From: "Osalbo, Faustino Jun" <>
Date: July 22, 2005 9:52:40 AM PDT
To: 'Mark Brest van Kempen' <>
Cc: "Brooks, Desley" <>, "Nadel, Nancy" <>, "Uzegbu, Marcel" <>,  "Estes, Lesley" <>, "Schwarz, Alison" <>, "''" <>, "''" <>, "''" <>, "Neary, Mike" <>,, 'Barbara Sutherland ' <>,  Office of the Mayor <>,  "''" <>, "''" <>, "Ward, Ron (PWA)" <>,  "Lau, David W" <>, "Sweiss, Fuad" <>, "''" <>, "''" <>,  "Madison, William"

Subject: RE: [Friendsof2Creeks] Re: Chimes Creek increased flow


1.         Most of the water currently draining into the detention pond is coming from the sub drains located on the Leona Quarry development site. Before grading started at the site, there was continuous flow of sub-surface water into Chimes Creek. Sub-surface flows are now more apparent in Chimes Creek because they are collected in the sub-drains and discharged directly to the detention pond and then pumped into the storm drain system on a weekly basis.
Water being applied to the ground for continuous dust control may contribute to the sub-surface flows through infiltration. Streets A, B, C, D, G & H now have 4-inch perforated pipes buried beneath the gutters to collect sub-surface flows.  These perforated pipes are connected to the inlets and drain into the detention pond.
2.         As a precautionary measure, the outlet of the detention pond is blocked to make sure that no turbid water would discharge inadvertently. Therefore, periodic pumping of the detention pond directly into the storm drain system is a necessary step to maintain the stormwater runoff design capacity of the detention pond. Turbidity is measured as "NTU" (nephelometric turbidity units), or "cloudiness" of the water.  The requirement we impose on the contractor is that the NTU reading of the water must be well below 50 NTU's before being released into the storm drain system. The pond water being released into Chimes Creek on June 27, 2005 measured 5 NTU. At the completion of the project, the block at the outlet will be removed to allow continuous discharge from the pond into the storm drain system.

Jun Osalbo