.
Since the berm provides protection from wave attack, damage to revetment is
reduced and is shown in Table 4.6b.
4-33
I
I
I
I 11888107M
Figure 4.6a Plan 6 - Beachfihl, Reaches I and 2 I
- - - - - - - - - - - - - - - - - - -
Line CB-820, Agua Hedionda - South
- - October 1991
- October 1990
- Carlsbad - Reach 3
Typical Cross-Section of Beachfill
Beachfill 20
---------------------------------------------------------------MLLW
0 100 200 300 400 500 600 700 800 900 1000
Range (ft Seaward of Range Line Monument)
Figure 4.6b Typical Cross Section of Beachfill - Reach 3 11888116M
Table 4.6a Carlsbad Reach 3 - Road Damage with Project Beachfill
Reach 3 - Carlsbad Blvd. Damage - With Project Condition
16.75 ft = road elevation
2,000 ft = Length of road damaged
Jan 83 storm, excess runup = 20.85 16.75 = 4.1 ft, erosion 50 ft
Assume excess runup of 3 ft and Less causing 0 ft erosion
$6.00 per ft"2 = Damage Repair
150 ft = Total Road Erosion
Return Wave Excess (ft) (ft'2) CS)
Period(yr) Runup(ft) Runup(ft) Erosion Area Damage
2 14.85 0 0 0 0
5 16.15 0 0 0 0
10 16.95 0.2 0 0 0
25 20.95 4.2 55 110,000 660,000
50 21.25 4.3 68 136,000 816,000
100 21.65 4.9 86 172,000 1,032,000
200 22.15 5.4 109 218,000 1,308,000
Table 4.6b Carlsbad Revetment Damages - With Project Conditions
Item 2-year 5-year 10-year 25-year 50-year 100-year 200-year -------
Results of Plans 5, 11 at North of Intake Jetties, 450 LF at $180.00/ft = $81,000
Damage(%) 0 0 0 13 28 43 60
Damage 0 0 0 $11,000 $23,000 $35,000 $49,000
Results of Plans 6, 7, 11 at South of Intake Jetties, 350 LF at $134.29/ft = $47,000
Damage(%) 0 0 0 30 65 100 100
Damage 0 0 0 $14,000 $31,000 $47,000 $47,000
4.2.6.3 Environmental Evaluation
The environmental effects of artificial beachfills have been discussed in Section
4.2.1.3, and the effects that the beachfill could have on Agua Hedionda Lagoon were
addressed in Section 4.2.5.3.
4.2.6.4 Economic Analysis
The costs associated with-this alternative are summarized in Table 4.6c and the
benefits are presented in Table 4.6d. The Benefit - Cost Ratio is shown in Table 4.6e.
4-36
Table 4.6c Plan 6 - Beachfill in Reach 3-Cost Estimate
.
Unit Cost without
Contingency
----------------Cost with
Item Quantity Unit Price Contingency Amount % Contingency
BEACHFILL
Mobilizationand Demob 1
New Beachfill 346,000
Advanced Nourishment 840.000
SUBTOTAL (Cost of 3 groins)
Job
cu yd
cu. Yd
L.S.
$3.00
$3.00
$500,000
$1,038,000
$2.520.000
$4,058,000
$125,000 25
$259,500 25
$630,000 25
$1,014,500
$625,000
$1,297,500
$3.150,000
$5,072,500
PLANNING/ENGINEER! MG/CONSTRUCT 1011
8 % Planning, Engineering, and Design $324,600 $81,200 25 $405,800
3 % Engineering during Construction $121,700 $30,400 25 $152,100
7 X Construction Management $284,100 571.000 25 $355,100
SUBTOTAL - - $730,400 $181,600 25 $913,000
INTEREST DURING CONSTRUCTION $190,400 $47,600 25 $238,000
Total First Cost of Construction 54.978.800 51243.200 56,223,500
ANNUAL COSTS
Annual Cost for First Costs $406,700 $101,500 $508,300
Annual Cost of Beachfitl Replenishment' $790,800 $197.700 $988.500
TOTAL ANNUAL COST $1,197,500 $298,200 $1,496,800
Replenishment = 4-year Cycle at 210,000 yd3/year (See Table 7.5 for sensitivity analysis of replenishment cycle)
I
I
4-37
Table 4.6d Annual Benefits -- Alternative 6
STORM DAMAGE REDUCTION BENEFITS
REACH 3 ... . .DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BENEFITS
Detour 5.20 0.00 5.20
Emergency 1.49. 1.49, 0.00
Revetment (north) 16.28 16.28 0.00
Revetment (south) 15.45 1.61 13.84
Roadway 244.82 42.43 202.39
Subtotal, Reach 3 283.24 61.81 221.43
TOTAL STORM DAMAGE REDUCTION BENEFITS 221.43
RECREATION BENEFITS (incidental)"
Reach 3 352.57
TOTAL BENEFITS, ALTERNATIVE 6 574.00
uvietnoaoiogy TOI oeierminirig recreation uerwiits uetiueu in Cuununuu P%ppIIUIA
Table 4.6e Plan 6: Economic Summary,
Annual Benefits ($1000) 574
Annual Costs ($1000) 1497
Benefit - Cost Ratio 0.38
4-38
4.2.7 Plan 7 - A Groin System with Beachfill in Reach 3
4.2.7.1 Description
As shown in Figure 4.7a, a system of two groins are used to stabilize the beachfill in
Reach 3. As in Plan 6, this plan will significantly reduce damages to Carlsbad Boulevard
while enhancing its recreational benefits.
The groins are 350 feet long and 900 feet apart. Figure 4.2b shows a typical cross-
section of the groin. As discussed below (Section 4.2.7.2), no renourishment is required.
Therefore there is no advanced nourishment required, thus only 346,000 yd of initial fill is
necessary. The elevation of the beachfill is + 10 feet MLLW and the width of the berm is
200 feet. The beach face slopes downward approximately 1 vertical on 20 horizontal from
the berm crest to the natural nearshore bottom. Figure 4.6b shows a typical cross-section
of the beachfill. Sand and rock sources are-discussed in Sections 4.2.1.1 and 4.2.2.1,
respectively.
4.2.7.2 Engineering Evaluation
Due to the reorientation of the shoreline after groin construction, the angle between
the shoreline and the incoming wave crests will be reduced. The net longshore transport
rate is assumed to be about 130,000 cubic yards per year. It is also assumed that Reach 3
will receive about 130,000 cubic yards per year from the sand bypass operation at Agua
Hedionda Lagoon. Thus, no beachfill replenishment is required.
4.2.7.3 Environmental Evaluation
The effects of both beachfill and groins have been previously discussed (Sections
I 4.2.1.3 and 4.2.2.3, respectively). The groins in this plan would cover two acres of
bottom area. The effects of this project on Agua Hedionda Lagoon are the same as
I
considered in Section 4.2.5.3. However, structures and beachfill may be prohibited in any
areas included in the Coastal Barrier Reef System. The USFWS has proposed that the area
around Agua Hedionda be included in this system.
I
4.2.7.4 Economic Analysis
I The costs associated with this alternative are summarized in Table 4.7a and the
benefits are presented in Table 4.7b. The Benefit - Cost Ratio is shown in Table 4.7c.
I
I 4-39
r::i
11888 108M
Figure 4.7a Plan 7 - Beachfihl with Groins, Reach 3
Table 4.7a Plan 7 - A Groin System with Beachfill in Reach 3 - Cost Estimate
Contingency
Unit Cost without ----------------Cost with
Item Quantity Unit Price Contingency Amount % Contingency
GROINS
350 ft groin:
A-12 Stone 2,800 tons $50.00 $140,000 $35,000 25 $175,000
A-7 Stone 2,800 tons $45.00 $126,000 $31,500 25 $157,500
B-i Stone 5,600 tons $35.00 $196,000 $49,000 25 $245,000
C-Stone 5,600 tons $30.00 $168,000 $42,000 25 $210,000
Excavation 10,000 cu yd $6.50 $65,000 $16,300 25 $81,300
Grouting 1 Job L.S. $100,000 $25,000 25 $125,000
Cost of each groin $795,000 $198,800 $993,800
SUBTOTAL (Cost of 2 groins) $1,590,000 $397,600 $1,987,600
BEACHFILL
BeachfitL 346,000 Cu yd $3.00 $1,038,000 $259,500 25 $1,297,500
Mobilization & Demob. 1 Job L.S. $500,000 $125,000 25 $625,000
SUBTOTAL (Cost of BeachfitL) $1,538,000 $384,500 $1,922,500
SUBTOTAL (BEACHFILL + 2 GROINS) $3,128,000 $782,000 $3,910,000
PLANNING/ENGINEERING/CONSTRUCTION
8 % Planning, Engineering, and Design $250,200 $62,600 25 $312,800
3 % Engineering during Construction $93,800 $23,500 25 $117,300
7 % Construction Management $219.000 $54,800 25 $273,800
SUBTOTAL $563,000 $140,750 $703,750
INTEREST DURING CONSTRUCTION $60,000 $15,000 25 $75,000
TOTAL FIRST COST OF CONSTRUCTION $3,751,000 $937,750 $4,688,750
ANNUAL COSTS
Annual Cost of First Costs $306,600 $76,600 $383,200
Annual 0&M Cost of Groins $9,400 $2,300 $11,700
TOTAL ANNUAL COST $316,000 $78,900 $394,900
Note: Replenishment = 0
4-41
Table 4.7b Annual Benefits --Alternative 7
STORM .DAMAGE REDUCTION BENEFITS
REACH 3 DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BENEFITS
Detour 5.20 0.00 5.20
Emergency 1.49 1.49 0.00
Revetment (north) 16.28 - 16.28 0.00
Revetment (south) 15.45 1.61 13.84
Roadway 244.82 42.43 202.39
Subtotal, Reach 3 283.24 61.81 221.43
TOTAL STORM DAMAGE REDUCTION BENEFITS 221.43
RECREATION BENEFITS (incidental)"
Reach 3 352.57
TOTAL BENEFITS, ALTERNATIVE 7 . 574.00
.. 4-... +....,..,., hn4.pe tid in Prnnnrnir Annandiv
Table 4.7c Plan 7: Economic Summary
Annual Benefits ($1000) 574
Annual Costs ($1000) 395
Benefit - Cost Ratio 1.45
4-42
PT
I 4.2.8 Plan 8 - An Offshore Breakwater System in Reach 3
U . 4.2.8.1 Description
I As shown in Figure 4.8a, three offshore breakwaters are used to provide protection
from wave action to the shoreline of Reach 3. This plan will reduce to zero damages to
Carlsbad Boulevard between the inlet and outlets to Agua Hedionda Lagoon.
