Master Plan of Drainage

What is a Master Plan of Drainage?

A Master Plan of Drainage (MPD) is a broad engineering analysis of an operator's drainage system. It takes into account standard design storm predictions, topography and land use, and the physical attributes of the storm drain system to identify deficiencies in the system. Once that is done, budget level cost estimates and priorities for addressing the deficiencies are determined to develop a plan to correct them.

What does RPV's Master Plan of Drainage tell us?

In October of 2013 the City Council awarded a contract to RBF Consulting, Inc. (now Michael Baker International) to develop an MPD for the City. In our case, the MPD is a GIS based, city-wide engineering analysis using computer modeling to identify the capacity deficiencies of the storm drain system in the City. The City's system was subdivided into 10 watersheds (or drainage areas - see map (PDF)) for convenience and the report deals with the watersheds chapter by chapter.

A study of this type is typically used as the basis of a capital improvement program for the asset class under review and that is its purpose for the City of Rancho Palos Verdes. The RPV MPD used capacity deficiency information, coupled with potential for and characterization of flooding risk, to prioritize projects. Because the analysis is City wide, it provides only a preliminary assessment of trouble areas. Further work will be done at each identified location to confirm the preliminary assessment, determine the design parameters for a correction and recommend an alternate for final design and construction. However, the RPV MPD is useful in developing budgets and priorities for the needed work.

Concurrent with the Master Plan of Drainage study, the Public Works Department collected data (through another contract) on the physical condition of various pipes that make up the system. A standardized rating system was used to rate the condition of the pipes in a range from 0 (needs no attention) to 5 (major deficiencies). Pipes with a rating of 3 to 5 are considered to be priorities for rehabilitation of replacement. This information was provided to Michael Baker Inc to be included in the prioritization scheme for the capital program.

Estimates to correct the deficiencies were made based on unit costs for similar work from the industry to give an "order of magnitude budget" of about $17.6 million. The study then used an annual funding estimate of $1.3 million to determine the length of time it would take to work through all the deficiencies. $1.3 million is the approximate average amount collected by the City's 10-year old Storm Drain User Fee each year. Although the Fee collection expires in Fiscal Year 2015 to 2016, it was assumed to continue for another 10 years at that level for the purposes of the study. Using these assumptions, a 10-year spending program was developed to serve as a budgeting guide for the City to tackle deficiencies in the storm drain system. It should be noted other sources of funding (besides a User Fee continuation at $1.3 million per year) will be required to accomplish this plan in 10 years.

Why is it important now?

The Master Plan of Drainage is posted on the City's website for easy public access in advance of upcoming discussions regarding the end of the Storm Drain User Fee and options for future funding of this program. The topic will be discussed this autumn in public meetings of the various advisory committees, including the Water Quality and Flood Protection Oversight Committee, the Infrastructure Management Advisory Committee and the Finance Advisory Committee. The City Council is expected to decide in early 2016 whether to ask the voters to extend the Storm Drain User Fee as a funding source for the City's storm drain improvements program.

How can I see the City's Master Plan of Drainage?

Click on the links on the right to see the various chapters, exhibits and technical appendices of the study.