THE LAUREL STREET GRADE SEPARATION PROJECT IN COLTON, CA: DRAINAGE CHALLENGES AND SOLUTIONS

Joseph Sawtelle, PE Project Engineer

TranSystems 6 Hutton Centre, Suite 1250

Santa Ana, CA 92707 714-708-6881

jwsawtelle@transystems.com

Courtney Endo, PE, TE Engineer

TranSystems 6 Hutton Centre, Suite 1250

Santa Ana, CA 92707 714-708-6895

caendo@transystems.com

Carl Sosa Senior Engineer

TranSystems 6 Hutton Centre, Suite 1250

Santa Ana, CA 92707 714-708-6873

cdsosa@transystems.com

4,237 Words ABSTRACT

The Laurel Street Grade Separation project in Colton, California, proposed lowering Laurel Street underneath six existing BNSF tracks. The project team coordinated closely with BNSF regarding construction of a three track shoofly and to minimize right-of-way impacts and impacts to the existing six-signal signal bridge.

The most unique challenge faced by the project was the high volume of storm water runoff and tributary flows. Before the project, this location suffered from a significant drainage problem. Lowering Laurel Street 26 feet created a “low point,” requiring creative solutions to these drainage issues. To prevent ponding in the newly constructed roadway, a 300-foot long double 14’ x 7’ Reinforced Concrete Box will be constructed underneath Laurel Street to store the storm water runoff. Secant pile walls along lowered Laurel Street are required to avoid impacting adjacent properties, constructed around the pumping facility for structural integrity. The facility will be constructed above the roadway and pump the runoff vertically 47 feet, before conveying the accumulated runoff via a force main, a third of a mile, to a new detention basin.

A metering device within the detention basin will restrict the outflow into an existing 84” storm drain connected to a Flood Control Channel. This solution does not overtax the existing storm drain, nor does it outlet directly into the existing Channel, eliminating impacts to the local flood control district drainage system. Innovative problem solving yielded an all-inclusive solution to mitigate the storm water runoff that is safe, environmentally sensitive, and cost effective.

INTRODUCTION

The City of Colton has a long history with the railroads. In 1875 the Southern Pacific Railroad (SP), now part of the Union Pacific Railroad (UPRR), began constructing the final transcontinental leg of the Southern Pacific Railway through Colton on the way to Los Angeles, which gave them a monopoly on the Southern California area. In 1882 the California Southern Railroad (CS), now part of Burlington Northern Santa Fe Railway (BNSF), reached Colton with a need to cross the UPRR tracks. This created one of the most intense Frog wars in railroad construction

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history with a showdown between the Governor and Virgil Earp. Virgil Earp was hired by SP to protect the tracks and prevent the construction of the CS tracks that would cross them. The Governor had to intervene with a court order to allow the crossing to be built. Until its recent grade separation in 2013, the Colton Crossing was one of the busiest at-grade railroad crossings in the United States. The project location is located about one mile north of the Colton Crossing along the BNSF Railway.

FIGURE 1: Project Location Map

The Laurel Street Grade Separation Project location is significant due to the high volume of rail traffic and the goal to create a quiet zone within Colton city limits. Approximately 90 trains per day utilize the six existing tracks at this crossing and a seventh track is scheduled to be added by Metrolink. It is the final location needed to be modified to allow completion of the City’s quiet zone, and the existing six tracks at the Laurel Street location prevent the construction of at-grade quiet zone crossing gates, thus requiring grade separation. This project, in conjunction with other proposed railroad improvements including the Colton Crossing, the closure of the “H” Street and “E” Street crossings, and the installation of quiet zone improvements at the Valley and Olive crossings, will result in a quiet zone corridor along the BNSF railroad line within the City of Colton.

