Differing Site Conditions

General
Due to the nature of highway construction and the conditions under which work is performed, designers cannot always accurately determine and describe the conditions existing at project sites. Consequently, actual conditions encountered during construction may differ from those indicated in the contract documents, resulting in a change in construction costs.
Situations may also develop during construction requiring the LG to order the contractor to slow down or stop construction through no fault of the contractor. These slowdowns or stoppages in the work may cause a change in construction costs. There also may be situations encountered during construction requiring the LG to make alterations to the design. In addition to changing the amount of contract work, such alterations could significantly affect the contractor’s production costs. In accordance with federal regulations, differing site or changed condition clauses must be included verbatim in the contract.
The standardized changed condition clauses in
23 CFR §635.109(a)
must be included verbatim in all contracts. The regulation requires the use of three different clauses, which are described in detail in the
LGPM Guide
:
  1. differing site conditions clause;
  2. suspensions of work ordered by the engineer (LG); and
  3. material changes in the scope of the work.
Federal Requirements
  1. 23 CFR §635.109
    design-bid-build
    1. Requires specific language be incorporated verbatim into all construction contracts. The language covers: differing site conditions; suspensions of work ordered by the engineer; and significant changes in the character of work. There are provisions for alternate language.
    2. FHWA’s
      Additional Guidance on 23 CFR 635A
      (formerly Federal-aid Policy Guide Non-regulatory supplement to 23 CFR Part 635 Subpart A) advises the “differing site condition” clause must be made part of the contract unless prohibited by state law.
  2. 23 CFR §635.109(c)
    design-build – Encourages administering agencies to use “suspensions of work ordered by the engineer” clauses and may consider “differing site conditions” and “significant changes in the character of work” clauses appropriate for the risks and responsibilities shared with the private entity.
State Requirements
  1. Texas Government Code §2269.363(1)(B)
    – Provides that, on design-build projects, the LG assumes the risks and costs associated with unknown or differing site conditions unless otherwise provided for in the request for proposals and final contract.
Required Practices
The LG must include the required contract language for differing site conditions as described in the
LGPM Guide
.