CITY OF PACIFICA
COUNCIL AGENDA SUMMARY REPORT
12/12/2022
1 SUBJECT:
2022 Storm Drainage Master Plan
RECOMMENDED ACTION:
Move to Adopt the Resolution of the City Council of the City of Pacifica adopting the City of Pacifica 2022 Storm Drainage Master Plan.
STAFF CONTACT:
Lawrence Henriquez, P.E., Associate Civil Engineer
(650) 738-3772
[email protected]
Lisa Petersen, P.E., DPW Director
(650) 738-3770
[email protected]
BACKGROUND/DISCUSSION:
The City collects and disposes storm water runoff generated within the City service area. The storm drainage system is designed to manage the runoff of rainwater and minimize the impact of significant rainfall. The City’s storm drainage infrastructure includes almost 55 miles of storm drainage lines spanning 4 to 90 inches in diameter, 8.7 miles of open channels, and two Cityoperated pump stations that ultimately discharge into the Pacific Ocean.
The purpose of the 2022 Storm Drainage Master Plan (2022 SDMP) is to identify capacity deficiencies in the storm drainage system, develop feasible alternatives to correct these deficiencies, and plan the infrastructure that will serve future development. The 2040 General Plan planning boundary was the study area boundary for the 2022 SDMP.
In 2012, the City hired Carollo Engineers to develop a Storm Drainage Master Plan that modeled the City’s existing storm drainage system. The 2012 plan identified several key infrastructure improvement projects including new storm drain lines on Linda Mar Boulevard, new storm drain lines on Avalon Drive and Edgemar Avenue, and a new storm drain pump station located in the vicinity of Clarendon Road and Lakeside Avenue, adjacent to the Sharp Park Golf Course. Although City staff sought funding for these projects, no funding was identified, and the projects were not constructed. In 2021 Carollo Engineers were hired to develop the 2022 SDMP with an emphasis on climate change impacts and identifying funding options such as grants or low interest loans, to ensure that projects can transition into the construction phase.
COMMUNITY OUTREACH:
The City collected input from Pacifica residents through varied and proactive outreach efforts.
Efforts included the establishment of a Storm Drain Plan webpage and e-mail through the City’s Pacifica City Council 2
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website creating an opportunity for residents to provide feedback on storm drainage-related matters in their respective neighborhoods. Other community outreach activities included a popup event held at the Farmer’s Market on November 10, 2021 at which flyers containing the Storm Drain Plan webpage and e-mail were distributed. On the social media side, Nextdoor and Facebook were the two platforms used to collect community information. The community information gathered was shared with Carollo Engineers for analysis and to offer solutions in the 2022 SDMP. The 2022 SDMP Final Draft (Exhibit A) is the culmination of community feedback, City staff input, and deficiencies that were identified through the Carollo Engineers hydraulic modeling. This document was placed on the City’s website and link to the document was provided on Nextdoor and Facebook on November 30th with information related to the document provided in Connect with Pacifica the same week.
COUNCIL STUDY SESSIONS:
Two study sessions with Council were held on July 11, 2022 and on September 26, 2022 regarding the 2022 Storm Drainage Master Plan (2022 SDMP). One of the purposes for the study sessions was to update Council on the progress of the 2022 SDMP and to obtain Council’s comments to help finalize the 2022 SDMP. Topics that were discussed at the July 11, 2022 and September 26, 2022 study sessions included flow monitoring, hydraulic modeling, public outreach efforts, design storms, funding options, Capital Improvement Program (CIP) project prioritizations, and potential impacts from climate change.
Below are follow-up topics of interest that were raised by City Council during the study sessions, along with staff corresponding responses:
1.) 100-Year Storm Design:
Council requested that the 2022 SDMP discuss the 100-year design storm. The 100- year storm is also called a 1% per year chance storm event. The 2022 SDMP final report identifies the volume of rain associated with the 100-year event per Council request (including the existing 100-year event and the future event with climate change impacts). As is the case for most municipalities, the City’s storm drainage system is not designed to accommodate a 100-year design storm and developing system improvements to accommodate that level of storm would be cost prohibitive, particularly considering the City’s current availability of funding for storm drainage projects. Additionally, waiting to secure this high level of funding to build such a system likely would delay drainage improvements for years. The 2022 SDMP designs improvements for 50-year storm events as this is considered a robust design and best practice. Additionally, flows related to projected climate change have been included in the design calculations, providing an added factor of safety. This allows for a good balance in the design of cost versus risk.
