The Town of Groton, population 10,772 (2010), is located in northeastern Massachusetts, 30 miles northwest of Boston. In 1980, the Town adopted TDR provisions designed to preserve scenic areas, environmentally-sensitive land, farmland and land important to the protection of Groton’s water supply. Although the ordinance allowed for a 25 percent increase in density for receiving site projects using TDR, no applications were made in the first eight years.

In 1988, the Town adopted major revisions to its zoning code. Although the original TDR provisions remained largely intact, Groton added a development rate limit provision to the code. After the 1988 revisions, the TDR option was used extensively because receiving site developers could choose between two incentives for using TDR: the original 25 percent density bonus or the ability to exceed the annual building permit quota.

The Process section immediately below describes the program as it existing in 2003. Addition changes occurring between 2003 and 2011 are not explained in detail but rather are summarized in the final Program Status section.

Process (As it existed in 2003)

The TDR process is only available for use in Groton’s Residential-Agricultural (R-A) zoning district. However, the R-A district accounts for roughly 90 percent of the Town’s land area. Owners of land in the R-A district can choose to develop under the traditional R-A regulations, which allow development at a density of one lot per 80,000 square feet of land area. Alternatively, landowners and developers can elect to apply for a special use permit under the Town’s Open Space Residential Development provisions.

The Open Space Residential Development code section is designed to achieve several purposes including the following: preserve open land for its scenic beauty; enhance agricultural, open space, forestry and recreational uses; protect the natural environment; perpetuate the appearance of Groton’s traditional New England landscape; and promote the development of affordable housing. Under this code section, developers can apply for reduced development requirements using either clustering or flexible development provisions. Prior to 1988, the clustering alternative did not involve TDR. Conversely TDR was, and is, allowed under the flexible development option discussed below.

Using the flexible development provisions, a developer can apply for reduced development requirements with or without using TDR. For example, this code section allows reductions in requirements for lot area, frontage and setbacks in return for the preservation of 25 percent of a development site as open space and the provision of an affordable housing unit for every ten market-rate units or payment of an in-lieu affordable housing fee. In addition, the density of a receiving site project can be increased by 25 percent through TDR using the “incentive lots” described below.

An incentive lot can be created by deed restricting 80,000 square feet of land in the R-A zone. Since the baseline density in the R-A zone is also one lot per 80,000 square feet, the program offers a one-to-one transfer ratio. The Planning Board must determine that a proposed sending site should remain undeveloped due to its significance for environmental, scenic, agricultural, open space or water supply purposes. However, wetlands cannot qualify as sending sites.

Prior to 1988, TDRs could only be used in receiving site projects in the R-A zone which follow the flexible development section of the code. To be awarded additional density through TDR, the Planning Board must determine that a proposed receiving site would not qualify as a sending site; in other words, it cannot have environmental, scenic, agricultural, open space or water-supply significance. The decision of the Planning Board is made after a public hearing and is final.

As stated in the Background section, in 1988, Groton added a Development Rate Limitation provision to its zoning code. Under this code section, building permits can only be issued if less than 120 dwelling units have been permitted in the last 24 months for the entire Town. Alternately, building permits can be issued if fewer than 12 units have been permitted in a single subdivision in the last 24 months. However, as an incentive to deed restrict sending sites, development rights can be used to build an extra six dwelling units per year in addition to the six units allowed under the development rate limits. In other words, a developer can double the number of units permitted per subdivision each year by using the development rights created by deed-restricting 80,000 square feet of sending site land.

Receiving site developers cannot use the same TDRs to both accelerate the pace of development and increase density on a receiving site; developers must chose to either use these development rights to build more units per year or increase density. TDRs can be used to accelerate development on receiving sites approved under the clustering as well as the flexible development provisions of the Open Space Residential Development zoning code section.

Finally, the Town allows sending site owners to deed restrict their land and sell the resulting TDRs at any time. Developers may buy these rights and hold them or resell them as well as use them immediately on receiving sites.

Program Status

Groton received no applications for TDR from 1980 to 1988, when the only incentive was a 25 percent increase in density for receiving site projects that use TDR. As reported by Michelle Collette, Planning Assistant for the Town, developers were reluctant to request special use permits knowing that adjacent property owners were likely to appear at the public hearing to protest the proposed density increase.

However, TDR use increased after the 1988 code change allowing developers to double the number of units they can build per year by using TDR. Ms. Collette estimated that from 50 to 100 sending site lots were permanently deed restricted between 1988 and 2002. All of these transfers were used to accelerate the pace of development rather than increase density at receiving sites. During that time period, Groton was going through an era of rapid development. With the Town generally reaching its overall limit of 60 units per year, TDR was the only way that developers could build more than six dwellings per subdivision annually. During that time frame, TDRs were used in every subdivision in the Town with more than six undeveloped lots. By 2002, these transfers had preserved an estimated 500 acres of land including farmland, properties important to the Town’s water supply and a greenway along the Nashua River.

In 2010, the Open Space Working Paper for the 2011 Master Plan update reported that Groton amended its development rights bylaw in 2003, increasing the incentive to use TDR by allowing two bonus lots for each TDR transferred. No estimate could be found regarding the total open space preserved by TDR since its inception.