PROJECT DESCRIPTION

The project was proposed by the San Bernardino Associated Governments (SANBAG), in cooperation with the City of Colton, Burlington Northern Santa Fe Railway (BNSF), and Union Pacific Railroad (UPRR). The project objectives are to separate vehicular traffic from rail traffic in order to establish a train horn quiet zone within the city limits of Colton, enhance safety, improve local traffic circulation, and reduce air quality emissions. The project site is located approximately 1.1 miles north of Interstate 10 (I-10) and 1.4 miles west of Interstate 215 (I-215), in the City of Colton.

Several alternatives were considered in an attempt to minimize right-of-way impacts, maintain access for property owners, and maximize the cost/benefit ratio. Only the Laurel Street Undercrossing alternative was found to be viable as all of the other alternatives would have right-of-way, constructability, cost, or schedule impacts that would be prohibitive. The selected undercrossing alternative includes the following improvements:

• Reconstruct Laurel Street by lowering the profile to pass underneath the six existing BNSF tracks.

• Construct retaining walls along both sides of Laurel Street.

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• Construct a bridge for the six existing BNSF tracks over lowered Laurel Street.

• Eliminate the North 8th Street connections to Laurel Street by constructing cul-de-sacs for North 8th Street both north and south of Laurel Street.

• Construct a bridge connecting the North 8th Street cul-de-sac on the west side of the tracks to the loading dock area for the property in the southwest quadrant to provide truck access.

• Modify access to nearby businesses.

• Construct a 300-foot long double 14-foot x 7-foot RCB to store the collected runoff.

• Construct a pumping facility connected to the double 14-foot x 7-foot RCB.

• Construct a new detention basin north of Miller Drive.

• Construct a new force main to convey collected flows from the pumping facility to the new detention basin.

• Relocate utilities that are in conflict with construction of the grade separation.

The railroad bridge will accommodate the existing six BNSF tracks and Laurel Street will be lowered 26 feet as an undercrossing. Additionally, the abutments for the future Metrolink crossing east of the existing BNSF tracks are included.

Miller Drive will be lowered approximately two feet to match the lowered grade at the Laurel Street intersection. Both the northwest and southeast quadrants of North 8th Street will be reconstructed into a cul-de-sac and will no longer connect to Laurel Street. Due to the lowering of Laurel Street, a number of existing driveways will be modified. Two residential driveways on the south side of Laurel Street, approximately 330 feet and 430 feet east of the existing tracks, will be eliminated requiring the full acquisition of the residential property they serve. This was the only full acquisition required for this project. Access will be maintained for all remaining businesses and residential properties. A new bridge is proposed to connect the North 8th Street cul-de-sac in the northwest quadrant to the loading dock for the property in the southwest quadrant in order to maintain truck access.

Laurel Street will be reconstructed with two 12-foot wide lanes with eight foot wide shoulders, six foot wide parkways, and five foot wide sidewalks on both sides. The parkway in the northwest quadrant was eliminated and replaced with an eight foot sidewalk wide. Figure 2 below shows the profile, project layout, and a typical cross section of Laurel Street.

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The proposed improvements will require new permanent right-of-way in the form of acquisitions, access easements, utility easements, and drainage easements. In addition, temporary construction easements (TCEs) will be required. In order to minimize impacts to existing property owners, top down construction and secant pile walls will be utilized. Secant pile foundations will be used for the bridge abutments as well to minimize impacts to the existing tracks. Top down construction involves drilling piles at-grade, constructing the abutments and bridge superstructure on the piles and earth without falsework, then digging out the street underneath.

For the BNSF underpass bridge, both pre-cast girders and cast-in-place options were compared. Pre-cast girders were selected because they are faster to construct and will result in shorter closure time for Laurel Street by approximately 45 days. The secant pile walls will consist of Cast-In-Drilled Hole (CIDH) piles placed with space left between the CIDH piles that is slightly less than the CIDH pile diameters. Then a parallel but slightly offset line of smaller CIDH piles will be added to fill the space between the larger piles. Finally, a six inch wide fascia wall will be constructed in front of the CIDH piles. All of the voids between the piles and the fascia wall will then be filled in with concrete, creating a continuous wall. This method is very effective for minimizing right-of-way impacts as well as for areas with space constraints.

