Water
Watermain Replacement
Plentywood, Montana
Client: City of Plentywood, Montana
The City of Plentywood retained Interstate Engineering to evaluate the existing water distribution system and make recommendations as to what improvements or upgrades needed to be made. The evaluation included review of hydrant flow tests, City Water Department staff knowledge and field review of the area. This review indicated that approximately 8,000 LF of existing waterline was undersized (4”), beyond its useful life and was badly deteriorated or experienced freezing problems. The total project budget was established at $1,000,000.00. Interstate assisted the City in securing a low interest loan package ($500,000 @ 2.25% and $500,000 @ 3.75%) to fund the improvements.
The project was designed and bid with four (4) waterline sections based on priority and four (4) asphalt street repair sections corresponding to the waterline sections. The results of the bid opening allowed the top two priority sections of waterline and street repair to be considered in the amount of $795,062.50 for 6,335 feet of watermain replacement, 23 gate valves and the corresponding water services. The underground contractor, Kemper Construction of Minot, North Dakota, proposed a pipe bursting alternate which would minimize the amount of asphalt repair to the pulling pits, valve replacement areas and service lines. This alternate method utilizes a cable pulled through the existing waterline, attached to a bursting head and heat fused HDPE pipe.
The cable and pipe assembly is pulled through the existing waterline, valves and service lines. Once the cable and pipe assembly are pulled through a 300 to 600 foot section of watermain, the ends are connected to the existing watermain and the new services dug in. Utilizing this alternate method, the City was able to replace nearly 1,400 more feet of waterline (7,714 vs. 6,335) for the same cost. This alternate method of waterline replacement has a higher per foot cost for the waterline than conventional open cut, but it greatly reduces the amount of asphalt surfacing that needs to be replaced, so more waterline can be replaced for the same overall cost.
