Newfound Watershed Preliminary Culvert Assessment December 2010
Prepared by the Newfound Lake Region Association as part of Newfound Lake Watershed Management Plan Implementation: Phase I
Newfound Watershed Preliminary Culvert Assessment December 2010 Table of Contents
1. Executive Summary 2. Introduction 3. SSPP Definitions and Modifications and Community Outreach o SSPP Definitions and Modifications o Community Outreach 4. Findings and Recommendations o Findings o Recommendations 5. Selected Technical References List of Tables Table 1 – Crossing Structure Scoring System and Rationale Table 2 – Summary Scores by Town Table 3 – Hydraulic Function Detail Scores (Highest One-Third) Table 4 – Summary Statistics Table 5 – Culvert Sizing Chart List of Figures Figure 1 – Priority Ranking Results in Newfound Watershed Figures 2-6 Priority Ranking Results by Town (Alexandria, Bridgewater, Bristol, Groton, Hebron) List of Appendixes Appendix A – Summary Report (on CD-ROM) Appendix A1 – Text, Tables and Figures Appendix A2 – Site Specific Project Plan (SSPP) Appendix A3 – Database Appendix A4 – Project Photos Appendix B – Selected Project Photos
1. Executive Summary As part of the implementation phase of Every Acre Counts: The Newfound Watershed master Plan, the Newfound Lake Region Association performed a watershed-scale reconnaissance of culverts and stream crossings of public roads. The purpose of this work was to assess and rank impairments to hydraulic function and habitat, and to provide local road agents and decision makers with a useful tool to prioritize mitigation and capital improvement project planning. During the summer of 2010, PSU intern Anthony Belmonte was hired by the NLRA with grant funds to map culvert locations and record and enter assessment criteria into the project database. Culvert locations were identified with an initial GIS analysis performed by Dan Sundquist of the Forest Society, and supplemented with field observations. Assessment criteria were developed from existing Vermont DOT and New Hampshire NHDES models, adopted to the level of accuracy and precision afforded by this initial reconnaissance. Relative numerical scores were assigned to criteria to allow basic statistical analysis to rank overall culvert conditions. Two hundred and fourteen (214) crossings (culverts and bridges) were mapped and assessed in accordance with a Site Specific Project Plan approved by NHDES, with primary focus on the major stream networks and in proximity to Newfound Lake. The data were entered into an AccessTM data base which generated summary rankings and reports based on algorithms created for this project. The results were divided into three cohorts based on total hydraulic function scores, with higher scores indicating lower quality crossings. We focused on the 71 “worst” crossings that had ranking scores between 20 and 36. These summary data are both tabulated and presented graphically in GIS within this report. Due to the steepness of the watershed, large percentage of unpaved roads, erodible soils and constrained local budgets, there are a number of crossings likely to impair flow, water quality and wildlife habitat, and that pose a threat to public infrastructure due to potential washout and ongoing maintenance requirements. The primary causes of hydraulic impairment are headwall condition, upstream entry angle and culvert capacity ratio (undersized culverts). These are often correlated, with one deficiency having an additive impact on another. Critical adverse habitat factors are perched outlets and lack of sediment in structures. The vast majority of culverts were identified as NOT passing through wetlands, a factor, along with other habitat functionality criteria, that is reserved for future consideration. While the intent was to survey only crossings under public roads, some of the mapped culverts may have been on private roads. In addition, we understand that State statutes prohibit towns from expending funds to maintain Class VI roads although these roads are considered public rights-of-way. Recommendations based on the findings of this preliminary reconnaissance include the following: •
When replacing crossings, apply best practices for both hydraulic and habitat functionality, considering both short- and long-term benefit. The primary factors to incorporate when replacing crossings are size, entry angle, headwall construction and grade:
o Size crossing to match upstream channel capacity, considering the frequency of large rainfall events. o Construct low upstream entry angle to reduce hydraulic stress on headwall and reduce scour potential. o Construct headwall to direct flow and resist scour (overall construction quality addresses damage leading to poor crossing condition). o Grade should match channel slope to prevent perching and allow wildlife passage through crossing. •
Additional analysis of habitat functionality should be considered, with additional monitoring and analysis of crossings known and suspected to be prone to failure.
•
Due to the extent and cost of replacing crossings, Town and State agencies should develop Capital Improvement Plans that prioritize and fund critical culvert system improvements.
Funding for this project was provided in part by a Watershed Assistance Grant from the NH Department of Environmental Services with Clean Water Act Section 319 funds from the U.S. Environmental Protection Agency.
