Overbrook Junior High School Site Development Study

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SITE DEVELOPMENT STUDY OF THE OVERBROOK JUNIOR HIGH SCHOOL SITE IN LINDENWOLD , CAMDEN COUNTY , NEW JERSEY

Prepared for: D' Anastasio , Lisiewski , Tarquini & Liszewski Architects, Engineers , Planners, Consulta n ts 1812 Federal Street Camden , New Jersey 08105

18 January 1978

CONTENTS Preface / 2 Regional Context / 3 Soils / 4 Vegetation / 5 Vegetation Survey & Management Recommendations / 7 The Pond & Stream: Conditions & Recommendations / 15 Attachments: Site Development Plans (scale: 1 " =60 ' ) of Soils, Drainage, Vegetation, Landscape Areas, and Landscape Management ; also included for review are two sketch plans of proposed athletic facility expansion

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PREFACE

The site of Overbrook Junior High School in Lindenwold, Camden County, New Jersey is remarkably diverse. The 32acre site is bissected by a stream which flows into a 2acre manmade lake, which then enters the North Branch of Big Timber Creek via a spillway. The landforms range from very steep slopes, gentle hills, to flat terraces. Except for the developed area and the pond, the site is entirely forested and supports floodplain swamps, lowland and upland forests, and some developing marsh.

At present, the site is underutilized and faces some serious environmental problems which limits its use.

Existing athletic facilities are inadequate and the use of available land is inefficient. The slopes adjacent to the parking lot are badly eroded and inhibit access to the lower playfields and the rest of the site. The forest vegetation on these steep slopes and along the stream has been disturbed and, in places, is rapidly declining. The lower playfields are inadequately drained and turf establishment is poor. The stream has been severely impacted by extensive development of its supporting watershed and locally by an on-site culvert draining part of the White Horse Pike. The floodplain has increased in size, with higher storm flows and greater sediment loads. As a result, the stream channel is very active and shifting. Sedimentation is severe in the pond and a great deal of sediment is being carried over the spillway into the North Branch of Big Timber Creek.

At the same time, however, this site, if properly managed, offers tremendous potential for future use. The proposed expansion of athletic facilities can be accommodated and will help to clearly organize the whole site. Although the pond and stream are impacted by many off-site conditions, the school property is large enough to allow for the amelioration of many current problems. The pond and spillway, dating from the 1930s and virtually untouched since then, are in need of repair, especially the spillway embankments which are currently in danger of collapse.

Upon redesign, however, the pond can serve as a significant

stormwater retention pond, making it of real benefit to downstream neighbors. At the same time, drainage of the lower playfields will be improved and some usuable land r e claimed adjacent to the p ond, permitting the establishment of a cross-country track.

The rehabilitation of disturbed forest areas is crucial to realizing the full potential of the site. On slopes, the local soils are highly erodible without a stable vegetative cover. The present vegetation of the slopes adjacent to the school has been repeatedly disturbed, primarily from filling, and the accumulated effects have dramatically 2

increased erosion. The access steps were recently removed,

having been badly undermined. Although reestablishment of vegetation on this scale is clearly a major undertaking, it is imperative to prevent further deterioration. Moreover, once adequate cover is present, barring future disturbance,

the slopes should require no further maintenance. Thus, the forest will be at once functional, healthy, and a ttractive .

The object of this landscape reclamation is not only to stabil ize the slopes but to return the forests to their former condition of health and longevity. This will require the planting of canopy trees, understory trees, shrubs, and ground layer herbaceous material and vines. Most of the plants can be installed easily and will naturally develop over time, affording a more natural looking and stable landscape than temporary measures.

The potential for student involvement in educational programs related to this interesting site is almost limitless. Some of the landscape reclamation could even be undertaken by students. Indeed, a complete horticultural studies program might be initiated along with concomittant work experience. Similarly, the site offers the opportunity for direct natural science field study, in keeping with the increasing interest in ecology and environmental concerns.