Each breakwater is 400 feet long and the gap between the breakwaters is 400 feet.
Figure 4.8b shows a typical cross-section of the offshore breakwater. Figure 4.8a also
shows the anticipated shoreline change associated with this offshore breakwater system.
Rock sources are the same as previously mentioned.
4.2.8.2 Engineering Evaluation
Assuming that there is enough longshore transport, salients will form as a response
to the breakwaters as shown in Figure 4.8a. As discussed in the Coastal Engineering
Appendix, the breakwaters are located in a water depth of -11.75 feet MLLW. With the
nearshore bathymetry, the distance from the original shoreline is about 900 feet. With a
breakwater length of 400 feet and a gap width of 400 feet, the formation of tombolo will
be precluded. The length of the salient is about 430 feet.
Assuming that the breakwater system will effectively control erosion and retain sand.
on the beach, the salients will provide better protection to the coastal structures than the
beachfill and groin systems. Thus, damages due to wave runup and wave action will
reduce to a minimum, except for the revetment located north of the intake jetties since the
revetment is located outside of the breakwater's shadow.
4.2.8.3 Environmental Evaluation
The environmental effects of breakwaters have been discussed in Section 4.2.3.3.
The bottom area affected by this plan is approximately 5.5 acres. As discussed above, a
project in this area may be affected by the Coastal Barriers Act of 1990.
4.2.8.4 Economic Analysis
U The costs associated with this alternative are summarized in Table 4.8a and the
benefits are presented in Table 4.8b. The Benefit - Cost Ratio is shown in Table 4.8c.
U
I . 4-43•
Agua
Hedionda
\\\ Lagoon
Pacific Ocean \ \\ c.
0 400 800 1200
Scale in feet
11888111M
Figure 4.8a Plan 8 - Offshore Breakwaters, Reach 3
I
I.
I
Shoreward Side Seeward Side
I A-16 Stone 18•
B2 __
Stone
1.5
%,1~.
Stone
Ila
L 5 C-Stone
2-3 6'
•
6'
- 11888117M
Figure 4.8b Typical Cross-Section of Offshore Breakwater - Reach 3
Table 4.8a Plan 8 - An Offshore Breakwater System in Reach 3 Cost Estimate
Contingency
Unit Cost without ----------------Cost with
Item Quantity Unit Price Contingency Amount % Contingency -----------
BREAKWATERS
400 ft Offshore Breakwater:
A-16 Stone 46,800 tons $56.00 $2,620,800 $655,200 25 $3,276,000
B-2 Stone 30,800 tons $42.00 $1,293,600 $323,400 25 $1,617,000
C-Stone 40,000 tons $26.00 $1,040,000 $260,000 25 $1,300,000
Cost of each breakwater 84.954.400 81.238.600 86.193.000
SUBTOTAL (Cost of 3 breakwaters) $14,863,200 $3,715,800 $18,579,000
PLANNING/ENGINEERING/CONSTRUCTION
B % Manning, Engineering, and Design $1,189,100 $297,300 25 $1,486,400
3 % Engineering during.Construction $445,900 $111,500 25 $557,400
7 % Construction Management 81.040.400 8260.100 25 81.300.500
SUBTOTAL $2,675,400 $668,900 $3,344,300
INTEREST DURING CONSTRUCTION - $871,200 $217,800 25 $1,089,000
TOTAL FIRST COST OF CONSTRUCTION 818.409.800 84.602.500 823.012.300
ANNUAL COSTS
AnnuaL Cost of First Costs $1,504,900 $376,200 $1,881,100
AnnuaL 0&M Cost 887.700 821.900 8109.600
TOTAL ANNUAL COST $1,592,600 $398,100 $1,990,700
4-46
Table 4.8b Annual Benefits -- Alternative 8
STORM DAMAGE REDUCTION BENEFITS
REACH 3 DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BENEFITS
Detour 5.20 0.00 5.20
Emergency 1.49 1.49 0.00
Revetment (north) 16.28 16.28 0.00
Revetment (south) 15.45 0.00 15.45
Roadway 244.82 0.00 244.82
Subtotal, Reach 3 283.24 17.77 265.47
TOTAL STORM DAMAGE REDUCTION BENEFITS 265.47
RECREATION BENEFITS (incidental)"
Reach 3 0.00
TOTAL BENEFITS, ALTERNATIVE 8 265.47
II I &I..IJI IIU UI, flpjjjcl IV IA
Table 4.8c Plan 8: Economic Summary
Annual Benefits ($1000) 265
Annual Costs ($1000) 1991
Benefit - Cost Ratio 0.13
4-47
4.2.9 Plan 9 - A Seawall in Reach 3
4.2.9.1 Description
As shown in Figure 4.9a, a 2,700-foot long sheetpile seawall with a concrete cap is
built in Reach 3 to protect the portion of Carlsbad Boulevard between the intake and outlet
at Agua Hedionda Lagoon. Figure 4.9b shows a typical cross-section of the seawall. This
plan will provide protection to Carlsbad Boulevard in Reach 3 between the inlet and outlets
of Agua Hedionda Lagoon.
4.2.9.2 Engineering Evaluation
Construction of a seawall at Reach 3, is anticipated to cause minimal effects to the
existing sediment transport mechanism, because the toe of the seawall is located at a
landward setback distance. Thus, there will be no adverse impact to the local coastal
processes.
The results of wave runup within Reach 3 will be similar to those of the without
project conditions. There will be no reduction in damage to the existing revetments
situated north of the intake jetties, because the seawall is designed to protect the
causeway section of Carlsbad Blvd. between the intake and outlet jetties of Agua Hedionda
Lagoon. Thus, the causeway will not be damaged by wave action. Since the seawall is
properly designed against wave attack, structure damage to seawall is also assumed to be
minimal.
4.2.9.3 Environmental Evaluation
The environmental effects of this sheetpile wall will be similar to that of the
revetment discussed in Section 4.2.4.3; however, scour of the beach in front Of the wall is
expected to increase due to this site's exposure to waves.
4.2.9.4 Economic Analysis
The costs associated with this alternative are summarized in Table 4.9a and the
benefits are presented in Table 4.9b. The Benefit - Cost Ratio is shown in Table 4.9c.
4-48
11888110M
Figure 4.9a Plan 9 - Seawall, Reach 3
M.,
Present Limit
of Sidewalk
Existing
Curb and
New 4" Slab on Grade
to Complete Sidewalk
42"
/ Elevation Varies
. Slope 1%
Two (2) Layer of
1.500 pound Stone
Approx 4 ft Thick
Reinf Conc Cap
+8.75' Filter Cloth Wrap
4 at Each End
Th..
