From: "Tony Ndah"
To: "Liang Lee" ,"Jason Christie" ,"Christy Chung" ,"Richard & Ellie Moll" ,"Susan Mandle"
CC: "Saeid Hosseini"
Subject: Summary of Field meeting regarding erosion repair alternative at Robinwood Pool Property
Date: Thu, 28 Jun 2007 14:28:47 -0700

All,

Below is a brief summary of the meeting we had on June 26, 2007 to discuss the erosion repair alternative for the Remmel/Robinwood Pool property. Richard also had 2 follow-up emails with questions related to the discussions at our meeting. The response to both emails is covered in the summary below.

Please let me know if you have any comments or edits.

District staff met at the Adobe Creek Upper Reach 5 project site to discuss erosion repair alternatives for the Remmel/Robinwood pool property. In attendance were Richard Moll, Susan Mandle, Jason Christie, Christy Chung, Liang Lee, and Tony Ndah.

The meeting began with a review of the plan sheets and Richard provided an overview of his concerns on the Pool property to the group. Liang Lee explained the concept of the log slope protection. Richard asked how the log slope protection would work since there is a cavity at the erosion location. Liang explained that with each log that is placed, there is soil that is placed behind it and compacted to fill the void. This allows existing roots from trees on site to remain. The design life for the log slope protection is about 20 years. Susan asked how the log slope protection would protect against flows from eroding the soil behind the logs. Liang explained that the soils are compacted in lifts and that the soil will get wet during high flows, but the soils will not be subject to the erosive forces of the flow. The group then went out to the field where we saw the condition of the pump house and the erosion at the Remmel/Robinwood Pool property line. Richard informed the group that during the development of the 2002 design, there was a plan for the Pool property owners to remove the equipment from the pump house, and that the District would demolish the structure has part of its work to rebuild the channel bank.

The group moved down into the channel to view the erosion. Tony took a few measurements for the limits of the erosion repair on the site, which measured about 45 feet from the existing phase of the gunite on the Remmel property. Liang suggested that the project team include a photo of the erosion site in the plans and include language in the specifications that allows the engineer to make field adjustments during the construction of the project.

At the end of the field visit the group agreed to use log slope protection for the erosion repair on the Remmel and Robinwood pool properties. The erosion repair would be up to the 10 year water surface elevation, with soil fill above the log protection.

Post Meeting Questions and Responses

Tony, was my offer of demolishing the pool pump house in order to stabilize the upper part of the bank accepted as part of the plan?
Demolishing the pump house was not accepted as part of the plan since the height of the log slope protection would not be impacted by the location of the pump house.

Regarding correcting the profile of the creek at the waterfall: in addition to just making it right, wouldn't it be beneficial to the contractor to have the correct profile at the waterfall in order to properly estimate the amount of rock needed for the step pools, and not be to surprised with the 2 foot deep pool at the downstream side of the waterfall - regarding construction techniques or work required, so you don't get hit with an expensive change order?

While the profile is important information in the plans, the contractor will rely on cross sections, section details, and average end calculations to determine its quantities. Hence, I think we have a good representation of the existing channel profile.

And what if that 2 feet deep pool actually penetrates down into the water table - any consequences?

The contract documents call out the possibility that the contractor will encounter groundwater on the site, so the contractor will bid the job accordingly. When the contractor encounters water on site he will have to perform dewatering activities prior to installing the channel features. This is fairly common on most natural creek jobs, so it not a big concern for the project.

Confirm the design flow rate below the waterfall for the project

The design flow rate for the project agreed by the Collaborative was 1,100 cfs for the creek upstream of Robleda storm drain and 2,560 cfs for the creek channel downstream of Robleda storm drain.