Both the stream and pond could be monitored by the students to determine sources and amounts of runoff, base flows,

sedimentation, as well as the ameliorative effects of altered management of the site. The aquatic populations and chemical characteristics of the pond and stream could also be surveyed and monitored. Furthermore, the entire site offers the opportunity for wildlife, vegetation, soils and geology studies as well.

It is obvious, if only judged from the large amounts of trash on the site, that the woodlands are abused and taken for granted . Actively involving the students in the study and repair of the landscape is probably the surest way to assure its proper care in the future.

Thus, despite current problems, it is possible to renew and fully utilize all of the school's property, enhancing both sports activities and the current curriculum, while averting future problems and reducing long-term maintenance costs.

REGIONAL CONTEXT

The OVerbrook Junior High School site is located on the Coastal Plain, a geologic formation that extends northward through Long Island to Cape Cod and southward along the coast into Mexico. The Coastal Plain is an elevated sea 3

bottom with very little topographic relief and is comprised of sedimentary deposits, clay, silts, sands, and gravel, representing various onshore, nearshore, and offshore

environments. Since the beginning of Cretaceous time until the present, the shoreline has gradually receded as the Coastal Plain has been elevated. The Coastal Plain is composed of two distinctive sections -- the Inner and Outer Coastal Plain -- separated by a belt of hills which are remnants of a landform called the cuestas. The Overbrook site lies at the very edge of the Inner Coastal Plain, almost at its juncture with the outer section.

The early Cretaceous deposits on the Inner Coastal Plain were nearly completely overlain by later sedimentary deposits made in interglacial Pleistocene times, and its soils have a larger propoertion of clay than the much sandier Pine Barrens soils of the Outer Coastal Plain.

SOILS

The soils of the Overbrook site are primarily of the Westphalia-Nixonton-Barclay association. All of the soils are formed in thick beds of fine sand in a geologic formation locally called the Kirkwood. Since these soils are made up of uniformly fine sands, the use of these soils is limited.

They have a moderately high water-holding capacity .

Permeability of the subsoil is slow because it contains slightly more clay than the surface layer. Also, these soils, when saturated, have low shear strength and flow readily. Vertical cuts and banks are highly erodible and prone to collapse. The Westphalia soils are extremely acid naturally, though liming associated with agricultural use has locally reduced acidity. These soils are moderately fertile and added fertilizer is not leached readily.

Loamy alluvial land. This soil is poorly drained because of its low position, subjecting it to a high or perched water table and also to flooding.

Westphalia soils, 10 to 20 percent slopes. Located primarily on steeply sloping land adjacent to the stream, these soils require permanent vegetative cover to prevent erosion, as the erosion hazard is severe. In texture, these soils range

from fine sandy loam to loamy fine sand .

Westpha1i路a and Nixonton -- Urban Land Complex. These soils vary considerably from site to site depending on past disturbance. In general, permeability of the subsoil is moderately slow, although in the substratum it is moderate to rapid. As in the whole Westphalia series, because of uniform texture, this soil type also collapses easily when saturated and subjected to stress.

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Although the soils mapping for this site is too gross for specific and accurate on-site application at this time, the Westphalia characteristics of high erodibility and instability when saturated are significant factors on the site and can be seen in the current problems of erosion and slumping on the slopes.

Recommended measures for slope stabilization are noted elsewhere in this report. The establishment of good quality turf for the playfields will require adequate subsurface drainage, fill material of suitable texture , and liming to reduce natural acidity.

VEGETATION

The site of the Overbrook school supports a varied and diverse vegetation. Located at the edge of the Inner Coastal Plain, the vegetation is an interesting blend of plants typical of both the Piedmont and Pine Barrens, though no extensive pitch pine areas occur. While sections of the site support relatively healthy, well established forest, for the most part disturbance to vegetation is notable.

