Summary of Potential Storm Drain Projects and Programs

Transcription

1 Summary of Potential Storm Drain Projects and Programs CAPITAL IMPROVMENTS PUMP STATION UPGRADES The storm runoff from a large portion of Palo Alto cannot flow by gravity into one of the local creeks. Because of the relatively flat slopes and low elevation of the eastern part of the City, the storm drains serving this area are significantly lower than the creeks, particularly when the creeks are flowing full during a storm event. As a result, storm runoff from these storm drains must be pumped into a creek. Pumps are also required at localized low spots such as roadway underpass structures. There are six primary City-owned storm water pump stations throughout Palo. These stations are critical components of the City s storm drain system. Failure of one of these stations would result in significant flooding over a widespread area. Staff has identified improvements at each of the stations that are needed to improve worker safety and station reliability and efficiency. The recommended infrastructure improvements include operational and safety-related upgrades to the City s storm water pump stations. 1 1 Pump station upgrades $2.09 Citywide

2 NORTHEASTERN PALO ALTO Some of the most severe and chronic ponding problems are in the northeastern portion of the City roughly bounded by University Avenue, El Camino Real, Seale Avenue, and San Francisquito Creek. This entire 1250-acre area drains through a single 96" outfall pipe into San Francisquito Creek downstream of Highway 101. There are longstanding, chronic drainage problems throughout this area. The drainage problems fall into two basic categories. In the upstream portions of the watershed, the storm drain pipes are undersized. During even moderate storms (2- to 5-year intensity storms), water ponds in the streets and floods intersections because the amount of runoff exceeds the capacity of the underground pipe network. The downstream portion of the drainage system was upgraded in the early 1970's, when the 96" outfall pipeline was constructed. Over time the performance of this system has deteriorated due to excessive siltation in San Francisquito Creek. The siltation has reduced the capacity of the creek, resulting in higher water levels in the creek during storm events. The higher creek levels, in turn, prevent the storm drain system from draining freely, causing the pipes to back up and pond into the streets and gutters. Chronic street ponding occurs initially on the 500 block of Greer Road and then spreads to the Hamilton Ave., Hilbar Lane, Rhodes Drive, Channing Avenue, and Walter Hays Drive areas. These areas remain ponded until the water level in the creek drops enough to allow the 96" pipe to drain freely again. Many of the recommended infrastructure improvements address the drainage deficiencies in this watershed area. Installation of a pump station at the 96" outfall and construction of a new pump station and outfall into the creek at Newell Road will alleviate the downstream area system backups. This work will have to be carefully coordinated with the Santa Clara Valley Water District as well as the cities of Menlo Park and East Palo Alto in order to avoid any negative flooding impacts on San Francisquito Creek. New pipelines on Newell Road, Harker Avenue, Lincoln Avenue, Kellogg Avenue, and Pitman Avenue will all address upstream drainage system deficiencies. The highest priority pipeline projects will improve the system performance by diverting runoff from existing undersized storm drains. These diversion pipelines will allow the existing pipelines to remain in service and will also provide improved local drainage on streets where they are constructed. 2 1 Pump 96 outfall into SF Creek $3.13 Northeastern Palo Alto 3 1 Newell Road pipeline and pump station $4.43 Green Gables

3 4 1 Harker Street pipeline $2.54 Community Center 5 1 Lincoln Avenue pipeline $2.36 Professorville 6 1 Parallel/Replacement pipelines $1.83 Professorville 15 2 Kellogg Avenue pipeline $1.79 Community Center 16 2 Pitman Avenue pipeline $3.90 Crescent Park 22 2 Replacement pipelines $0.73 Green Gables 27 3 Dana Avenue pipeline $1.66 Green Gables MATADERO PUMP STATION WATERSHED A large portion of southeastern Palo Alto drains to Matadero Creek by way of the Matadero Storm Water Pump Station. The watershed area is roughly bounded by Seale Avenue, Highway 101, Barron Creek, and Alma Street. Most of this 1200-acre area drains through a network of pipelines to a pump station located adjacent to Matadero Creek, just upstream of West Bayshore Road. Much of the land in this area, particularly the eastern portion near Highway 101, is lower than the creek water level during storm events. Without the pump station, this land would be unable to drain until the creek recedes, several hours after the rainfall stops. Problems in this watershed include undersized pipes, the capacity of the pump station itself, and several areas that are not connected to the pump station. The recommended infrastructure improvements include upgrades to the Matadero Pump Station and the construction of replacement or parallel pipelines for several of the pipelines feeding the pump station. The Master Plan analysis showed that several of the large pipelines that drain to the Matadero Pump Station (including those along Loma Verde Avenue, the drainage easement north of Colorado Avenue, and the drainage easement east of Maddux Drive and Kenneth Drive) are undersized and need to be replaced with larger pipelines or supplemented with parallel pipelines. 1 1 Upgrade Matadero Pump Station $1.04 Midtown/South Palo Alto 18 2 Loma Verde/Sterling Canal/Seale- $7.50 Midtown/South Palo Alto

