Olmos Dam was originally constructed in 1925-1927 as part of the City of San Antonio’s early efforts to effectuate a flood control plan for San Antonio at a cost of $1.5 million.
In 1973-1974 the city hired Hensley-Schmidt, Inc., Consulting Engineers, to investigate the structural integrity, stability and carrying capacity of the dam. The findings indicated th at the reservoir would contain a 200-year frequency flood but had stability and erosion problems if tested under certain storm conditions. Modifications to the structure were therefore recommended.
In 1976, the City of San Antonio secured federal participation from the Economic Development Administration (EDA), and the mayor appointed an Olmos Dam task force to provide citizen and organization input to help define the criteria to incorporate into the project.
On completion of the Task Force recommendations and engineering plans, the San Antonio River Authority, as project participant and construction coordinator, bid and awarded the construction contract to Clearwater Constructors, Inc., in March 1979. The project included strengthening and anchoring the dam, modifying the gate operations, providing an emergency spillway, relocating Olmos Drive, providing a pedestrian walkway, and improving Devine Road for a total cost of approximately $10 million.
A subsequent contract was awarded to Hogan Mechanical, Inc., in January 1989. The contract consisted of replacing the original gate hoist operators with new Limitorque operators and controls and installing monitoring instrumentation and controls for these gate operators at the Nueva Street Control Center at a total cost of $335,000.
The gates of Olmos Dam can now be monitored and/or controlled from the Nueva St. Dam Control Room.
The San Antonio River Betterments III Project—Durango Boulevard to Nueva Street was designed and administered by the Authority as part of a six phase project which included the structural modifications to the Arsenal Street Bridge. The betterments III project ties into the Nueva Marina and Dam complex. In addition to the improved flood carrying capacity of a “U” framed channel constructed by the U. S. Army Corps of Engineers, a number of amenities were realized as a result of the betterments III project. These amenities include sidewalks, handicapped access ramps stairways and extensive planting and irrigation was added. This linear greenway along the river ties into the historic Robert H.H. Hugman design river walk in the downtown area to the historic King William District and the nationally recognized Blue Star Art Space to the south.
More specifically the Arsenal Street Bridge repair project renovated an existing historic bridge at a cost of $254,486. The repairs were done by H.B. Zachry Company of San Antonio. The bridge not only had to be structurally reinforced by replacing deteriorated bridge members and fasteners and byresealing the asphalt on the bridge – it also was modified to allow for universal access. Lighting was added to the bridge for added security and the bridge’s appearance was improved by removing the existing deteriorated concrete railing and replacing it with a more historically-sensitive ornamental steel railing and lattice panels. The wooden sidewalk was retained and the existing members were replaced with treated wood planking.
The Betterments III project was administered by the San Antonio River Authority and funded by the City of San Antonio in the amount of $1.3 million. The U frame channel modifications constructed by the U.S. Army Corps of Engineers only allowed for the flood control of the river channel. The amenities were designed to follow the design guidelines as originally conceived and constructed by the original architect of the San Antonio Riverwalk, Robert H.H. Hugman. With the necessary engineering and improved channel completed, the betterments were designed by Ford, Powell, and Carson Landscape Architects and the San Antonio River Authority. These two phases of the six-phase project were complete by November 1987.
Espada Dam and Davis Lake
PROJECT DESCRIPTION: This project, completed in September 1987, consisted of an underground boat repair and storage marina, a leaf gated flood control dam across the San Antonio River, and reconstruction of the Nueva Street Bridge. An elevated control tower on the west bank of the river is now being fitted to serve as the headquarters of the San Antonio River Tunnel control system.
The marina facility was previously located under the old main library building on St. Mary’s Street. The new marina facility is used by the City of San Antonio’s Parks and Recreation Department to support river operations, and provides a docking facility for 20 dinner barges,ten maintenance barges, andtwo ranger patrol boats. A wood shop, sandblast booth, paint booth, and small engine repair shop help in the maintenance of the barges. A fabridam at the entrance to the marina ensures a constant level of water in the marina during flood situations. When the leaf gates drop immediately south of the marina, the fabridam inflates and maintains the water level to prevent the boats from “bottoming out.” Office space and street level parking were also provided as part of this project.
