Welcome to the Engineering section of Carmel Area Wastewater District’s web site.

The Engineering section performs plan checks, issues permits, develops, implements and manages capital projects, assists the operations departments and otherwise performs or contracts out all of the engineering functions of the District.

This site provides information with regard to the following:

  1. Permits
  2. Maps for the District’s collection system (pipelines).
  3. Current construction projects.
  4. Standard plans and Specification
  5. Uniform Plumbing Ordinance

For further information please contact Principal Engineer at (831) 624-1248 or lander@cawd.org

Current Projects

For detailed information on Engineering Projects, please contact Principal Engineer at (831) 624-1248 extension 203 or email lander@cawd.org

Current Projects

Engineering Services page imageIn March 2012, the Carmel Area Wastewater District (CAWD) retained Kennedy/Jenks Consultants, (Kennedy/Jenks) to perform a condition survey of the assets at the wastewater treatment plant (WWTP), and to develop an asset database to document and analyze the asset condition data. The results of the survey were described in a Technical Memorandum (TM) dated April 11, 2012. It was apparent from the survey results that the rate of renewal of the aging assets had not kept up pace with the rate of deterioration, resulting in the noticeable physical condition deficiencies of assets currently at the WWTP. When investment in asset
renewal lags behind the rate of consumption of the assets, this is referred to as “mining of assets”. The net result is that many of the treatment plant assets are in need of significant repairs to preserve the ability of these assets to reliably meet their service levels. Based on these findings CAWD has initiated an asset management program to improve the management of the WWTP assets. In April 2012, CAWD authorized Kennedy/Jenks to expand the asset data for the WWTP and develop a 15-year capital improvement program (CIP) plan based on the asset management data developed.
The 15-year CIP plan that is presented herein is based on asset data developed over the past year and on detailed pre-design work for several major process areas. Kennedy/Jenks conducted onsite training sessions and collaborative work sessions with CAWD staff to refine the projects in the CIP. The District’s goal in implementing the CIP is to efficiently utilize capital
to upgrade its assets and reduce risk. The data used to develop this report provides a foundation for CAWD to continue to apply asset management and develop asset management best practices within the organization.

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The Board of Directors approved a resolution on December 9, 2010 awarding a contract to Robert F. Enz Construction, Inc. in the amount of $251,700 for the Grease Receiving Facility Project. This project is slated for completion in 2011.

Waste grease can be accepted from restaurant grease traps and fed directly into digesters to increase digester gas production. It is readily and almost completely biologically converted to digester gas. The gas production can be increased significantly if there is sufficient excess digestion capacity and available grease. CAWD’s primary digester is lightly loaded with wastewater bisolids and has the capacity for a large amount of grease digestion. The increase in digester gas production from about 1,500 gpd of grease would be sufficient to fully fuel the microturbines and provide sufficient digester gas to fuel the sludge heater.

A Belt Filter Press is a biosolids/sludge dewatering device that applies mechanical pressure to a chemically conditioned slurry, which is sandwiched between two tensioned belts, by passing through a serpentine of decreasing diameter rolls. The machine can be divided into three zones: gravit zone, where free draining water is drained through a porous belt; wedge zone, where the solids are prepared for pressure application; and pressure zone, where medium and then high pressure is applied to the conditioned solids. Typically, a belt filter press receives a slurry ranging from 1-4% feed solids and produces a final product of 12-35% cake solids. Performance of the belt press depends on the nature of the solids being processed.

The District installed and operates two Moyno progressive cavity, positive displacement sludge feed pumps in 1985 that reached the end of their useful lives. Due to the extent to which the drive units had worn down, the District replaced the feed pump assemblies completely in 2010.

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No 4 missing with red dye

In July 2010, North Coast Divers, conducted a visual inspection of the District’s outfall diffusers as part of routine maintenance activities. In conjunction with the inspection, a dye test was performed to detect any leaks in the outfall pipe. During the course of the inspection it was reported that diffuser #4 was missing (there are 10 diffusers with #1 being closest to shore and the most downstream diffuser designated as #10).

The District was “lucky” in that the missing diffuser was recovered. We don’t know what caused the damage, but we do know that the bolts gave way before there was substantial damage to the outfall and the diffuser was in good enough condition that it could be successfully reattached. Our one significant remaining problem was sand – the level of sand at diffuser #4 was ½ of the pipe; diffuser #6 the pipe was full and all flows were obstructed. With this obstruction it was questionable whether maximum flows during the coming winter could be accommodated.

