An Approach to Specialty Municipal Excavation Requirements

In almost all cases, excavation requirements are put in place by the local Authority Having Jurisdiction (AHJ) over a given project. This AHJ can be a municipality, building or structure owner, a railroad agency, an important utility owner, or multiple at once. Understanding how to manage these requirements and effectively communicating with all parties involved is key to being a productive shoring engineer.

Successfully navigating these requirements is how D.H. Charles Engineering has been adding value to projects and helping our clients prosper through these requirements for decades. When it comes to municipalities having strict excavation rules, typically, but not always, these requirements are in the largest cities in the country, such as Los Angeles, New York, and Chicago, however, more and more are popping up all the time, taking many of our customers by surprise. We are going to take a quick look at Los Angeles and Chicago to outline some of the common issues and challenges.

Los Angeles:

In Los Angeles, there are multiple authorities that commonly review shoring design plans, and have set performance standards, but we are going to focus on two very significant agencies, for work performed in the public right away and on private property.

Los Angeles Bureau of Engineering (LABOE) typically has authority on public areas such as roadways or sidewalks, while Los Angeles Department of Building and Safety (LADBS), typically has authority on private property. Although they both are in the same city, each agency has separate requirements for shoring design submittals, plans, and calculations that are quite different from each other, as well as that of most of the country.

A couple items that set LABOE apart from other reviewing agencies are their loading and performance requirements. LABOE shoring systems must be designed for minimum lateral earth pressures and surcharge pressures outlined directly by LABOE. Often these minimum design loads are significantly higher than those that would be produced by the actual site soil conditions. In addition to the higher design loading, they have implemented a deflection standard for all shoring, regardless of location, as well as a secondary tier deflection limit when the shoring is close to structures and specific utilities. These higher loads, along with strict deflection requirements, often result in significantly more costly and complicated shoring systems than would be required elsewhere in the country.

LADBS is similar to LABOE, however, the designation of the design parameters is fully in the hands of the Geotechnical Engineer. LADBS projects are required to have loading, deflection, and other shoring specific requirements, clearly outlined in the geotechnical report. The geotechnical engineer is required to stamp the shoring plans, and therefore their involvement is critical in a project’s smooth completion. Because each geotechnical engineer is different and every project has its own specific conditions and challenges, these reports and design guidelines can vary drastically from project to project.

In addition, what really sets LADBS apart is that they will not accept tabulated data for pre-fabricated shoring products like slide rail and trench shields. Instead, they require all shoring components to be checked independently, and full fabrication drawings reproduced on the site-specific plan, with site-specific backup calculations for all framing members. Since many products are propriety, it takes careful coordination with the manufacturers and the time and cost to prepare all the paperwork can often be fairly significant.

This is not a comprehensive list of all requirements, but are the ones that tend to have the most impact when choosing what equipment is appropriate for the job. Given the large number of reviewers within the City, often times each reviewer is unique in their expectations so these must be taken into account on a project-by-project basis.

Chicago:

OUC (Office of Underground Coordination) is a group within the Chicago Department of Transportation (CDOT) and is a clearinghouse of all the local utilities whose goal is to vet each project that excavates underground against conflicts to other utilities, structures, etc. The goal of the OUC is to protect the public way. Any excavation that goes deeper that 12’ below grade must go through a further process entailing a “Deep Excavation” Review.

The “Deep Excavation” Review contains many guidelines for both what the submittal drawing package must include in addition to design parameters that must be adhered to. There are strict allowable deflection requirements, depending on what type of structure, the depth and how far away the excavation is.

The drawing requirements require showing all adjacent utilities, right-of-way lines and all sloping, to name a few. The shoring design requirements include following the prescribed parameters, showing all work and providing a detailed calculation package for review.

There are many transit authorities and railroads spread out across the United States and Canada, each with their own specific requirements. These requirements will be examined under a different post in the future.

As we learned previously, many municipalities have strict requirements for shoring. Years of experience and working with the reviewing agencies have provided DHC with the ability to successfully design excavation shoring projects through these authorities. Contact the excavation shoring experts at D.H. Charles Engineering any time, as we are here not just to prepare shoring plans but to help educate those involved in the industry and help avoid frustration and confusion amongst contractors throughout North America.