Based on the Memorandum of Understanding (MOU) that was executed between the City of Colton, SANBAG, UPRR, and BNSF, ten percent of the project cost would be the responsibility of BNSF. This involvement, as well as the significance of this location for the BNSF commercial freight corridor, resulted in BNSF coordination being a critical component of the successful completion of this project.

A three track shoofly was agreed upon for the closure of the six tracks during construction. The shoofly will be constructed to the east, adjacent to the existing tracks, to allow construction of the bridge underpass. Five alternatives for construction of the railroad bridge were developed and discussed with BNSF in an effort to maximize safety and minimize any negative impacts to the railroad:

Option A: Bridge construction occurs in four phases with three active tracks at all times. Option B: Bridge construction occurs in two phases with three active tracks at all times using one shoofly

track. Option C: Bridge construction occurs in two phases with four active tracks at all times. Option D: Bridge construction occurs in one phase with three active tracks at all times. Option E: Bridge construction occurs in two phases with three active tracks at all times using two shoofly

tracks.

These options were presented to BNSF Railway and that coordination resulted in the selection of Option D as the preferred option due to increased safety and reduced cost and schedule impacts. Option D will construct the bridge in one phase and maintains a minimum of three tracks active at all times utilizing either the three track shoofly that will be constructed as part of this option, or the existing tracks before they are closed for construction. This option also eliminates the need for the contractor to work between active tracks. Laurel Street will be closed during the construction of the shoofly and the top down bridge construction, with a detour route provided using C Street to the south around the section of Laurel Street that will be closed. For the second phase of construction, after the new bridge underpass has been completed, the tracks will be re-constructed to their original alignment and the shoofly will be removed. The remaining portions of Laurel Street including the new access bridge and the retaining walls will then be completed.

Additionally, there was an existing six-track signal bridge located approximately 100 feet south of the project site. Either the signal bridge would need to be permanently relocated, temporarily relocated, or not impacted by the project. The final solution was to move the signal bridge north approximately a quarter of a mile. BNSF completed all of the signal plans.

The proposed lowering of the Laurel Street profile by 26 feet created a number of utility relocation challenges. A total of nine utility companies were impacted by the project. A 12-inch City of Colton water line, AT&T telecommunications line, a Sprint telecommunications line that runs parallel to the tracks, and a City of Colton electric line which is proposed to be relocated under the tracks by jack and bore. Originally, the proposed shoofly was to cross the existing Sprint line and the line was to be protected in place, then relocated to its permanent location within the BNSF bridge fascia beam, however the line was too shallow to protect in place. As a result, the

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line will be lowered underneath the walls prior to construction. The relocation work will require a 900-foot long directional bore with a maximum depth of 90 feet. An additional challenge with all utility relocations is to maintain service to the greatest extent possible during construction. Significant utility coordination and analysis of various options were completed in order to develop the optimal utility relocation plan.

EXISTING DRAINAGE FEATURES

The largest challenge that required an innovative solution was how to properly manage drainage for the project. A lack of existing drainage systems within the rail corridor along with existing flooding issues provided the basis for this challenge. Drainage runoff within the project limits generally flows north to south on slopes ranging from moderate to flat. Lowering Laurel Street under the tracks would create a sump condition which would cut off the existing surface flow of water to the south along the tracks. An existing earthen detention basin is in the northeast quadrant of the project site and regularly overflows during storms (shown in Figure 3). This creates a hazard to rail operations, pedestrians and vehicular traffic.

Not only is the ultimate drainage condition a concern, but also the temporary drainage during construction once the existing detention basin has been removed since construction is anticipated to extend into at least one rainy season. Temporary drainage facilities were provided with provisions in the contract to provide a “Temporary De-Watering” system consisting of generator driven portable submersible pumps and hoses to remove any temporary standing water.

