POPULATION HOLDING CAPACITY ASSUMPTIONS & METHODOLOGY
DEVELOPMENT CAPACITY ANALYSIS
Summary
The land use capacity analysis provides a range of theoretical buildout capacities for each planning subarea (see Chapter V - "Land Use Element," Figure V-1). It first determines which lots are undeveloped, underdeveloped and developed. Taking the lots that remain suitable for future development, it removes areas that are unbuildable due to environmentally sensitive areas (ESAs), providing an estimated number of buildable lots. Buildout is then calculated on a range of potential minimum lot sizes: 5,000 square feet; 10,000 square feet; and 20,000 square feet. To add further detail to the calculations, three scenarios for future development patterns were also used: "existing," "conservative, "and "ultimate"). These scenarios attempt to address how development actually occurs, or may occur in the future. For instance, a minimum lot size does not mean houses will only be built on one lot parcels. In Port Townsend for example, homes are typically built on two 5,000 square foot lots. The "conservative" and "existing" scenarios take this typical development pattern into account. However, the "ultimate" buildout scenario assumes that in the future, higher land values will lead to houses being built on single lots. The product of the development capacity analysis in a range of buildable lots for each planning subarea.
Methodology
The development capacity analysis model assumes single unit residential use. The assumption made when calculated developed parcels is that area is determinant. Small, one or two lot parcels are considered developed under a given scenario, provided they have an assessed building value over $10,000.
All rights-of-way in previously planed areas where removed from the calculation. In unplatted areas, 30% of land was devoted to rights-of-way for parcels greater than 80,000 square feet in size. This modification is done when available lots have been determined. Uptown Port Townsend has approximately 40% of its area devoted to rights-of-way. For the purposes of this analysis, it was assumed that future road infrastructure would occupy less space in platted areas than has historically been the case.
The base lot size used for all calculations was 5,000 square feet. The existing conditions information contained in Chapter IV - "Description of the Planning Area," suggests that typical platted lots within Port Townsend are 5,000 square feet in size.
The scenarios listed (i.e., "existing," "conservative," and "ultimate"), refer to a set of assumptions that condition the calculations. The assumptions are as follows:
CURRENT | EXISTING | CONSERVATIVE | ULTIMATE |
2 lots per parcel | 2 lots per parcel | 1 lot per parcel |
FUTURE | 1 lot per parcel | 2 lots per parcel | 1 lot per parcel
|
These figures act as multipliers for base lot size and scenario lot size. Current values affecting base lot size and future values affecting scenario lot size.
Determination of Parcels Available
Variables for Examples:
Base lot size - 5,000 square feet
Scenario lot size - 5,000 square feet
Undeveloped Parcels
Definition: All parcels designated as 9100 or "vacant" by the Jefferson County Assessor, or which have an assessed building value of less than $10,000.
2 parcels: | 25,000 square feet (5 lots) |
| 5,000 square feet (1 lot)
|
1. | Existing Scenario: | |
| Current | Future |
| 2 parcels | 6 parcels |
| | 0 undevelopable |
2. | Conservative Scenario: | |
| Current | Future |
| 2 parcels | 2 parcels |
| | 1 undevelopable |
3. | Ultimate Scenario: | |
| Current | Future |
| 2 parcels | 6 parcels |
| | 0 undevelopable
|
In this case, the number of parcels is unaffected by the base lot size. In all scenarios, there are tow existing parcels. In scenarios 1 and 3, parcels in the future are assumed to consist of one lot. As the scenario lot size is the same as the existing lots, the two existing parcels can be further subdivided into six. None become too small to develop. In scenario 2, it is assumed that future parcels will consist of two lots. Parcel A can therefore be divided into two lots. Lot B becomes undevelopable, because it is smaller than 10,000 square feet.
Developed Parcels
Definition: Parcels designated as 7600 (community areas), 7400 (recreation), 9700 (exempt), 7311 (fairgrounds), and 8100 (open space) by the Jefferson County Assessor.
Number of parcels small than or equal to one or two (based on scenario) times the base and scenario lot size, and not designated as 9100 by the Assessor.
1. | Existing Scenario: | |
| Current | Future |
| 2 parcels | 1 parcel (2 underdeveloped) |
| | 0 undevelopable |
2. | Conservative Scenario: | |
| Current | Future |
| 2 parcels | 2 parcels (1 underdeveloped) |
| (1 underdeveloped) | |
3. | Ultimate Scenario: | |
| Current | Future |
| 1 parcel | 1 parcel (2 underdeveloped)
|
1. Existing Scenario: Under this scenario, parcels B and C are under or equal to twice the base lot size (2 x 5,000), and are therefore considered developed. In the future, it is assumed that 1 lot is one parcel, and thus only C is considered fully developed. The remaining parcels, A and B, are then underdeveloped.
