2013 Water System Plan, Volume II - Seattle City Clerk's Office - City ...

Chapter 5 Water Infrastructure
Following chlorine disinfection contacting, samples for bacteriological analysis must be
taken per the requirements of Standard Specification 7-11.3(12) A.
All samples must meet the bacteriological criteria. If any sample does not meet the
criteria, the installation must be flushed, and re-tested until acceptable bacteriological
results are achieved as required by Standard Specification 7-11.3(12)M.
Post-installation taste and odor testing may also be required as described in and
Standard Specification 7-11.2(3).
F. Dechlorination
Chlorinated water from the disinfection of water mains must be dechlorinated before
discharge.
Depending on discharge location, water drained from pipelines before shutdown must
also be dechlorinated.
Typically, SPU uses an ascorbic acid (vitamin C) injection system for dechlorination. The
chlorine concentration acceptable for discharge may vary depending upon the type and
point of discharge. Discharges to a combined sewer may have some chlorine residual.
Discharged water that may enter the environment, either through direct discharge to
the ground for infiltration or via a storm drain, should have zero chlorine residual. The
design engineer should clearly establish the acceptable points of discharge and chlorine
residual criteria in the contract specifications. On most projects, dechlorination of
disinfection water is the contractor's responsibility.
5.10.4 Customer Impacts and Service Disruptions
The design engineer or project manager should coordinate with SPU’s Communications and
Customer Service Branch to determine timelines associated with water main shutdowns.
5.10.4.1 Customer Impacts
All known or potential impacts to customers associated with construction or repair of water
system facilities must be identified. Community notification requirements vary depending on
the following:
Length or size of the project area
Number of customer services impacted, including anticipated service disruptions
Number and type of streets and street intersections in the project area
Extent of work outside of public ROW, such as work within temporary or permanent
easements
Access to project area, including points of access, types of construction
vehicles/equipment, and frequency of construction vehicle trips
Length of time and schedule constraints of the project
Work hours (day, night, weekends) needed to meet the project schedule and/or
minimize community impacts
SPU Design Standards and Guidelines
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