« PreviousContinue »
85. Extent of local cooperation required.--It is essential to propera maintenance of the project and satisfactory working agreements between the United States and local interests that suitable improve ment districts or other legal authorities be formed to include all the ti areas to be protected in Pajaro Valley and the vicinity of Gileti Before any construction is started, local interests should provide, wit so out cost to the United States, all lands and easements required for the beau project, and give assurances satisfactory to the Secretary of War that can they will maintain and operate the levee systems under regulations along to be prescribed by him, and hold and save the United States free ajero from damages from the construction and operation of the projet works.
86. Local interests should also agree to make, at their own experre, the necessary alterations, relocations, and improvements on and ads penita cent to the proposed right-of-way to permit use thereof for projetos purposes, including relocation of farm buildings, pumping plans, semua irrigation pipe lines, wells, sumps, fences, farm roads, and other to res necessary incidental items; to raise Thurwachter Bridge and of Tres proaches; and to improve the waterway under the Main Stretion of Bridge in Watsonville. Unless satisfactory clearances at the Vanatora Street Bridge are provided or definitely arranged for before constra 1.400. tion of the levee project is started, local interests should pay to the incre United States $46,000 as the estimated cost of special excavatia, ter paving, and other channel works shown at this bridge on enclosure order and described as part of plan A recommended herein, which works i more required on account of the inadequate clearance and channel area itali the existing bridge.
DISCUSSION 87. Flood conditions. - The flood problems in various parts of the sus inve drainage basin are outlined at length in paragraphs 54 to 63, inclusiva bu oby The principal flood problems are here recapitulated with some fuited discussion of related problems in the several areas. 88. In the Carnadero-Llagas Creek and San Felipe Lake regia
, uredi overbank flow follows low swales and depressions between the normal stream channels, merging into a large flood plain extending from the stencia vicinity of Gilroy to San Felipe Lake and Sargent. Along the upper liber reaches of the streams tributary to the upper Pajaro River, especialy defe in the irrigated lands of South Santa Clara Valley, water conservatunturisit is desired by local interests. For this reason, reservoir control of floods would have popular support, possibly as dual-purpose projektuose There are, however, no favorable reservoir sites at which significant ple en reaches bordering the upper Pajaro River, there is a serious drainage the late flood control in this area could be accomplished. In the lower the part problem in the flood plain areas.
The impracticability of attempts 28.600. further spreading of water for flood control in this poorly draira area is indicated by the report that the Pacheco Pass water distrert has been threatened with litigation by land owners in the bottom lands along the upper Pajaro River on account of damages incurred throu complete waterlogging of the ground in this area by releases from its reserrur constructed on Pacheco Creek in 1938. Extensive and drainage is inseparably a part of any plan of improvement in this part of the watershed. In this area, however, extension and enlarge he estim ment of the Carnadero Creek levee project near Gilroy is the odp
92. Pa PANSION
plan of improvement for flood control for which the prospective benefits would be commensurate with the costs.
89. In the San Benito River-Tres Pinos Creek region, bank erosion constitutes the principal flood damage. There is little inundation outside the natural stream beds. These streams carry great quantities of sand and silt which are deposited in the Pajaro River. During the summer months, the presence of San Benito River sand in the Pajaro River is regarded as beneficial by local interests in that it causes delay in the depletion of ground water supplies along the upper Pajaro River. In the winter, the prolonged discharge from the San Felipe Lake area carries much of this sand out of the river into Monterey Bay.
90. In South Santa Clara Valley around Hollister, and also in San Benito Valley around San Juan Bautista, local interests desire reservoirs above all other means of flood control. Investigations have demonstrated that only one site exists at which an effective flood-control reservoir could be constructed. This is just below the confluence of Tres Pinos and Bird Creeks with the San Benito River. Construc-tion of an adequate flood control reservoir at this site, which is not favorable geologically, would cost more than $3,000,000, of which only $1,400,000 is justified by the prospective flood control benefits. То secure water conservation benefits, it would be necessary to build a larger and more expensive dual-purpose reservoir in which water conservation interests would have to pay the large flood-control deficit of more than $1,600,000 in addition to the other development costs. Local interests have failed to agree on either of two reservoir and spreading schemes developed by the Hollister irrigation district since 1925, and there is evident disagreement regarding the distribution of costs and benefits proposed in these previous schemes, one of which was investigated in considerable detail. In view of this situation and the obvious lack of advantage to local interests in joining with the United States in the construction of a dual-purpose reservoir at this site, formulation of a detailed plan for such a reservoir is not considered warranted at this time.