FIGURE 3: Existing Earthen Basin Overflowing After Rain

The project is located within the Upper Santa Ana River Watershed and the two existing major drainage systems within the area are the Citrus Street Storm Drain to the north and the Lytle-Cajon Channel to the northeast. The

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Citrus Street Storm Drain is an 84-inch reinforced concrete pipe (RCP) north of the project limits that flows from west to east draining into the Lytle-Cajon Channel and falls under the jurisdiction of the City of Colton. The Lytle-Cajon Channel is a concrete lined rectangular open channel that flows from north to south, and is under the jurisdiction of the San Bernardino County Flood Control District (SBCFCD). The system discharges into the Santa Ana River just over a mile south of the project area. Drainage from area north of Citrus Street is gathered by catch basins along Citrus Street, Pennsylvania Avenue, and North 8th Street, which connects to the existing Citrus Street Storm Drain.

Laurel Street’s existing condition is crowned at the centerline and has existing high points both east and west of the railroad tracks with the existing western high point located near the intersection of 6th street. Flows are currently contained within the existing curb and gutter. Westerly flows from the high point are picked up by catch basins connecting to a 30-inch RCP at the intersection with Pennsylvania Avenue, draining south along Pennsylvania Avenue. The existing eastern high point is located near the intersection of the southern leg of North 8th Street. Existing flows from the high point drain towards the east and are gathered by catch basins at the intersection of La Cadena Drive and Bordwell Avenue, connecting to a 4-foot x 1.25-foot RCB, draining southerly along Bordwell Avenue. Runoff along intersecting streets and alleys north of Laurel Street drains southerly to Laurel Street, and runoff along intersecting streets and alleys south of Laurel Street, drains towards the south.

The Laurel Street runoff between the two existing high points drains to a low point at the intersection of Laurel Street and the railroad tracks. There are no catch basins or storm drain facilities along Laurel Street between these two points. Runoff from the low point on Laurel Street drains southerly along the railroad tracks. Runoff within the railroad right-of-way is gathered by drainage swales flowing from north to south. A high point along the north side of Laurel Street restricts some flows from crossing Laurel Street which are then collected in an earthen basin on the east side of the tracks north of Laurel Street. The remaining flows along the railroad tracks are conveyed in drainage swales from Laurel Street to the south. The properties along the north side of Laurel Street drain towards the south to Laurel Street.

All the properties along the south side of Laurel Street drain towards the south with one exception, the warehouse facility and paved loading dock located just west of the railroad tracks. Roof runoff from a portion of the warehouse drains toward a low point within the loading dock area with two private catch basins that connect to a “sludge pump.” All runoff gathered by the “sludge pump” is pumped through an existing four inch drain that outlets along Laurel Street and continues into the railroad right-of-way.

North 8th Street is crowned at the centerline, between Citrus Street and Laurel Street. Runoff along North 8th Street drains south along the curb and gutters to Laurel Street. Miller Drive and Laurel Street to the east of the project are both crowned at the centerline. Miller Drive runoff drains south to Laurel Street and then continues along Laurel Street to the existing storm drain systems at the intersection of Bordwell Avenue and La Cadena Drive. Figure 4 shows the drainage areas and the proposed drainage improvements below. Treating the sheer volume of water that will be collected as a result of this project was a significant challenge that, due to the limited right-of-way, required innovative solutions.

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FIGURE 4: Drainage Areas and Proposed Improvements

PROPOSED DRAINAGE FEATURES

The City of Colton approved the 25-year return frequency storm as the basis for design on this project, which is consistent with the design of the drainage systems along Citrus Street. The Rational Method Equation was utilized to analyze the existing and proposed hydrologic condition as the total drainage area is less than 640 acres. The Advanced Engineering Software (AES) was used to model the hydrology. It was assumed that the land use for both existing and proposed conditions were the same, industrial/commercial/residential with an associated impervious percentage of 90 percent.

The proposed project will alter some of the existing flow patterns within the project limits. The drainage was divided into three distinct drainage area boundaries that will be created by the project. The three boundaries are:

Drainage System to Pumping Facility: Those areas that will drain to the pumping facility, with a peak runoff of 73.1 cubic cfs.