2. Conservative Scenario: As with the existing scenario, two parcels are deemed developed. In the future, however, a parcel will comprise two lots. Lots B and C are both smaller or equal to 10,000 square feet, and so are considered developed. Once again. Lot A is underdeveloped.
3. Ultimate Scenario: Only parcel C is considered as having been developed, because it is equal to or smaller than the current base lot size of 5,000 square feet. With a scenario lot size of 5,000, in the future, 1 lot is also considered developed. The remaining parcels are later analyzed as underdeveloped parcels. If the scenario lot size were changed to 10,000, in the future, two lots would be indicated as having been developed.
Underdeveloped Parcels
Definition: Excludes lots that are established as being developed or undeveloped. Comprises parcels that are one or two times (scenario assumption) the base lot size.
1. | Existing Scenario: | |
| Current | Future |
| 1 parcel | 2 parcels |
2. | Conservative Scenario: | |
| Current | Future |
| 1 parcel | 1 parcel |
3. | Ultimate: | |
| Current | Future |
| 2 parcels | 4 parcels
|
1. Existing Scenario: Only one parcel is greater than twice the base lot size. Removing first the principle lot leaves one parcel for potential development. The right-of-way condition applies in this case as well.
2. Conservative Scenario: Again, only one parcel is greater than twice the base lot size. Removing the principle lot leaves one parcel for potential development. The right-of-way condition applies in this case as well.
3. Ultimate Scenario: Two parcels exist that are greater than the base lot size, and are therefore underdeveloped. Removing the two base lots, four remain for further development. For parcels greater than 80,000 square feet in size, however, 30% of the land area is removed after the principle lots are removed. The area is then divided by the scenario lot size.
Treatment of Environmentally Sensitive Areas (ESAs)
Four ESA types were factored into this analysis: wetlands; landslide/erosion hazard areas; drainage corridor (with 50 foot buffers); and fish and wildlife habitat conservation areas. The adjoining illustrations indicates how ESAs can impact the development potential of a parcel. The ESA coverage was overlaid with the ownership coverage to create the data for this analysis.
The ESAs used are those that have been mapped in Ac City's geographic Information system (CIS). Other ESAs exist and have been generally identified, but have not yet been mapped. In particular, the wetlands map does not show the full extent of wetlands known to exist within the City.
The approach used to determine the impact of ESAs was to simply remove the area from the calculation. The area of an ESA within a parcel was removed, not the entire parcel. The remaining area was then subject to the same calculations that derived basic capacity. The manner in which the parcel polygons and ESA polygons intersect affects the base values. Base capacity using the ESA/Ownership database will be slightly lower than with the ownership database. Some parcels that formerly would have been included in the calculation are now dropped because they do not meet the threshold size.
TREATMENT OF ENVIRONMENTALLY SENSITIVE AREAS
POPULATION HOLDING CAPACITY ANALYSIS
Summary
The development capacity analysis, outlined above, was used to estimate the population holding capacity under each of the alternatives for analysis within the draft environmental impact statement (DEIS) (see Chapter X -"The Proposed Action & Summary of Alternatives; and Chapter XI - "Environmental Review of the Alternatives"). Each subarea has a range of buildable lots, depending upon the development scenario applied (i.e., "existing," "conservative, "and "ultimate"). These numbers can be used to estimate the number of dwelling units which could be constructed under each DEIS alternative, and in turn, the population holding capacity of each alternative. Each alternative has an overall conceptual density and development pattern (see Figures X-3 through X-5). For each subarea, the number of buildable lots was chosen from a scenario that most closely approximates the level of development envisioned for the DEIS alternative. The scenarios chosen for each subarea and DEIS alternative are documented in the below. Once an appropriate development scenario is chosen for each of the subareas under the different DEIS alternatives, the number of buildable lots can be totaled to arrive at the total number of buildable lots within the City for each alternative. This figure is multiplied by the estimated household size at the end of the 20 year planning period (i.e., 2.232) to give the number of additional residents. Adding the number of additional residents to the existing population of 7,940 produces the estimated population holding capacity for each DEIS alternative. For DEIS alternatives #2 and #3, which anticipate a possible expansion of the Port Townsend UGA into the Glen Cove area, the number of buildable lots within the potential unincorporated portion of the UGA was added to the City's total number of buildable lots.
Assumptions for Each Alternative by Subarea
Note: Assumptions for each subarea exclude the following environmentally sensitive areas (ESAs): wetlands; fish & wildlife habitat areas; landslide hazard areas; and drainage corridors.