91. Pajaro River, existing levee improvement. -Overbank flow is extensive in Pajaro Valley and causes most of the flood damage. Neither tides nor sand bar formations at the river mouth materially affect flood flows in this reach of the river. Consequently, there is no necessity for attempting to maintain an open river mouth by means of jetties, or otherwise, for the purpose of flood protection. Irrigation is almost universally practiced here, but ground water supplies are ample and appear to suffer only minor depletion during dry cycles. The partial flood protection afforded by the existing levee system in the Watsonville area provides average annual benefits estimated at $28,600. The estimated annual cost of these levees is $14,870 giving an economic ratio for the existing work of 1.92 to 1.0.
92. Pajaro Valley levee project X.-It is estimated that the proposed extensions of the existing levee system in this plan would effect nearly complete protection of most of Pajaro Valley against all floods up to the magnitude of the 1-percent-chance flood in the urban areas and the 2-percent-chance flood elsewhere. The additional average annual benefits expected to accrue under this plan are estimated at $40,600, The estimated annual cost of the proposed additions and extensions is
$35,000, giving an economic ratio of 1.16 to 1.0 for the added benests such and added costs of this project. The degree of flood protection whith ration would be provided by the complete levee system may be expressed s praise about 85 percent of total protection of the entire Pajaro Valley from 0.1 floods of all magnitudes.
93. Pajaro Valley levee project B.—The alternate plan of impronal inte ment in this area would comprise only that portion of the recon- 42 an mended project which would strengthen the existing levees and the re adequately tie them to suitable points to provide positive flood pois of i tection against all floods up to the magnitude of the 1-percent-chave nee the flood. This plan would effect additional average annual benefisson o estimated at $17,100 at an added annual cost estimated at $13,62, lonterer giving an economic ratio of 1.25 to 1. The degree of flood protectination vi which would be provided by the modified levee system may be mposed expressed as about 55 percent of total protection of the entire Pają walce Valley from floods of all magnitudes. The plan contains a very lowel inte undesirable floodway feature at the upstream and downstremidled terminals.
94. Carnadero Creek levee project. The existing levee on Carnadao aprovem Creek was designed to protect the town of Gilroy and was part 43300 rebuilt in 1938 as a Works Progress Administration project. It is reek pro found that this levee is inadequately constructed to resist the largest 3.00 al floods. Strengthening and extending it somewhat would adequater ist are protect the town and some nearby agricultural areas from all floods afinitely up to the magnitude of the 1-percent-chance flood, thereby providing keration additional average annual benefits estimated at $3,100. The estimats w mated added annual cost of the project is $2,570, giving an economic terests ar ratio of 1.20 to 1.0 for the proposed new work. While this plin liver br) would afford nearly complete flood protection for Gilroy and the ad the re agricultural lands between it and the levee, this protection woululades bio amount to only about 25 percent of complete flood protection de represe Carnadero Creek. However, flood damages are not found to be oma Priet sufficiently concentrated elsewhere on the creek or in South Sandis its are on Clara Valley to justify the construction of extended flood-protectie pied the work.
95. Selection of the most practicable plans of improvement.--In vi of the economic justification established above for the extension of the existing levee system to protect most of Pajaro Valley and the fixt ajamo soil that the interests of the community as a whole would be served
hotels by the larger project, it is concluded that project A should be regarded assessm as the most practicable plan of improvement for flood control in Pajaro Valley. This project would adequately meet the desires of local interests in Watsonville and vicinity and receive strong leal tion of Gilroy as the most practicable plan of improvement for fod 99. The di support. The selection of the Carnadero Creek levee for the prote
, ea oration amended
: control in South Santa Clara Valley is based entirely on economie That bination of irrigation and drainage project is found to be economicas mplete pro studies. At this time no other flood control or multi-purpose cinepres of loc irrigation or drainage become more pressing and construction or that justified in the Pajaro Basin. However, in the future, if the needs hieron reservoir storage or other work is undertaken primarily for such catro purposes, then the possibility may develop that some considerationservation, should be given to flood control in connection with such constructin Bieber
stified at t Net printed.
n such a case, flood control would be only incidental to water con
ervation or drainage and the possible benefits to be gained should be appraised at that time.
