REPORT OF THE CHIEF OF ENGINEERS, DEPARTMENT OF THE ARMY


Department of the Army,
Office of the Chief of Engineers,
Washington 25, D.C., January 21, 1954

Subject: San Lorenzo Creek,Calif.
To: The Secretary of the Army

1. I submit herewith for transmission to Congress the report of the Board of Engineers for Rivers and Harbors in response to resolution of the Committee on Flood Control of the House of Representatives, adopted May 14, 1945, requesting the Board to review the report on the San Lorenzo Creek, Calif., submitted to Congress on June 8, 1943, with a view to determining the advisability of undertaking improvements for flood control on the San Lorenzo Creek, Calif., at this time.

2. After full consideration of the reports secured from the district and division engineers, the Board recommends the improvement of San Lorenzo Creek in Alameda County, Calif. for flood control to provide for channel improvements, levees, and appurtenant works generally in accordance with the plan of the district engineer and with such modifications thereof as in the discretion of the Chief of Engineers may be advisable; at an estimated cost to the United States of $3,644,000 for construction; provided local interests give assurances satisfactory to the Secretary of the Army that they will (a) provide without cost to the United States all lands, easements, and rights-of-way necessary for the construction of the project; (b) make all necessary vehicular bridge and utility alterations or replacements; (c) contribute 2.6 percent of the actual cost of the channel improvements, levees, and railroad bridge revisions, presently estimated at $96,000, or perform the equivalent thereof in construction of such improvements; (d) hold and save the United States free from damages due to the construction works; (e) maintain and operate the project after completion in accordance with regulations prescribed by the Secretary of the Army; and (f) prevent encroachment on the project channels which might interfere with their proper functioning for flood control.

3. After due consideration of these reports, I concur in the views and recommendations of the Board.

S. D. STURGIS, Jr.,
Major General, Chief of Engineers.


REPORT OF THE BOARD OF ENGINEERS FOR RIVERS AND HARBORS

CORPS OF ENGINEERS, UNITED STATES ARMY,
BOARD OF ENGINEERS FOR RIVERS AND HARBORS,
Washington 25, D. C., September 4, 1953.

Subject: San Lorenzo Creek, Calif.
To: The Chief of Engineers, Department of the Army.

1. This report is submitted in response to the following resolution adopted May 14, 1945:

Resolved by the Committee on Flood Control of the House of Representatives, That the Board of Engineers for Rivers and Harbors, created under sectIon 3 of the River and Harbor Act approved June 13, 1902, be, and is hereby, requested to review the report on the San Lorenzo Creek, Callfornia, submitted to Congress on June 8, 1943, with a view to determining the advisability of undertaking, improvements for flood control on the San Lorenzo Creek, California, at this tIme.
2. San Lorenzo Creek drains an area of 61 square miles in Alameda County, Calif., on the east side and near the southern end of San Francisco Bay. The upper 45 square miles of the basin, above Foothill Boulevard in the town of Hayward, lie in the Coast Range foothills and contain the principal tributaries: Cull, Crow, and Palomares Creeks. These streams form a fan-shaped drainage pattern which in combination with their steep slopes, ranging to over 100 feet a mile, produces rapid concentration of runoff. San Lorenzo Creek is deeply entrenched from the mouth of Palomares Creek, 8.3 miles above the bay, downstream to Foothill Boulevard, mile 5.4. Below Foothill Boulevard, the channel becomes shallower and slopes flatten progressively to less than 10 feet a mile in the lower reaches. The lower 4 miles of the creek, from the vicinity of Bridge Street in Hayward, run along the crest of an alluvial cone. Levees have been constructed between Hesperian Boulevard, mile 2.3, and the bay. Under an emergency work project in 1933, channel clearing and levee work between Hesperian Boulevard and the Southern Pacific coastline bridge, mile 0.7, were accomplished at a cost of $78,880. These improvements have deteriorated through lack of maintenance although some emergency repairs to the levees were made in 1951 and 1952 at a Federal cost of about $22,600. Alameda County, Calif., and local landowners have constructed bank-protection works at several points of severe erosion. The present replacement cost of the works constructed by private interests is estimated at $220,000.