Without appropriate vegetation management, many sections of the forest will change dramatically and elsewhere dieback is expected to路 be severe, which will further aggravate erosion problems on the site.

The vegetation has been classified into four broad categories: instituti路onal landscape, which contains those areas planted and managed by the school; floodplain swamp, which is located primarily on the floodplain along two streams; lowland forest, which is located in low-elevation areas subject to very poor drainage; and upland forest, which occupies most of the sloping areas of the site.

Virtually no forest on the site is truly undisturbed , since most were subject, at the very least, to repeated cutting in the past. At the same time, however, most of the forest has not been cut recently and the second-growth forest is reasonably mature. The major sources of current disturbance include filling and dumping associated with the school site , impacts from clearing of the playfields, alterations to the stream channel and floodplain, due in large part to the extensive development of the watershed upstream and past erosion.

The relative distu路r bance on the site has been classified as low, moderate, and severe. In areas of low disturbance,

the forest vegetation is well represented in all layers that is, canopy, understory, shrub, and herbaceous or

groundlayer. Reproduction is in evidence and the forest compo sition is reasonably stable. No management is presently required, nor should it be if no further disturbance occurs.

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In areas of moderate disturbance, the canopy, though thin, is present. However, very little canopy reproduction or normal shrub development is in evidence. Excessive succes-

sional growth is apparent. Although disturbed, the vegetation is coping with the impacts. Some replanting is required to control erosion adequately.

In areas of severe disturbance, the vegetation is rapidly declining . Usually the gro undlayer vegetation is absent and erosion severe, preventing reproduction. Excessive filling

and erosion have also destroyed most of the understory and the canopy trees are gradually dying. In these areas, problems will only get worse over time unless restoration measures are undertaken. The remaining canopy trees are

under severe stress and, once dead, their root systems will no longer help stabilize the steep slopes. In general, complete rehabilitation of these areas is required, both to alleviate existing problems and to prevent future problems.

The recommendations for reestablishment of stable vegetation on this site are described below, along with a description of each area. The emphasis of these recommendations is on replanting a complete forest situation, replacing canopy species where required and planting additional shrub and ground cover plants. Due to the nature of the soils on the steep slopes and the impacts of development on the stream, there is no simpler way to deal with existing problems.

Good >forest cover is a long-term solution eventually requiring practically no maintenance. The root systems of the fully layered vegetation affords stability on the surface and at depth. There is no effective short-term solution.

Commonly used shelter-belt and protective- cover plantings for slope stabilization, typical of highway embankments, are not appropriate here. This method is a short-term solution and is dependent upon eventual volunteering of native materials, which in the case of the OVerbrook site would be slow and ineffective on these soils. Moreover, the installation and establishment of such short-term cover would require extensive clearing of most of the canopy to provide adequate light levels, and this would only further jeopardize the slopes and dramatically increase disturbance during this phase.

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VEGETATION SURVEY & MANAGEMENT RECOMMENDATIONS

The following areas are keyed to the Vegetation map.

IL-l, Institutional Landscape: Ornamental plantings and turf maintained

Description: The school landscape shows no major problems in terms of maintenance. Although neat in appearance, the landscape is very austere and does not reflect the rich character of the native landscape surrounding it. Fill operations associated with the temporary fence jeopardize several large oak trees and should be remedied as soon as possible.

Recommendations: (Pending further design development) IL-2, Institutional Landscape: Turf playfields maintained Description: The upper playfields support turf and are maintained for athletic acitivities. Though established, the grass is only in fair condition, primarily due to the sandy soils at the surface. No evidence of serious drainage problems were observed; however, the Westphalia-Nixon ton soils on which these playfields are located are subject to seasonal high water table. Flooding problems have occurred in the past and, if serious, improved drainage may be required, especially for the existing track.

Recommendations: (Pending further design development) Unless water table drainage problems have occurred, moderate regrading and a topsoil dressing should be adequate to prepare these fields for turf rehabilitation.