The District contracted with North Coast Divers to dredge out all sand from the end of the pipe at diffuser #10 all the way to the wye, or where it bends away from shore. The work was completed in October 2010, below budget.

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The CAWD/PBCSD Reclamation Project (the project) is a cooperative effort involving the Carmel Area Wastewater District (CAWD), the Pebble Beach Community Services District (PBCSD), the Monterey Peninsula Water Management District (MPWMD), and the Pebble Beach Company (PBCo). This cooperative effort did not create a new or separate legal entity. Therefore, the Project is a proprietary (enterprise) fund of Monterey Peninsula Water Management District, the issuer of the Certificates of Participation which financed the Project’s first construction project.

The Project provides treated wastewater to irrigate golf courses and open space areas in Pebble Beach, which freed up potable water previously used for irrigation. The original Project involved the construction of a new tertiary treatment plant and laboratory facilities located on the site of the existing CAWD secondary wastewater treatment plant, the construction of a new reclaimed distribution system, including a 2.5 million gallon storage tank, and irrigation system improvements. Construction of the original Project began in January 1993 and was completed in October 1994. The tertiary treatment plant produces water which meets Title 22 standards specified by the California Department of Health Services, which is a quality acceptable for human contact

The Microfiltration/Reverse Osmosis (MF/RO) phase of the project, located at the CAWD plant site, began design in 2006 and construction was completed in 2009. The intent of the MF/RO phase is to reduce the sodium content of the tertiary reclaimed water from 150 mg/l to less than 55 mg/l to reduce the stress on the golf greens and eliminate the need for flushing the courses with potable water. The design capacity for the MF/RO is 1.5 million gallons with an expected blend of 80% MF/RO water and 20% MF water. The cost of the MF/RO phase was approximately $20 million.

The cost of the Expanded Project was financed through the sale of water entitlements owned by PBCo to residential property owners within Pebble Beach, currently at $250,000 per acre foot, which is subject to change. At June 30, 2009 approximately $26 million had been raised through these sales and interest. The funds from the sales were deposited in a restricted escrow account where they were invested in short-term federal government securities before being spent for the Expanded Project. All project costs in excess of those raised through the sale of Water Entitlements are being covered by the PBCo.

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In 1973, a new concrete under river crossing structure was built to accommodate 24” and 20” pipelines. The 24” pipeline became the new plant influent line and the 20” pipeline was used as a conduit for the 14” recycled water distribution line. Both of these lines are active today.

In July 2010 the Monterey Peninsula Water Management District alerted the District to the declining sediment level in the river which had exposed our structure. The top of the structure is now approximately 2 feet above the river bottom on the downstream side and approximately level with the river bottom on the upstream side. The concern is not only that the structure may become an impediment to fish migration, but also, whether the exposed structure is now subject to forces that may damage the structure. In addition to the hydraulic forces acting on it, there is potential for large debris coming downstream striking the structure and causing damage.

The District Board approved a contract with Cornerstone Structural Engineering in December 2010 to evaluate the structure itself and also the potential consequences of hydraulic scour and seismic activity.

Engineering Services page imageThe District’s long term master capital plan provides for the continued replacement or rehabilitation of its existing collection system lines on an annual basis. CAWD has over 80 miles of collection lines and 5 employees whose job is to ensure that it is able to collect and transport wastewater to the District’s Wastewater Treatment Facility. The District is committed to ensuring the integrity of its collection system – to meet this goal means that our crews are out in the field every week cleaning and maintaining the lines. However, although a sewer line can last over 50 years if well maintained, we still have the need to replace lines that have developed problems due to shifting earth, infiltration and inflow, cracks in the pipes, etc.

 

currentproject-sewerlining-2District crews replace or repair main lines, manholes, wet wells, and cleanouts. Large scale jobs are typically contracted out to a firm that specializes in replacement or rehabilitation of sewer mains. The District utilizes several techniques, depending on the terrain and conditions – but we find more and more that we are depending on some type of pipe bursting or pipe lining technology because of its cost savings and ease of installation. Both of these technologies create very little disturbance for the public. In fact, people can walk right past the truck parked by one of our manholes and not have any idea of the work that is being done underground.

