Report on Performance of the Wastewater Collection System

July 2, 2004 Rain Event

 

 

 

 

 

This report provides information on the performance of the Wastewater Collection System during the July 2, 2004 rain event.  The report contains the following sections:

 

 

 

1)         Description of the Storm Event

 

 

2)         Response by the Wastewater Collection Division

 

 

3)         Lift Station Alarms

 

 

4)         Performance of Recent CIP Projects During the Storm Event

 

 

5)         Flow Monitoring Results Pertaining to Future CIP Projects

 

 

6)         Flows Received at WWTP Headworks

 

 

7)         Summary

Description of the Storm Event

 

           27th and Naismith Park (North)                        PS #31 2838 Meadow Drive

 

 

Tipping bucket rain gauges were downloaded at three locations by Collection Division Staff on Tuesday, July 6, 2004.  Rain gauge data showed rain amounts of between 3.75” and 4.5” for July 2, with rains beginning around 10:30 a.m. and ending around 4:00 p.m. in most locations.  The intensity of the rain was above average for a brief period around noon, then leveled off to a heavy, soaking rain the remainder of the afternoon.  This rain event was preceded by June 2004 rainfall totals averaging 4.25” at the three rain gauge locations.

 

 

Response by the Wastewater Collection Division

 

The Wastewater Collection Division implemented the Rain Response Plan (RRP) once rainfall totals eclipsed one inch.  Line maintenance crews were sent to inspect channel crossings and areas where high flow has been noted in the past.  Two separate trucks were sent to respond to the sixteen (16) sewer backup calls, enabling staff to respond to most calls within the 45 minute optimum response time.  Lift station crews began checking vulnerable pump stations via on-site visits and polling of data at the computer lift station monitoring work station.  The Inflow/Infiltration Technician and summer intern inspected flows at locations listed on the Wastewater Master Plan Watch List, a list of locations where modeling by Black and Veatch shows the possibility of surcharged lines. Reporting requirements, responding to alarms and backup calls (16 calls), and continual monitoring of the system after the rain event resulted in significant overtime hours for Collection Division staff.

 

 

 

 

Lift Station Alarms

 

HWW = high wet well  NOP = no operational problems

 

 

PS #3               720 Grant                                 HWW – NOP

 

PS #5b             2701 Delaware (HINU)           HWW – NOP

 

PS #6               2449 Massachusetts                 HWW – NOP

 

PS #16             220 West 6th                            HWW – NOP  (*)

 

PS #26             4118 Trail Road                       HWW – NOP  (**)

 

PS #28             507 Sandpiper                          HWW – NOP  (***)

 

PS #33             4820 Clinton Pkwy                   HWW – NOP

 

PS #39             912 North Michigan                 HWW – NOP

 

PS #40             4622 Trail Road                       HWW – NOP

 

PS #41             2504 East 27th Terrace HWW – NOP  (****)

 

PS #43             4117 West 13th                        HWW – NOP

 

 

(*)        PS #16 (220 West 6th) bypassed an estimated 6,000 + gallons into the Kansas River over several hours

(**)      PS #26 (4118 Trail Road)  street flooding spilled over into pump station area; staff used mobile pumps to discharge water from wetwell into the storm sewer system to prevent basement damage to adjacent homes;  Total discharge estimated to be 2,000 gallons

(***)    PS #28 (507 Sandpiper) staff used mobile pumps to discharge water from the wetwell to a storm sewer to prevent basement damage to adjacent homes; total discharge estimated to be 2,000 gallons

(****)  PS #41 (2504 E. 27th Terrace) staff used mobile pumps to discharge water from the wetwell to a storm sewer to prevent basement damage to adjacent homes; total discharge estimated to be 1,000 gallons

 

All sanitary sewer bypasses have been reported by phone to KDHE as required.  Written reports will be sent to KDHE, along with lab results, prior to the given deadlines.

 

 

 

Performance of Recent CIP Projects During the Storm Event

 

The following information was gathered using flow monitoring, direct observation, and review of backup reports and lift station alarms.