4 Wooster Canal pipelines 26 3 Waverley Street outfall to Matadero Ck $1.49 Old South Palo Alto 32 3 Louis Road outfall to Matadero Ck. $0.56 Midtown 33 3 Middlefield Road outfall to Matadero $0.68 Midtown Creek CHARLESTON TERRACE/GREENDELL/GREENHOUSE/SAN ANTONIO AVENUE AREA The Charleston Terrace, Greendell, Greenhouse, and a portion of Greenmeadow neighborhoods, and San Antonio Avenue between Charleston Road and Alma Street are served by a 36" storm drain that flows by gravity into Adobe Creek behind Bibbits Drive. This 280-acre watershed is roughly bounded by Adobe Creek, Nelson Drive, Ferne Avenue, Alma Street, San Antonio Avenue, and East Charleston. Once the water level in Adobe Creek rises to a depth of approximately four feet, the 36" pipeline cannot drain by gravity. Subsequently, water begins ponding on Bibbits Drive and Gailen Avenue, and extends upstream in the drainage system. Several of the storm drains that feed into the 36" pipeline are also undersized and subject to backup. The recommended infrastructure improvements include the construction of an 1,800-foot extension of the of 36" storm drain to connect it to the existing Adobe Creek Pump Station, a new diversion pipeline on Middlefield Road, and parallel pipelines for several storm drains that feed into the 36" pipeline. Connection of this watershed s drainage system to the pump station will allow the streets to be drained regardless of the creek level. The Middlefield Road pipeline will divert runoff from the undersized San Antonio Avenue storm drain. New parallel pipelines along East Charleston Road and Montrose Avenue will supplement existing undersized storm drains. 7 1 Extend Gailen Avenue/Bibbits Drive $1.10 Charleston Terrace outfall to Adobe Pump Station 20 2 Parallel pipelines $2.89 Charleston Terrace 21 2 Middlefield Road pipeline $0.68 Charleston Terrace

5 ALMA STREET There are several locations along southbound Alma Street where storm runoff drains onto Peninsula Corridor Joint Powers Board railroad property and is absorbed into the ground. When the ground becomes saturated, water begins to pond onto the roadway, creating hazardous driving conditions. There are no underground storm drains in these areas to collect the runoff and convey it to a creek. The recommended infrastructure improvements include the construction of several new catch basins along the southbound side of Alma Street and installation of approximately 4,400 linear feet of new storm drain pipelines to properly drain the street. 8 1 Improve draiange along Southbound Alma Street $1.28 Alma Street

6 CLARA DRIVE Clara Drive currently drains to Matadero Creek by gravity. Water ponds in the street during even moderate storm events, with the extent of the ponding increasing with the creek level. It is recommended that the Clara Drive storm drains be extended to connect with the Matadero Pump Station. Connection to the pump station will allow Clara Drive to drain regardless of the creek level. 9 1 Connect Clara Drive to Matadero Pump Station $0.58 De Anza

7 CONDITION ASSESSMENT REPAIR PROJECTS The City s existing storm drain system has been constructed incrementally over the past 75 years. Portions of the system are nearing the end of their useful life. The 1993 Storm Drain Condition Assessment report contains an assessment of the existing storm drain system and recommendations for repair or replacement of deteriorated storm drain pipelines, drain inlets, and manholes. A portion of the recommended work has already been completed. The recommended infrastructure improvements include the completion of the replacement and repair projects recommended in the 1993 Condition Assessment report Complete balance of previously identified rehabilitation projects from 1993 Condition Assessment $4.38 Citywide

