A recently completed construction project entailed installing watermain crossings under two of the busiest roadways around Minnesota’s Twin Cities. Open-trench excavation was not a viable option, so pipe ramming (or jacking) was chosen for installation of a 42-inch watermain under I-394 near Golden Valley and a 60-inch casing housing two watermains under Highway 100 in St. Louis Park.

Area soils range from peaty with man-made fill to silty and sandy. This variability poses a significant challenge as pipe ramming in these conditions may cause movement at the surface or result in development of a sinkhole. Pavement slumping under these roadways during ramming or the preceding dewatering would be hazardous for commuters.