2. Introduction As part of the implementation phase of Every Acre Counts: The Newfound Watershed Master Plan, the Newfound Lake Region Association (NLRA) performed a watershed-scale reconnaissance of 214 culvert and stream crossings of public roads. The purpose of this work was to assess and rank impairments to hydraulic function and habitat, and to provide local road agents and decision makers with a useful tool to prioritize mitigation and capital improvement project planning. Figure 1 shows the roughly 63,000-acre Newfound watershed that comprises the project area and the locations of visited crossings. The watershed encompasses all or parts of nine towns, with roughly 95 percent of the land and population contained in the five towns of Alexandria, Bridgewater, Bristol, Groton and Hebron. During the summer of 2010, we mapped and assessed 214 culverts in general accordance with a Site Specific Project Plan (SSPP) approved by the New Hampshire Department of Environmental Services (NHDES; included in Appendix A). Our primary focus was on the major stream networks (i.e. Fowler and Cockermouth Rivers, Georges and Dick Brown Brooks) and crossings in close proximity to Newfound Lake. The data were entered into an AccessTM data base developed by Deborah Clark using relative rankings and algorithms based on previous work by the Vermont Agency of Natural Resources and the NHDES, as outlined in the SSPP. The results were divided into three cohorts based on total hydraulic function scores, with higher scores indicating lower quality crossings. We focused on the “worst” one-third of the culverts with summary hydraulic ranking scores between 20 and 36. These culverts were also assessed and ranked for habitat functionality. Table 1 provides the crossing structure scoring system and rationale used in our data base to generate the rankings discussed in this report. To prepare field observations for semiquantitative analysis, we assigned numeric values to key parameters. The scoring system was designed so that lower values represent a more favorable condition and higher values a less favorable condition. Values were typically one (good) or 5 (not good), although criteria deemed less critical were assigned values of 1 (good) or 2 (not good). Note that this is a relative, rather than absolute, ranking system intended to assist decision makers in prioritizing further investigation or possible mitigation. 3. SSPP Definitions and Modifications and Community Outreach SSPP Definitions and Modifications
Based on early field observations and data analysis, we refined several definitions and made some modifications to the SSPP. SSPP Definitions: •
Upstream (US). US reference’s the upstream side of the structure and any point of the channel beyond the structure entrance.
•
Downstream (DS). DS reference’s the downstream side of the structure and any point of the channel beyond the structure exit.
•
Stream Crossing (SC) - These are mapped crossings generated by ESRI ArcGIS computer mapping software using data from the New Hampshire GRANIT database. SC’s show intersections of mapped roads and streams. There were initially 109 SC’s identified, with some located on private property (not managed by municipal agents).
•
Ditch crossing (DC) – Initially defined any unmapped crossing located in the field. To allocate time to structures more likely to have a meaningful role in hydraulic or habitat functionality, our definition of DC evolved to include unmapped locations with a defined US channel.
•
Left/Right – All references to “left” and “right” assume that the observer is facing upstream.
•
Flat-Bottom Arch – Crossing Type 9 in the SSPP is defined as an embedded elliptical pipe, of which none were observed. Flat-Bottom arch is a crossing type not accounted for in the SSPP, of which several were located. We modified the SSPP so that crossing Type 9 refers to a Flat-Bottom Arch.
SSPP Modifications: •
Culvert Capacity Ratio (CCR). An important assessment of the ability of a crossing to transmit stream flow, this is the ratio of the culvert cross section to that of an idealized rectangular US cross-section (see Appendix A). A definable stream channel is required to perform this calculation. There were 46 of 214 sites (22%) that lacked a defined channel and that were assessed for other field criteria before we modified our definition of Stream and Ditch Crossings. We included all 214 sites in our analysis, creating slightly lower scores than if they were excluded, but with no significant effect on the report conclusions or recommendations.
•
Bridge Measurements – Crossing Type 2 is a bridge with abutments. Measurements for bridges are recorded as L x W x H, in that specific order. There is a data field for length of stream through crossing. The other 2 fields, W x H, are recorded in the US/ DS diameter field. Measurement “A” is always width, and Measurement “B” is always height.
•
Multiple Culverts – Multiple Culverts are recorded from left to right and entered into the US/DS field accordingly. Field “A” is always the leftmost pipe; Field “B” is always the rightmost pipe. Only double-culvert crossings observed.