IL-3, Institutional Landscape: Turf playfields, poorly established Deseription: The lower playfields have very poorly established grass. The surface soil is very sandy and drainage poor. The two swales do not adequately drain the fields, due in part to the high water table conditions. The grading is also poor and too rough to support good grass.

Recommendations: (Pending further design development) The lower playfields are at present not suitable for turf maintenance. The drainage problem, however, will be con-

siderably alleviated by the lowered pond and stream elevations from the spillway reduction . Underdrainage may sti l l be required, but the required fill will not be as extensive due to the lowered路 stream elevation. Complete regrading is needed as well as a dressing of topsoil and turf establishment.

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VEGETATION SURVEY & MANAGEMENT RECOMMENDATIONS

FS-l, Floodplain Swamp: Willow, red mapl e , sycamore; moderate disturbance Des c ripti on: Located along the stream, this swamp has be en subjected to severe sedimentation and some channel migration, due in part to increased flows and erosion from

development in the watershed upstream. Large, old black willows (Salix nigra) occur on the large silt island between the main and flood channels, interspersed with occasional sweetgum (Liquidambar styraciflua) , red maple (Acer rubrum) , and sycamore (Platanus occidentalis) are abundant throughout the canopy. The shrub layer has been reduced by disturbance and is comprised of swamp azalea (Rhododendron viscosum) , sweet pepperbush (Clethra alnifolia) , southern arrowwood (Viburnum den tatum) , swamp swee tbells (Leucothoe race mosa), wild rose (Rosa sp.), and young box elder (A c er negundo). Although the shrubs form dense thickets in a few places , the forest is, for the most part, relatively open . At the edge of the swamp, vines, including honeysuckle (Loni c era japonica) , are developing

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in the understory. Due to the winter season , a survey of herbaceous material was not possible; however, it seems

unlikely that a healthy diversity of aquatic plants occur along the sandy, disturbed channels.

Recommendations: Although the canopy presently appears to be reasonably healthy, some canopy planting is advisable where trees are thin. By providing denser shade, such canopy reestablishment will aid in the control of vines and invading weedy vegetation, and thus reduce long-term maintenance and site problems. At the same time, some additional shrubs material should be reestablished along the stream to help stabilize the channels and trap sediment. Lastly, the establishment of herbaceous material would provide additional stability to the stream banks and increase the cleaning of the stream through biologic activity.

FS- 2 , Floodplain Swamp: Willow, a lder, phragmites; moderate disturbance

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Descripti on: This section of floodplain swamp is located j ust a bove where the stream enters the pond and is character ized by exce ssive amounts of s e diment accumulation, both on the floodplain and on a small delta forming in t he pond. A few black willows occur along the channel, with occasi ona l smooth and spe ckl ed alder s (Alnu s rugo s a , A. incana). Gi ant r e ed (Phra gmites c ommunis) is rapidly co l onizing the silty area s adjace nt to the stream and rushes (J uncus effusi s) are becoming established on the

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delta . Species diversity is very low in this disturbed area and its general appearance is rather weedy.

Recommendations: In order to control sedimentation and stabilize the stream channel, this area should be heavily planted with a variety of plants in all layers -- canopy , understory, and ground. Where the marsh is forming in the delta area, a broader diversity of he rbaceous material will help this rapidly changing area to better adjust over time.

The gradual establishment of marsh adjacent to the pond will also enhance wildlife habitat on the site, and the appearance of the area, as well as its stabilizing functions, will be greatly improved as a more diverse vegetation is established.