96. Willingness and ability of local interests to meet the requirements I local cooperation.-In view of the favorable statements made by ical interests at the public hearing (see par. 46 and also appendix 1, p. 42 and 44), it is believed that they are able and will agree to meet
the requirements for cooperation set forth herein. No modificaisions of improvements desired have been submitted by local interests be ince the preliminary examination was held. However, informal discussion of the proposed projects, with responsible local interests in
Ionterey, Santa Clara, and Santa Cruz Counties and in the towns of
roposed plans of improvement for flood control, provided the nonfoederal costs can be equitably allocated to the benefited communities.
ocal interests, at the time of the public hearing, advanced plans that avolved the expenditure of $155,000 of local funds of which about 91,000 was primarily for flood control. In the proposed plans of mprovement, the project first-cost allocations to local interests are 243,300 for the Pajaro Valley project and $6,000 for the Carnadero reek project. Annual costs allocated to local interests amount to 15,100 and $280, respectively, for each project. These increased osts are recognized by local interests. However, local opinion is efinitely in favor of furnishing to the best of their ability such coperation as may be necessary to construct these two flood-control rojects when Federal funds are available after the war. Local aterests are well organized and are represented on the lower Pajaro liver by Monterey and Santa Cruz Counties, the city of Watsonville, nd the recently organized Pajaro soil conservation district, which acludes both banks of the river. The interests on Carnadero Creek re represented by Santa Clara County, the city of Gilroy, and the
oma Prieta soil conservation district. Both soil conservation disricts are organized under California laws. No difficulties are anticiated that would defeat the forming of these two flood-control istricts, each with the necessary authority and ability to fulfill the ooperation requirements of section 3 of the Flood Control Act of 1936 s amended. A resolution was received from the directors of the 'ajaro soil conservation district, indicating that there is a reasonable robability that local interests will organize an effective flood-control nd assessment district on the lower Pajaro River in the vicinity of Vatsonville. A copy of this resolution is presented in appendix Ť.
97. The district engineer finds:
(a) That the construction of works which would meet all the lesires of local interests, as stated at the public hearing, and provide omplete protection from floods in the Pajaro River and its tributaries s not economically justified by the prospective benefits at this time.
(b) That construction of reservoirs in the basin primarily for iood control or as multipurpose projects in combination with water onservation, or with other works for drainage, is not economically ustified at this time. However, in the future, if construction is * Not printed.
undertaken primarily for irrigation or drainage needs, the possibilty may develop that incidental flood-control benefits could be gained through proper cooperation at that time.
(c) That damages from excess water in the lowland area between Gilroy, Sargent, and San Felipe Lake are caused partly by poor drainage and that in some alkaline areas, these damages are oftet alle by substantial benefits from flooding:
the (d) That the most practicable plan of improvement in Papro
Orict Valley would consist of reconstruction and extension of the exisng levee system in the vicinity of Watsonville to provide nearly compare flood protection for the valley (designated plan A) at an estimated first cost of $741,000 and an annual cost of $35,000, and would atird additional flood control benefits evaluated at $40,600 annually,
(e) That the most practicable plan of improvement in South Suta Clara Valley would consist of reconstruction and extension of the existing levee in the vicinity of Gilroy at an estimated first cost of celif $65,000 and a total annual cost of $2,570, and would afford additical,: Th flood-control benefits evaluated at $3,100 annually.
98. The district engineer recommends that the existing lerees in the vicinities of Watsonville and Gilroy be reconstructed and extended eind by the United States at an estimated first cost of $741,000 for the Pajaro Valley levee (plan A), of which $497,700 would be made avalable from Federal funds and $243,300 is allocated to local interess: shin and at an estimated first cost of $65,000 for the Carnadero Creek lesee near Gilroy, of which $59,000 would be made available from Fedralen of funds and $6,000 is allocated to local interests; provided that, pror
2T) to construction, local interests in each of their respective areas:
(a) Provide, without cost to the United States, the required lads mity and easements for construction and maintenance, estimated to astmou $125,000 for the Pajaro Valley project and $4,000 for the Carnadro Creek project. (6) Provide at their own expense on the Carnadero Creek projet
, flowage rights for flooding adjoining lands, estimated to cost $2,00.
(c) Relocate, at their own expense, on the Pajaro Valley projet all existing improvements to lands in the levee right-of-way, estimaid to cost $63,300.
(d) Agree to accomplish, at their own expense, on the Pain Valley project all required modifications in the Thurwachter Brige and approaches, estimated to cost $9,000.
(e) Pay to the United States the sum of $46,000 as the estimated cost of paving special channel transition and other works required is the Pajaro Valley project to enlarge the inadequate clearance under the present Main Street Bridge at Watsonville, or, as an alternsie
, adequately increase the channel capacity at their own expense by means of suitable bridge modifications.
(1) Establish satisfactory arrangements for cooperation with the United States and maintenance of the projects through city, coumi or other suitable authorities.
(9) Give assurances satisfactory to the Secretary of War that they will: Maintain and operate the project works in accordance
Wild the i estima
its affor stimated
pojertest Mitutes a