Community Outreach
A key project objective was to involve road agents for their local knowledge, to learn about and address their needs, and to build relations between the NLRA and the public. During the data collection process we met with Jeff Cantara (Alexandria), Buck Cate (Bridgewater), Roger Bedard (Hebron), and Marc Avery (NH DOT District 2), and spoke with Mark Bucklin (Bristol) via telephone. Meetings were typically an hour long and the responses enthusiastic. Road agents
from the five main watershed towns and the NHDOT were invited to review draft results and provide their input at a December 3, 2010 meeting hosted by NLRA. Their comments have been incorporated into this report, as appropriate. Each town will be presented with at least one printed and electronic copy of this report to assist in their future roadway management. 4. Findings and Recommendations Findings
Figure 1 shows the 71 culverts with highest (worst) summary scores as red dots, the middle cohort as yellow and the lower cohort as blue. The purpose of this ranking is to present a manageable number of crossings to assess and prioritize for possible mitigation, as time and funds allow. The rankings are relative and semi-quantitative. In the interest of this preliminary assessment, we focused most of our efforts on analyzing the criteria underlying the highest ranking (poorest quality) 71 crossings, based on hydraulic scoring criteria. Note that 12 of the 71 sites lack CCR values, creating a low bias to the summary scores but having no significant effect on the relative rankings, and thus our conclusions and recommendations. Appendix B contains selected photographs of crossings that represent each of the three ranking cohorts. These photographs are presented for illustration purposes only. They are not meant in any way to reflect how a town manages its roadways. Instead, they are intended to help people visualize the wide range of stream crossings and conditions found in the Newfound watershed. Review of these photographs, as well as of additional pictures taken of visited sites (Appendix A) should provide a clear sense of the challenges that arise when trying to maintain miles of paved and unpaved roads in rural and steep terrain. Figures 2 – 6 show ranking results for mapped crossings within each of the five major watershed towns (Alexandria, Bridgewater, Bristol, Groton and Hebron). A large-scale paper map will provided to each town as part of this report. The Site ID numbers shown on each map match site IDs in Tables 2 and 3, and color codes are similar to Figure 1. The purpose of these maps is to assist road agents and other decision makers with locating the assessed culverts for further evaluation. Electronic copies of all maps, as well as the full contents of this report and a copy of our database, are provided in Appendix A.
Table 2 summarizes all sampling locations, and hydraulic and habitat functionality scores by Town. The number of crossings depended on miles of road and terrain within the watershed of each town, with steeper land and larger areas (Alexandria and Groton) having the most sites. Note that the high number of sites in Groton (85) is due in part to mapping Province Rd. before we redefined crossings to require an upstream channel – many of these sites are small diameter crossings to drain ditches fed mainly by road surface runoff, thus not meeting our revised crossing definition. Table 3 summarizes detailed hydraulic ranking results for the priority (worst) 71 crossings. We ranked crossings using hydraulic summary scores, and then examined the data to identify the underlying causes of the higher scores. This cohort was also used to assess habitat functionality, although our premise is that hydraulic functionality is the primary concern of this study. Note that 6 of the 27 sites identified in Groton lacked CCR values.
Table 3 also identifies hydraulic assessment criteria that are the source of the higher summary scores. By counting the number of maximum scores for each hydraulic criterion, we found the underlying drivers for high summary scores, in descending order (with number of occurrences): Headwall Condition (29), Upstream Angle (28), Culvert Capacity Ratio (24), Culvert Condition (20), and Upstream Scour (17). These criteria are often inter-related, for example an undersized culvert with a high angle of stream entry is often associated with upstream scour and a degraded headwall. Table 4 provides summary statistics for each of the towns, using both the full data set and the top-third in hydraulic ranking. Several key observations include: • • •
Average hydraulic scores for all sites ranged from 15.8 to 19.7. Average hydraulic scores for the top-third crossings ranged from 23.6 to 26.9. Percentage of top-third sites varied by town. Bristol, with the lowest number of mapped sites, had the highest percentage of top-third crossings (7 of 16, or 44%). Alexandria, with the largest land area in the watershed, had the lowest percentage of top-third crossings (12 of 48, or 25%).
It is clear that each town faces challenges in maintaining its roadways, based on the complexity and number of the many crossings present in the watershed. Note that towns do not typically maintain crossings on private property, and are reportedly prohibited from expending funds to maintain crossings on Class VI (public) roads. Recommendations
Recommendations based on the findings of this preliminary reconnaissance include the following: •
When replacing culverts apply best practices (see Table 5 and Selected Technical References below for guidance) for both hydraulic and habitat functionality, considering both short- and long-term benefit. Based on our preliminary analysis, top factors to consider when replacing culverts are size, entry angle, headwall construction and grade: o Size crossing to match upstream channel capacity, considering the frequency of large rainfall events. o Construct low upstream entry angle to reduce hydraulic stress on headwall and reduce scour potential. o Construct headwall to direct flow and resist scour (overall construction quality addresses damage leading to poor crossing condition). o Grade should match channel slope to prevent perching and facilitate wildlife passage through crossing.
• •
Additional analysis of habitat functionality should be considered, with additional monitoring and analysis of crossings known and suspected to be prone to failure. Due to the cost of replacing crossings, Town and State agencies should develop Capital Improvement Plans that prioritize and fund thee critical infrastructure improvements.