Drainage System to Bordwell Ave: Those areas that will drain into the Bordwell Avenue Storm Drain System with a peak runoff of 14.8 cfs.

Drainage System to Citrus St.: Those areas that will drain into the 84-inch Citrus Street Storm Drain with a peak runoff of 15.6 cfs.

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PROPOSED DRAINAGE SYSTEM

The proposed drainage system will collect the highest amount of runoff within the project limits. Drainage of the low point along the lowered profile of Laurel Street will require a pumping facility to remove accumulated runoff and prevent flooding of the lowered street. The pumping facility will be located in the northeast quadrant of the Laurel Street Undercrossing. Several new catch basins for runoff collection will be constructed along the lowered profile grade of Laurel Street, along the North 8th Street cul-de-sac, and behind the new retaining wall in the northwest quadrant. These catch basins will be connected to a proposed “Collector-Storage” system which will consist of a double 14-foot x 7-foot RCB closed at both ends with openings in the center wall to allow runoff to equalize within. The double RCB will be 300 feet in length yielding nearly 60,000 cubic feet of storage space for the runoff. This double RCB, almost 440,000 gallons in size or 70 percent the size of an Olympic sized swimming pool, will be constructed underneath Laurel Street to store the water until it can be lifted to the pumping facility.

Runoff from the drainage areas behind the northern retaining walls will be conveyed into the double RCB via pipes crossing over the wall. The RCB will collect and store peak storm flows before conveying the flows through three 36-inch pipes that connect the RCB to the pumping facility. The pumping facility will include three vertical turbine pumps that will lift the collected runoff approximately 50 feet. After being conveyed to the pumping facility, the water will need to be moved off site. The decision was made to use an existing storm drain system to outlet the water into the Lytle-Cajon Channel. By utilizing the existing storm drain system, environmental coordination and coordination with the regional water quality control board would not be necessary. However, the volume of water is anticipated to far exceed what could reasonably be added directly, unmetered, to the existing storm drain system. As a result, a solution needed to be devised that would slow the rate at which the runoff would enter the existing storm drain system. The solution with the fewest impacts to the project is the construction of a detention basin to store the water and slow its introduction to the 84-inch existing Citrus Street storm drain.

Due to the right-of-way constraints and the volume of water that must be detained, determining a location where a new detention basin could be constructed was another challenge. A location was found approximately one third of a mile north on land that was partially owned by BNSF and leased by Metrolink and by a private owner. The exact area of the basin was coordinated with Metrolink to ensure it would not impact their future expansion plans for their maintenance facility. A triangular basin was designed that will be approximately 40,000 square feet and five and a half feet deep. Security fencing around the basin will be provided around the basin to mitigate safety concerns of potential drowning during heavy rain storms. The runoff will be pumped up Miller Street from the pumping facility to this detention basin through a 24-inch force main. Flows will be stored in the detention basin then conveyed through the “metering device” into the Citrus Street 84-inch RCP storm drain.

In addition to the design of a system that would be able to meet the drainage needs of this project, multiple techniques will be employed to reduce the volume of water running through the pumping facility. One of the most efficient techniques is to divert runoff into existing systems whenever possible. This technique has minimal cost and schedule impacts to the project while maximizing benefit.

Along the eastern side of the project, runoff is collected along Miller Drive. In order to minimize the runoff to the pumping facility, this runoff will be diverted to the east along Laurel Street to Bordwell Avenue. A series of catch basins at the northwest corner of Miller Drive and Laurel Street will collect this runoff in a 24-inch storm drain pipe, diverting the runoff to existing storm drains at Bordwell Avenue, thereby utilizing an existing system to reduce the impact to the pumping facility.