FS-3, Floodplain Swamp: Red maple, sweetgum, tulip poplar, sycamore; low disturbance

Description: Located in the large , broad floodplain area on the North Branch of Big Timber Creek, this dense swamp is designated as a wetland by the State, and therefore any alterations impacting on the wetland or stream would be subject to approval by the New Jersey Department of Environmental Protection. Large, well-spaced canopy trees occur on the slope edging the swamp, including several relic sweetgum exceeding three feet in caliper. Red maple, tulip poplar (Liriodendron tulipifera) , and sycamore also are predominant. The understory layer is very dense and supports a wide variety of shrubs and tree thickets, including box elder, red maple, southern arrowwood, highbush blueberry (Vaccinium corymbosum) , swamp azalea, sweet pepperbush, swamp sweetbells, and staggerbush (Lyonia mariana). Despite heavy sedimentation in the creek and locally increased flooding, the swamp is presently quite healthy and shows no evidence of deterioration.

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Recommendations: Except for cleaning out the accumulated rubbish and debris, no major vegetation management recomendations are required for this area. However, no

additional school-related activity is suggested here and , as long as disturbance does not increase dramatically, the area should remain healthy.

FS-4, Floodplain Swamp: Sassafras, sweet pepperbush, alder; low disturbance Description: This area of the least disturbed pond edges supports dense thickets of wetland trees and shrubs, which is essential to the control of erosion and stabilization of the banks. Sassafras (Sassafras albidum) , sweet pepperbush, and alder are predominant, with sweetbay (Magnolia virginiana) , red maple, tupelo (Nyssa sylvatica) , sycamore also abundant, as well as a wide variety of wetland shrubs characteristic of these swamps, as noted in FS-3 above.

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Recommendations: Where dense, broad, and established, these young swamps offer a model for well protected pond and stream edges , requiring no additional work. The entire perimeter of the pond should eventually support vegetation of this kind and replanting in this manner has therefore been recommended for the ope n , poorly vegetated stream banks, as noted in FS-l ifnd ' FS-2 above .

LF-l, Lowland Fore st: Oak, bee ch, sweetgum; severe disturbance

Description: Several large relic white oaks (Quercus alba) , predating the pond's excavation, remain adjacent to the pond. On the slope immediately adjacent to the stream channel, a narrow band of beech (Fagus americana) and sweetgurn, with occasional mountain laurel (Kalmia 1atifolia) occurs. Elsewhere, understory and ground layer vegetation is largely absent and bare mineral soil is exposed. Vegetation on the sandy excavated pond edge is very poorly developed.

Recommendations: As recommended previously in FS-4, the pond edge should be stabilized with a variety of native plants. The oaks , though in reasonable condition, are fairly old and canopy replacement trees should be planted , as well as understory and groundlayer plants. This area is limited in size, relatively dry, and quite flat, and thus has the potential to be used for passive recreation.

LF-2, Lowland Forest: Sweetgum, red maple, tupelo; moderate disturbance Description: This area is adjacent to the stream floodplain

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and is comprised of a young lowland forest. The canopy is predominantly sweetgurn, red maple, and tupelo, with a few large old tulip poplars and developing thickets of sassafras , sweet pepperbush, and southern arrowwood in the more open areas. Because the stream channel is farily active and subject to severe flooding, the vegetation is not well developed along the stream and, in general, the vegetation is less diverse and less dense than would be advisable.

Recommendations: Similar to other disturbed areas of the

site, the layers to problems. should b e

vegetation here should be represented in all reduce long- term maintenance and environmental Where thin, canopy, understory, and ground layers replanted, although such work need not entail

extensive measures. To lessen sedimentation and erosion,

the channe l banks along the stream's entire course should be stabilized with v e getation.

UF-1 , Uplan d Forest : Tu l ip p o pl a r, oak, s ycamore , red maple ; mo d e rate disturban c e

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UF-l, Upland Forest: Tulip poplar , oak, sycamore, red maple; moderate disturbance

Description: This area of successional forest supports occasional tulip poplar , sycamore, red maple, and a variety

of oaks, including red (Quercus rubra), black (Q. velutina) , and chestnut (Q. prinus) oak. The edges of this forest adjacent to the playfields, Elm Avenue , and the church grounds have been subject to disturbance and cutting ; a right-of-way across the forest interior has been cleared t711t?W.5 tJarnltn and maintained. The shrub layer ' is very poorl y developed , orw¢~f:;1 I/fne.s . although where the canopy is fairly open , dense thickets of tupelo , sweetgum, red maple, and sassafras occur.