2.) Low Impact Development (LID):
LID measures are used to reduce runoff and mimic a site’s predevelopment hydrology. They retain and treat stormwater runoff using infiltration, evapotranspiration, rainwater harvesting/use or biotreatment. One such example is a bioretention basin located on Crespi Drive, adjacent to Cabrillo School. Stormwater runoff flows into the bioretention basin so that any debris from the street can settle out of the stormwater and be treated by the retention basin. Examples of LID measures were provided during the staff presentation during the September 26, 2022 Study Session.
3.) Wastewater Treatment Plant (WWTP) Data Volumes:
The WWTP flow average between wet weather months and dry weather months is
0.84 MGD (Million gallons per day). The implementation of a sewer system infiltration and inflow (I/I) reduction program on the City’s sewer system, as is proposed in the current Wastewater Capital Improvement Program, will likely reduce the amount of I/I Pacifica City Council 3
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that runs through the system and is treated at the plant. The ultimate success of I/I reduction programs varies depending on a number of factors, including the sources of I/I, and nature and extent of I/I mitigation performed. Reducing I/I into the WWTP would provide a significant benefit; however, it is not possible to accurately quantify the impact this would have on the City’s storm drainage system. One of the reasons related to this is the unknown nature of where blocked I/I will flow. It may not necessarily flow to the storm drain system and may instead flow to waterways, continue as groundwater, or become surface drainage. The City continues to assess the issue of I/I in the sewer system and will also assess impacts of I/I repairs on the City’s storm drain system.
Categorization of Recommended Improvements:
The 2022 SDMP was developed using 10- and 50-year storm events and allowable flood depths were evaluated for each design storm (including future increases in the 10- and 50-year design storms due to climate change). The hydraulic models for 10-year, 24-hour events and for 50- year, 24-hour events were analyzed, and the recommended improvements were classified into three types:
• Category 1 Improvements - These projects are needed to mitigate severe flooding concerns under the 10-year and 50-year design storms. Based on the risk of severe flooding that may cause property damage, these are identified as the highest priority storm drain projects and include the Lower Linda Mar, Monterey Road, and Sharp Park Improvements.
• Category 2 Improvements - These projects are needed to address ongoing drainage issues that are considered less severe than the Category 1 improvements (i.e., areas where there is a lower potential for property damage compared to the Category 1 improvements). The project is comprised of Edgemar Avenue Improvements. • Category 3 Improvements - Category 3 includes projects to address model simulated flooding under the 50-year design storm that have not historically been observed by City staff, nuisance drainage as well as other projects to extend storm drain infrastructure to unserved areas. Although important, delay in constructing these projects is not anticipated to cause near-term property damage. These projects could be implemented during larger utility upgrade or development projects. These projects include Madeira Drive, Rockaway Beach Avenue, and Lauren Avenue.
Planning Level Costs:
Planning level construction costs for the proposed improvements shown in the 2022 SDMP were developed in conjunction with Freyer & Laureta, an engineering firm specializing in storm drain improvement costing. The Association for the Advancement of Cost Engineering (AACE) defines an Order of Magnitude Estimate for master plan studies as an approximate estimate made without detailed engineering data. These are considered high-level estimates and a final detailed project design would be necessary for more accurate costing. Higher contingencies are included as part of the estimate to account for this.
These high-level project cost estimates are calculated based on a variety of elements, such as the project location, size, length, land acquisition needs, and other factors. As noted above, allowances for project contingencies (consistent with an “Order of Magnitude” type estimate) are also included in the project costs prepared as a part of this study for better cost accuracy. The proposed system improvements, capacity upgrades, and long-term maintenance plan set the foundation for the City’s storm drainage system CIP. The cost estimates presented in this study Pacifica City Council 4
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are developed from bid tabulations, cost curves, information obtained from previous studies, and Carollo Engineers’ experience on other projects. The costs below are based on the Engineering News Record Construction Cost Index (ENR CCI) and are shown in 2022 dollars:
Category 1 Improvement Construction Costs:
As noted, these projects are needed to mitigate severe flooding concerns under the 10-year and 50-year design storms. These are the highest priority projects due to the higher risk of flooding and include:
• Lower Linda Mar Boulevard - Installation of new 30” and 36” storm drain lines on Linda Mar Boulevard and installation of larger catch basins on Arguello Boulevard and Anza Drive - approximate project cost $5,200,000.
• Monterey Road - Installation of new storm drain lines and catch basins on Monterey Road - approximate project cost $6,900,000. Variation may include a new storm drain line within Big Inch Creek.
• Sharp Park - Construction of a new storm drainage pump station, storm drain lines to pump station, force main, and new outfall to the Pacific Ocean - approximate project cost $6,000,000.