In order to minimize the runoff to the pumping facility, new catch basins along North 8th Street will collect flows, and channel them directly into the existing Citrus Street 84-inch storm drain. This existing system is comprised of catch basins and an existing 84-inch reinforced concrete pipe (RCP) which outlets into existing Lytle-Cajon Channel. By utilizing the existing system, this reduces the impact on the proposed pumping facility without constructing an additional drainage system.

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CONCLUSION

The drainage and other challenges faced by this project were unique and required extensive study and coordination with all associated agencies and project stakeholders including BNSF, Metrolink, the City of Colton, and the San Bernardino Associated Governments. In order to address each separate challenge, several study alternatives were required to develop cost effective and viable solutions that all project partners could agree upon. An important component of this project was drainage and effectively managing 104 cfs of runoff which needs to be collected and conveyed away from vehicular, pedestrian, and rail traffic in a safe and environmentally sensitive manner.

Development of an innovative drainage solution that efficiently meets the needs of this project was achieved through a combination of methods. These methods include:

Utilization of existing systems

Construction of a large detention system underneath the undercrossing to store runoff

Construction of a pump station and a force main that is a third of a mile long to convey that water to a 40,000 square foot detention basin

Implementation of a “metering device” to control output from the detention basin to an 84-inch RCP draining to Lytle-Cajon Channel

Utilizing existing drainage systems will allow the reduction of flow to the pump station. A total of 30 cfs will be directed away from the pump station. 14.8 cfs will be redirected along Laurel Street east to an existing system in Bordwell Avenue. 15.6 cfs will be redirected north along North 8th Street to the 84-inch RCP along Citrus Avenue. This lowers the potential flow to the pump station from 103 cfs to 73 cfs. This in turn reduces the size of the storage RCB under Laurel Street, pump station size including the number and size of the pumps, the force main diameter from 36 inches to 24 inches and upstream detention basin size. These reductions saved project cost and will result in a reduction of future maintenance costs. Additionally, the proposed drainage improvements will redirect a large volume of water from North of Laurel Street that was previously flowing along the tracks South of Laurel Street. This represents a significant benefit for BNSF.

Each challenge required that numerous potential solutions be examined and evaluated and the overall result is a complex partnership of components that work together as a team to effectively solve a complex challenge of safely keeping storm water runoff from impacting rail and traffic operations.

LIST OF FIGURES

FIGURE 1: Project Location Map FIGURE 2: Profile, Project Layout, and Typical Cross Section FIGURE 3: Existing Earthen Basin Overflowing After Rain FIGURE 4: Drainage Areas and Proposed Improvements

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Joseph Sawtelle - TranSystems

Joe is an Assistant Vice President and Design Manager at TranSystems, a transportation engineering

consulting firm. Mr. Sawtelle has 20 years of roadway design experience involving highway and roadway

projects in southern California. Joe has been with TranSystems for over 5 years. Mr. Sawtelle holds a

Bachelors of Science degree in Civil Engineering from the California State University, Chico and is a

licensed Professional Engineer in California. Mr. Sawtelle’s transportation experience includes performing

geometric calculations; assisting with traffic circulation studies; preparing drainage designs, cost estimates,

project reports, and assisting with environmental documents; and coordinating utility relocations.

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Introduction• CITY OF COLTON, CA

• LONG HISTORY WITH THE RAILROADS

• COLTON CROSSING

Project Location Map

Project Description• SANBAG, CITY OF COLTON, BNSF, & UPRR

• LOWER LAUREL ST. UNDER SIX EXISTING TRACKS

• CONSTRUCT THE BRIDGE FOR SW PROPERTY ACCESS, FUTURE METROLINK ABUTMENTS AND THE BRIDGEFUTURE METROLINK ABUTMENTS, AND THE BRIDGE FOR THE BNSF TRACKS

• MODIFY EXISTING ACCESSES

• UTILITY RELOCATION AND DRAINAGE FEATURES

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• THE SW PROPERTY ACCESS BRIDGE