No Action Alternative (Existing Plans & Regulations)
Assumptions by Subarea:
1. Blue Heron - 5,000 s.f. scenario lot size; existing build-out: 1,220 buildable parcels
2. Urban Waterfront - assumed to be exclusively commercial: 0 buildable parcels for residential use
3. Castle Hill - 5,000 s.f. scenario lot size; existing build-out: 1,192 buildable parcels
4. Fort Worden - 5,000 s.f. scenario lot size; existing build-out: 474 buildable parcels
5. Gateway - assumed to be exclusively commercial and light manufacturing: 0 buildable parcels for residential use
6. Hastings - 5,000 s.f. scenario lot size; existing build-out: 2,170 buildable parcels
7. North Beach - 5,000 s.f. scenario lot size; existing build-out: 646 buildable parcels
8. South Bay - 5,000 s.f. scenario lot size; existing build-out: 166 buildable parcels
9. Uptown - 5,000 s.f. scenario lot size; existing build-out: 658 buildable parcels
10. Western - 5,000 s.f. scenario lot size; existing build-out: 2,137 buildable parcels
11. Winona - 5,000 s.f. scenario lot size; existing build-out: 2,486 buildable parcels
TOTAL == 11,149 buildable parcels
Holding Capacity Calculations:
Step One: 11,149 buildable parcels x 2.232 (i.e. estimated household size at the end of the planning period) =24,885
Step Two: 24,885 +7,940 (i.e., 1994 OFM population estimate) =32,825
Estimated Population Holding Capacity of the No Action Alternative =32,825
Alternative #1 - Residential Community (Dispersed Growth)
Assumptions by Subarea:
1. Blue Heron - 5,000 s.f. scenario lot size; conservative build-out: 559 buildable parcels
2. Urban Waterfront - assumed to be exclusively commercial: 0 buildable parcels for residential use
3. Castle Hill - 5,000 s.f. scenario lot size; existing build-out: 1,192 buildable parcels
4. Fort Worden - 5,000 s.f. scenario lot size; existing build-out: 474 buildable parcels
5. Gateway - assumed to be exclusively commercial and light manufacturing: 0 buildable parcels for residential use
6. Hastings - 5,000 s.f. scenario lot size; existing build-out: 2,170 buildable parcels
7. North Beach - 5,000 s.f. scenario lot size; existing build-out: 646 buildable parcels
8. South Bay - 5,000 s.f. scenario lot size; conservative build-out: 68 buildable parcels
9. Uptown - 5,000 s.f. scenario lot size; conservative build-out: 247 buildable parcels
10. Western - 5,000 s.f. scenario lot size; existing build-out: 2,137 buildable parcels
11. Winona - 5,000 s.f. scenario lot size; existing build-out: 2,486 buildable parcels
TOTAL =9,979 buildable parcels
Holding Capacity Calculations:
Step One: 9,979 buildable parcels x 2.232 (i.e., estimated household size at the end of the planning period) = 22,273
Step Two: 22,273 4-7,940 (i.e., 1994 OFM population estimate) =30,213
Estimated Population Holding Capacity of Alternative #1 =30,213
Alternative #2 - Community Neighborhoods (Focussed Growth)
Assumptions by Subarea:
1. Blue Heron - 5,000 s.f. scenario lot size; existing build-out: 1,220 buildable parcels
2. Urban Waterfront - 5,000 s.f. scenario lot size; conservative build-out: 45 buildable parcels (Note:Under Alternative #2, it is assumed that all subareas, even those which are zoned for significant amounts of commercial development like the Urban Waterfront Subarea, will support some residential growth)
3. Castle Hill - 5,000 s.f. scenario lot size; existing build-out: 1,192 buildable parcels
4. Fort Worden - 5,000 s.f. scenario lot size; existing build-out: 474 buildable parcels
5. Gateway - 5,(XX) s.f. scenario lot size; conservative build-out: 227 buildable parcels (Noe: Under Alternative #2, it is assumed that all subareas, even those which are zoned for significant amounts of commercial and manufacturing development like the Gateway Subarea, will support some residential growth)
6. Hastings - 5,000 s.f. scenario lot size; existing build-out: 2,170 buildable parcels
7. North Beach - 10,000 s.f. scenario lot size; conservative build-out: 54 buildable parcels
8. South Bay - 5,000 s.f. scenario lot size; existing build-out: 166 buildable parcels
9. Uptown - 5,000 s.f. scenario lot size; existing build-out: 658 buildable parcels
10. Western - 10,000 s.f. scenario lot size; existing build-out: 1,083 buildable parcels
11. Winona - 20,000 s.f. scenario lot size; conservative build-out: 130 buildable parcels