Unlike the Tainter gate that was replaced, thetwo new leaf gates are controlled by automatic level sensors to maintain a constant water level in the downtown river loop. The gates are designed to pass a flow rate at 14,300 cubic feet per second (cfs). The downtown side of the leaf gates are screened by a waterfall effect over the gates. The gate control tower not only contains the tunnel control system but also houses the backup generator for the dam.
The new Nueva Street Bridge provides for an extratwo lanes for traffic with pedestrian walkways on either side. Maintenance vehicles access the river using the circular ramp.
The City of San Antonio paid for all costs associated with the marina while the San Antonio River Authority paid for the balance of the project at a total combined cost of $8.6 million.
Houston to Lexington
Commerce to Houston
PROJECT DESCRIPTION: The labyrinth weir dam project was designed to replace an existing failing double gated structure built in 1973. The 2,000 foot-long labyrinth weir design was conceived in order to accommodate the floodwater in an area only 350 feet wide.
LABYRINTH WEIR DAM: Construction began in November 1993 after an extensive review process by the City of San Antonio Parks and Recreation Department, Planning Commission, Historic and Design Review Commission and Public Works Department, the Texas Natural Resource Conservation Commission, the U. S. Army Corps of Engineers and an adjacent neighbor, Our Lady of the Lake University. The Labyrinth Weir Dam was designed by Brown & Root, Inc. of Houston, Texas. Fernandez, Frazer, White and Associates of San Antonio, Texas did the landscape architectural design.
The $2.8 million construction contract was built by Shannon-Monk, Inc. of San Antonio, Texas. The costs were shared by the City of San Antonio (which contributed $1.2 million) and the San Antonio River Authority, through Bexar County Contract (which contributed $1.6 million). The above costs include design, right-of-way, construction, and administration for the project.
The project was completed in April 1995 and features a 2,000-foot fixed labyrinth weir flood control dam with a 10-foot depth at the dam, maintenance and siltation removal access ramps, improved security lighting around the perimeter of the dam and 19th Street bridge, sidewalks and improved landscape amenities to tie into the existing park space surrounding the project. The dam has a 100 year Q of 18,500 with a design depth of 1.9 feet over the spillway. Approximately 11,800 cubic yards of concrete were used to construct this dam.
PROJECT DESCRIPTION: The San Antonio River was the focal point and life line of the early Spanish missionaries and colonists. The missions were in fact located in close proximity to the San Antonio River because it was the last source of water before moving into the great Chihuahua desert to the south. Mission San Juan Capistrano was one of the five colonial missions established along the San Antonio River. The Spaniards and the Native Americans built a dam and acequia to divert fresh water to the mission and to irrigate mission fields. Water flowed in the acequia for over two hundred years and was still used to irrigate pecan orchards long after the secularization of the mission when a realignment and channelization project for flood control stopped the flow of water. The San Juan Acequia was also eroded by increased flood water flowing down the Asylum and No Name Creeks, causing a breach in the acequia as it crossed the creeks. The purpose of this project was to restore the flow of water down the acequia and to repair the acequia where it crossed the creeks. Restoration of the flow of water in the acequia satisfies the oldest water right in the State of Texas with a priority date of December 31, 1731.
The San Juan Pump Station can supply 21 cfs of flow to the San Juan Acequia and 5 cfs to the Symphony Lane Neighborhood. Symphony Lane is located along an old bend of the river and also was isolated as a result of the channelization project. The pump station consists of two48-inch 6.5 cfs screw pumps and one 60-inch 13 cfs screw pump. The screw pumps lift water to the San Juan Acequia and the west side of the river for the Symphony Lane Neighborhood. The pump station can be programmed to deliver variable amounts of water at various pumping schedules. Automatic shut down of the pumps occurs when the water elevation drops to five feet above the diversion dam (elevation 545) during flood conditions.