 

North Lawrence Pump Station (#5RB-596) This 1996 project involved construction of a new pump station to convey all North Lawrence flows to the WWTP.  The station operated as designed during the rain event. There were no known sewer backups or sanitary sewer bypasses in the North Lawrence area.

 

Four Seasons Pump Station and Force Main (#1RB-S97)  This 1997 project involved construction of a new pump station and in-line storage basin in the Four Seasons area.  The pump station did perform as designed during the rain event, however there were a couple of problems that may need to be addressed.  A swale in the interior service road turned into a fast moving, 4’ deep channel that prevented operators from safely reaching the critical control room and valve vault during the storm (see photo)

 

 

Memorial Stadium Relief Sewer (1WW-198)  This 1998 project involved upsizing a trunk line between Memorial Stadium and a location close to the WWTP.  A second line was upsized on Connecticut Street between 8th and 13th.  This relief line operated as designed during the storm.  An absence of backup calls from Old West Lawrence and the Connecticut Street corridor (areas formerly plagued by sewer backups during rain events) suggest that the project was timely and appropriate.

 

Fall Creek Farms Relief Sewer (6WW-798)   This 1998 project involved construction of a relief line to remove 3 pump stations from operation.  The relief sewer conveyed flow as designed during the rain event.

 

South East Pump Stations (#1WW-199)   This 1999 project involved replacing two pump stations (PS #19 and P #32) in southeast Lawrence with new pump stations.  The new stations performed as designed during the rain event.  Absence of basement flooding in the service area of these pump stations (formerly known for basement flooding) suggests that this project was timely and appropriate.

 

Trail Ridge/Greystone Relief Sewer (2WW-599)   This 1999 project involved construction of a relief line to remove 2 pump stations from service near 6th and Country Club Terrace.  The relief sewer conveyed flow as designed during the rain event.

 

Yankee Tank Relief Sewer (1WW-101)  This 2001 project involved construction of a relief line between 6th and 15th  just east of the SLT.  The service area is currently mostly undeveloped. The relief line conveyed flow as designed during the rain event.

 

Manhole and Pipeline Renewal Programs:   Staff is still reviewing data to determine the effectiveness of the Manhole Rehab and Insituform projects that have occurred over the past few years.  Studies prior to this rain event suggest that the programs are successful and cost effective.

 

 

Flow Monitoring Results Pertaining to Future CIP Projects

 

This storm (estimated to be between a 5 year storm and a 10 year storm) provided a rare chance to observe system response in areas where flow monitors have been placed.  The eight (8) monitoring locations consist mostly of areas where CIP projects are slated for the near future.  The collected data will assist the Collection Division and its consultants in determining size and scope of the projects.

 

Shown in the table below are some general flow monitoring results.  

 

 

Location

Normal Average Flow (gpm)

Peak flow (gpm) from July 2-6, 2004

Peaking Factor

24th and Crossgate

337

8517.22

25.25

23rd and Naismith

225

1093.09

4.85

1330 Westbrooke

212

6790.90

32

29th and LA

125

1350.94

10.8

Lawrence and Harvard

29

1315.65

45.4

20th and Ousdahl

31

147.12

4.75

1112 Williamsburg

130

516.69

4.0

Dad Perry Park

140

950.74

6.8

 

 

 

 

Flows Received at the WWTP Headworks

 

Reports from WWTP staff on July 2 indicated that flows were coming into the plant at the rate of 88 mgd.  Additionally, screening facilities at the plant headworks were being inhibited by debris such as grass clippings and construction material.  Wastewater Collection staff traced part of the problem to a stormwater project currently under construction at 12th and Haskell.  Covers had been left off 4 newly constructed sanitary sewer manholes, allowing storm water flow to enter the collection system at that point. (see photos).  The contractor was contacted and required to install lids on the manholes.

 

         12th and Haskell                                                      12th and Haskell

 

Staff will continue to monitor this project, and it’s effect on the wastewater collection system, as it is constructed.

 

 

Summary

 

This report reflects information at the time it was written.  Additional information may become available that will change the conclusions of this report.

 

 

 

 

Jim Stuit

Field Operations Supt. – Collection Division

July 6, 2004