April 26, 2006
To: Lake Merced Task Force
From: Dick Allen
After reading the Public Draft, Vista Grande Watershed Plan, I am going to offer an idea that may result in a more productive and reasonable approach to flood abatement along John Muir Drive during major storms.
At the outset, I will readily acknowledge that I am outside of the insiders loop pertaining to the Vista Grande Watershed Plan. What compels me to respond to this study however, is what seems to me as a lack of priority status assigned by the SFPUC and Daly City to get our rainfall into the Westside Basin Aquifer. Based on the Vista Grande Watershed Plan, the major goal appears to be, get the rain water out to the ocean so we won't experience flooding during major storms.
The proposed Vista Grande Watershed Plan focuses on:
1) Regional Detention Storage
2) Direct Discharge to Lake Merced
3) Detention Basin At Vista Grande Canal
4) Structural Control Followed by Treatment Wetland
5) New Parallel Tunnel and New Tunnel South of County Line,
6) Bank Armoring Wetland Construction
7) Storm Drain Improvements
8) Runoff Reduction Practices
9) Storm Drain Master Planning
10) And finally lots of money, like $165,000,000 or more.
2) Direct Discharge to Lake Merced
3) Detention Basin At Vista Grande Canal
4) Structural Control Followed by Treatment Wetland
5) New Parallel Tunnel and New Tunnel South of County Line,
6) Bank Armoring Wetland Construction
7) Storm Drain Improvements
8) Runoff Reduction Practices
9) Storm Drain Master Planning
10) And finally lots of money, like $165,000,000 or more.
The project that I would like to see get traction is based on two very common events that just about all of us are familiar with and is analogous to recharging the overdrafted Westside Basin Aquifer. First example, if a person's bank account is overdrawn, a high priority is to replenish the bank account with more money. The second example, if a person becomes dehydrated, a high priority would be to replace their fluids if they want to go on living. (It is common knowledge that aquifers around the world are being over drafted to meet increasing demand for water)
Well, I would like to see our Westside Basin Aquifer go on living forever, and become fully recharged over time through the employment of injection wells with rainwater into the aquifer instead of flowing out to the ocean.
I would encourage the SFPUC and Daly City to evaluate the benefits of constructing a gallery or line of injection wells parallel to the Vista Grande Canal, and in detention basins. These injection wells would be engineered to recharge the Westside Basin Aquifer with fresh rainwater and eliminate the risk of flooding during major storms.
Without these injection wells there would be the typical unimpeded outflow of rainwater to the ocean. Is this good public policy?
Instead, where amounts of water are withdrawn by the gallery of injection wells located in detention basins and along the Vista Grande Canal, the amount of rain water transported to the ocean decreases and the risk of flooding is eliminated. Would this be better public policy? Just curious.
Homeowners are encouraged by the SFPUC to install water flow reducers on their showers and toilets in order to conserve water. However, now under the proposed Vista Grande Watershed Plan, the SFPUC and Daly City are proposing to enlarge the flow of rainwater to the ocean by spending millions of dollars on an enlarged tunnel. This seems to be a contradiction of public policy relating to good water conservation and management practices.
It is my hope that Daly City and our SFPUC will have a public dialog reviewing this alternative method of flood control.