Table 5 is a quick-reference for culvert sizing from the Indiana Department of Natural Resources (Forestry), and provides a relationship between culvert size, area drained (in acres), soil type and
slope. As with all such charts, the underlying basis should be understood by road managers to ensure that the assumptions apply to their unique site conditions. Selected technical references that contain more extensive and detailed culvert design and installation information from State and federal agencies are provided below. 5. Selected Technical References These references and the data in Table 5 were identified as part of a preliminary research of webbased resources for drainage design and other roadway management issues. While our goal is to assist road agents and other decision makers in their work, we do not represent that these references or the recommendations in this report are fully authoritative. Summary guide on roadway maintenance for local agents http://www.fs.fed.us/eng/pubs/html/00771803/00771803.html
UNH Technology Transfer Center web site Home Page http://www.t2.unh.edu/
UNH Technology Transfer Center web site link for publications http://www.t2.unh.edu/video_pub/publist.html
Indiana Dept of Natural Resources (Forestry) - Culvert Sizing Chart http://www.in.gov/dnr/forestry/4589.htm
Drainage Criteria Manual http://www.udfcd.org/downloads/pdf/critmanual/Volume%202%20PDFs/090%20Chapter%2009 %20Culverts%202001-07%20rev.pdf
HEC 10 Culvert Capacity Charts (Federal Highways) http://www.fhwa.dot.gov/engineering/hydraulics/pubs/hec/hec10.pdf
TABLE 1 – CROSSING STRUCTURE SCORING SYSTEM Newfound Lake Watershed Preliminary Culvert Assessment December 2010
Storm Water / Hydraulic Functionality Scoring (lower numbers = better condition) Criterion (from Appendix B) Road in Floodplain? Culvert : Channel capacity ratio
Culvert slope
Ranking
Rationale
Yes (2; not good) / No (1; good) 1 (good) to 5 (bad) 1 = ratio > 1; 5 = ratio < 0.5
Constricted flow in flood prone areas creates higher risk of road washout As culvert capacity decreases relative to channel capacity, the culvert is more undersized. This is a calculation that compares idealized (rectangular) bankfull and culvert cross sections. Variations in slope from channel to culvert create potentially harmful flow regimes.
Scour at structure (Upstream) Scour at structure (Downstream) Headwall condition
Same (1; good), different (2; higher or lower, not good) 1 (good) to 5 (bad) Circle observation of condition 1 (good) to 5 (bad) Circle observation of condition 1 (good) to 5 (bad) Circle observation of condition 1 (none) to 5 (> 50%) Circle observation of condition 1 (none) to 5 (> 50%) Circle observation of condition 1 (no scour) to 5 (highly scoured) 1 (no scour) to 5 (highly scoured) 1 (good) to 5 (bad)
Spillway condition
1 (good) to 5 (bad)
Condition of crossing
Channel angle near structure (Upstream) Channel angle near structure (Downstream) Obstructions (Upstream) Obstructions (Downstream)
Crushed or damaged culverts constrict flow and are more prone to failure High-angle channel approach to structure increases potential for erosion and avulsion High-angle channel exiting structure increases potential for erosion and avulsion Obstructed culverts constrict flow and are more prone to failure Obstructed culverts constrict flow and are more prone to failure Scour potentially weakens structure, leading to culvert failure Scour potentially weakens structure, leading to culvert failure Eroding headwalls make structure more prone to failure Eroding headwalls make structure more prone to failure
TABLE 1 – CROSSING STRUCTURE SCORING SYSTEM Newfound Lake Watershed Preliminary Culvert Assessment December 2010
Habitat Functionality Scoring (lower numbers = better condition)