1
5' airi
6 inch Thick Quarry Run
Material Underlain by
Filter Fabric
Undisturbed Soil
Use 30' Long Sheet Piling
Bethlehem steel PLZ-23 or
Syrd Steel SPZ-23 or
Approved Equal -
—17
11888118M
Figure 4.9b Typical Cross-Section of Seawall - Reach 3 (Datum: MLLW)
Table 4.9a Plan 9- A Seawall in Reach 3 - Cost Estimate
Contingency
Unit Cost without ----------------Cost with
Item Quantity Unit Price Contingency Amount X Contingency
SEAWALL
Mobilization & Demob. 1 Job L.S. $280,000 $70,000 25 $350,000
Sheet Pile Wall 2,700 In feet $475.00 $1,282,500 $320,600 25 $1,603,100
Concrete Cap 2,170 . cu yd $510.00 $1,106,700 $276,700 25 $1,383,400
1,500-pound Toe Rock 8,090 tons $31.00 $250,800 $62,700 25 $313,500
C-Stone 750 cu yd $31.00 $23,300 $5,800 25 $29,100
Fitter Cloth 7.760 sq yd $3.70 $28.700 $7.200 25 $35900
SUBTOTAL (Cost of Seawall) $2,972,000 $743,000 $3,715,000
PLAWN I NG/ENGINEERING/COISTRUCT ION
8 % Planning, Engineering, and Design $237,800 $59,500 25 $297,300
3 % Engineering during Construction $89,200 $22,300 25 $111,500
7 % Construction Management $208.000 $52,000 25 $260000
SUBTOTAL $535,000 $133,800 $668,800
INTEREST DURING CONSTRUCTION $68,000 $17,000 25 $85,000
TOTAL FIRST COST OF LONSTRUCTION $3.575.000 $893.800 $4.468.800
ANNUAL COST
Annual Cost • $292,400 $73,100 $365,500
Annual O&M Cost $17.500 $4.400 $21.900
TOTAL ANNUAL COST $309,900 $77,500 $387,400
Note: Design of seawall was obtained from the City of Carlsbad. . -
Table 4.9b Annual Benefits -- Alternatives 9, 10
STORM DAMAGE REDUCTION BENEFITS
REACH 3 DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BENEFITS
Detour 5.20 5.20 0.00
Emergency 1.49 1.49 0.00
Revetment (north) 16.28 16.28 0.00
Revetment (south) 15.45 0.00 15.45
Roadway 244.82 0.00 244.82
Subtotal, Reach 3 283.24 22.97 260.27
TOTAL STORM DAMAGE REDUCTION BENEFITS 260.27
RECREATION BENEFITS
Reach 0
TOTAL BENEFITS, ALTERNATIVES 9, 10 260.27
- - uvueinouoiogy ior ueiermining recreation oeneiiis aetaiieo in cconomic Mppenoix
Table 4.9c Plan 9: Economic Summary
Annual Benefits ($1000) 260
Annual Costs ($1000) 387
Benefit - Cost Ratio 0.67
4-52
4.2.10 Plan 10 - A Rubble-Mound Revetment in Reach 3
4.2.10.1 Description
As shown in Figure 4.10a, a 2,700-foot long rubble-mound revetment is built in
Reach 3 to protect the portion of Carlsbad Boulevard between in intake and outlet at Agua
Hedionda Lagoon. Figure 4.10b shows a typical cross-section of the revetment. Rock
sources are the same as previously mentioned.
4.2.10.2 Engineering Evaluation
Construction of a rubble-mound revetment at Reach 3 is anticipated to have similar
effects as construction of the seawall described in Plan 9.
4.2.10.3 Environmental Evaluation
The environmental effects of this revetment will be similar to that of the revetment
discussed in Section 4.2.4.3, however, scour of the beach in front of the wall is expected
to increase due to this site's exposure to waves.
4.2.10.4 Economic Analysis
The costs associated with this alternative are summarized in Table 4.10a and the
benefits are the same as in Plan 9 and are presented in Table 4.9b. The Benefit - Cost
Ratio is shown in Table 4.10b.
3
4-5a
0 400 800 1200
Scale in feet
Agua
Hedionda
1000 Lagoon
Revetment -.
00,
C,
jc
racinc L'cean • . \:\\ %k.
I
[TI
I
1
• :
0• .•
I
I
11888109M
• I
Figure 4. 1Oa Plan 10 - Rubble-Mound Revetment, Reach 3
Top of Carlsbad Blvd
Elev +16.75 MLLW
Elevation 17.75"MLLW
6-ton Quarrystone Armor
Exisiting Beach 1.5' Thick Core
Layer of C-Stone
Bedrock
11888119M
Figure 4.10b Typical Cross-Section of Revetment - Reach 3
Table 4.1 Oa Plan 10 - A Rubble-Mound Revetment in Reach 3 - Cost Estimate
Contingency -
Unit Cost without ----------------Cost with
Item Quantity Unit Price Contingency Amount % Contingency
REVETMENT
A-6 Stone 58,410 tons $45.00 $2,628,500 $657,100 25 $3,285,600
C-Stone 9.740 tons $30.00 $292,200 $73,100 25 $365,300
SiEtotat $2,920,700 $730,200 $3,650,900
PLANNING/ENGINEERING/CONSTRUCTION
8 % Planning, Engineering, and Design $233,700 $58,400 25 $292,100
3 % Engineering during Construction $87,600 $21,900 25 $109,500 *
7 % Construction Management $204,400 $51,100 25 $255,500
SUBTOTAL $525,700 $131,400 $657,100
INTEREST DURING CONSTRUCTION $67,200 $16,800 25 $84,000
TOTAL FIRST COST OF CONSTRUCTION $3,513,600 $878400 $4,392,000
I
ANNUAL COST
Annual Cost $287,200 $71,800 $359,000
Annual O&M Cost $17,200 $4,300 $21,500
TOTAL ANNUAL COST $304,400 $76,100 $380,500
Table 4.10b Plan 10: Economic Summary
Annual Benefits ($1000) 260
Annual Costs ($1000) 381
Benefit - Cost Ratio 0.68
4.2.1 1 Plan 11 - Beachfill and Structures in Reaches 1, 2, and 3
4.2.11.1 Description
As shown in Figure 4.11 a and 4.11 b, a 200-foot berm is constructed in Reaches 1,
2, and 3. It is to be contained by an extension of the north Agua Hedionda jetty and by
two groins between the inlet and outlet to the lagoon. This plan is a combination of Plans
5 and 7, developed to provide protection to the areas suffering the most damages --
Reaches 1 and 3 -- while enhancing recreation to all three of the most northern reaches.
The elevation of the beachfill is + 10 feet MLLW and the length of the beachfill is
about 7,400 + 2,700 = 10,100 feet. Initial beachfill will be 1,431,700 yd and the
4-56
.01
Agua
Hedionda
goon
11888113M
Figure 4.11a Plan II - Beachfill with Structures, Reaches 1, 2, and 3
renourishment of 600,000 yd' would be done at six year intervals. The beach face slopes
downward approximately 1 vertical on 20 horizontal from the berm crest to the natural
nearshore bottom. The typical cross-sections of the beachfill are shown in Figures 4.1 b
and 4.6b. Sand sources are the same as discussed in Section 4.2.1.1.
As in Plan 5, the north intake jetty at Agua Hedionda Lagoon is extended 200 feet,
to a total of 400 feet. The typical cross-section of the extended jetty is similar to that
shown in Figure 4.2b. As shown in Figure 4.11a and lib, a system of two groins are used
to stabilize the beachfill in Reach 3. The groins are 350 feet long and 900 feet apart.
Figure 4.7b shows a typical cross-section of the groin. The 26,400 tons of rock required is
available from sources discussed in Section 4.2.2.1.
4.2.11.2 Engineering Evaluation
Extension of the north intake jetty will result in the shoreline reorienting itself more
nearly parallel with the prevailing incident wave crests. Net longshore transport rates along
the reoriented shoreline will be lower because the angle between the average incoming
wave crests and the new shoreline will be smaller. Thus, a net Iongshore transport rate of
200,000 cubic yards per year has been assumed. It is also assumed that Reaches 1 and 2
will receive 100,000 cubic yards per year from the sand bypass operation at Oceanside
Harbor. Thus, a beachfill replenishment rate of 100,000 cubic yards per year has been
used in the optimization of replenishment frequency. The beachfill will be replenished on a
6-year cycle. The results of storm damage will be similar to those of Plans 1, 2, 5, 6, and
7.
4.2.11.3 Environmental Evaluation
The effects of beachfill and the jetty extension have been examined in Sections
4.2.1.3 and 4.2.2.3, respectively. Approximately three acres of bottom area are affected.
The effects on the lagoon were discussed in Section 4.2.5.3.
4.2.11.4 Economic Analysis
The costs associated with this alternative are summarized in Table 4.11a and the
benefits are presented in Table 4.11 b. The Benefit - Cost Ratio is shown in Table 4.11 c.
