The City maintains approximately 130 miles of both improved and unimproved roadways. Street maintenance involves not only pavement maintenance, but includes installing and repairing guardrails at dangerous locations, replacing and repairing street name signs, stop signs, and a variety of other informational and restrictive signs used to warn and guide the public. The Public Works Department also is responsible for painting center line stripings, replacing ceramic dots, painting red curbs, and refreshing and repainting crosswalks that become worn off with the scuffing action of traffic. Traffic signal operations and repair are also the responsibility of the Public Works Department. However, traffic signal timing and the decision to install or remove traffic control devices such as stop signs, red curb and cross walks are the responsibility of the Engineering Services Department.
The City, in maintaining street pavement, utilizes various techniques that fall into several broad categories. These include:
- Pothole patching (cold patch material for immediate/emergency repair)
- Crack filling (cold or hot applied asphalt liquid applied to large cracks)
- Permanent patch paving (hot mix asphalt concrete in small areas)
- Surface sealing (cold applied asphalt emulsion and aggregate mixtures)
- Rehabilitation (hot mix asphalt concrete overlays)
- Reconstruction (removal and replacement of entire pavement section)
Pothole Patching and Crack Filling
Pothole patching is a quick, inexpensive and low-tech way to prevent existing failed pavement from failing further and to provide immediate distress relief in order to insure safe driving conditions. Pothole patching is often conducted using a patching material known as “cutback”, which remains permanently soft and is utilized as an emergency repair to fill a hole and resolve an immediate need. Pothole patching varies significantly from permanent patch paving in that it is not intended to be the permanent repair, but is intended to be a stopgap measure until weather or financial conditions permit a permanent patch repair to be made.
Pot holes, or localized areas of severely deteriorated street pavement should be reported to the Public Works Corporation Yard at (925) 252-4936.
Crack filling consists of applying a bituminous mixture into large pavement cracks to inhibit the intrusion of water. Like potholes, which also allow water to enter the pavement subgrade, large cracks can allow water from rain and irrigation sources to enter the pavement subgrade thereby softening and weakening the subsoils ability to support the pavement above. A weakend subgrade will lead to more rapid pavement failure under vehicle loads. Crack filling is a very cost effective and inexpensive means of retarding the deterioration of existing pavement.
Permanent Patch Paving
Patch paving is a permanent repair of completely failed pavement in localized areas. The patch pavement is typically applied in an area as small as one square yard or as large as the full width of a traveled lane, or 12 feet, by as much as 100 feet long. Projects larger than this are usually relegated to the permanent repair category (rehabilitation/reconstruction) because their cost becomes prohibitive and must be done as part of an Engineering Services Department Capital Improvement Project. Both City crews and independent contractors hired by the Public Works Department perform permanent patch paving on various streets on a priority basis throughout the City each Spring and Summer. Permanent patch paving typically is not performed in the wintertime or late Fall because moisture and temperature conditions do not allow for quality workmanship.
Surface seals come in a variety of types, but most typically include chip seal, which is the application of a thin film of asphalt emulsion on the street, followed by a layer of fine aggregate which is embedded into the asphalt previously applied through the use of large rubber tired rollers. Slurry seal, which is a mixture of sand aggregate, cement and bituminous material, is applied like a thick, heavy paint on the top of an existing pavement. A CAPE seal is a combination of first applying a chip seal and following that application with a conventional slurry seal. Surface seals serve three primary purposes:
- To reduce the oxidation of the asphalt in existing asphalt conceret pavement which is attacked by oxygen in the air, oxidation makes the pavement harder, more brittle and prone to cracking and failure under traffic loads;
- To prevent the intrusion of water through a multitude of fine cracks that are sealed by the surface seal, and
- Replacement of fine aggregates that can be stripped off of the surface of an existing asphalt concrete pavement over long periods of time by traffic, water and oxidation.
The City currently has a very effective surface seal program using both slurry seals, and CAPE seals on more distressed streets, in order to prevent the further deterioration of existing streets. The City has insufficient funds to repair all of the major deteriorated streets with more costly treatments, such as asphalt overlays or full reconstructions. Therefore, the Public Works Department has been very aggressive in the use of CAPE seals to return as many streets as possible to an acceptable appearance and condition of ride quality, although many of these streets do require, and will require, the more costly asphalt overlay in the future.
At as little as ten cents per square foot ($0.10/sf) surface seals are very inexpensive for the benefits they provide. Especially when compared to two to ten dollars per square foot ($2.00/sf - $10.00/sf) for permanent patch paving, asphalt concrete overlays or full pavement reconstruction. The timely application of surface seals can dealy the need for these much more costly repairs for many, many years.
Asphalt Concrete Overlays
An asphalt concrete overlay is the enhancement of the structural section of the road by applying 1½ - 3 inches of new asphalt concrete over the top of an existing pavement. Sometimes this asphalt is also under laid with a layer of reinforcing fabric to prevent reflected cracking from a lower pavement propagating up through the new pavement section. This type of project is quite expensive and only a few streets can receive this treatment in any given year. These projects are normally handled by the Engineering Department as a major Capital Improvement Project and are constructed by independent contractors hired by the Engineering Department.
Street pavement reconstruction is the most expensive street maintenance process that can be performed. It is, in effect, a complete reconstruction or installation of a brand new street, which not only includes the cost of a complete new pavement section, but includes the cost to remove the existing pavement section. Projects of this type range from half a million dollars to several million dollars, depending on the scope of the project and the length of the street involved. The City currently only has the financial capacity to fund pavement reconstruction on a very small number of streets in any given year.
To find out when your street may be scheduled for a surface seal, asphalt concrete overlay, or full reconstruction, contact the Public Works Administration office at (925) 252-4936.
Because the City has a large inventory of City streets, and insufficient funds to maintain all of those streets at the maximum level possible, a method must be utilized to prioritize the application of funds available to ensure the maximum benefit can be achieved for the overall good of the street system as a whole. To manage the City street system, the Public Works Department, like many public works departments throughout the Greater Bay Area, utilizes the Metropolitan Transportation Commission (MTC) “Paver” Pavement Management System (PMS). This computer-based program uses data collected on the condition of city streets to prioritize the application of street maintenance dollars and major reconstruction projects for the maximum benefit of the overall system. Data is gathered for the PMS on a annual and semi-annual basis so that the data in the computer is continually updated with worsening conditions on some streets and improved conditions on streets that have been repaired. However, the Public Works staff does not utilize this system as a “black box”, blindly following its recommendations.
The computer-based PMS is unaware of other environmental factors which could change the priorities of street maintenance needs. For example, many streets are under lain by deteriorating sewer and water utilities. If the pavement management system indicates a street should receive a major reconstruction or overlay, but the City staff knows that the utilities under that street are also in bad condition, the repair of that street will be postponed until the underlying utilities can also be repaired. In this way the large investment required from these major pavement repair projects will not be wasted through excavations of the new pavement to repair deteriorating utilities underneath. For this reason, many needed streets are often not receiving major repairs because staff is waiting for the necessary funds to be allocated for underground utilities to also be repaired at the same time. The Public Works and Engineering Department staff are working closely to coordinate the repair of buried utilites in advance of major pavement repair projects.
If you have questions regarding the City’s pavement management system or the priorities for pavement repairs, surface sealing, and overlays, contact the Public Works Administration office at (925) 252-4936.