3. The population of the San Lorenzo Creek Basin was about 40,100 in 1950. Principal centers are the town of Hayward and the unincorporated communities of Castro Valley and San Lorenzo Village. Approximately 75 percent of the basin residents work in the large cities of the San Francisco Bay area. The remainder are engaged principally in local service establishments and agriculture. Much of the agricultural land in the lower basin has been converted to residential use and continuation of that trend is assured by the desirability of the area for homesites in connection with the rapid industrial and commercial expansion in the San Francisco Bay area. Two railroads, a Federal highway, and a State highway cross the basin, and a freeway, now under construction, will provide rapid transit to Oakland and San Jose.

4. Rainfall records beginning in 1905 indicate that occurrences of high-intensity rainfall have produced 13 floods on San Lorenzo Creek during the period 1905 to 1950, inclusive. The greatest flood during that period, occurring in February 1925, produced a peak discharge estimated at 6,800 cubic feet per second. Flows concentrate rapidly, reaching a maximum in 3 to 4 hours after peak rainfall. Attendant high velocities cause severe erosion along the stream channel. As the channel capacity diminishes progressively downstream, overflow increases and spreads laterally over the alluvial cone. In certain areas below Lorenzo Avenue, mile 1.8, urban development has been restricted pending remedial measures to alleviate the flood hazard. Several newly developed residential areas are in need of storm drainage but residents of the flood plain oppose any further concentration of storm waters in the presently inadequate natural channel. From a study of topographic features and flood hydrology, 4,400 acres along the main stream and on the alluvial cone are estimated to be susceptible to flood damage. Property in the flood plain has an estimated value of $53,420,000 under market prices prevailing in 1950. A flood similar to that of February 1925 would cause damages of $2,400,000 under present conditions of development. Estimated future average annual flood damages total $180 500.

5. Local interests desire protection from floods on San Lorenzo Creek. They suggest that solution of the flood problem can be found in channel enlargement and improvement, construction of multiple-purpose reservoirs, or a combination of such works. They believe that channel improvements would be justified by the damages prevented and that reservoirs, in addition to the prevention of damages, would provide recreational advantages and increase water supply for domestic and industrial use. The Board of Supervisors, Alameda County Flood Control and Water Conservation District, indicates its willingness and ability to cooperate in a project for channel improvement along San Lorenzo Creek.

6. The district engineer finds that reservoirs would not control floods on San Lorenzo Creek without extensive downstream channel improvements and that the cost of the combination would far exceed the benefits including those from water conservation. He finds that the best plan for flood protection would provide for local improvements along the creek channel to permit safe passage of a peak flow of 9,700 cubic feet per second which is over 40 percent in excess of the estimated peak discharge of the flood in February 1925. Such a flood has a probability of occurrence of only once in several hundred years, The project would consist of channel clearing, revetting the banks, and constructing sills across the streambed as required to prevent erosion and channel degradation from the B Street Bridge, about one-half mile below the mouth of Palomares Creek downstream to Foothill Boulevard; a reinforced concrete lined channel between Foothill Boulevard and a point 1,600 feet below Lorenzo Avenue; and a riprapped channel with confining levees between the latter point and San Francisco Bay. Alteration of bridges at Lorenzo Avenue, Hesperian Boulevard, East 14th Street, and the Southern Pacific Railroad (coastline) crossing would be required and a small farm bridge below Lorenzo Avenue would be abandoned. An existing water main near Lorenzo Avenue bridge would be lowered to clear the proposed channel section. The district engineer notes that the Lorenzo Avenue and Hesperian Boulevard bridges are practically obsolete for present traffic conditions and are to be altered or replaced in the near future. Current plans for these structures are coordinated with plans for the proposed channel improvements. The estimated first cost of the flood-protection project, on the basis of December 1952 prices, is $4,275,000, of which $3,644,000 is Federal cost of construction and railroad bridge revision, and $631,000 is non-Federal, consisting of $535,000 for lands, easements rights-of-way, bridge replacements, and utility alterations, and $96,000 in cash or equivalent construction work. Annual carrying charges are estimated at $165,700 of which $129,000 is Federal, and $36,700, including $12,500 for maintenance and operation and $2,000 for replacements, is non-Federal. Average annual benefits from prevention of future flood damages are estimated at $179,200. Alleviation of the flood hazard to certain areas in the flood plain would permit residential development in those areas and provide a net annual benefit from higher land use estimated at $11,000. An annual benefit of $3,000, equal to the estimated annual cost of two new bridges, is estimated to accrue from replacement of these obsolete structures. Unevaluated benefits would accrue from provision of an outlet for storm drainage systems and from general improvement of the health and morale of the affected communities. The evaluated benefits total $193,200 and the benefit-cost ratio is 1.17. The district engineer concludes that the project is economically justified. However, he believes that, in recognition of the benefits from higher land values, local interests should, in addition to providing normal items of local cooperation, contribute $96,000 in cash or its equivalent in work toward the construction of the project. Accordingly, he recommends adoption by the United States of a project for the improvement of San Lorenzo Creek in Alameda County, Calif., for flood control by construction of the proposed works, subject to such reasonable modification at the time of construction as the Chief of Engineers may find advisable, at an estimated Federal cost of $3,644,000 for construction and $500 annually for periodic inspection of the works after completion; subject to the condition that local interests give assurances satisfactory to the Secretary of the Army that they will provide without cost to the United States the lands, easements, and rights-of-way required for construction of the recommended improvements; modify or replace the existing vehicular bridges at Lorenzo Avenue, Hesperian Boulevard, and East 14th Street, and make minor alterations and relocations of utilities in accordance with plans approved by the Chief of Engineers; contribute $96,000 in cash or its equivalent in constrution work in accordance with plans approved by the Chief of Engineers; maintain and operate the project after completion in accordance with regulations prescribed by the Secretary of the Army; hold and save the United States free from damages due to the construction of the project; and prevent encroachment on the project channels which might interfere with their proper functioning for flood control. The division engineer concurs.