4-59
Table 4.11a Plan 11 - Beachf ill and Structures in Reaches 1, 2, and 3 - Cost Estimate
Contingency
Unit Cost without ----------------Cost with
Item Quantity Unit Price Contingency Amount % Contingency
GROINS --
200-ft north intake jetty extension - Reach 1 and Reach 2:
A-12 Stone 1,600 tons $50.00 $80,000 S20,000 25 $100,000
A-7 Stone 1,600 tons $45.00 $72,000 $18,000 25 $90,000
8-1 Stone 3,200 tons S35.00 $112,000 $28,000 25 $140,000
C-Stone 3,200 tons $30.00 $96,000 $24,000 25 $120,000 Grouting 1 Job L.S. $100,000 $25,000 25 $125,000
SUBTOTAL (Cost of Jetty Extension) $460,000 $115,000 $575,000
350-ft groin - Reach,3:
A-12 Stone 2,800 tons $50.00 $140,000 $35,000 25 $175,000
A-7 Stone 2,800 tons $45.00 $126,000 $31,500 25 $157,500
B-i Stone 5,600 tons $35.00 $196,000 $49,000 25 $245,000
C-Stone 5,600 tons $30.00 $168,000 $42,000 25 $210,000
Excavation 25,000 cu yd $6.50 $162,500 $40,600 25 $203,100
BackfilL 15,000 cu yd $4.50 $97,500 $24,400 25 $121,900
Grouting 1 Job L.S. $100,000 $25,000 25 $125,000
Cost of 1 350-ft Groin $990,000 $247,500 $1,237,500
SUBTOTAL (Cost of 2 350-ft Groins) $1,980,000 $495,000 $2,475,000
BEACHFILL
BeachfiLL (initial) 1,331,700 cu yd $3.00 $3,995,100 $998,800 25 $4,993,900
BeachfiLL (advance) 600,000 cu yd $3.00 $1,800,000 $450,000 25 $2,250,000
Mobilization and Demob 1 Job $500,000 $500,000 $125,000 25 $625,000
SUBTOTAL (BeachfiLL) $6,295,100 $1,573,800 $7,868,900
SUBTOTAL (BeachfitL + Structures) $8,735,100 $2,183,800 $10,918,900
PLANN I MG/ENGINEER I MG/CONSTRUCTION
8 % Planning, Engineering, and Design $498,800 $174,700 25 $873,500
3 .% Engineering during Construction $262,100 $65,500 25 $327,600
7 % Construction Management $586,300 $146,600 25 $732,900
SUBTOTAL $1,547,200 $386,800 $1,934,000
INTEREST DURING CONSTRUCTION $440,000 $110,000 25 $550,000
TOTAL FIRST LOST OF CONSTRUCTION ' $10,321,100 $2,580300 $12,901,400
ANNUAL COST
Annual Cost of First Costs $843,700 $210,900 $1,054,600
Annual Cost of BeachfiLL Replenishment (0&M) $370,000 $92,500 $462,500
Annual O&M Cost of Structures $14,400 $3,600 $18,000
TOTAL ANNUAL COST $1,228,100 $307,000 $1,535,100
Note: Replenishment = 6-year Cycle at 100,000 yd3/year
(See Table 7.8 for sensitivity analysis of replenishment cycle)
'4-60
Table 4.11 b Annual Benefits -- Alternative 11
STORM DAMAGE REDUCTION BENEFITS
REACH 1 DAMAGES WITHOUT
PROJECT
DAMAGES WITH PROJECT BENEFITS
Landscaping 3.41 1.98 1.43
Revetment 49.63 5.03 44.60
Structure 53.28 26.13 27.15
Content 22.15 8.18 13.97
Content 10.40 0.00 10.40
Subtotal, Reach
1
138.87 41.32 97.55
REACH 0 0 0
REACH 3
Detour 5.20 0.00 5.20
Emergency 1.49 0.00 1.49
Revetment
(north)
- 16.28 . 0.00 16.28
Revetment
(south)
Roadway
15.45
244.82
0.00
0.00
15.45
244.82
Subtotal, Reach
3
283.24 0.00 283.24
TOTAL STORM DAMAGE REDUCTION BENEFITS 380.79
RECREATION BENEFITS (incidental)**
Reaches 1, 2, and 3 500.00
TOTAL BENEFITS, ALTERNATIVE 11 880.79
content carnage resuitung Trom structural iaiiure
** Methodology for determining recreation benefits detailed in Economic Appendix
ri
4-61
I
Table 4.11c Plan 11: Economic Summary
Annual Benefits ($1000) 881
Annual Costs ($1000) 1535
Benefit - Cost Ratio, 0.57
4.2.12 Plan 12 - A Rubble-Mound Revetment in Reach 5
4.2.12.1 Description
As shown in Figure 4.12, a 1,000-foot long rubble-mound revetment is built in Reach
5 to protect the portion of Carlsbad Boulevard at which the road elevation is 18.25 feet
MLLW. The typical cross-section of the revetment is similar to that shown in Figure 4.l 0b.
The required 16,170 tons of rock are available from sources discussed in Section 4.2.2.1.
4.2.12.2 Engineering Evaluation
Construction of a rubble-mound revetment at Reach 5 is anticipated to have similar
effects as construction of the seawall described in Plan 9.
4.2.12.3 Environmental Evaluation
The environmental effects of this révetment will be similar to that of the revetment
discussed in Section 4.2.4.3, however, scour of the beach in front of the wall is expected
to increase because this site is more exposed to waves.
4.2.12.4 Economic Analysis
The costs associated with this alternative are summarized in Table 412a and the
benefits are presented in Table 4.12b The Benefit - Cost Ratio is shown in Table 4.12c.
4-62
11888114M
Figure 4.12 Plan 12— Rubble-Mound Revetment, Reach 5
Table 4.12a Plan 12 - A Rubble-Mound Revetment in Reach 5 - Cost Estimate
-- Contingency
Unit Cost without ----------------Cost with
Item Quantity''Unit Price Contingency Amount % Contingency
REVETMENT
A-4 Stone 13,620 tons $43.00 $585,700 $146,400 25 $732,100
C-Stone 2,550 tons $30.00 $76,500 $19,100 25 $95,600
SUBTOTAL COST $662,200 $165,500 $827,700
PLANNING/ENGINEERING/CONSTRUCTION
8 % Planning, Engineering, and Design $53,000 $13,300 25 $66,300
3 % Engineering during Construction $19,900 $5,000 25 $24,900
7 % Construction Management $46,400 $11,600 25 $58,000
SUBTOTAL $119,300 $29,900 $149,200
INTEREST DURING CONSTRUCTION $15,200 $3,800 25 $19,000
TOTAL FIRST COST OF CONSTRUCTION $796,700 $199.200 $995900
ANNUAL COST
Annual Cost of First Costs $65,100 $16,300 $81,400
Annual ON Cost $3,900 $1,000 $4,900
TOTAL ANNUAL COST . $69,000 $17,300 $86,300
Table 4.12b Annual Benefits -- Alternative 12
STORM DAMAGE REDUCTION BENEFITS
REACH 5 DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BENEFITS
Roadway 60.96 0.00 60.96
TOTAL STORM DAMAGE REDUCTION BENEFITS 60.96 1
RECREATION BENEFITS-
Reach 5 0
TOTAL BENEFITS, ALTERNATIVE 12 60.96
e* Methodology for determining recreation benefits detailed in Economic Appenoix
4-64
Table 4.12c Plan 12: Economic Summary
Annual Benefits ($1000) 61
Annual Costs ($1000) 86
Benefit - Cost Ratio 0.71-
4.2.13 Plan 13 - A Groin System with Beachfill in Reach 1
4.2.13.1 Description
As shown in Figure 4.13, a 200-foot berm with two end groins is constructed in
Reach 1. The 4000 foot beachfill provides protection to all structures in Reach 1 and
concentrates the improvements in areas requiring protection.
The elevation of the beachfill is + 10 feet MLLW and the length of the beachfill is
about 4,000 feet. The initial beachfill requires 533,333 yd of sand, available from sources
discussed in Section 4.2.1.1. The beach face slopes downward approximately 1 vertical on
20 horizontal from the berm crest to the natural nearshore bottom. A typical cross-section
of the beachfill is shown in Figure 4.1b. Two 400-foot groins are used to stabilize the
beachfill requiring 29,200 tons of stone (same sources as previously mentioned). A typical
cross-section of the groin is shown in Figure 4.2b.
4.2.13.2 Engineering Evaluation
Construction of the two end groins will result in the shoreline reorienting itself more
nearly parallel with the prevailing incident wave crests. Net longshore transport rates along
the reoriented shoreline will be lower because the angle between the average incoming
wave crests and the new shoreline will be smaller. Thus, a net longshore transport rate of
135,000 cubic yards per year has been assumed. It is also assumed that Reach 1 will
receive 100,000 cubic yards per year from the sand bypass operation at Oceanside Harbor.
Since there is continuous dredging of about 120,000 cubic yards per year at Agua
Hedionda Lagoon and beach disposal of the dredged materials north and south of the
lagoon, it is further assumed that Reach 1 will receive 60,000 cubic yards per year from
this sand bypass operation. Moreover, it is assumed that there is an offshore loss rate of
25,000 cubic yards per year. Thus, beachfill replenishment is not required for this plan.
4-65
11888106M
Figure 4.13 Groin System with Beachfihl
The results of wave runup and damages to the coastal structures are the same as
those of Plan 1. Structural damage to this revetment is reduced as shown in Table 4.1 b.
4.2.13.3 Environmental Evaluation
The effects of beachfill and the groins have been examined in Sections 4.2.1.3 and
4.2.2.3, respectively. Approximately four acres of bottom area are affected. The effects
on the lagoon were discussed in Section 4.2.5.3.
4.2.13.4 Economic Analysis
The costs associated with this alternative are summarized in Table 4.13a and the
benefits are presented in Table 4.13b. The Benefit - Cost Ratio is shown in Table 4.13c.
