Take the first step
Due to the different types of practices, uncertainty about the prevalence levels within their patient population and their specific funding situations, it is not always clear what level of integration is optimal.  Rather than trying to plan, justify and fund an Integrated Behavioral Health program in a single step, it is better to define a migration path, demonstrate need and increase the level of integration appropriately.  

The first step in this migration path is to start an automated screening program (screening is needed for all levels of integration anyway).  Within a relatively short period of time (100 - 200 cases) and small cost, a prevalence graph like the one shown above, may be automatically generated that will break down your practice's population with a reasonable degree of certainty and you will have the data to show the initial level of need for Behavioral Health services.  

The natural reaction to taking this first step is that it will open the flood gates.  This does not happen in practice.  Adoption of the screening program is a slow process and automated electronic screening is at least time neutral.  Specifically, the time required to process screening results are offset by the time saved getting to the root causes of presented problems that are masked by psycho-social issues (estimated nationally at partially up to 70% of the time and exclusively 20% of the time).  The PCP is better able to treat (medications or counseling) or refer appropriately and their job has not really changed, they just have better information to do it.

Once your practice gets a handle on the prevalence distribution for its population, you can take the next step,  looking at whether it would be cost-effective to support the PCPs with a Behavioral Health Care Coordinator/program or possibly move to a Triage Therapist or Behavioral Health Consultant on staff.  Move to the higher levels of integration, only when it makes sense.