The Asylum and No Name Creeks portion of the project provides improved flood control, erosion control and newly constructed earthen berms to improve the flow of flood water as it flows of the acequia.
The $6.7 million project was built by Bryan Construction Company, Inc. of Bryan, Texas and was completed in the summer of 1994.
The San Antonio River has a new, modern flood control system in downtown San Antonio. The new system will be much more convenient for all city personnel involved with the operation and maintenance of the flood control gates.
Gates #3, #4 and #5 were installed in 1929 as part of the River Loop bypass channel construction. Gate #3 is just north of Commerce Street and is on the northern intersection of the River Loop and the main channel. Gate #4 is just north of Villita Street and is on the southern intersection of the River Loop and the main channel. Gates #3 and #4 had previously worked in concert to isolate the River Loop from the main channel’s flood water. Gate #5 is just south of Nueva Street on the main river channel. Gate #5 is the gate that controls the water’s elevation in the river’s main channel and the River Loop during normal operation.
With the replacement of Gate #5, the fire department will no longer be required to monitor and regulate the gate during inclement weather. Gate #5 now automatically maintains a constant water elevation upstream, eliminating the need to totally drain the main river channel during a moderate rainfall event.
While Gate #4 is not a constant level gate, it has been changed from a manually-operated gate to a semi-automatic operation. This means that if the sensor in the main flood channel indicates a water elevation that is too high for the river loop, Gate #4 will close completely, protecting the River Loop from flooding while the high water problem in the main river channel is being resolved. Conversely if the sensor in the main channel indicates a water elevation too low for the River Loop area, Gate #4 will raise to the weir setting. This will allow the River Loop to continue operating at the normal water elevation while pouring water into the main river channel. However, Gate #4 will not automatically lower after it has been engaged at either of these settings. It can only be lowered after a visual inspection to ensure that the situation causing the operation has passed.
With new Gates #4 and #5, the use of Gate #3 should be greatly decreased. Gate #3 will only be closed should Gate #5 malfunction and not maintain a constant water elevation in the main river channel.
Five Points Area Construction
The San Pedro Creek flood diversion tunnel is approximately 6,000 feet long with a finished inside diameter of 24 feet, 4 inches lined with precast concrete segments. It commences near the Interstate 35-Interstate 10 interchange, between N. Santa Rosa Street on the west and Camaron Street on the east, where an intake approach channel is constructed (See Figure 2 for route). The tunnel inlet shaft is constructed downstream of the approach channel and is 24 feet by4 inches in diameter dropping approximately 119 feet to the tunnel invert. The tunnel outlet shaft is 35 feet in diameter and contains embedded piping for dewatering facilities. One (1) 18-foot diameter maintenance shaft, two (2) 4-foot diameter ventilation shafts and two (2) 12-inch diameter hydraulic instrumentation shafts are provided at intervals along the tunnel length.
The tunnel alignment between Interstate 35 and Guadalupe Street follows the alignment of San Pedro Creek adjacent to an area of small industrial/commercial buildings.
An 18-foot diameter maintenance shaft is located approximately 220 feet north of West Houston Street at San Pedro Creek. Two (2) 4-foot diameter ventilation shafts are located approximately 100 feet south of Salinas Street at San Pedro Creek and approximately 100 feet north of East Durango Boulevard at San Pedro Creek, respectively.
The tunnel outlet shaft is located north of Guadalupe Street on the west side of San Pedro Creek. Adjacent to the site are S.X. Callahan, Inc., an automotive hardware outlet store and Richter Bakeries, Inc. On the east side of San Pedro Creek is a railroad yard. San Pedro Creek is located in a concrete channel with vertical walls at this location. A portion of the existing channel wall on the west side is removed to accommodate the ramp structure.
The tunnel inlet, outlet and maintenance shafts were constructed by conventional methods. The tunnel was constructed using a tunnel boring machine (TBM). The TBM was lowered through the outlet shaft in sections and assembled underground. The TBM bored the tunnel going upstream and in August 1989, the TBM was removed in sections through the tunnel inlet shaft. Excavated materials were removed through the tunnel outlet structure and transported to a disposal site. The tunnel became operational in June 1991.