Honeysuckle is rapidly colonizing these disturbed edges and, in general, the appearance of this forest is weedy and unattractive.

Recommendations: This area provides an i mportant buffer to the str eam , in that i t greatl y reduces the impacts of adjacent deve l opment on these unstable soi l s. Maximizing this buffering function will require a major c l eaning out of debris and developing honeysuckle. The disturbed forest edges should have additional planting to "seal off" further deterioration of the forest interior, and this wi l l also aid in the control of weedy growth . Shoul d any deve l opment or clearing be required in this area , the newly exposed edges shou ld be seal ed with vegetation t o prevent disturbance to the rest of the forest. Barring excessive

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or improper development on adjacent areas, such measures

should be adequate to stabilize this area as a buffer and thus reduce long-term costs and damages here and elsewhere on the site. ~

UF-2, Upland Forest: Oak , maple, honeysuckle; severe disturbance Description: In this area , which is severely disturbed from the clearing and grading associated with the playfields , honeysuckle is rampant and , except for a few oaks and red maple , is fast replacing the native vegetation. Honeysuckle is unattractive and much less effective in holding the soil than the native trees , shrubs, and groundcovers of a healthy upland forest.

Recommendations: Since this area can potentially be used for recreational facility development, vegetation management measures will be specified as part of its overall design.

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UF- 3 , Upland Forest: Oak, sassafras; moderate disturbance Description: Widely spaced, large white , red, black, and chestnut oaks occur in this upland forest. The understory layers appear to have been disturbed and are very thin.

Some evidence of fire damage was observed, although it is not known how extensive an area was involved. Sassafras is

the predominant understory species, growing thickly where the canopy is thin. Occasional sweet pepperbush was also 11

observed. Some vines, including honeysuckle and greenbrier (Smilax rotundifolia) occur at the woodland edges.

Recommendations: No replanting is recommended if no future disturbance occurs. New forest edges created by playfield expansion should be sealed with vegetation to prevent excessive weedy growth into the forest.

UF-4 , Upland Forest: Sassafras, cherry,路 tupelo; moderate disturbance Description: Dense successional thickets of sassafras, black cherry (Prunus serotina) , and tupelo are developing on this strip of cleared land adjacent to Elm Avenue. These thickets are beginning to seal the forest edge and help provide stable cover.

Recommendations: Except where vegetative cover is discontin-

uous, no further planting is required. Open areas at the edge should be planted in with young oldfield vegetation similar to the existing thickets to discourage weedy vine and bramble growth which might otherwise be injurious to the health of the forest.

UF-5, Upland Forest: Oak , pitch pine; moderate disturbance Description: This is one of the two areas on the site which supports vegetation typical of the Outer Coastal Plain and thus greatly contributes to the natural diversity of the site. A single large pitch pine (Pinus rigida) as well as tupelo, southern red oak (Quercus falcata) , and black oak occur in the canopy. Scrub oak (Quercus ilicifolia) , also typical of the Pine Barrens, and holly (Ilex opaca) are present in the understory.

Recommendations: Pending recommended measures taken for the adjacent areas, as noted in UF-l, no special management is

required here.

UF-6, Upland Forest: Beech, oak, sweetgum; low disturbance Description: This long, narrow remnant of upland forest, between the south side of the lower playfields and the stream, supports well established beech and oak, including white, chestnut, southern red, red, and black, as well as several large, old relic sweetgurn trees. The understory is quite diverse, supporting mountain laurel, highbush blueberry, sweet pepperbush, swamp azalea, and spicebush (Linden benzoin) .