4-67
Table 4.13a Plan 13 - A Groin System with Beachfill in Reach 1- Cost Estimate
Contingency
Unit Cost without ................Cost with
Item Quantity Unit Price Contingency Amount % Contingency
GROIN
400 ft groin
A-12 Stone 3,200 tons $50.00 $160,000 $40,000 25 $200,000
A-7 Stone 3,200 tons $45.00 $144,000 $36,000 25 $180,000
B-i Stone 6,400 . tons $35.00 $224,000 $56,000 25 $280,000
C-Stone 6,400 tons $30.00 $192,000 $48,000 25 $240,000 Excavation 10,000 Cu yd $6.50 $65,000 $16,300 25 $81,300
Grouting 1 Job L.S. $100,000 $25,000 25 $125,000
Cost of each groin $885,000 S221,300 $1.106.300
SUBTOTAL (Cost of 2 groins) $1,770,000 $442,600 $2,212,600
BEACHFILL
BeachfiLL 533333 Cu yd $3.00 $1,600,000 $400,000 25 $2,000,000
Mobilization & Demob. 1 Job L.S. $500,000 $125.000 25 $625,000
SUBTOTAL (Cost of BeachfiLL) $2,100,000 $525,000 $2,625,000
SUBTOTAL (BEACHFILL + GROINS) S3.870.000 $967400 $4.837600
PLANNING/ENGINEERINGflXINSTRUCT ION
8 % Planning, Engineering, and Design $309,600 $77,400 25 $387,000
3 X Engineering during Construction $116,100 $29,000 25 $145,100
7 Construction Management $270,900 $67,700 25 $338,600
SUBTOTAL $696,600 $174,100 $870,700
INTEREST DURING CONSTRUCTION $76,400 $18,600 25 $93,000
TOTAL FIRST COST OF CONSTRUCTION $4,641,000 $1,160,300 $5,801,300
ANNUAL COST
Annual Cost S379.300 V $94,800 $474,100
Annual 0&M Cost of Groins $10,400 $2,700 $13,100
TOTAL ANNUAL COST $389,700 $97,500 $487,200
Note: Replenishment = 0
SM
Table 4.13b Annual Benefits -- Alternative 13
($1000)
STORM DAMAGE REDUCTION BENEFITS
REACH 1 DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BENEFITS
Landscaping 3.41 1.98 1.43
Revetment 49.63 5.03 44.60
Structure 53.28 26.13 27.15
Content 22.15 8.18 13.97
Content 10.40 0.00 10.40
Subtotal, Reach 1 138.87 41.32 97.55
REACH 0 0
[
0
_____________
TOTAL STORM DAMAGE REDUCTION BENEFITS
RECREATION BENEFITS _(incidental)
Reaches I and 2 447.45
TOTAL BENEFITS, ALTERNATIVE 13 545.00
k ornuni uiamagu resuiiing irum siruciurat iiiure
Methodology for determining recreation benefits detailed in Economic Appendix
Table 4.13c Plan 13: Economic Summary
Annual Benefits ($1000) 545
Annual Costs ($1000) 487
Benefit - Cost Ratio 1.12
4-69
4.214 Plan 14 - A T-Groin with Beachfill in Reach 3 1
4.2.14.1 Description
As shown in Figure 7.14, a T-groin is used to stabilize a beachfill in Reach3. This
plan reduces damages to Carlsbad Boulevard while increases recreation benefits.
The beachfill is about 2,700 feet long. The elevation of the beachfill is + 10 feet
MLLW and the width of the berm is 200 feet. As discussed below (Section 4.2.14.2), no
renourishment is required: Therefore there is no advanced nourishment required, thus only
346,000 yd of initial fill is necessary. The beach face slopes downward approximately 1
vertical on 20 horizontal from the berm crest to the natural nearshore bottom. A typical
cross-section of the beachfill is shown in Figure 4.6b. The sand is available from offshore
sources discussed in Section 4.2.1.1. The groin is about 350 feet long and the T-shaped
end is about 200 feet long. The 26,400 tons of rock are available from sources discussed
in Section 4.2.2.1. A typical cross-section of the groin is shown in Figure 4.7b.
4.2.14.2 Engineering Evaluation
Due to the reorientation of the shoreline after groin construction, the angle between
the shoreline and the incoming wave crests will be reduced. The net longshore transport
rate is assumed to be about 130,000 cubic yards per year. It is also assumed that Reach 3
will receive about 130,000 cubic yards per year from the sand bypass operation at Agua
Hedionda Lagoon. Thus, no beachfill replenishment is required. I
The results of wave runup and damages to coastal structures will be the same as
those of Plan 6. 1
4.2.14.3 Environmental Evaluation
The effects of beachfill and the groins have been examined in Sections 4.2.1.3 and
4.2.2.3, respectively. Approximately 1.5 acres of bottom area are affected. The effects I on the lagoon were discussed in Section 4.2.5.3.
4.2.14.4 Economic Analysis
The costs associated with this alternative are summarized in Table 4.14a and the
benefits are presented in Table 4.14b. The Benefit - Cost Ratio is shown in Table 4.14c.
4-70 1
Table 4.14a Plan 14 - A T-Groin with Beachfill in Reach 3 - Cost Estimate
Contingency
Unit Cost without ................Cost with Item Quantity Unit Price Contingency
-
Amount % Contingency
GROIN
350 ft groin:
A-12 Stone 2,800 tons $50.00 $140,000 $35,000 25 $175,000 A-7 Stone 2,800 tons $45.00 $126,000 $31,500 25 $157,500 B-i Stone 5,600 tons $35.00 $196,000 $49,000 25 $245,000 C-Stone 5,600 tons $30.00 $168,000 $42,000 25 $210,000 Excavation 10,000 Cu yd $6.50 $65,000 $16,300 25 $81,300 Grouting 1' Job L.S. $100,000 $25,000 25 $125,000 SUBTOTAL (Cost of Groin) $795,000 $198,800 $993,800
200 ft 1-ends:
A-12 Stone 3,200 tons $50.00
B-i Stone 3,200 tons $35.00 C-Stone 3.200 tons $30.00
SUBTOTAL (Cost of 1-ends)
$160,000 $40,000 25 $200,000 $112,000 $28,000 25 $140,000 $96,000 $24,000 25 $120,000 $368,000 $92,000 $460,000
SUBTOTAL (Cost of 1 1-groin) $1,163,000 $290,800 $1,453,800
BEACHFILL
BeachfitL 346,000 Cu yd $3.00 $1,038,000 $259,500 25 $1,297,500 Mobilization & Demob. 1 Job L.S. $500,000 $125,000 25 $625,000 SUBTOTAL (Cost of BeachfiLL) $1,538,000 $384,500 $1,922,500
SUBTOTAL (BeachfiLt + Groin) $2,701,000 S675.300 $3,376,300
PLANNING/ENGINEERING/CONSTRUCTION
8 % Planning, Engineering, and Design $216,100 $54,000 25 $270,100 3 % Engineering during Construction $81,000 $20,300 25 $101,300 7 % Construction Management $189,100 $47,300 25 $236,400 SUBTOTAL $486,200 $121,600 $607,800
INTEREST DURING CONSTRUCTION $94,400 $23,600 25 $118,000
TOTAL FIRST COST OF CONSTRUCTION $3,281,700 $820,400 $4,102,100
ANNUAL COST
Annual Cost $268,300 $67,000 $335,300 Annual O&M Cost of Groins $6,900 $1,700 $8600 TOTAL ANNUAL COST $275,200 $68,700 $343,900
Note: Replenishment = 0
4-72
Table 4.14b Annual Benefits -- Alternative 14
STORM DAMAGE REDUCTION BENEFITS
REACH 3 DAMAGES
WITHOUT
PROJECT
DAMAGES WITH
PROJECT
BENEFITS
Detour 5.20 0.00 5.20
Emergency 1.49 1.49 0.00
Revetment (north) 16.28 16.28 0.00
Revetment (south) 15.45 1.61 13.84
Roadway 244.82 42.43 202.39
Subtotal, Reach 3 283.24 61.81 221.43
TOTAL STORM DAMAGE REDUCTION BENEFITS 221.43
RECREATION BENEFITS (incidental)"
Reach 3 352.57
TOTAL BENEFITS, ALTERNATIVE 14 574.00
Metnoaoiogy tar aetermuning recreation Denetuts aetailea in tconOMIC Appenoix
Table 4.14c Plan 14: Economic Summary
Annual Benefits ($1000) 574
Annual Costs ($1000) 344
Benefit - Cost Ratio 1.67
4-73
I
able 4.15 Summary of Descriptions of Alternatives and Cost Estimates
Annual Cost (S/year) of Plan
First Cost
P..
scription and Assumption of Alternatives Construct'
cp,.enIsn-
First Cost ON ment Total
BeachfiLL in Reaches 1 and 2. 7,722.9
-------
631.3 0 766.8 1,398.1
5,000 ft Long and 200 ft wide beachfiLL.
Net Longshore transport rate 270,000 yd3/yr.
Sand bypass = 100,000 yd3/yr from Oceanside Harbor.
Replenishment = 170,000 yd3/yr at 5-year cycle.
2 A Groin System with BeachfiLL in Reaches 1 and 2. 12,010.4 981.8 31.9 157.8 1,171.5
5,000 ft Long and 200 ft wide beachfiLL
and 3 600-ft groins.
