Drainage user fee would pay to eliminate
Article Launched:02/07/2007 02:31:38 PM PST
Two sites in Ross and another in San Anselmo create the worst
bottlenecks in Corte Madera Creek, topping a list of seven prime
culprits that cause flooding in the Ross Valley, engineers say.
The blockages, where flooding would occur first during heavy rainfall,
were identified in a new hydraulic computer model developed by
engineering consultants hired by the county.
Marin County Supervisor Hal Brown said the information will be used to
decide how to spend taxpayer money if voters approve a new storm
drainage user fee on a proposed April ballot.
Most homeowners would be asked to pay $125 or less per year, but the
maximum charged homeowners will be $180 a year - for 20 years.
Fees will vary according to the size of parcels and the amount of
impervious surfaces on the property.
Brown is leading an ambitious new effort to reduce the risk of flooding
in Marin's Ross Valley. A storm that hit Marin early in the morning of
Dec. 31, 2005 damaged about 1,200 homes and businesses. Most were
located along Corte Madera Creek.
Brown said the plan is to ask voters to approve the user fee in April.
"We don't want to put this off again," he said.
Two of the three worst blockages are in Ross - where a U.S. Army Corps
of Engineers flood control project has been stalled since 1971. The
Ross choke points are at the Lagunitas Road Bridge and a wooden fish
ladder about 600 feet downstream from the bridge.
Equally troublesome is the Madrone Avenue Bridge in San Anselmo, said
Jack Curley, who is overseeing the county's participation in the flood
Using a computer model of the creek, engineers found that water would
spill over the creek's banks at those three sites first, Curley said.
When the model simulated additional rainfall, flooding occurred on the
creek where it is spanned by a commercial building at 636 San Anselmo
Ave. in downtown San Anselmo, and along a 550-foot-long culvert that
runs under downtown Fairfax. Two other San Anselmo bridges, at Nokomis
and Sycamore avenues, would flood next if even heavier rainfall
occurred, the model indicated.
The results came as no great surprise.
"These are all the prime suspects that everybody in San Anselmo will
tell you about," Curley said.
Nevertheless, Curley said he didn't expect the fish ladder to rank at
the top. "I knew it was a constriction. I just didn't know it was such
a limiting constriction," he said.
The Army Corps of Engineers is waiting for Friends of Corte Madera
Creek Watershed, an environmental group, to submit recommendations for
replacing the fish ladder. The fish ladder is included in the Army
Corps' plan to widen an 800-foot stretch of the creek near the Ross
Post Office and to erect flood walls along the creek. The plan has been
in the works for decades.
Last week, the effort suffered its latest setback when the House of
Representatives voted to strip "earmarks" - legislators' pet projects -
from the fiscal 2007 federal budget. Marin County had hoped to get
$700,000 this year to move the project through the planning process.
Jim Miller, who manages the project for the Army Corps, said there is
still a chance that some of the federal money will be made available.
"We don't know yet," Miller said.
Curley said that the computer model indicated that even if all
bottlenecks are removed from Corte Madera Creek, flooding would still
occur in the Ross Valley in case of a storm like the one that hit Dec.
31, 2005. But storms of that magnitude occur only about once every 100
years, Curley said.
The model showed that the construction of catch basins upstream could
further reduce flood risk. Basins capable of holding 1,300 acre-feet of
water would need to be built and all the bottlenecks removed to prevent
flooding during another 100-year event, Curley said.
"The community may decide in the long run that 50-year protection is
all they're willing to pay for," Curley said.
IF YOU GO: Supervisor Hal Brown and county staff will review data on
Corte Madera Creek bottlenecks and share information about the flood
protection program's progress at 9:30 a.m. Saturday at Sir Francis
Drake High School, 1327 Sir Francis Drake Blvd., San Anselmo.
Contact Richard Halstead via e-mail at email@example.com