Recommendations: Pending recommended measures taken for the adjacent playfields and floodplain swamp (FS-2), no special management is required here.

UF-7, Upland Forest: Beech, oak , sweetgum, laurel; low

disturbance Description: This forest is the least disturbed on the site and is both mature and well estab li shed . Large chestnut oak

12

Recommendations: The restabilization of these slopes is crucial to realizing the full potential of the site. If the current deterioration is left unchecked, the eventual collapse of these slopes will threaten existing parking areas and outbuildings as well as aggravate existing sedimentation in the stream and creek. Appropriate access to the lower playfields and the rest of the site also requires stable conditions on these slopes. In places, especially near the newly installed chain-link fence, the recent filling must be removed or reduced to prevent killing important major trees. Slight regrading is also required throughout to redistribute some of the fill and to fill gullies. Dead trees must be removed. Some damaged trees can be saved by pruning and feeding. A top ' . dressing of topsoil to provide better growing conditions for new plantings is needed and should be held in place initially by tacked on jute matting until the vegetation is established. Planting of future canopy replacement trees as well as understory trees, shrubs, and groundlayer is also required to fully establish long-term vegetative cover that will hold the slopes. At the same time, proper drainage of the parking areas and adjacent grounds is needed to control long-term maintenance of the slopes. until the vegetation is well established and slopes stabilized, it is imperative that pedestrian traffic be directed only onto designated paths. At no time is the use of minibikes and other offtrail vehicles acceptable, since the soils of the site are simply too erodible once disturbed.

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14

THE POND & STREAM: CONDITIONS & RECOMMENDATIONS

Although a comprehensive pond and stream survey was not possibl e at this time of year, several site visits were made and observations recorded during dry weather, during two rainstorms, and two visits shortly after heavy rains.

The stream shows signs of severe disturbance, caused

primarily by excessive sedimentation. The major sources appear to be from extensive development upstream as well as from drainage of a portion of White Horse Pike, although the problem is aggravated by on-site erosion of the steep slopes adjacent to the school. Development in the watershed upstream has also resulted in increased peak flows in the stream and a concommittant reduction in base flow. In addition, the accumulation of rubbish and debris has disrupted the channel course in places.

At the present time, the stream channel appears to be very active and is shifting in order to adjust to the higher sedimentation and peak flows. Numerous overflow channels are evident and, in places, the sediment load is so great that it has produced some braiding in the channel. Numerous backwater channels occur, with several blocked by debris.

Although tree cover is present for the entire length of the stream, shrub and herbaceous vegetation has been disrupted by the channel activity and has precluded effective channel stabi lization and sediment trapping. In dry weather, however , the stream runs reasonably clear.

Contamination of the stream water is a certainty, both from development in the watershed and highway drainage. A fine layer of iron hydroxide on the stream bottom is indicative, however, of a relatively high level of acidity, which is normal for streams on soils in this area.

The pond has also been impacted severely by sedimentation, delivered primarily by the stream and somewhat aggravated by on-site erosion. A small delta is forming in the pond where the stream enters and can be expected to enlarge over time. Moreover, a great deal of sediment was observed coming over the spillway and entering the North Branch of Big Timber Creek , although the impact on the creek would be far worse if the pond were not there, since it now traps and holds much of the sediment. Although no summer observations were made, it appears unlikely that algae blooms and uncontrolled vegetative growth are present problems , in part due to the acid nature of the water. At the same time, however , there is little chance that a truly healthy pond can occur in this l ocation because of continued upstream contamination.

The spillway appears to be in good condition, but the embankments next to the dam are eroding. Thi s is a dangerous situation that must be dealt with to prevent a breakthrough.

