This is an example of the calculations done for an NRPZ subdivision. It is based on the approved Overlook Drive subdivision off Old Northfield Road. The right hand columns show the actual numbers for the approved subdivision (Existing) and the calculated results if the same parcel was developed using NRPZ.
Using NRPZ three calculations are done. The first determines the number of dwelling units. The second determines the amount of open space. The third is the amount of developable land.
| Dwelling Units | Existing | NRPZ |
| #1. Determine acreage of the entire project. | 19.65 | 19.65 |
| #2. Determine the acreage in the Residential/Agricultural zone. | 19.65 | 19.65 |
| #3. Determine the acreage of constrained lands: 10% of developable area, 1/2 of slopes >15%; all slopes >25%, and all freshwater wetlands and buffer zones, water resource areas, and restricted areas. | N/A | 8.54 |
| #4. Subtract, as indicated above, the acreages in #3 from the total area of the Residential/Agricultural zone in #2. | N/A | 11.11 |
| #5. Divide the remainder acreage in the Residential/Agricultural zone by five (5) and round down to equal the base number of dwelling units. | N/A | 2 |
| #11. Add in any dwelling units from density bonuses and/or TDR to arrive at the maximum dwelling units (may not exceed 1.25X the base number from #10). | 6 | 2 |
| Open Space | Existing | NRPZ |
| #12. Multiply the total Residential/Agricultural acreage (from #2) by .80. | N/A | 15.72 |
| #15. Add any additional open space from density bonuses, if any, to arrive at total acreage of open space to be preserved. | N/A | 15.72 |
| Developable Land | Existing | NRPZ |
| #16. Subtract #15 from #1 to arrive at the acreage remaining for development as house lots and streets. | 19.65 (3.8 ac per lot) | 3.93 (1.96 ac per lot) |
1. There are two versions, one showing a conventional outcome as applicant proposed (Existing), the other showing an NRPZ outcome per current draft #4 (NRPZ). Conventional development figures are in the first column, NRPZ numbers in the second. Shaded rows are the important outcomes of the analysis.
2. There were no scaled plans to work from, nor precise knowledge of acreages of wetland and steep slopes. Therefore, I relied on information provided by Alan Pease.
3. I have included the two ANR lots that derive their frontage from Route 31 in this analysis. I did so because they both gain their actual vehicular access through the four-lot subdivision via a shared driveway off the subdivision road.