A subsequent San Antonio River Authority contract added additional pumping capacity for tunnel recirculation. Construction of this phase was completed in June 1997.
The San Antonio River flood diversion tunnel is approximately 16,200 feet long with precast concrete segmented liners of 24 feet by4 inches inside diameter. The tunnel starts near Josephine Street where the tunnel inlet shaft is constructed adjacent to the existing channel (See Figure 2 for the tunnel’s route). The inlet shaft is 24 feet by4 inches in diameter dropping approximately 118 feet to the tunnel invert. The tunnel outlet shaft near Lone Star Boulevard is 35 feet in diameter and contains embedded piping for dewatering facilities. Two (2) 18-foot diameter maintenance shafts, three (3) 4-foot diameter ventilation shafts and two (2) 12-inch diameter hydraulic instrumentation shafts are provided at intervals along the tunnel length.
The tunnel intake shaft is located between West Josephine Street and Highway 281 North (See Figure 3 for profile of the San Antonio River Tunnel). Borden’s Dairy is on the west side of the river and a small manufacturing plant is located on the east side of the river.
The tunnel generally follows the San Antonio River alignment between Josephine Street and 13th Street. The tunnel alignment between 13th Street and Brooklyn Avenue is west of the river.
A 4-foot diameter ventilation shaft is located near the Camden Street bridge on the north bank of the river. An 18-foot diameter maintenance shaft is located at Brooklyn Avenue and the river.
The tunnel, between Brooklyn Avenue and the junction of North and South Alamo Streets, passes under severaltwo tothree stories high commercial/industrial type structures. The largest structure in this reach is the 15-story Valero Energy Building at Avenue B and 6th Avenue. The tunnel passes under the parking lot of this building.
A 4-foot diameter ventilation shaft is located at the edge of the Broadway Avenue pavement between Third and Fourth Streets.
The tunnel, between North Alamo Street and South St. Mary’s Street, follows the alignment of South Alamo Street. Alamo State Park and the Alamo, Hemisfair Plaza, LaVillita, Paseo del Rio, the Convention Center and Beethoven Hall are located along this reach of the tunnel. The larger structures along this reach are the 8-story Gibbs Building, the 20-story Hilton Hotel and the 7-story Four Seasons Hotel.
An 18-foot diameter maintenance shaft is located approximately 400 feet south of Durango Boulevard adjacent to the fire station on Water Street.
The tunnel alignment, from the junction of South Alamo Street and Camargo Street, continues in a southerly direction to South St. Mary’s Street then continues along South St. Mary’s Street to the Eagleland Street intersection. From Eagleland Street, the tunnel alignment follows a southwesterly direction to the San Antonio River under the Southern Pacific Railroad viaduct.
The tunnel alignment along this reach is under small commercial/industrial/residential buildings ofone ortwo stories. A 4-foot diameter ventilation shaft is located north of Pereida Street and 20 feet east of South St. Mary’s Street.
The tunnel outlet structure is located south of the Southern Pacific Railroad, north of Lone Star Boulevard and west of the river.
Construction for the San Antonio River Tunnel Inlet Structure started in September 1993. The contractor, BRH Garver, constructed a water feature, park facilities, betterments, channelization and tunnel recirculation for the flood control tunnel. A pumphouse was also constructed, mostly below ground level to operate pumps to recirculate tunnel water to supplement river flow during the summer months. This project is a coordinated effort between the U.S. Army Corps of Engineers and the San Antonio River Authority. The Corps bid the project on behalf of the River Authority. Total construction cost was $16.9 million.