15

The pond has been virtually untouched since its construction in the 1930s, and its status as well as the stream condition should be carefully reviewed. In general, the major impacts on the stream and pond occur off-site and are not under the contro l of the s chool. At the same time, these condition s are not likely to improve and significant me asures must be

taken on-site to improve the quality of the stream and pond.

If the pond and stream are left in their present states, the current problems will continue to g e t wor se . Sedimentation

will over time result in filling of the pond. The artifically high water tables maintained by the spillway will also continue to pos e serious drainage problems for the lower

playfields. And the appearance of the pond and stream will deteriorate progressively.

On the other hand, outright elimination of the pond is not feasible. At present it serves as a significant sediment, contaminant, and nutrient trap and affords limited storage of floodwaters. The loss of these functions is very unlikely to be approved by the County or the State regulatory agencies, especially given some local flooding problems downstream on the North Branch of Big Timber Creek. In addition, the gradients of the slopes on site would be steepened and become more difficult to stabilize. Most of the land gained would be unusable and could not be filled due to floodplain restrictions. Also, a long repair period would ensue, during which the pond and stream would be very unattractive.

Complete utilization of the site is dependent upon a successful resolution of the existing problems relating to the stream and pond. Lowering the pond elevation by approximately one to two feet (pending further data collection) offers several benefits and could be accomplished by a simple notch in the spillway. The overall size of the pond would be reduced by about one third, providing better flushing and improved water quality. The notch would be sized to accommodate base, or average, flow, thereby

increasing the flood storage capacity and partially alleviating downstream flooding conditions. with the reduced pond elevation, the elevation of the stream and adjacent ground waters would also be reduced, and thus provide improved drainage on the lower playfields. The braiding pattern of the stream should also be r e duced by reopening the former main channel. After a period of adjustment, during which there will likely be some tempora ry scouring of the stream bed and sedimentation in the pond, re contouring o f the pond bottom and newly expo s ed banks can be undert a ken and the stream channel through the p ond deepe ned. The effe ctiveness of the pond as a s edime nt t r ap will no t be significantly reduced. The lowered stre am and pond e l evation s will a l so slig htly inc r ease the amount o f usuabl e l a nd, which can be profitably use d for c ro ss -cou n t r y tr a il s .

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Measures can also be taken to improve the quality of the stream, mitigating some of the off-site impacts and further improving the pond. It is during storms that the most damage occurs, especially in the 'first burst' when the heaviest sediment and contaminant loads occur. Small check dams on the stream would provide trapping of sediment and nutrients as well as slight retention of peak flows. The check dams also will reduce the scouring that takes place during storms and the disruption of streamside plantings.

The reestablishment of dense vegetation along the channel, including trees, shrubs, and herbaceous material, would

also help trap sediment and improve water quality by taking up nutrients and some contaminants. A thorough cleaning of the channel is required, mainly to remove debris and accumulated litter. Lastly, these measures would greatly improve the appearance of the stream and pond and increase the area's utility for wildlife habitat.

The effectiveness of these measures also relies upon the reduction of on-site impacts, particularly as described in the vegetation management recommendations.

A comprehensi"ve site drainage plan also should be implemented. Recent temporary measures to improve parking lot drainage have reduced downslope runoff, however some further drainage improvements are still required. Small retention basins may be needed for draining the lower playfields without undue stream disturbance. More complete drainage plans would be prepared during the design development phase.

Some initial monitoring is required to establish this remedial program for the stream and pond. Stream flows must be monitored, sediment sources and amounts determined, and

the pond bottom contours delineated. An accurate site survey is also needed.

The stream and pond have long been neglected and restorative measures are fairly extensive. However, it is likely that no major changes will occur in the watershed in the near future to aggravate upstream conditions. The recommendations herein provide long-term solutions to the problem. Longterm maintenance will be minimal. The sediment traps in the check dams will require cleaning at regular intervals (which is too soon to determine) but vehicular access is provided and the operation is a simple one. The slopes, o nce well fore s ted, should require minimal maintenance.

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