 

currentproject-sewerlining-3Pipe bursting is a process that is designed for replacing existing pipelines with new and larger pipelines. A new pipe of equal or larger diameter is inserted into the existing pipeline by bursting open the existing pipe and pulling or pushing the new pipe into the old pipe and expanded surrounding soil. Pipe bursting is suitable for replacing pipes made of brittle material such as vitrified clay, un-reinforced concrete, asbestos cement, some polyvinyl chloride (PVC) and cast iron. Bursting progress of 2 to 10 feet per minute is possible.

 

 

currentproject-sewerlining-4What are the benefits of pipe bursting?

Pipe bursting has several advantages over open-cut trenching and other trenchless rehabilitation methods:

Pipe bursting allows for replacement of pipes without disturbing surface structures.

Potential problems with existing pipes are minimized because pipe-bursting methods follow the existing pipe path.

For smaller sizes of pipe, pipe bursting is the only trenchless technology that can be used to upsize the existing pipe.

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Because it is trenchless, excavation is minimized, which lessens effects on existing landscaping and structures. The bursting heads on the piercing tool can be removed at the end of the line so that the tools may be removed through the new line. This eliminates the need for an exit pit in some instances.

Pipe bursting reduces the amount of site restoration required.

currentproject-sewerlining-6Pipe lining was first put into practice in the United Kingdom in the early 1970s. The process involves inserting a resin-saturated flexible lining into the existing sewer. Air or water under pressure is forced into the tube, which turns the lining inside out and causes it to fit tightly to the existing sewer walls. Hot air or water is circulated throughout the tube to harden the resin, completing the curing process. When the curing process is completed, a new pipe has been created that is free of cracks and holes that allow rainwater and roots to enter the sewer and cause operational problems such as stoppages and overflows.
What are the benefits of Pipe Lining?

Pipe Lining has many advantages, including:

Pipe Lining allows for replacement of pipes without disturbing surface structures or other utilities.

It produces a seamless, jointless pipe lining with minimal reduction of the original pipe diameter and leaves no voids to be grouted after the liner is installed.

Though the liner system reduces pipe size by the thickness of the liner, the smooth interior of the liner reduces friction, which increases flow capacity.

Private service connections are reconnected without excavation. A dimple is formed where the lining passes a service connection. Close circuit TV easily locates the dimple and cuts out the lining using remote techniques.

The finished product has a 50-year design life, the same as that of a brand new pipe.

CAWD reports all sanitary sewer overflows (SSOs) electronically to the California Integrated Water Quality System (CIWQS). The electronic SSO data, as well as information regarding regulatory actions, is available at: www.waterboards.ca.gov/waterissues/programs/ciwgs/publicreports.shtml

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The trestle bridge across the Carmel River was built in 1938 and is part of the original treatment plant facility. The structure is a steel framed trestle with support via suspension cables. The structure provides not only a footbridge across the river to the north side of the Carmel River but also supported the former influent pipelines. It has been modified over the years to increase both the capacity of the influent pipelines and to improve the structure. In 2010 the Treatment Facility Superintendent noted the deterioration of the concrete abutment of the pipe trestle structure and the District made the decision to contract with Cornerstone Structural Engineering to evaluate the bridge.

After the evaluation is complete the District will work with other local agencies to determine if there is interest in incorporating the bridge into the Coastal Access Trail

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Before

Wetwell rehabilitation is part of the District’s periodic repair and maintenance program to ensure that our system’s integrity is 100%. Wetwell rehabilitation is done for the purpose of eliminating infiltration, providing corrosion protection, repair of voids, and restoration of the structural integrity of the manhole/wetwell. Our plan in 2010 is to rehabilitate wetwells in 4 pump stations. The walls in the wetwells at the Hacienda Carmel, Bay & Scenic, Monte Verde & 16th Ave., and Calle La Cruz pump stations are deteriorating due to hydrogen sulfide gas. Unless the walls of the wetwells are protected from further deterioration, structural integrity will be compromised. It is proposed that the walls of these wetwells be coated with an epoxy coating to prevent further degradation. Estimated cost for this work is $50,000 per wetwell plus $50,000 for engineering for a total of $250,000.

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After

Sewer locations shown on these maps are schematic and should not be used for design or construction purposes. To confirm actual location of sewer structures please contact the District at (831) 624-1248 or lander@cawd.org

[Click Images to Enlarge]

CAWD Map 1
CAWD Map 1
CAWD Map 2
CAWD Map 2