Notice to proceed for the San Antonio River Tunnel Outlet Structure was given to Martin K. Eby Construction Company, Inc. on May 5, 1995 and the project was completed in December 1997 at a total cost of $10.1 million. This project includes a water feature, a galvanized steel trellis over a pedestrian plaza, park facilities, betterments, channelization and a gatehouse for tunnel water recirculation. The project was jointly administered by the U.S. Army Corps of Engineers and the San Antonio River Authority.
|Scheduled:||Start of Project:||(Shafts) November 1987 (Tunnel) September 1989|
|Became Operational:||August 1996|
|Tunnel Inlet and Outlet Complete:||December 1997|
|Instrumentation and Controls Complete (Projected):||1999|
|Size:||Approximately 16,330 feet of 24 feet by4 inches diameter inverted siphon at a depth of approximately 140 feet.|
|Estimated Total Project Cost (Tunnel, Inlet and Outlet):|
|Federal Cost (approximate)||$84,400,000|
|Local-City of San Antonio & San Antonio River Authority (approximate)||$27,000,000|
|Total Project Cost:||$111,400,000|
|Location:||Inlet at U.S. Highway 281 near East Josephine Street: east bank of the San Antonio River. Tunnel is built under existing public right-of-way and the San Antonio River for a major portion of the tunnel route. Outlet at San Antonio River and Lone Star Boulevard: west bank of the San Antonio River across from Lone Star Brewery and Roosevelt Park.|
|Designed:||To carry 6,700 cfs of peak rainfall runoff and bypass 1,100 cfs to the San Antonio River.|
|Inlet Structure:||As constructed by the BRH Garver Company, the Inlet structure directs water from the San Antonio River into the tunnel and consists of a 120 foot-long intake ogee weir and apron structure 63 feet long with cast-in-place roof and trash racks. A sloped apron collects water behind ogee weir and then transitions to a 25-foot diameter vertical shaft leading to the 24-foot diameter tunnel. The River Authority is providing landscaping, an aerating water feature, disinfection and recirculation pumps to recirculate the base flow of the San Antonio River for water quality enhancement.|
|Outlet Structure:||As constructed by the Martin K. Eby Company, the Outlet structure directs discharge from the tunnel shaft to the San Antonio River and measures 230 feet across the front; 50 feet across the rear and 94 feet from front to rear. The outlet consists of cantilevered retaining walls, trash racks and grated roof. The tunnel shaft transitions from a 24-foot diameter shaft up to a 35-foot diameter shaft at the base slab of the outlet. Water features are included to enhance the appearance of the outlet structure.|
|Tunnel:||The Ohbayashi Corporation excavated the tunnel by tunnel boring machine. The diameter of tunnel is 24 feet, 4 inches using pre-cast concrete segmented lining.|
|Maintenance Shafts:||Two (2) maintenance shafts (each 18 feet in diameter) are installed over the tunnel at the following locations: #1 at Brooklyn Street at San Antonio River; #2 at Durango Boulevard at Alamo Street.|
|Ventilation & Instrumentation Shafts:|
|Three (3) ventilation shafts, 4 feet in diameter, are located at appropriate intervals to ventilate the tunnel during maintenance.|
|SAN PEDRO CREEK TUNNEL||SAN ANTONIO RIVER TUNNEL|
|24 feet||24 feet|
Depth from surface to invert of tunnel
|119 feet||118 feet|
|35 feet||35 feet|
Depth from surface to invert of tunnel
|144 feet||144 feet|
|4 feet||4 feet|
Depth from surface to top of tunnel
|118 feet and 117 feet||130 feet, 126 feet and 123 feet|
|18 feet||18 feet|
Depth from surface to top of tunnel
|116 feet||133 feet, and 124 feet|
|Hydraulic Instrumentation Shafts:|
|12 inches||12 inches|
Depth from surface to top of tunnel
|118 feet and 110 feet||120 feet, and 123 feet|
|24 feet by4 inches||24 feet by 4 inches|
Length to centerline of shafts
|5,985.05 feet||16,224.37 feet|
Average depth from surface to invert
|142 feet||151 feet|
|Capacity Flow of Tunnel||4,600 cfs+||6,700 cfs+|
|Water Flow Velocity||10 ft/sec+||15 ft/sec+|