To counter these stresses, sanitary districts such as DGSD regularly inspect sewer systems and make repairs to replace damaged pipes and control I/I levels to enable the system to function as designed.
DGSD, however, had used chemical grouting on previous rehabilitation projects with reasonable success in terms of I/I reduction.
"Our previous experience indicated to us that chemical grouting was a viable, cost-effective solution to reduce I/I," says Bob Swirsky, DGSD's sewer system maintenance supervisor.
For this project, DGSD identified particular areas where pipe conditions were optimum for grouting--i.e.
For example, since inspections of DGSD pipe had shown significant root intrusion, after the pipes had been cleaned and roots cut, a chemical growth inhibitor was added to the grout to curtail future root intrusion.
As noted, DGSD has conducted flow-metering of the 149 basins in its system for almost 20 years and has assembled GIS data on pipe condition, peak flows and I/I for each basin.
That procedure --using three crews in the same basin--allowed DGSD to assign only one inspector to the basin, freeing other personnel for District work.
The grout used in the DGSD project was an Acrylamide grout complying with ASTM F2304.
The DGSD inspector on site found the result to be a solid lining and we approved moving forward with the lining procedure for the remaining manholes.
With that "saved" funding, DGSD and the contractor identified two additional basins that could be treated with chemical grouting, bringing the total number of basins grouted to 17.
Also, he points out, removal of roots and the use of additives to inhibit future intrusion reduces the workload of the DGSD's maintenance crews, freeing them for other work.
These final own-initiative Guidelines have been developed according to Article 16 and 26(2) of Regulation (EU) No 1093/2010 (EBA founding Regulation) in order to promote a common and consistent approach to cooperation agreements between DGSs throughout the Union, which must be in place in accordance with Article 14(5) of the DGSD
, and to contribute to strengthening the European system of national DGSs in accordance with Article 26(1) of the EBA founding Regulation.