Inter-Departmental Correspondence

Department of Public Works



October 9, 2008


October 28, 2008







Honorable Board of Supervisors


James C. Porter, Director of Public Works


Accepting the Facilities Plan for the Pescadero Community Sewer Project and Designating a Preferred Alternative for the Environmental Assessment



Adopt a resolution accepting the Facilities Plan for the Pescadero Community Sewer Project and designating Wastewater Treatment Plant SITE 3 and a conventional gravity collection system as the preferred alternative for the environmental assessment.



Commitment: Ensure basic health and safety for all.

Goal(s): Maintain and enhance the public safety of all residents and visitors.


The construction of a wastewater treatment plant for the community of Pescadero will improve their sanitary sewer facilities for the benefit of the public.



Previous Board Action:


Adopted Resolution No. 068624 on March 27, 2007, authorizing the Department of Public Works to serve as the lead agency in the application and acceptance of a grant from the State Water Resources Control Board to perform a feasibility study for installing a sanitary sewer system in the Community of Pescadero.



Adopted Resolution No. 069050 on October 2, 2007, authorizing execution of an agreement with Hydroscience Engineers, Inc. in the amount of $154,228 for engineering services in connection with said feasibility study.



In 2004, the Regional Water Quality Control Board adopted Resolution 04-R2-0088 supporting a Public Health Declaration of public health threat related to sewage disposal for the Community of Pescadero, and the establishment of a wastewater treatment improvement project for the community by July 1, 2009.


Pursuant to the Regional Board’s Resolution, the County obtained grant funding from the State Water Resources Control Board under their 2004 Small Community Wastewater Grant Program, and the County retained the services of Hydroscience Engineers, Inc. to perform a feasibility study for a sanitary sewer system in the Community of Pescadero. The Planning Phase of the State’s grant program requires the submittal of the Facilities Plan Report, Draft Revenue Program, and Environmental Documentation.


Hydroscience Engineers, Inc. has produced a draft feasibility study titled “Pescadero Community Sewer Project, Facilities Planning Report,” dated June 2008, hereinafter referred to as “Report”.



In the Report, there are two (2) options discussed for the wastewater collection system:



Gravity Collection System – A gravity system typically consists of a sewer main with service laterals extending to each individual parcel. Sewage would flow by gravity only, except where lift stations are required due to topography. There are three such locations: (1) Pescadero Creek crossing at North Street and Stage road; (2) Butano Creek crossing at Pescadero Creek Road; and (3) the fire station on Pescadero Creek Road.



Septic Tank Effluent Pump or Gravity or Septic Tank Effluent Gravity System (STEP/STEG) – The difference between the STEP and STEG is that effluent from the septic tank reaches a pressurized collection system either by pumping or gravity, respectively.


The gravity collection system is the more conventional and recommended option, with both Capital and Operation & Maintenance costs being lower than for a STEP/STEG system. The STEP/STEG system requires more energy to run the required pumps and more maintenance of the pressurized system. A cost comparison for the two options is summarized in the attached Exhibit A, Table 1.


The cost shown in Table 1, Exhibit A also includes the wastewater treatment process. The options, as discussed in the report, for treating the sewage include:



Immersed Membrane Bioreactor (MBR) – Conventional wastewater treatment plants utilize an activated sludge process. An MBR utilizes the same biological principles, but with solids separation accomplished via membrane technology to physically separate solids, instead of a clarifier for gravitational separation of solids. MBR further consolidates many of the unit processes required in a conventional activated sludge design.



Integrated Membrane Activated Sludge (IMAS) – IMAS systems differ from the conventional MBR process by using separate biological and membrane filtration units.



Integrated Surge Anoxic Mix (ISAM) Sequencing Batch Reactor (SBR) with Tertiary Filtration – With ISAM, stabilization and solids separation are sequentially accomplished with batch treatment in a single reactor, while a surge tank is used for equalization and some treatment prior to entering the SBR.


Due to reliability and a demonstrated quality of the process throughout California, the MBR plant for wastewater treatment is recommended. Whereas the SBR and tertiary treatment process requires a two-step treatment process with two unit processes, and the IMAS system is a relatively new product with no historical reliability data available.


Further summarized in Exhibit A is the projected annual cost to property owners. These costs are based on the estimated project costs and assuming receipt of the full State grant funding qualified for. If 100% of the State grant monies is applied to the capital costs for this project, the remaining capital cost burden would be $3,023,355 that the Owner/Operator of the system would fund through assessments and sewer rates.


To calculate projected assessments and sewer rates, various existing land uses must be converted to equivalent dwelling units, which conversion is also included in Table 2, Exhibit A. The number of units is then used to determine the annual cost to property owners, as shown in Table 3, Exhibit A.


Hydroscience Engineers, Inc. has identified three potential sites for the location of the wastewater treatment plant, as shown on Exhibit B. Because the environmental impacts would vary depending upon the site chosen, selection of a preferred site is required prior to performing the environmental assessment.


Wastewater Treatment Plant Site 1 is proposed to be located at the County’s Pescadero Corporation Yard on top of a capped landfill. This site is at the lowest elevation of the three sites and is adjacent to a potential surface water discharge location. However, access to the site would be through the County’s Corporation yard. Furthermore, the Wastewater Treatment Plant would be located over the capped landfill, thus necessitating coordination with the County’s perpetual responsibility for the site while possibly limiting the subsurface activities of the plant. There are mixed riparian and marsh existing at this site which will make the environmental assessment and mitigation more complicated.


Site 2 is proposed to be located along the service road to the existing water well and water storage tank serving the community. This site’s elevation would require increased pumping, and access to the road would require County approval. Additionally, the access road would need to be upgraded. Furthermore, the County’s Utilities-Flood Control-Watershed Protection Section has expressed concern for the potential for contamination of the community’s potable water supply due to the close proximity of this site to the water storage tank.


Site 3 is proposed to be located at the top of the hill southeast of the Corporation Yard. The advantages and disadvantages of this site are the similar to those of
Site 2, except that the proximity to the water storage tank is no longer an issue.


The estimated cost of developing a plant at each of the sites is included in Exhibit A.


Public Works staff and the consultant have presented the findings at a Pescadero Municipal Advisory Council meeting in August. The community supports a local sewer system, but they have concerns with the high capital cost and the on-going operation and maintenance cost. Some members of the community indicated that there are other priorities, such as addressing frequent flooding, that are more important than constructing the sewer system. In order to obtain reimbursement from the grant, the County needs to complete the environmental assessment and submit the full report to the SWRCB.


The Resolution has been approved as to form by County Counsel.



There is no impact to the General Fund for accepting the Facilities Plan and designating the preferred alternative.



Exhibit A


Exhibit B