City Secures $1.06 Million for Flood Control – Immediate Improvements to Follow

Posted Date: 4/20/2016 10:00 AM

The City of Mill Valley is on target to obtain more than $1 million in funding from the County of Marin’s Flood Control and Water Conservation District, an allocation that will allow the City both to make immediate improvements in one of Mill Valley's most flood-prone areas and to continue its ongoing efforts in developing a City-wide master plan for flood control and drainage.


"This is a huge step forward in the City's longstanding efforts to address the flooding issue on Miller Avenue, but also to continue the important work of creating a long-term plan to manage the creeks and storm drainage facilities throughout the City," said former Mayor Garry Lion, who represents the City on the District’s Zone 3 Advisory Board along with fellow former Mayor Bob Burton.


The District’s geographical boundary is the same as the County’s. Each of the District’s eight flood control zones cover distinct geographical areas and receive funding via taxes and fees applied to annual property tax bills.


The City is in Zone 3, which encompasses the City of Mill Valley as well as the unincorporated areas of Alto, Sutton Manor, Almonte, Tamalpais Valley, Homestead Valley and parts of Strawberry Point.


The City’s 2016 funding request to the District of $1.06 million was for far more than in years past. The first action from the new funding – $650,000 for immediate flood control measures – will be part of the Miller Avenue Streetscape Project, the $14.8 million overhaul of approximately two miles of Miller Avenue, one of Mill Valley’s two main arteries. The project, which begins in June, stretches from Almonte Boulevard near Tamalpais High all the way to Sunnyside Avenue near downtown.


The largest component of the $650,000 work focuses on the flood-prone area of Miller Avenue and Montford Avenue near the 2am Club and Joe’s Taco Lounge. It calls for the creation of a bypass storm drain to divert stormwater away from Miller Avenue and Montford Avenue, where the Arroyo Corte Madera del Presidio creek is quite narrow and thus serves as a frequent drainage “pinch point,” causing flooding around the businesses at that intersection. The bypass will divert stormwater in an underground bypass down the middle of Miller Avenue to the Reed Street and Valley Circle intersection, discharging it into Reed Creek, which runs into a section of Arroyo Corte Madera del Presidio that is much wider and can handle the extra flow from high tides and storms.


Bob Peterson, who served as Interim Director of Public Works, and spearheaded the funding request with City Manager Jim McCann, notes that the estimated $250,000 improvement is an initial improvement as the City works toward the much longer-term fix of a 4.5-foot deep, 26-foot wide bypass channel recommended by the Stetson Study, an evaluation of conceptual flood reduction alternatives in the Arroyo Corte Madera del Presidio (ACMdP) watershed. The significantly larger bypass channel is estimated to cost “tens of millions of dollars” and thus is not seen as a viable option in the short term, Peterson said.


The second component of the Miller Avenue-area improvements is the installation of new tidal flap gates along Miller between the Redwoods senior community and the adjacent Pickleweed Apartments, replacing the existing 30-inch diameter culvert with two 48-inch diameter culverts with headwalls. That improvement is intended to prevent high tide flooding at Miller Avenue and Camino Alto. Its cost is estimated to be $197,000.

The project also calls for a pair of improvements on Miller Avenue just north of Almonte Boulevard near Tam High, a section of the road that often floods during high tides, forcing road closures. The first improvement is installing two check valves on the storm drain pipes in the area and the second improvement is raising the pavement of Miller Avenue just north of Almonte Boulevard by about 10 inches, as well as a 200-foot portion of the median in that area by about 12 inches, to prevent flooding during high tides. The cost of those two improvements is estimated at $203,000.


“We thought that our work on Miller Avenue would be a great way to demonstrate the ability to reduce flooding through focused and practical improvements – people will see some benefits right away,” Peterson said.


In addition to the Miller Avenue projects, the District’s budget allocation also includes $265,000 for comprehensive study of the City’s vast inventory of creeks, storm drains, pipes and culverts, providing much-needed additional analysis that will inform the City’s creation of a Master Plan on flood control and drainage. “Basically, everything except the Arroyo Corte Madera del Presidio, which was the sole focus of the Stetson Study,” said Peterson, noting that the Master Plan would be the beginning of the City’s community outreach efforts about priorities and funding options for the much larger and more costly long-term measures to be taken to addressing flooding and sea level rise.


The study will essentially evaluate “everything that the Stetson Study didn’t look at, including storm drain systems throughout the City, including the size and condition of all storm drain pipes and thus the potential trouble spots within the system. We’ll couple that information with the data developed through the Stetson Study to fully understand the causes of our flooding and practical solutions,” Peterson said.


The City also budgeted $55,000 for the re-evaluation of some elements of that Stetson Study, as data collected since the study was done found that Arroyo Corte Madera del Presidio has a larger capacity than indicated in the study, requiring new calculations, Peterson said.

The allocation also includes $90,000 for creek maintenance (almost tripling the amount the City has received in past years), including $55,000 for traditional creek maintenance but also another $35,000 for permitted and approved sediment removal at the City’s culverts, particularly under La Goma Bridge and at Reed Creek.


“The team effort to bring this forward and to facilitate such a positive outcome was significant and quite effective,” City Manager Jim McCann said. “We are extremely pleased with this great news and excited about what it will bring to our community.”