Home Foxhall Project Project History FAQ’s Fact Sheet BZA Application Traffic Reports Environmental Info Archaeology Arborist Reports Operations Plan CHNA Provisions Key Team Members Barnes Vanze Elm Street Development Wells & Associates Sasaki Associates St. Patrick's About St. Patrick's Contact Us	Arborist Reports Friends of St. Patrick’s 1801 Foxhall Road, NW Washington, DC There are 3 major concentrations of trees over this 17.3 acre site: • One occurs in the northern dell, and includes a large stand of good, mature walnut trees and other species. • Another occurs around the old estate footprint and includes a stand of mature conifers. • A third occurs along Hoban Road and is generally comprised of less significant and less healthy trees, with the exception of several large sycamore trees. In the northern dell and around the old estate, the healthy trees are being preserved in groves and copses.  Along Hoban Road, a large sycamore is a focal point for the residential entrance.  Several other mature trees will also be preserved along Hoban Road, adding significant canopy to the streetscape. Throughout the site, careful study has been given to the respective critical root zones, by species, of all the healthy special trees.  This, combined with a careful layout of roads and building sites, has afforded a preservation of at least 50% of the healthy special trees on the site.   In addition, care has been taken to preserve healthy, smaller caliber trees where possible, as these add to the structure and density of the preserved groves, and help with the regeneration of the mature canopy about the site. TREE PRESERVATION PROCESS FOR 1801 FOXHALL ROAD., NW WASHINGTON, D.C. Authored by: Keith Pitchford, President/Arborist, Pitchford Associates, LLC Commissioned by: Friends of St. Patrick’s Episcopal Day School and Vestry of St. Patrick’s Parish, on behalf of the St. Patrick’s Episcopal Church and Day School Date: February 17, 2006 I. Tree inventory – The first tree inventory of this property was done for the Friends of St. Patrick’s Episcopal Day School (“FOSP”) by the firm of Macris, Hendricks & Glascock, P.A. They surveyed all trees on the site and identified those trees 8” or more of trunk diameter at breast height (“dbh”). A total of 606 trees was identified by genus, species, dbh, and condition. Of these 606 trees, 281 trees were at least 55” of circumference (or 18” of dbh), which categorizes them as “special trees” under the District of Columbia’s Urban Forest Preservation Act of 2002. These same trees were surveyed a second time by Pitchford Associates (“PA”) to review the identification and condition ratings and to determine which of the special trees were preservation candidates. Condition ratings were determined by using a standard methodology based upon visual inspections of tree vigor and the presence and failure potential of defects. Condition ratings range from poor to excellent. Only trees found to be in “good to fair” condition, or better, were considered to be preservation candidates. At the time of the survey, of the 281 special trees identified, 177 trees were deemed to be preservation candidates at the time of the PA survey. This updated tree inventory was used by the design team in formulating the Project layout in order to include tree preservation as a significant element in the design. As part of the final engineering and design for the site, an update of the tree inventory will be performed closer to the time of implementation of the project design to determine the size and condition ratings of the trees. For example, some trees that were previously identified as preservation candidates may no longer be suitable for preservation because of a decline in condition (such as changes due to storm damage or insect or disease infestations). On the other hand, some trees may become “special trees” due to their increase in dbh. Therefore, the exact number and location of preservation candidates will be determined at the time of the final engineering and design. The FOSP and St. Patrick’s Episcopal Church and Day School (“School”) are expecting to save at least 50 %, and possibly more, of the healthy, viable special trees on the Property as identified on the final tree survey. Further, some limited number of smaller-diameter existing trees may be transplanted as a way to increase the numbers of trees retained. In addition, many new trees will be planted on the Property as part of the landscape master plan. II. Tree protection zones – Two protection zones were established by PA around each preservation candidate. These are the minimum clearance zone (“MCZ”) and the critical root zone (“CRZ”). Minimum Clearance Zone (MCZ): The MCZ is drawn as a circle around the base of the tree. It has a radial dimension of 6” for each inch of trunk diameter (dbh). For instance, a tree with a 20” dbh will have a MCZ of 10’. Within the MCZ are found the large, woody roots that emanate from the root flares. These roots are called scaffold roots and they are critical for the structural stability of the tree, and therefore cannot be severed. The severing of these roots will also result in the loss of a large percentage of absorbing roots which extend from the scaffold roots. These cuts can also open up wounds to infection by soil-borne wood decaying pathogens. Critical Root Zone (CRZ): This zone is established to protect an adequate surface area of the non-woody, absorbing roots necessary to provide water and nutrients to the tree. The difference between the MCZ and the CRZ is that the CRZ does not have to be a circle, but can be irregular in shape. The important consideration is not the shape, but the surface area protected in the CRZ. In all cases, the CRZ will encompass the MCZ. The standard methodology for determining the CRZ is to start by drawing a circle around each tree with a radial dimension of 1.0-1.5’ for each inch of dbh. The larger value is used for trees that are known to be sensitive to root loss. For example, red maple, elm, birch, hickory, and sycamore are a few of the trees in our area that are tolerant of root loss and they are often assigned smaller CRZ’s. On the other extreme, tulip