Criterion (from Appendix B) Ranking Road cross wetlands Yes (1; good), No (2; not good) Sediment w/in structure
Yes (1; good), No (2; not good)
Water velocity in crossing matches stream Water depth in crossing matches stream Inlet (circle observation of condition)
Yes (1; good), No (2; not good) Yes (1; good), No (2; not good) At grade (1) to freefall (5)
Outlet (circle observation of condition)
At grade (1) to freefall (5)
Rationale Higher density of animals using culvert crossings to travel in wetland areas Natural substrate encourages migration, artificial substrate discourages migration Unperturbed velocity regime less of a barrier to migration Similar depth regime less of a barrier to migration Difference in grades between crossing and stream increases barrier to migration Difference in grades between crossing and stream increases barrier to migration
TABLE 2 - SUMMARY SCORES BY TOWN Newfound Watershed Preliminary Culvert Assessment December 2010
Site ID SC072 SC035 SC052 SC056 SC093 SC000 SC129 SC095 DC090 SC070 SC004 SC084 DC082 SC091 DC081 DC078 SC032 SC088 DC087 SC090 DC089 SC079 SC071 SC096 DC091 SC021 SC028 SC102 SC117 SC023 SC001 SC112 SC363 SC008 SC040 SC086 SC002 SC041
Town Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria
Hydraulic Functionality Score
Habitat Functionality Score
Total Score
32 31 31 29 26 25 24 23 23 21 20 20 18 18 17 17 16 16 16 16 15 15 15 15 15 14 14 14 14 14 13 13 13 13 13 13 12 12
7 8 10 7 6 6 7 7 8 7 8 8 8 8 12 3 6 7 8 8 7 7 8 8 10 6 7 7 7 7 3 7 7 10 12 12 7 8
39 39 41 36 32 31 31 30 31 28 28 28 26 26 29 20 22 23 24 24 22 22 23 23 25 20 21 21 21 21 16 20 20 23 25 25 19 20
TABLE 2 - SUMMARY SCORES BY TOWN Newfound Watershed Preliminary Culvert Assessment December 2010
Site ID DC115 SC101 SC018 DC116 DC113 SC022 SC050 DC114 SC039 DC077 SC077 SC110 DC107 DC100 DC094 SC104 DC101 SC043 SC074 DC093 DC092 DC105 DC097 DC102 DC109 SC120 SC042 DC098 SC127 SC128 SC009 DC103 SC078 SC108 DC096 SC053 SC109 DC108
Town Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Alexandria Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater
Hydraulic Functionality Score
Habitat Functionality Score
Total Score
12 11 11 11 11 10 10 10 10 7 31 30 27 26 25 22 22 21 21 20 20 20 19 18 17 17 17 17 16 15 14 14 14 14 13 13 12 12
12 4 5 8 12 7 7 8 12 3 11 7 12 12 7 10 12 7 7 8 12 12 12 12 8 8 11 12 12 11 7 12 12 12 8 13 4 8
24 15 16 19 23 17 17 18 22 10 42 37 39 38 32 32 34 28 28 28 32 32 31 30 25 25 28 29 28 26 21 26 26 26 21 26 16 20
TABLE 2 - SUMMARY SCORES BY TOWN Newfound Watershed Preliminary Culvert Assessment December 2010
Site ID SC010 SC097 DC095 SC044 DC099 DC106 DC104 SC048 DC079 SC075 DC080 DC002 SC049 SC087 SC045 SC089 SC092 SC055 SC054 SC076 SC103 SC020 DC083 SC034 DC033 DC037 DC027 SC046 DC030 DC007 DC009 DC029 DC026 SC033 DC011 SC083 DC020 DC021
Town Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bridgewater Bristol Bristol Bristol Bristol Bristol Bristol Bristol Bristol Bristol Bristol Bristol Bristol Bristol Bristol Bristol Bristol Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton
Hydraulic Functionality Score
Habitat Functionality Score
Total Score
12 12 11 11 10 10 9 8 33 31 25 23 22 21 20 15 14 12 12 11 11 11 10 9 28 27 27 27 26 26 25 25 25 25 24 24 23 23
8 12 9 11 12 12 12 8 6 8 6 8 12 3 7 6 6 6 8 7 7 8 7 4 5 5 6 10 5 12 6 7 8 12 6 7 6 6
20 24 20 22 22 22 21 16 39 39 31 31 34 24 27 21 20 18 20 18 18 19 17 13 33 32 33 37 31 38 31 32 33 37 30 31 29 29
TABLE 2 - SUMMARY SCORES BY TOWN Newfound Watershed Preliminary Culvert Assessment December 2010
Site ID SC014 DC028 DC010 DC035 DC008 DC040 DC032 DC066 DC015 DC034 DC038 DC025 DC041 DC049 DC016 SC100 DC024 SC080 DC036 DC039 DC013 DC014 DC012 SC122 DC006 SC116 SC105 DC023 DC085 DC047 DC044 DC061 DC068 DC069 DC043 SC015 SC119 DC22
