Some infrastructure or building projects specify SCM minimums to reduce the carbon impacts of the mix. Examples include the following:
- Seattle Department of Transportation (SDOT) specifying that all sidewalks be constructed with a minimum of 25% SCM (Tracy, 2014 ‘add citation”).
- California’s High Speed Rail project also specifies minimum SCM for specific applications (cite http://www.hsr.ca.gov/docs/programs/construction/RFP_B4-PtC1_StandrdSpecification.pdf).
Minimum SCM specifications opens up a potential perception that the owner is starting to specify means and methods. With that comes a potential liability if mix designs meeting a target do not perform as expected (Sound Transit, December 2014). Although the risk of liability seems quite low, it is still a valid consideration when writing specifications. Another downside of minimum SCM specifications is that the carbon savings are not actually quantified. As expected, with higher the SCM percentages, the carbon impact of the mix is reduced. However, without quantifying business as usual compared to the low carbon mixes, governments may have a difficult time tracking the carbon savings that result from their purchases. In an era of increasingly important Climate Action Plans, quantifying carbon savings is an important factor.