SEWAGE SPILLS--A TYPICAL WEEK

During the first 3 1/2 months of this year, the county Department of Health Services recorded 216 sewage spills--ranging in volume from 100 gallons up to 20 million gallons--within the San Diego city limits. One week (Feb. 4-10), 34 spills were reported.

Under Proposition 65, the Safe Drinking Water and Toxic Enforcement Act of 1986, county officials are required to report every sewage discharge believed to be a threat to the public health or safety.

Although aging sewer pipes and faulty pump stations are two of the culprits, root and grease blockages and manhole collapses also wreak frequent havoc on the municipal sewage system.

A glance at a recent, typical week:

Tuesday, May 19

Root blockage in an Ocean Beach sewer pipe caused 300 gallons of sewage to spill from a manhole at 620 Catalina Blvd. No surface waters were contaminated.

About 600 gallons of untreated sewage overflowed from a manhole at 2744 Gregory St. in Southeast San Diego. Cause unknown.

Wednesday, May 20

Grease and roots clogged a six-inch sewer main at 4753 Lotus St. in Ocean Beach, causing a 60-gallon spill that did not reach waterways.

About 120 gallons of sewage seeped from a sewer pipe at Broadway and 15th Street near downtown. There was no pollution problem from the spill, caused by grease blockage.

Thursday, May 21

A 200-yard section of Mission Bay near Dana Landing was closed to bathers after 1,875 gallons of raw sewage spewed from a manhole. Cause was listed as grease blockage.

Monday, May 25

A portion of San Diego Bay near Shelter Island was quarantined after 1,200 gallons of raw sewage spilled into a storm drain at the corner of Shafter and Canon streets. Cause unknown.