Town Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton
Hydraulic Functionality Score
Habitat Functionality Score
Total Score
23 23 23 23 23 22 22 21 21 21 20 20 20 19 19 19 19 19 19 19 18 18 18 17 17 16 15 15 15 14 14 14 14 14 14 14 14 14
6 8 9 10 12 7 9 4 6 9 5 10 13 4 5 7 8 8 10 11 6 6 13 4 5 8 7 11 12 3 4 4 4 4 8 8 8 14
29 31 32 33 35 29 31 25 27 30 25 30 33 23 24 26 27 27 29 30 24 24 31 21 22 24 22 26 27 17 18 18 18 18 22 22 22 28
TABLE 2 - SUMMARY SCORES BY TOWN Newfound Watershed Preliminary Culvert Assessment December 2010
Site ID DC053 DC062 DC018 DC019 DC046 DC070 DC071 DC072 DC031 SC082 SC099 SC124 DC048 DC051 DC017 DC042 DC054 DC050 DC052 DC064 DC045 DC063 DC065 DC073 DC075 DC055 DC056 DC057 DC058 DC059 DC060 DC067 DC076 SC037 DC084 DC004 SC012 DC005
Town Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Groton Hebron Hebron Hebron Hebron Hebron
Hydraulic Functionality Score
Habitat Functionality Score
Total Score
13 13 13 13 12 12 12 12 12 12 12 12 11 11 10 10 9 9 9 9 6 6 6 6 6 5 5 5 5 5 5 5 5 36 30 29 28 28
4 4 7 8 4 4 4 4 7 7 8 8 4 4 12 10 3 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 7 12 12 6 7
17 17 20 21 16 16 16 16 19 19 20 20 15 15 22 20 12 13 13 13 10 10 10 10 10 9 9 9 9 9 9 9 9 43 42 41 34 35
TABLE 2 - SUMMARY SCORES BY TOWN Newfound Watershed Preliminary Culvert Assessment December 2010
Site ID SC063 DC003 DC117 DC001 SC065 SC029 SC051 SC061 DC110 SC106 SC066 SC00X SC031 SC064 SC098 SC107 SC068 DC118 DC111 SC047 DC112 SC067 SC007 DC86
Town Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Hebron Plymouth unk
Hydraulic Functionality Score
Habitat Functionality Score
Total Score
26 26 24 24 23 22 19 19 18 18 18 16 16 15 14 14 13 12 12 11 11 11 21 23
13 14 12 13 13 11 6 6 11 11 12 6 7 13 7 9 7 8 12 7 12 14 8 12
39 40 36 37 36 33 25 25 29 29 30 22 23 28 21 23 20 20 24 18 23 25 29 35
TABLE 2 - SUMMARY SCORES BY TOWN Newfound Watershed Preliminary Culvert Assessment December 2010
Average Values for Scores by Town Town
Hydraulic Habitat
Total
Alexandria
16.4
7.6
24.1
Bridgewater
16.9
10.1
27.0
Bristol
17.5
6.8
24.3
Groton
15.8
6.6
22.3
Hebron
19.7
9.9
29.7
Site ID
Town
TABLE 3 - HYDRAULIC FUNCTION DETAIL SCORES (HIGHEST ONE-THIRD) Newfound Watershed Preliminary Culvert Assessment December 2010 Culvert Hydraulic Capacity Culvert Angle Angle Obstruct Obstruct Scour Scour Headwall Ratio Condition (US) (DS) ed (US) ed (DS) (US) Score (DS) Condition
Habitat Score
Total Score
SC072
Alexandria
32
1
5
5
2
1
1
5
5
5
7
39
SC035
Alexandria
31
1
4
5
5
1
1
5
3
4
8
39
SC052
Alexandria
31
5
4
5
1
5
1
1
2
5
10
41
SC056
Alexandria
29
1
5
3
1
1
1
5
5
5
7
36
SC093
Alexandria
26
5
3
1
1
5
5
1
1
1
6
32
SC000
Alexandria
25
5
3
2
1
3
1
1
1
5
6
31
SC129
Alexandria
24
1
3
1
1
1
1
5
5
4
7
31
DC090
Alexandria
23
5
1
5
1
1
1
5
1
8
31
SC095
Alexandria
23
1
4
3
1
1
1
5
3
2
7
30
SC070
Alexandria
21
1
3
1
1
1
1
4
4
3
7
28
SC004
Alexandria
20
1
1
5
2
3
1
1
3
1
8
28
SC084
Alexandria
20
1
3
3
1
1
1
3
2
3
8
28
SC077
Bridgewater
31
5
4
5
1
5
1
1
2
5
11
42
SC110
Bridgewater
30
5
5
3
1
1
1
5
2
5
7
37
DC107
Bridgewater
27
1
5
5
1
2
1
1
5
5
12
39
DC100
Bridgewater
26
5
4
3
1
1
1
3
2
5
12
38
DC094
Bridgewater
25
5
4
3
5
1
1
1
1
3
7
32
DC101
Bridgewater
22
1
3
2
3
2
2
2
2
4
12
34
SC104
Bridgewater
22
1
3
2
2
2
1
5
1
3
10
32
SC043
Bridgewater
21
5
1
5
3
1
1
2
1
3
7
28
SC074
Bridgewater
21
1
5
4
2
1
1
1
1
3
7
28
DC092
Bridgewater
20
1
2
1
5
5
1
1
1
2
12
32
DC093
Bridgewater
20
5
1
4
3
1
2
1
1
1
8
28
DC105
Bridgewater
20
1
5
2
2
1
1
1
5
1
12
32
DC079
Bristol
33
5
5
4
1
1
5
5
5
6
39
SC075
Bristol
31
5
5
1
1
1
5
1
5
8
39
5
Site ID
Town
TABLE 3 - HYDRAULIC FUNCTION DETAIL SCORES (HIGHEST ONE-THIRD) Newfound Watershed Preliminary Culvert Assessment December 2010 Culvert Hydraulic Capacity Culvert Angle Angle Obstruct Obstruct Scour Scour Headwall Ratio Condition (US) (DS) ed (US) ed (DS) (US) Score (DS) Condition