poplar and beech are intolerant of root loss so they are provided with a much larger CRZ. Therefore, a tulip poplar with a 20” diameter would have a CRZ with a radial dimension of 30’. Alternatively, an elm with the same radius could tolerate a smaller CRZ of perhaps just 20’. Additionally, adjustments to the CRZ may be made based on the overall health of the tree, and not all of the CRZ needs to be preserved in an undisturbed state. Wherever possible, the CRZ’s are preserved as circles. However, this is not always possible because of conflicts with homes, roads, retaining walls or other surface features. In these instances, the CRZ’s must be captured within an irregular shaped area. This method works because the absorbing roots are known to spread well beyond the dripline and may be found at great distances from the base. Therefore, as long as the necessary area of these roots is captured within the maximum anticipated extent of the root system, then CRZ can be irregular in shape. III. Site plan considerations – Once steps I and II are complete, the initial site plan is overlain with the tree inventory and reviewed by PA and members of the site plan development team. During this process, some site plan elements, such as lot lines and road configurations, are changed where possible to allow for adequate protection zones. In addition to these modifications, other options are available to mitigate the potential for stress to the preservation candidates. Some of these methods include the use of pier footings with grade beams to span over portions of the MCZ and/or CRZ’s, retaining walls and tree wells to offset the impacts of adding soil near trees, tunneling utilities under the root zone and the use of structural soils and permeable pavement surfaces where roads or sidewalks bisect a root zone preservation area. The suitability of these methods must be evaluated on a case-by-case basis. This is a part of a multi-step process of refining the site plan to save as many trees as possible. IV. Pre-construction arboricultural treatments – It is preferable to improve the health of a preservation candidate before the start of construction. In fact, a year’s lead time is the best scenario. Within this amount of time, it is feasible to identify most, if not all, of the biotic and abiotic factors stressing a tree. The abiotic factors are usually site specific problems such as drainage or soil fertility. Biotic factors include insects and/or diseases that may be harming a tree. Because insects and diseases do not occur at the same time throughout the year, it is advantageous to have a full year to treat these pathogens and their causes. Several of these treatments have already been identified by PA and given to the FOSP representatives for approval. These treatments could begin in March of this year. Additional pre-construction treatments may include crown cleaning to remove dead, dying or crossing limbs, the addition of cables or braces to improve the structural integrity of the crown, removal of invasive vines from the trunk and crown, root pruning in anticipation of root loss, fertilization, and the addition of mulch within the tree save areas to retain soil moisture. Assuring adequate soil moisture to preservation candidates is perhaps the most important consideration for reducing stress. Therefore, establishing a soil moisture monitoring program is paramount to any successful tree preservation program. Each tree is tested at the beginning of the growing season and then monitored throughout the year at appropriate intervals as determined by the consulting arborist. V. Pre-construction tree protection measures – Once the limits of rough grading have been determined, through the coordinated input from the arborist and engineers, the tree protection fencing is installed. The fencing is installed before any construction activities begin. The material customarily used is blaze orange, plastic (or fabric) or wire mesh fencing. This fencing will capture the area of the CRZ determined to be necessary to insure that these trees have the best chance of survival. This zone is off limits to construction activities without the consent of the consulting arborist. Only the consulting arborist can make the determination of which activities may occur within these fenced areas. It is especially important to exclude rough grading from the tree protection area. Any grading done here is considered “fine grading” and it is done only by small, low-impact construction equipment, such as bobcats. These low-impact machines are used to minimize root disturbance from soil compaction. Utility lines should also be routed around these areas, or be bored under the root zone if necessary. Signage is then attached to the fencing which clearly delineates this as a tree protection area. The general contractor must be made aware of the importance of these areas, and the fact that monetary penalties will be assessed for any violations. VI. Construction phase – During this phase, periodic inspections are made by the consulting arborist to insure that the tree protection fencing is intact and that no violations have occurred. During this phase, it is also important to monitor the soil moisture and to be prepared to provide artificial irrigation during periods of drought. Additionally, remedial treatments such as soil amendments, root growth treatments and/or insect and disease control will be provided whenever necessary. Back To Top - - Friends of St. Patrick’s Episcopal Day School LLC (“FOSP”) is a private, limited liability corporation which was formed to purchase the property at 1801 Foxhall Road, N.W. in order to donate it to the Vestry of St. Patrick’s Episcopal Parish (“Parish”) for the purpose of building a middle school/high school campus for St. Patrick’s Episcopal Day School (“School”).  FOSP has donated approximately one-half of the property to the Parish and intends to sell the remainder to a for-profit developer for the construction of a residential development.  Neither the Parish nor the School are members of the FOSP and neither have any control, direct or indirect, over the FOSP or the construction of the residential development.