Net Longshore transport rate becomes 135,000 y&/yr
due to reorientation of shoreline.
Sand bypass = 100,000 yd3/yr from Oceanside Harbor.
Replenishment = 35,000 yd3/yr at 10-year cycle.
3 An Offshore Breakwater System in Reaches 1 and 2. 48,274.4 3,946.1 219.2 0 4,165.3
3 800-ft offshore breakwaters with 800-ft gaps.
4 New and Repaired Revetments in Reach 1. 1,360.8 111.3 6.7 0 118.0
New construction of revetments and repair of
existing revetments.
5 BeachfiLL and North Intake Jetty Extension in 7,599.5 621.0 6.0 0 627.0
Reaches 1, 2, and 3.
7,400-ft beachfiLL and North Intake Jetty
extended to 600 ft Long. BeachfiLL width varies
from 200 ft to 330 ft.
Net Longshore transport rate becomes 135,000 yd3/yr
due to reorientation of shoreline. Sand bypass:
100,000 yd3/yr from Oceanside Harbor and 60,000 yd3/yr
from Agua Hedionda Lagoon. Offshore Loss = 25,000 yd3/yr.
Replenishment = 0.
6 BeachfiLL in Reach 3. 6,223.5 508.3 0 988.5 1,496.8
2,700 ft Long and 200 ft wide beachfiLL.
Net Longshore transport rate = 270,000 yd3/yr.
Sand bypass = 60,000 yd3/yr from Agua Hedionda Lagoon.
Replenishment = 210,000 yd'/yr at 4-year cycle.
7 A Groin System with BeachfiLl in Reach 3. 4,688.8 383.2 11.7 0 394.9
2,700 ft Long and 200 ft wide beachfiLL and 2
350-ft groins.
Net Longshore transport rate becomes 130,000 yd3/yr
due to reorientation of shoreline. Sand bypass
= 130,000 yd3/yr from Agua Hedionda Lagoon.
Replenishment = 0.
I
1 Includes interest during construction
EMU
Table 4.15 (continued) Carlsbad - Summary Cost Estimate of Alternatives
I .
First Cost
Annual Cost ($/year) of Plan
of Replenish-
Description and Assumption of Alternatives Construct First Cost O&M ment Total
I 8 An Offshore Breakwater System in Reach 3. 23,102.3 1,881.1 109.6 0 1,990.7
3 400-ft offshore breakwaters with 400-ft gaps.
9 A Seawall in Reach 3 4,468.8 365.5 21.9 0 387.4
I 2,700 -ft seawall.
10 A Rubble-Mound Revetment in Reach 3. 4,392.0 359.0 21.5 0 380.5
2,700-ft rubbLe-mound revetment.
11 I BeachfilL and Structures in Reaches 1, 2, and 3. 12,901.4 1,054.6 18.0 462.5 1,535.1
10,100 ft Long and 200 wide beachfiLL, North
Intake Jetty extended to 400 ft tong, and 2
I 350-ft groins.
Net Longshore transport rate = 200,000 yd3/yr.
Sand bypass = 100,000 yd3/yr from Oceanside Harbor.
Replenishment = 100,000 yd3/yr at 6-year cycle.
I 12 A Rubble-Mound Revetment in Reach 5. 995.9 81.4 4.9 0 86.3
1,000-ft rubble-mound revetment.
13 A Groin System with Beachfill in Reach 1, 5,801.3 474.1 13.1 . 0 487.2
4,000 ft long and 200 ft wide beachfiU and I 2 400-ft end groins.
Net tongshore transport rate becomes 135,000 yd3/yr
due to reorientation of shoreline. Sand bypass:
100,000 yd3/yr from Oceanside Harbor and 60,000 yd3/yr I from Agua Hedionda Lagoon. Offshore toss = 25,000 yd3/yr'
Replenishment = 0.
14 A 1-Groin with Beachfill in Reach 3. 4,1021 335.1 8.6 . 0 343.9
2,700 ft long and 200 ft wide beachfitt and one
350-ft 1-groin.
Net tongshore transport rate becomes 130,000 yd3/yr
due to reorientation of shoreline. Sand bypass - I = 130,000 yd3/yr from Agua Hedionda Lagoon.
Replenishment = O
.
I
I
I
.
. .
I
I
I
4-75
e
BENEFIT COSTM jAND NET BENEFITS jX
BY AL1EHNA1WE
. ...
.........
($1000)
ALT. I . ALT. II ALT. III ALT IV ALT. V
U.I"..
ALT. VI ALT. VII ALT. VIII . ALT. IX ALT. X ALT. ALT. XI ALT. XII
.
ALT. XIII ALT. XIV
Beochfill Boachfill Break. Revet- Beachfill Beochfjtl Boachfill Break- Seawall Revetment Baachfill Revet- Beechtull BéachfiIl
.......I
IGroins waters mont lJetty /Groins water. . . IJetty mont /Groins . ,IT-Gr&n -
-
, Extension . . . . -. /Groins - .. .
Reach Affected 1, 2 1. 2 1. 2 . 1 1, 2, 3 3 3 3 3 3 . 1. 2, 3 5 1 3
COSTS
FIRST COST lot 87.723 812.010 848.274 81.361 87.600 86.224 84.689 823:012- 84.469 84.392 812.901 8996 85801 .84.102
construction) .-
TOTAL ANNUAL 81.398 *1.172 84.185 $118 8627 *1.497 [ •3 81.991 $387 $381 t.$1.535 $86 . $487 . *344
ANNUAL
BENEFITS
Damage Reduction $97.6 $97.6 8138.9 $79.7 8112.6 $221.4 8221.4 8265.5 8260.3 8260.3 8380.1- 880.1 897.6 :8221.4
8447.4 8447.4 80 . 80 $450.4 $352.6 $352.6 80 $0 80 8500.0 .80 . 8447.4 8352.6
[
Recreauon
(inddentel) . . - . . . . j
Total $545.0 8545.0 8138.9 879.7 $563.0 8574.0 8574.0 . 8265.5 8260.3 $260.3 $880.8 $69.1 - $545.0 574.0
BENEFIT-COST
RATIO
Storm Damage 07 - 08 .68 56 - .1 .87 .68 .25 .70 .20 . .84
only
Storm Damage .39 .47 .03 .68
and Recreation
.90 .38 - 1.45 .13. .67 .68 .57 .70 - .1.12 1.67
NET BENEFITS 1$8531 . 186271 ($4,028) ($38) - ($64) .- ($923) 8179 1'.($1.725111 18127) ($121i .[ (8654). - ($25) $58 [ $230--1
l.D.C.: Interest During Construction, - . . - . . . ..
4.3 Identification of Justified Projects
As a result of--the Pacific Coast Shoreline, Carlsbad Reconnaissance Study effort,
fourteen plans were developed and analyzed for the problem areas defined in Chapter 3.
Table 4.16 summarizes the benefit cost ratio for each alternative. Three alternatives,
Alternatives 7, 13, and 14 have benefit-cost ratios greater than 1 and are therefore justified
economically.
4-77
5.0 FEDERAL INTEREST DETERMINATION
5.1 General
This section presents the evaluation of the Federal interest in those plans
found justified on economic and environmental considerations presented in Section
4. The evaluation is based on determining the consistency of the feasible plans
based on existing Federal policy and guidance for Federal participation in shore
protection projects as contained in the following Corps of Engineers regulations
and other documents:
ER 1105-2-100, Planning Guidance, dated 28 December 1990;
ER 1165-2-130, Federal Participation in Shore Protection, dated 15 June
1989;
Policy Guidance Letter No. 7, Cost Sharing For Shore Protection, dated 23
February 1989; and
Policy Guidance Letter No. 11, Credit For Lands, Easements, and Rights
of Way (LER) at Shore Protection Projects dated 13 October 1988.
5.2 Purposes of Federal Participation
Under existing shore protection laws, Congress has authorized Federal
participation in shore protection projects to prevent or reduce damages caused by
wind and tidal generated waves along the Nation's coasts and shores. In general,
the purposes of Federal shore protection projects are associated with reducing
storm damages to existing public and private development and/or improving
recreation. In addition, Federal shore protection projects may be considered to
reduce impacts caused by Federal navigation improvements. The level of Federal
participation in shore protection projects is dependent on the purpose(s) of the
project and shore ownership as summarized in Table 5-1, and explained in the
subsequent paragraphs.
5.2.1 Hurricane and Storm Damage Reduction
Federal participation in a shore protection project is limited to 65 percent of
the costs assigned to the purpose of storm damage reduction. Non-Federal
interests must provide a minimum of 35 percent of the costs assigned to this
purpose and must participate in the National Flood Insurance Program and other
5-1
Table 5.1 Shore Ownership and Levels of Federal Participation
I
Shore ownership (4) Maxitnurn Level of Federal Participation
and Project Purposes or Benefits Construction (2) Operation
- M—aintenance
Rehabilitation
fOKR-R)
I. Federally owned (1.) -
Hurricane & Storm Damage Reduction 100% 100%
Loss of Land 100% 100%
Recreation (Separable Costs) (7) 100% l00%
Publicly and Privately owned
(protection results in public
benefits) (3)
Hurricane & Storm Damage Reduction 65% (8) . none
Loss of Land (5)(6) 50% (8) none
Recreation (Separable Costs) (7) 50% (8) none -
Privately owned, use limited
to private interests
Hurricane & Storm Damage Reduction none none
Loss of Land - none none
Recreation (Separable Costs) (7) none none
See paragraph 4-15e on protecting other Federal agency shores.