Habitat Score
Total Score
DC080
Bristol
25
5
3
1
4
1
1
2
3
3
6
31
DC002
Bristol
23
5
4
1
1
2
2
2
1
2
8
31
SC049
Bristol
22
3
1
3
3
3
2
3
2
12
34
SC087
Bristol
21
5
5
2.5
3
5
3
3
3
5
3
24
SC045
Bristol
20
1
2
3
1
1
1
4
1
4
7
27
DC033
Groton
28
5
2
5
3
5
3
5
3
3
5
33
DC027
Groton
27
1
5
5
5
3
1
1
1
3
6
33
DC037
Groton
27
5
5
1
1
5
1
1
1
5
5
32
SC046
Groton
27
5
3
4
1
3
2
1
3
3
10
37
DC007
Groton
26
1
4
5
1
5
1
1
1
5
12
38
DC030
Groton
26
1
3
5
3
1
1
4
1
5
5
31
DC009
Groton
25
5
5
3
1
2
1
1
5
6
31
DC026
Groton
25
1
5
1
1
5
5
1
1
3
8
33
DC029
Groton
25
1
2
5
1
1
1
5
1
5
7
32
SC033
Groton
25
5
1
1
1
1
5
4
5
12
37
DC011
Groton
24
5
1
5
5
1
1
1
1
1
6
30
SC083
Groton
24
1
5
1
1
1
1
1
5
5
7
31
DC008
Groton
23
1
2
1
5
3
1
3
1
4
12
35
DC010
Groton
23
4
1
1
5
1
1
3
5
9
32
DC020
Groton
23
1
1
5
3
2
5
1
1
5
6
29
DC021
Groton
23
1
1
5
1
1
1
5
1
5
6
29
DC028
Groton
23
1
5
5
1
1
2
4
2
8
31
DC035
Groton
23
3
5
1
2
1
3
1
5
10
33
SC014
Groton
23
1
4
5
1
1
1
3
1
4
6
29
DC032
Groton
22
5
4
1
1
3
3
1
1
2
9
31
DC040
Groton
22
1
1
1
1
1
1
5
5
4
7
29
TABLE 3 - HYDRAULIC FUNCTION DETAIL SCORES (HIGHEST ONE-THIRD) Newfound Watershed Preliminary Culvert Assessment December 2010
Site ID
Town
Culvert Hydraulic Capacity Culvert Angle Angle Obstruct Obstruct Scour Scour Ratio Condition (US) (DS) ed (US) ed (DS) (US) Score (DS)
DC015
Groton
21
DC034
Groton
21
DC066
Groton
21
DC025
Groton
20
DC038
Groton
DC041
Headwall Condition
Habitat Score
Total Score
3
5
1
3
1
4
1
4
6
27
2
1
1
1
1
1
2
5
9
30
5
2.5
3
5
5
3
3
5
4
25
1
5
5
1
1
1
1
1
3
10
30
20
1
3
3
1
3
3
1
1
3
5
25
Groton
20
5
3
3
1
3
1
1
1
1
13
33
SC037
Hebron
36
5
5
2
2
5
5
2
2
5
7
43
DC084
Hebron
30
1
3
5
3
1
1
5
4
5
12
42
DC004
Hebron
29
1
5
5
1
1
1
5
3
5
12
41
DC005
Hebron
28
1
3
1
5
5
5
1
1
3
7
35
SC012
Hebron
28
5
4
1
1
2
1
5
2
4
6
34
DC003
Hebron
26
5
2
5
3
2
1
2
1
3
14
40
SC063
Hebron
26
3
5
1
2
1
3
3
5
13
39
DC001
Hebron
24
3
1
2
2
1
1
3
3
13
37
DC117
Hebron
24
3
1
1
1
5
2
1
2
12
36
SC065
Hebron
23
1
1
3
5
2
1
2
2
3
13
36
SC029
Hebron
22
1
3
5
1
1
1
1
1
5
11
33
SC007
Plymouth
21
1
4
2
3
1
1
3
1
3
8
29
DC86
unk
23
1
3
3
1
1
1
3
4
4
12
35
71 3.1 28
71 2.1 10
71 2.5 17
71 2.2 9
Total Sites 71 Avg. 24.5 High Score Count
5
5
59 2.6 24
71 3.4 20
71 2.2 13
71 1.6 7
71 3.7 29
71 8.5
71 33.1
TABLE 3 - HYDRAULIC FUNCTION DETAIL SCORES (HIGHEST ONE-THIRD) Newfound Watershed Preliminary Culvert Assessment December 2010 NOTES:
Bold Site ID indicates no bank full data, therefore no CCR value and total score is biased low 2 High Score Count indicates number of maximum values in criterion - a relative ranking of basis of total Hydraulic Function score
1
TABLE 3 - HYDRAULIC FUNCTION DETAIL SCORES (HIGHEST ONE-THIRD) Newfound Watershed Preliminary Culvert Assessment December 2010
Average Scores, Top Third, by Town Town
Hydraulic
Habitat
Total
Alexandria
25.4
7.4
32.8
Bridgewater
23.8
9.8
33.5
Bristol
25.0
7.1
32.1
Groton
23.6
7.7
31.2
Hebron
26.9
10.9
37.8
TABLE 4 - SUMMARY STATISTICS Newfound Watershed Preliminary Culvert Assessment December 2010
Town
Average Values, All Data
Average Values, Top-Third
Total Sites Hydraulic Habitat Total
Total Sites
Hydraulic Habitat
Total
Alexandria
48
16.4
7.6
24.1
12
25.4
7.4
32.8
Bridgewater
36
16.9
10.1
27.0
12
23.8
9.8
33.5
Bristol
16
17.5
6.8
24.3
7
25.0
7.1
32.1
Groton
85
15.8
6.6
22.3
27
23.6
7.7
31.2
Hebron
27
19.7
9.9
29.7
11
26.9
10.9
37.8
NOTES: 1 Total Sites include one location in Plymouth and one unmapped location 2 Province Rd. in Groton was mapped prior to revising crossing definition to include defined stream channel 3 7 of 27 (26%) of Top-Third sites in Groton lack defined channels, and are of low hydraulic significance
TABLE 5 - Culvert Size Guidelines Light Soils (Sands) Medium Soils Acres Drained