• METROLINK ABUTMENTS

• BNSF BRIDGEBNSF BRIDGE– PRE-CAST GIRDERS

– SECANT PILE WALLS

– TOP DOWN CONSTRUCTION

– FASCIA WALL

Structures Layout

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Shoofly and Bridge Construction

• CLOSURE OF ALL SIX TRACKS DURING CONSTRUCTION

• THREE TRACK SHOOFLY AGREED TO EAST OF THE TRACKSTRACKS

• RELOCATION OF SIGNAL BRIDGE

• FIVE ALTERNATIVES DEVELOPED (OPTIONS A-E)

• OPTION D CHOSEN, CONSTRUCTION IN ONE PHASE WITH THREE ACTIVE TRACKS AT ALL TIMES

Shoofly Layout

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Existing Flooding on Laurel Street

EAST OF THE TRACKS WEST OF THE TRACKS

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Drainage Strategies

• UTILIZE EXISTING DRAINAGE SYSTEMS WHEREVER POSSIBLE TO REDUCE THE RUNOFF VOLUME

• MINIMIZE RIGHT-OF-WAY IMPACTS BUT MAXIMIZE SAFETY AND EFFICIENCY

• MINIMIZE ENVIRONMENTAL IMPACT AND REQUIRED AGENCY COORDINATION

Utilization of and Connection to Existing Drainage Systems

• 14.8 CFS TO BORDWELL AVENUE SYSTEM

7.5 ACRES

• 15.6 CFS TO CITRUS STREET AND THE 84-INCH STORM DRAIN

5.9 ACRES

Connection to Bordwell Avenue Systemon

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Proposed Drainage Features

• 300-FOOT LONG DOUBLE 14-FOOT BY 7-FOOT RCB

• PUMPING FACILITY

• 1/3 MILE LONG FORCE MAIN• 1/3 MILE LONG FORCE MAIN

• DETENTION BASIN NORTH OF MILLER DRIVE

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Outlet to Lytle-Cajon Channel• METERING DEVICE FROM DETENTION BASIN TO

84-INCH CITRUS STORM DRAIN

• STORM DRAIN OUTLETS TO LYTLE-CAJON CHANNEL

• MINIMAL IMPACTS AND MINIMAL COORDINATION WITH ADDITIONAL AGENCIES REQUIRED.

Meeting Project Drainage Challenges

ONE OF THE MOST CHALLENGING COMPONENTS OF THIS PROJECT WAS EFFECTIVELY MANAGING 104 CFS

OF RUNOFF WHICH NEEDS TO BE COLLECTED AND CONVEYED AWAY FROM VEHICULAR PEDESTRIAN ANDCONVEYED AWAY FROM VEHICULAR, PEDESTRIAN, AND

RAIL TRAFFIC IN A SAFE AND ENVIRONMENTALLY SENSITIVE MANNER.

Innovative Drainage Solution• UTILIZATION OF EXISTING SYSTEMS

• CONSTRUCTION OF A LARGE DETENTION SYSTEM UNDERNEATH LAUREL STREET

• CONSTRUCTION OF A PUMP STATION AND A FORCECONSTRUCTION OF A PUMP STATION AND A FORCE MAIN TO CONVEY THAT WATER TO A 40,000 SQUARE FOOT DETENTION BASIN

• IMPLEMENTATION OF A “METERING DEVICE” TO CONTROL OUTPUT FROM THE DETENTION BASIN TO AN 84-INCH RCP DRAINING TO LYTLE-CAJON CHANNEL

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Conclusion

EACH CHALLENGE REQUIRED THAT NUMEROUS POTENTIAL SOLUTIONS BE EXAMINED AND EVALUATED

AND THE OVERALL RESULT IS A COMPLEX PARTNERSHIP OF COMPONENTS THAT WORKPARTNERSHIP OF COMPONENTS THAT WORK

TOGETHER AS A TEAM TO EFFECTIVELY SOLVE A COMPLEX CHALLENGE OF SAFELY KEEPING STORM

WATER RUNOFF FROM IMPACTING RAIL AND TRAFFIC OPERATIONS.

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