Construction dewatering for waterproofing
In the early planning stages of the project, the process of dewatering a project site should look beyond what is required for structural and shoring requirements, taking into account the requirements of the below-grade waterproofing system. This upfront coordination will result in fewer surprises in the field during construction and, ultimately, a more efficient, better-coordinated, and more successful project.
In addition to structural requirements, more rigorous waterproofing-related items should also be considered regarding construction dewatering, such as:
- selecting and specifying an appropriate shoring system that take into account the requirements of the waterproofing to provide a dry substrate for the application of the waterproofing;
- including post-installation shoring system wall leakage repair recommendations as necessary;
- defining the performance of the dewatering at horizontal and sloped excavations to include providing an adequately dry substrate (i.e. no dampness that would interfere with the membrane installation, adhesives, etc.) for the application of the waterproofing;
- coordinating the shoring system and excavation layout and extents to provide a fully dewatered condition at their junction; and
- providing an efficient, redundant dewatering system that is able to deliver water from points of collection at vertical, sloped, and horizontal extents through to the point of disposal.
If a shoring system is a delegated design component, then coordination between its design (by the shoring sub) and the waterproofing requirements (specified by the architect) is critical.
| CONSTRUCTION DEWATERING REGULATIONS |
|
Governing authorities for the projects regulate construction dewatering, which is generally classified as non-routine, episodic, or other temporary discharge use.* Regulation is by permit, which sets forth the requirements by which the project is allowed to discharge into the sewer system, including testing requirements, the quantity and duration of the dewatering, and discharge fees. Depending on the project conditions and shoring system used, there may be significant discharge fee savings associated with either changing to a more watertight shoring wall system or the repair of excessive shoring leakage to meet the requirements of the below-grade waterproofing substrate, or both. * More information can be found in the San Francisco Public Utilities Commission’s, Batch Wastewater Discharge Requirements (May 2012), and Sanitation Districts of Los Angeles County, Chapter 11—“Hydrology, Water Quality and Public Health” (January 2012). |
Daniel G. Gibbons, PE, associate principal with Simpson Gumpertz & Heger (SGH) specializes in new design, including design consultation and construction administration of building envelope systems. He consults with architects, contractors, and developers on structures ranging from residential to high-rise construction, and works on a variety of building types, including condominiums, hotels, and mixed-use projects. Gibbons investigates existing building envelopes and is involved in new design of a variety of systems, including below-grade waterproofing, plaza deck waterproofing, exterior wall assemblies, balcony waterproofing, window assemblies, and roofing. Gibbons is practice leader for SGH’s Roofing & Waterproofing Practice Group. He can be reached via e-mail at dggibbons@sgh.com.
Payal R. Vora, LEED AP, has seven years of experience in the design and investigation of commercial, institutional, and residential buildings for waterproofing issues including roofs, plaza areas, below-grade spaces, and exterior walls. She has consulted with architects, contractors, and building owners on the repair and rehabilitation of contemporary and historic buildings. Vora can be reached at prvora@sgh.com.
This article is really informative and educational. I have not had to deal with many dewatering projects because of most of my excavation experience has been in the state of Arizona. That being said, I can see how the use of dewatering can be the difference maker in a good project.
I am interested
To do a work Dewatring
If you provide work
Plz call me 9690401593
Can dewatering permanently affect my well? My city is dewatering approximately 30-40 feet in order to install new sewage which is around 100 feet in front of my property and The project is around 3 miles long. My home was built in 1974 and my well is probably also around 30-40 feet. Ever since the city started the project last year my water pressure started failing and now a year into the project with at least another year to go there is heavy sediment, mud, rocks and sludge making its way into the house. My filters are constantly getting clogged and my Water system and water heater has started to show signs of failure. The city claims it has nothing to do with the dewatering but my neighbors are also experiencing the same issues. Two of my neighbors’ wells have already dried up. I’m afraid this is going to become a major problem for us. What is your suggestion. Thank you
Sounds like a meeting with your neighbors and an attorney is in order. The short answer is YES, what they are doing is causing your problems. I know this has been a few years ago, but I hope you made out okay. After they are done, the city will stop dewatering and levels should return near normal levels.