Flat
Heavy Soils (Clay)
Mod. Steep Flat Mod. Steep Flat Mod. Steep
0-5% 5-15% 15%+ 0-5% 5-15% 15%+ 0-5% 5-15% 15%+ Culvert diameter in inches
5
18
18
18
18
18
21
21
21
24
10
18
18
18
21
24
27
27
27
36
20
18
18
18
24
27
36
36
36
42
30
18
18
18
27
30
36
36
42
48
40
18
18
18
27
36
42
42
48
50
18
18
18
30
36
48
48
48
75
18
21
21
36
42
100
21
21
24
36
48
150
21
24
24
42
200
24
30
30
48
250
27
30
30
300
30
36
36
350
30
36
42
400
36
36
42
Indiana Dept. of Natural Resources (Forestry) http://www.in.gov/dnr/forestry/4589.htm
FIGURE 1 – SITE LOCATIONS AND RANKING RESULTS Newfound Watershed Preliminary Culvert Assessment December 2010
FIGURE 2 – ALEXANDRIA SITE LOCATIONS AND RANKING RESULTS Newfound Watershed Preliminary Culvert Assessment December 2010
FIGURE 3 – BRIDGEWATER SITE LOCATIONS AND RANKING RESULTS Newfound Watershed Preliminary Culvert Assessment December 2010
FIGURE 4 – BRISTOL SITE LOCATIONS AND RANKING RESULTS Newfound Watershed Preliminary Culvert Assessment December 2010
FIGURE 5 – GROTON SITE LOCATIONS AND RANKING RESULTS Newfound Watershed Preliminary Culvert Assessment December 2010
FIGURE 6 – HEBRON SITE LOCATIONS AND RANKING RESULTS Newfound Watershed Preliminary Culvert Assessment December 2010
APPENDIX A – SUMMARY REPORT ON CD-ROM Newfound Watershed Preliminary Culvert Assessment December 2010
APPENDIX B – SELECTED PROJECT PHOTOGRAPHS Newfound Watershed Preliminary Culvert Assessment December 2010
APPENDIX B1 – SELECTED PROJECT PHOTOGRAPHS Newfound Watershed Preliminary Culvert Assessment Good Quality Crossings
This crossing appears adequately sized and is constructed at grade and with durable materials.
This is a newly built bridge. It has strong headwalls and is likely engineered to flood conditions.
APPENDIX B1 – SELECTED PROJECT PHOTOGRAPHS Newfound Watershed Preliminary Culvert Assessment Good Quality Crossings
This culvert appears large enough to handle flood conditions, has enough sediment to mimic the natural stream bed and is in excellent condition.
This structure is at the same level as the stream bed and there is no evidence of scour.
APPENDIX B1 – SELECTED PROJECT PHOTOGRAPHS Newfound Watershed Preliminary Culvert Assessment Good Quality Crossings
This is a natural crossing due to its open bottom.
This bridge appears adequately sized, is constructed of durable materials and is in excellent condition.
APPENDIX B2 – SELECTED PROJECT PHOTOGRAPHS Newfound Watershed Preliminary Culvert Assessment Moderate Quality Crossings
This shows the beginnings of scour and a perched outlet.
This crossing shows minor scour holes on the bottom corners.
APPENDIX B2 – SELECTED PROJECT PHOTOGRAPHS Newfound Watershed Preliminary Culvert Assessment Moderate Quality Crossings
This crossing has erosion to the structure at the road surface.
APPENDIX B3 – SELECTED PROJECT PHOTOGRAPHS Newfound Watershed Preliminary Culvert Assessment Poor Quality Crossings
This culvert is nearly 100% obstructed and diverted flow may damage roadway.
This culvert has been crushed and has reduced flow capacity.
APPENDIX B3 – SELECTED PROJECT PHOTOGRAPHS Newfound Watershed Preliminary Culvert Assessment Poor Quality Crossings
This crossing headwall is constructed of unsecured stone with a high level of scour at the footings.
This crossing has a high level of scour.
APPENDIX B3 – SELECTED PROJECT PHOTOGRAPHS Newfound Watershed Preliminary Culvert Assessment Poor Quality Crossings
The footer on the right is undermined and the bridge deck is deteriorating.
The roadway has been damaged, possibly by storm water runoff from the road surface.
APPENDIX B3 – SELECTED PROJECT PHOTOGRAPHS Newfound Watershed Preliminary Culvert Assessment Poor Quality Crossings
This pipe is perched ~15 feet, creating a barrier to aquatic wildlife.