12. Glen Cove - assume that the minimum number of additional residential dwelling units estimated for the unincorporated Glen Cove area under the "Community-Serving" UGA option (See Appendix 7 to the Draft Plan & EIS - "Glen Cove Water & Wastewater Needs") is identical to the number of "buildable parcels" for this area: 724
TOTAL =8,093 buildable parcels
Holding Capacity Calculations:
Step One: 8,093 buildable parcels x 2.232 (i.e. estimated household size at the end of the planning period) = 18,064 (i.e., estimated additional population capacity)
Step Two: 18,064 +7,940 (i.e. 1994 OFM population estimate) =26,004 (i.e., total population capacity at build-out, including areas within the City limits and the unincorporated portion of the UGA)
Step Three: 8,093 (i.e. total buildable parcels) - 724 (i.e., buildable parcels in Glen Cove) =7,369 (i.e., buildable parcels "in-City") x 2.232 (i.e. estimated household size at the end of the planning period) =16,448 + 7,940 =24,388 (i.e., total population capacity at build-out, including only areas within the City limits)
Step Four: 26,004 (i.e. total population holding capacity of alternative, including incorporated and unincorporated areas) - 24,388 (i.e., total population holding capacity of incorporated portion of UGA) =1,616 (i.e., total population holding capacity of unincorporated portion of UGA)
Total Estimated Population Holding Capacity of Alternative #2 = 26,004
Incorporated Portion of UGA: 24,388
Unincorporated Portion of UGA: 1,616
Alternative #3 - Urban Community (Concentrated Economic Growth)
Assumptions by Subarea:
1. Blue Heron - 5,000 s.f. scenario lot size; existing build-out: 1,220 buildable parcels
2. Urban Waterfront - 5,000 s.f. scenario lot size: conservative build-out: 45 buildable parcels
3. Castle Hill - 5,000 s.f. scenario lot size; ultimate build-out: 1,352 buildable parcels
4. Fort Worden - 5,000 s.f. scenario lot size; existing build-out: 474 buildable parcels
5. Gateway - assumed to be exclusively commercial and light manufacturing: 0 buildable parcels for residential use
6. Hastings - 5,000 s.f. scenario lot size; existing build-out: 2,170 buildable parcels
7. North Beach - 5,000 s.f. scenario lot size; existing build-out: 646 buildable parcels
8. South Bay - 5,000 s.f. scenario lot size; ultimate build-out: 206 buildable parcels
9. Uptown - 5,000 s.f. scenario lot size; existing build-out: 658 buildable parcels
10. Western - 5,000 s.f. scenario lot size; existing build-out: 2,137 buildable parcels
11. Winona - 10,000 s.f. scenario lot size; existing build-out: 1,083 buildable parcels
12. Glen Cove - assume that the minimum number of additional residential dwelling units estimated for the unincorporated Glen Cove area under the "County-Wide Retail/Manufacturing" UGA option (see Appendix 7 to the Draft Plan & EIS - "Glen Cove Water & Wastewater Needs") is identical to the number of "buildable parcels" for this area: 2,276
TOTAL =12,267 buildable parcels
Holding Capacity Calculations:
Step One: 12,267 buildable parcels x 2.232 (i.e., estimated household size at the end of the planning period) = 27,380
Step Two: 27,380 +7,940 (i.e., 1994 OFM population estimate) =35,320
Holding Capacity Calculations:
Step One: 12,267 buildable parcels x 2.232 (i.e., estimated household size at the end of the planning period) = 27,380 (i.e., estimated additional population capacity)
Step Two: 27,380 +7,940 (i.e., 1994 OFM population estimate) =35,320 (i.e., total population capacity at build-out, including areas within the City limits and the unincorporated portion of the UGA)
Step Three: 12,267 (i.e., total buildable parcels) - 2,276 (i.e., buildable parcels in Glen Cove) =9,991 (i.e., buildable parcels "in-City") x 2.232 (i.e. estimated household size at the end of the planning period) =22,300 + 7,940 =30,240 (i.e., total population capacity at build-out, including only areas within the City limits)
Step Four: 35,320 (i.e., total population holding capacity of alternative, including incorporated and unincorporated areas) - 30,240 (i.e. total population holding capacity of incorporated portion of UGA) =5,080 (i.e., total population holding capacity of unincorporated portion of UGA)
Total Estimated Population Holding Capacity of Alternative #3 = 35,320
Incorporated Portion of UGA: 30,240
Unincorporated Portion of UGA: 5,080