Where appropriate, periodic nourishment is considered "construction."
Privately owned shores under public control, as through a sufficiently
long-term lease assuring realization of public benefits throughout the
economic life of the project. See paragraph 4-15d concerning incidental
protection of privately owned shores.
(4)- Indian shores do not usually fall within categories of shore provided.
The status of such lands will depend upon the particular treaty provisions
pertaining to the lands under consideration and will need to be examined
in each instance. Specific cases should be referred to CECW-P for
guidance.
Non-Federal public shores dedicated to recreation or fish and wildlife
purpose.
Adjusted by the ratio of public to total shore protection benefits along
the protected shore. .-
Department of Army Policy precludes civil works funding of separable
recreation measures at shore protectioti projects.
The fair market 4alue of LERRD is included in these cost sharing
percentages, unless the land has no value.
I applicable Federal floodplain management programs. The fair market value of
lands, easements, rights of way, relocations, and disposal or borrow areas
I provided by the non-Federal interests is included in the total project cost, and they
receive credit for the value of these contributions towards the non-Federal share of
the total project cost. Land needed for the placement of project features that
I prevent the loss of the land itself has no value for crediting purposes.
5.2.2 Recreation
Federal participation in measures to provide separable recreation I opportunities at shore protection projects is not permitted by current budget
policies. However, the Corps can participate in shore protection plans that result
I in recreation benefits if those benefits are incidental to storm damage reduction
features and not the primary output. Paragraph 9c(1) of ER 1165-2-130 indicates
that these recreation benefits are considered in the economic analysis but are
considered incidental for cost-sharing purposes. Recreation benefits produced as a
consequence of the storm damage reduction project may exceed 50 percent of
total project benefits, but economic justification must be demonstrated on the
I basis of recreation benefits limited to 50 percent of total project benefits (Benefit
to cost ratio based on storm damage reduction only must be at least 0.5 and total
benefits with recreation must exceed 1.0).
I
5.2.3 Mitigation of Shore Damage Due to Federal Navigation Projects
Section 111 of the River and Harbor Act of 1968, as amended, provides for
Federal construction of measures for the prevention or mitigation of erosion or
shoaling damages attributable to Federal navigation features. The cost for such
measures are shared in the same proportion as the cost sharing provisions
applicable to the project causing or projected to cause such erosion or shoaling.
The target degree of mitigation is the reduction of erosion or accretion to the level
which would have existed without the influence of the navigation features, at the
time such navigation features were accepted as a Federal responsibility. Section
111 authority is to be used to provide a justified level of damage reduction; it is
not meant to restore shorelines to historic dimensions.
5.3 Shore Ownership
Current shore protection law provides for Federal participation in restoring
and protecting publicly owned shores available for use by the general public.
Federal participation may be recommended for the protection of developed private
shores if the use of such shores is not limited to private interests. Private property
5-3
can also be included if such protection and restoration is incidental to protection of
publicly owned shores or if such protétion would result in public benefits. Items
affecting public use areas follows:
Access. Reasonable public access must be provided in accordance with
the recreational use objectives of the particular area. Paragraph 6h(3) of ER
1165-2-130 indicates that public use is construed to be effectively limited to
within one-quarter mile from available points of public access to any
particular shore. In the event public access points are not within one half
mile of each other, an item of local cooperation must be included that such
access will be provided or the area will be considered a private shore.
Parking. Lack of sufficient parking facilities for the general public
(including nonresident users) located reasonably near and accessible to the
project beaches may constitute a de. facto restriction on public access arid
use of such beaches, thereby precluding eligibility for Federal assistance.
Street parking is riot,considered acceptable in lieu of parking lots unless
curbside capacity will accommodate' existing and anticipated demands.
Parking should be sufficient to accommodate .the lesser of the, peak hour
demand or beach capacity. Public transportation facilities may substitutb for
or complement parking facilities.
(C) Other restrictions. User fees that are not uniformally applied to the
general public, limitations of beach use by private organizations, or
communities are also considered restrictions on public use and would
preclude Federal participation in shore protection improvements.
5.3.1 Non-Federal Public Shores-Park and Conservation Areas,
Lands dedicated to non-Federal park and conservation areas will normally be
valued on the basis of loss of recreation outputs. Federal 'costsharing in shore
protection projects for such lands is limited to 50 percent of total project cost.
5.4 Beach Creation
Existing shore protection authorities provide for restoration and protection of
beaches. It does not provide for Federal cost sharing in extending a beach beyond
its historic shoreline unless the extension is needed for engineering reasons to
provide protection from erosion within the historic shoreline.
5-4
5.5 Periodic Nourishment
The Federal Government can participate in the cost of periodic nourishment
and can consider such nourishment as "construction" for cost-sharing purposes,
when in the opinion of the Chief of Engineers, such periodic nourishment is found
to be more economical erosion protection measures than retaining structures such
as groins or when nourishment is expected to be of benefit of downcoast beaches.
Projects with such structures included to maintain a shore alignment, but not to
materially prevent littoral drift from downcoast beaches such as low profile groins
and offshore breakwaters, are eligible for periodic nourishment. Federal
participation is not recommended when the sand replacement is proposed as a
maintenance measure, as for example when it would serve to maintain protective
beach accompanied by structures intended to confine the benefits of the sand
within a beach compartment rather than serving as a full or partial alternative to
such structures.
5.6 Maintenance
Except as noted above, maintenance of shore protection structural features
such as groins and breakwaters are generally a non-Federal responsibility.
5.7 Local Cooperation Requirements
I A public agency, authorized under State law, must be willing and able to
fulfill the non-Federal obligations of water resource projects recommended for
Federal participation. Prior to construction of the project, the public agency will
I enter into a written Project Cooperation Agreement (PCA), as required by Section
221 of Public Law 91-611, as amended, to provide local cooperation satisfactory
to the Secretary of the Army. Such local cooperation will include the following
I non-Federal responsibilities in addition to the responsibility for fulfilling the
requirement of law for the recommended project:
I a. Provide to the United States all necessary lands, easements, rights-of-
way, relocations, and suitable borrow and/or disposal areas required for
construction and subsequent maintenance of the project, including that
I required for periodic nourishment;
I b. Hold and save the United States free from claims for damages which may
result from construction and subsequent maintenance, operation, and public
use of the project, except damages due to the fault or negligence of the
United States or its contractors;
I I 5-5
II
Maintain continued public ownership and public use of the shore upon
which the amount of Federal participation is based during the economic life
of the project (normally 50 years);
Maintain and repair the protective measures and/or structures during the
economic life of the project as required to serve the intended purposes at
their design levels of storm damage protection and in accordance with
regulations prescribed by the Secretary of the Army;
Provide and maintain necessary access roads, parking areas, and other
public use facilities open and available to all on equal terms;
Participate in and comply with applicable Federal flood, plain management
and flood insurance programs prior to initiation of construction and during
the economic life of the project;
Contribute in cash the appropriate percentage of project construction
cost, the percentage to be in accordance with existing law and based on
shore ownership and use at the time of implementation, provided that credit
will be given for the value of lands, easements, rights-of-way, and
relocations;
Contribute the local share of periodic beach nourishment, where and to
the extent applicable (up to 50 years) as required to serve the intended
purposes;
Specific cases may also warrant assigning other additional local
responsibilities, such as: providing appurtenant facilities required for
realization of recreational benefits. -
5.8 Determination of Federal Interest in Shore Protection Plans at Carlsbad,
California
The alternative plans found to be economically justified to provide storm
damage protection and incidental recreation at Carlsbad, shown in Table 26,
include Plans VII, XIII, and XIV, with benefit to cost ratio's ranging from 1.0 to
1.3. These plans were evaluated to determine whether Federal participation is
warranted and the extent of such participation based on the requirements
presented in the above paragraphs.
5.8.1 Requirement for Plans to be Justified Primarily on Storm Damage Reduction
Benefits
5-6
As indicated in paragraph 5.2.2, that because of low priority on recreation, it
must be demonstrated that the jutification of a project for shore protection must
be based primarily on storm damage reduction to recommend Federal participation.
It is noted that the formulation of all the alternative plans did not include any
separable elements for recreation, and that the recreation benefits claimed for each
plan is based on incidental recreation use of the protective beaches designed for
storm damage reduction. A review of the information presented in Table 26
indicates that the only plans to meet this requirement are Plans VII and XIV, which
provide storm damage protection to Reach 3. Because of the relatively low storm
damage potential in Reaches 1 and 2, the remaining plans which include protection
for these reaches are justified primarily on recreation benefits and consequently are
low priority and cannot be recommended for Federal participation at this time.