8 SOUTHGATE NEIGHBORHOOD The Southgate neighborhood, bounded by Churchill Avenue, the Caltrain Corridor, Park Boulevard, and El Camino Real, drains to a single storm drain inlet at the corner of Mariposa and Sequoia Avenues. There are no underground storm drain pipelines to serve the neighborhood, and there are many sections of uneven curb and gutter that pond water during rain events. The recommended infrastructure improvements include the construction of additional storm drain inlets, new pipelines, and curb and gutter repairs to eliminate street ponding in the Southgate neighborhood. This project will also accommodate runoff from the Palo Alto High School property Southgate neighborhood drainage $1.88 Southgate

9 CHAUCER STREET Storm runoff ponds at the intersection of University Avenue and Chaucer Street during heavy storms. The runoff is conveyed to San Francisquito Creek via a 10" storm drain on Chaucer Street. The ponding occurs when the creek rises to a level high enough to prevent the storm drain from emptying freely. The recommended infrastructure improvements include the replacement of the Chaucer Street storm drain with a 21" pipeline fitted with a flapgate. The larger pipe will provide increased underground storage for storm runoff while the creek is running high, and the flapgate will prevent the creek waters from flowing back up into the pipeline and into the street. These improvements will greatly reduce the occurrence of ponding at the University Avenue/Chaucer Street intersection Chaucer Street pipeline $0.19 Crescent Park

10 BAYLANDS/EMBARCADERO ROAD Periodic street ponding occurs along Embarcadero Road east of Highway 101 due to undersized storm drain pipelines. These pipelines drain to the Airport Storm Water Pump Station. Ponding occurs because the existing pipes are not large enough to convey the peak storm runoff to the pump station. The recommended infrastructure improvements include the replacement of 400 linear feet of 12" pipe with 18" pipe at the intersection of East Bayshore and Embarcadero Roads and the installation of 1,400 linear feet of new 24" pipe. These improvements will increase the capacity of the drainage system serving the Embarcadero/East Bayshore intersection and will provide a more direct route to the Airport Pump Station Embarcadero Road parallel pipes $0.69 Baylands 14 2 Increase capacity at Embarcadero/East Bayshore Roads $0.50 Baylands

11 EAST MEADOW CIRCLE Periodic street ponding occurs along East Meadow Circle during heavy storms. The runoff is conveyed to Barron Creek via an 18" storm drain, fitted with a flapgate. The ponding occurs when the creek rises to a level high enough to prevent the storm drain from emptying freely. The recommended infrastructure improvements include the installation of a pipeline to connect the East Meadow Circle storm drains to the Adobe Storm Water Pump Station. Connection to the pump station will allow East Meadow Circle to drain even when the creek level is high East Meadow Circle pipelines $0.63 Ortega

12 INSTALL PIPELINES TO ELIMINATE SIPHONS The existing storm drainage system includes approximately 45 siphons located at various points throughout the City. A siphon consists of a pair of drain inlets connected by a short length of underground pipe designed to convey storm runoff across an intersection. Runoff flows into the upstream drain inlet, through the pipe beneath the roadway, and back out and up into the gutter at the downstream inlet structure. Leaves and debris chronically accumulate in the pipe, often leading to blockages. Siphons also generate complaints related to odor problems, since the pipe remains filled with standing water after the storm ends until it evaporates. As a result, siphons must be cleaned more often than the rest of the drainage system, and siphon blockages frequently cause intersection flooding. Siphons were constructed in the past as an inexpensive means to convey water from one side of a street to the other, but they should be eliminated as part of the upgrade of the City s storm drain system. The recommended infrastructure improvements include the installation of approximately 9000 linear feet of 12"-, 15"- or 18"-diameter pipes to connect the siphons to existing storm drains. Once the siphons have been connected to the storm drain system, storm runoff will flow into the drain inlets and be conveyed all the way to a local creek via the underground drainage network Install pipelines to connect siphons $3.5 Various areas