Question $3$: Sewer CSO Regulator $(20$ points$)$

A sewer regulator is used to relieve a sewer system at a Combined Sewer Outfall when

the sewer Hydraulic Grade Line $($HGL$)($water level$)$ in the regulator upstream of this

Combined Sewer Outfall exceeds $8$ feet from the invert of the regulator. The sewer

regulator $($plan view, not to scale, below$)$ does this by discharging flow over a sharp$-$

crested weir $($section view, not to scale, below$).$

a$)$ Determine the flow rate discharged to the Combined Sewer Outfall if the HGL in the

regulator upstream of the Combined Sewer Outfall weir is $9$ feet from the regulator

invert during overflow to CSO.

Plan View

Sectlon View of Welr

b$)$ What would the regulator flow to CSO become if the HGL was maintained at $9$ feet

above the regulator invert behind the weir during overflow, but weir contractions were

removed $($creating a standard, uncontracted horizontal weir at the same location$)?$

c$)$ When maintenance workers enter the regulator to check for debris, what dangers do

they encounter which are specific to a confined space with wastewater flow? What

steps can they take to mitigate these risks?