5.8.2 Requirement for Public Use, Access, and Parking
Reach 3 is publicly owned by the State of California and managed by the
City of Carlsbad, both of which support beach restoration in the Reach 3 area as
reflected by the disposal of Agua Hedionda maintenance dredging in this reach.
The Reach 3 beach area is presently used as a popular recreation area with access
all along the reach. Parking areas are available as well as public transportation
which are expected to be adequate to serve peak demands related to the
recreation benefits. Accordingly, this requirement for Federal participation in Plans
VII and XIV is considered met.
I 5.8.3 Mitigation of Impacts from Federal Navigation Projects
I As indicated in paragraph 5.2.3, Section 111 of the 1968 River and Harbor
Act allows for Federal construction of shore protection projects to mitigate impacts
caused by Federal navigation projects. It has been recognized that the Federal
navigation project at Oceanside Harbor has impacted the volume of littoral material
transported to the downcoast beaches. However, the magnitude of this impact
and the effect on the Carlsbad beach area, in particular Reach 1, is somewhat
I uncertain since it appears that the Carlsbad beach areas were eroding prior to
construction of the harbor, and there has been substantial beach fills as well as a
number of major storms, seawall and river projects that all impacted on the
I shorelines in the Oceanside littoral cell. The Los Angeles District is presently
conducting a reconnaissance study for Federal shore protection along the City of
I
Oceanside, California. If a Federal shore protection project is determined justified
for the Oceanside area, it is likely that such project, if it includes beach restoration
and nourishment, will have beneficial impacts for the Reach 1 area, and possibly
I
other Reaches in Carlsbad. Plans for Oceanside may also mitigate impacts from
Oceanside harbor and reduce the cost for alternative plans for Reach 1, resulting in
I 5-7
I
restoration of beaches in Reach 1 meeting Federal participation requirements. I Accordingly, a review of the Federal interest in the alternative plans for Reach .1
will be performed as part of the Oceanside Reconnaissance Study.
For Reachii I
It is noted that a plan to. reduce potential Storm damages (no recreation
benefits) in Reach 5 had aBenefitto Cost- ratio-of about 0.9, and that the cost of
the plan was less that one million dollars. It is also noted that present plans of the
City of Carlsbad is to place material from a wetland restoration project at
Batiquitos Lagoon along Reach 5 which should provide a protective beach that will
reduce the storm damage problem in Reach 5. If in the future the storm damage
potential in Reach 5 increases, consideration of a Federal shore protection project
could be reviewed under Section 103 of the Continuing Authority Program. I
5.8.5 Conclusion of Federal Interest Determination
Based on the above, it is concluded that Federal participation in a shore
protection project for Reach 3 is justified and consistent with Federal policy and
requirements. Federal participation in shore protection for Reach 1, is not warranted
at this time because the primary output is recreation in this Reach, however,
Federal participation in Reach 1 will be reviewed as part of the Oceanside
reconnaissance study. Federal participation in Reach 5 is not economically justified
at this time, however if the storm damage potential increases in The future,
consideration of a Federal project may be made under the Section 103 Continuing
Authority Program.
I
5.9 Federal and Non-Federal Requirements For Implementation of Shore Protection
in Reach 3 I
Table 5.2 presents an estimate of the Federal and non-Federal cost-sharing
requirements for implementing a shore protection project for Reach 3 using existing
Federal policy and guidance presented in the above paragraphs. Plan XIV is used
as a basis of these estimates at this time. Further development of this plan and
other alternatives will be required in the Feasibility phase to better define these 1 costs.
5.9.1 Cost sharing of First Cost
Non-Federal share of the First cost of shore protection project is 35 percent
5-8
in accordance with the 1986 Water Resources Development Act. Non-Federal
requirements to provide LERR canbe credited to the 35 percent share of the first
cost. Real estate requirements and credit for Plan 3 are expected to be minimal,
since the beach area is presently owned by the State and the project area involves
an area that is presently eroding and will be protected by the project.
5.9.2 Cost sharing of Periodic Nourishment and Maintenance
It is expected that maintenance dredging of Agua Hedionda by San Diego
Gas and Electric will continue in the future and the placement of the dredged
material on Reach 3 will be adequate to maintain the protective beaches. The City
of Carlsbad will be required to assure this continues in the future as well as be
responsible for maintaining any groin structures included in the final plan.
5.9.3 Other non-Federal requirements
In addition to providing 50 percent of the cost for the Feasibility Phase
I
studies, the City of Carlsbad will also be required, prior to construction to enter
into contract with the United States, assuring they will accomplish the local
cooperation items indicated in paragraph 5.7.
I
I
TABLE 5.2
ESTIMATED COST-SHARING OF FEDERAL SHORE
PROTECTION PROJECT FOR REACH 3
I ITEM TOTAL FEDERAL NON-FEDERAL
First Cost $3,984,000 $2,590,000 (65%) $1,394,000 (35%)
Average A,Ibat Maintenance Cost
Periodic Nourishment 0' 0' (65%) 0' (35%)
Maintenance Groins $8,600 O (0%) $8,600 (100%)
Periodic nourishment based on San Diego Gas and Electric continuing to place dredged material from Agua
Hedionda at no cost.
5-9
I
I 6.0 IPMP/FEASIBILITY PHASE REQUIREMENTS
I For the study to proceed to the Feasibility Phase, the City of Carlsbad will be
required to enter into a Feasibility Cost Sharing Agreement requiring the City to
provide 50% of the Feasibility Study cost as described in the Initial Project
I Management Plan (IPM P).
The IPMP describes Feasibility Study activities, and establishes an Executive
Committee and a Study Management Team, consisting of representatives of the
Los Angeles District, U.S. Army Corps of Engineers and the City of Carlsbad.
Subsequent to the Reconnaissance Review Conference, negotiations will be
I initiated with the City of Carlsbad to consider cost sharing arrangement, including
in-kind services, and the assignment of responsibilities for the completion of the
I will
various study activities. When agreements are reached on these items, the IPMP
be completed.
I
I
I
6-1
7.0 CONCLUSIONS
The Reconnaissance Study findings indicate there is a potential for
significant storm damages to existing public and private development along three
of the five reaches of the shoreline in the City of Carlsbad. In Reach 1, the area
south of Buena Vista Lagoon and north of the City seawall, storm damages for a
100-year event are estimated to be $3.8 million and average annual equivalnt.
damages are estimated at $138,000. Damages will occur primarily to private
residential and commercial structures which are unprotected or have inadequate
protection, and to the protective features themselves.-
In Reach 3, the area fronting Agua Hedionda Lagoon, storm damages for a
100-year event are estimated to be $2.2 million and average annual equivalent
damages are estimated at $283,000. The vast majority of these damages will
occur to the 2700 foot reach of Carlsbad Boulevard between the inlet and outlet to
the lagoon as it is largely unprotected from storm waves due to the absence of a
substantial protective beach or any other protective feature.
In Reach 5, the box culvert at Encinas Creek is anticipated to be exposed to
average annual equivalent damages of $61,000 per year.
The severely eroded beach conditions are also inadequate along all five
reaches to meet the recreation demands of the area.
Fourteen plans were developed to reduce storm damage potential. These
I alternatives were evaluated based on economic and environmental criteria and
existing policy and guidance defining requirements for Federal interest in shore
I . protection projects. Based upon a thorough evaluation of these alternatives, it has
been determined that the only feasible solutions for a Federal project, Plan 7 and
Plan 14, both groin systems with beachfill, involve providing protection to Carlsbad
Boulevard in Reach 3.
I
In Reach 1, Plan 13 is justified, but most of the benefits are from recreation,
and therefore a Federal project is not being considered at this time. However,
Federal interest in storm damage protection in Reach 1 may be influenced by
I possible shore protection plans in Oceanside and consequently will be reviewed in
the ongoing Oceanside Shoreline Study.
In Reach 5, one project is marginally not economically justified at this time.
The cost for the justified project is to be shared at 65% Federal expense and 35%
local. Based upon Plan 14, a preliminary estimate of Federal and non-Federal costs are
$218,000 per year and $117,000 per year, respectively. Non-Federal interests would be
responsible for maintenance and other local cooperation items.
An Initial Project Management Plan was prepared for the Feasibility Phase of the
study. The study cost is estimated to be $960,000 (with 20% contingencies,
$1,152,000), and take two years and eight-months to complete. Negotiations concerning
study responsibilities, cost sharing, and the Feasibility Cost Sharing Agreement (FCSA) are
Underway. The City has indicated interest in continuing with the Feasibility study, subject
to final negotiations of the IPMP and FCSA, and reviewing of the availability of city funds.
8.0 DISTRICT ENGINEER'S RECOMMENDATION
The Pacific Coast Shoreline, Carlsbad Reconnaissance Study findings show
there are two feasible plans to reduce storm damages and provide incidental
recreation for Reach 3 which are in the Federal interest based on existing policy
and guidelines. The City of Carlsbad has indicated interest in continuing with
these projects including cost sharing in the Feasibility Phase as outlined in the
IPMP.
Accordingly, I recommend that the Pacific Coast Shoreline, Carlsbad Study
proceed into the Feasibility Phase. -
2ntwerp LTC L-' L. Vao
\ &olonel, Corps of Engineers
District Engineer