7. Local interests were informed of the nature of the reports of the district and division engineers and afforded opportunity to present additional information to the Board. Careful consideration has been given to the communications received.


VIEWS AND RECOMMENDATIONS OF THE BOARD OF RIVERS AND HARBORS

8. The Board of Engineers for Rivers and Harbors concurs generally in the views of the reporting officers. The improvements proposed by the district engineer constitute the most feasible plan for alleviation of damages from floods on San Lorenzo Creek. They would permit removal of restrictions on desirable urban development in portions of the flood plain and serve incidentally as an adequate outlet for storm systems in newly developed areas, construction of which is now opposed by residents of the flood plain on account of the presently inadequate stream channel. Benefits to be derived from the improvements are in excess of the costs and participation by the United States in the project construction is warranted. The district engineer notes that benefits from increased land values due to removal of development restrictions are primarily local in character and warrant local participation in project construction in addition to the normal provisions for local cooperation. He has determined that a cash contribution of $96,000 or its equivalent in construction work by local interests is equitable in recognition of these benefits. The Board is of the opinion that the recommended contribution is equitable on the basis of present estimates, but in view of possible future fluctuation in price levels, it should be expressed as a percentage of the actual project construction costs when undertaken. The Board believes that the small amount of funds estimated as the annual requirement for periodic inspection after the improvements are turned over to local interests for maintenance need not be authorized for the project. Funds for that purpose can be provided through general authorizations and used more effectively in accordance with present practice.

9. The Board recommends the improvement of San Lorenzo Creek in Alameda County, Calif., for flood control, to provide for channel improvements, levees, and appurtenant works generally in accordance with the plan of the district engineer and with such modifications thereof as in the discretion of the Chief of Engineers may be advisable; at an estimated cost to the United States of $3,644,000 for construction; provided local interests give assurances satisfactory to the Secretary of the Army that they will (a) provide without cost to the United States all lands, easements, and rights-of-way necessary for the construction of the project; (b) make all necessary vehicular bridge and utility alterations or replacements; (c) contribute 2.6 percent of the actual cost of the channel improvements, levees, and railroad bridge revisions, presently estimated at $96,000, or perform the equivalent thereof in construction of such improvements; (d) hold and save the United States free from damages due to the construction works; (e) maintain and operate the project after completion in accordance with regulations prescribed by the Secretary of the Army; and (f) prevent encroachment on the project channels which might interfere with their proper functioning for flood control.

For the Board:

B. L. ROBINSON,
Major General, Chairman.