Total Category 1 Project Costs: $18,100,000
Category 2 Improvement Construction Costs:
These projects are needed to address ongoing drainage issues that are considered less severe than the Category 1 improvements would experience (i.e., areas where there is a lower potential for property damage compared to the Category 1 improvements). These projects include:
• Edgemar Avenue - Upsize existing storm drain line and adding new storm drain lines on Manor Drive, Edgemar Avenue and Avalon Drive - approximate project cost $5,000,000
Total Category 2 Project Costs: $5,000,000
Category 3 Improvement Construction Costs:
Category 3 includes projects to address model simulated flooding under the 50-year design storm that have not historically been observed by City staff, nuisance drainage as well as other projects to extend storm drain infrastructure to unserved areas. These projects include:
• Maderia Drive - Upsize existing storm drain line from 21” to 30” for capacity - approximate project cost $500,000
• Lauren Avenue - Install new 15” storm drain line on Lauren Avenue - approximate project cost $1,200,000
• Rockaway Beach Avenue - Install new 15” storm line on Rockaway Beach Avenue and outfall to creek - approximate project cost $700,000 Total Category 3 Project Costs: $2,400,000
The Executive Summary from the Master Plan provides an overview of the effort involved in the completion of the Master Plan. The City Manager is recommending approval of the 2022 Storm Drainage Master Plan.
ALTERNATIVE ACTION:
There are no alternative actions identified.
RELATION TO CITY COUNCIL GOALS AND WORK PLAN:
The 2022 Storm Drainage Master Plan is consistent with the following Council adopted Goals:
• Stewardship of City Infrastructure: includes repairing/replacing outdated city Pacifica City Council 5
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facilities such as city hall, the libraries, fire stations, etc., improving streets, and responding to impacts of sea level rise. The 2022 Storm Drainage Master Plan makes recommendations for areas in the City to improve the stormwater drainage infrastructure network while taking into account the effects of sea level rise.
FISCAL IMPACT:
There is no fiscal impact associated with adopting the City of Pacifica 2022 Storm Drainage Master Plan.
ORIGINATED BY:
Engineering
ATTACHMENT LIST:
Exhibit A - 2022 Storm Drainage Master Plan (PDF)
Pacifica City Council 6
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RESOLUTION NO. _________
A RESOLUTION OF THE CITY COUNCIL OF THE CITY OF PACIFICA ADOPTING THE CITY OF PACIFICA 2022 STORM DRAINAGE SYSTEM MASTER PLAN
_____________________________________________________________________ RESOLVED by the City Council of the City of Pacifica, California, that WHEREAS, A Storm Drainage Master Plan for the City of Pacifica was completed in 2012 by Carollo Engineers, and
WHEREAS, to ensure that drainage facilities are properly planned, constructed and maintained the City of Pacifica contracted with the consulting firm of Carollo Engineers to update the City of Pacifica 2012 Storm Drainage System Master Plan with the 2022 Storm Drainage System Master Plan, which is attached hereto as Exhibit A, and WHEREAS, the 2022 Storm Drainage System Master Plan is based on existing land use and future buildout according to the proposed City of Pacifica 2040 General Plan update, and WHEREAS, the 2022 Storm Drainage System Master Plan develops a citywide drainage system hydraulic model to assess current and future capacity requirements including the impacts of climate change, and
WHEREAS, the 2022 Storm Drainage System Master Plan addresses the City’s drainage issues by ranking and prioritizing in a manner that makes the most effective use of the City’s resources, and
WHEREAS, on July 11, 2022 and September 26, 2022, study sessions were held where Carollo Engineers presented and reviewed the 2022 Storm Drainage System Master Plan with the City of Pacifica City Council and the public, and
WHEREAS, approval of the 2022 Storm Drainage System Master Plan provides planning and policy direction from the City Council,
NOW, THEREFORE, BE IT RESOLVED that the City Council of the City of Pacifica hereby adopts the 2022 Storm Drainage System Master Plan attached hereto as Exhibit A.
Pacifica City Council 7
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• • • • •
PASSED AND ADOPTED at a regular meeting of the City Council of the City of Pacifica, California, held on the 12th day of December, 2022, by the following vote:
AYES, Councilmembers:
NOES, Councilmembers:
ABSENT, Councilmembers:
ABSTAIN, Councilmembers:
Mary Bier, Mayor
ATTEST: APPROVED AS TO FORM:
______________________________ ______________________________ Sarah Coffey, City Clerk Michelle Kenyon, City Attorney